------------------------------------------------ S19-01 HIGH LATITUDE HF INDUCED PLASMA TURBULENCE B. ISHAM (1), C. La Hoz (2), M. T. Rietveld (1,3), F. T. Djuth (4), T. Hagfors (3), and T. Grydeland (2) (1) EISCAT Scientific Association, Troms\o Norway (2) University of Troms\o, Troms\o Norway (3) Max-Planck-Institute f\"ur Aeronomie, Katlenburg-Lindau, Germany (4) Geospace Research Inc., El Segundo, California, USA E-mail: isham@eiscat.uit.no Incoherent scatter radar (ISR) is an ideal diagnostic tool for use in investigations of HF-pump-induced Langmuir turbulence in space. Since the first such experiments at Arecibo in the early 1970s, ISR has been the principle diagnostic for such studies. At high latitudes EISCAT, which operates high resolution incoherent scatter radars at 224 and 931 MHz and an HF transmitter possessing more than 1 GW in effective radiated power, is the only facility where such experiments may be performed. EISCAT is located in northern Scandinavia where the geomagnetic field lines are offset from vertical by just 13 degrees, making possible a wide variety of interesting active ionospheric radio propagation, wave interaction, and HF Langmuir turbulence experiments. Significant improvements have recently been made in theoretical concepts, computer models, and experimental techniques designed to aid in improving our understanding of Langmuir turbulence. In particular, progress has been achieved at EISCAT towards scientific agreement on a set of phenomena that are universally observed during both high and low latitude ionospheric Langmuir turbulence experiments. Other experiments have made use of the geomagnetic geometry as a tool to create and study HF-induced Langmuir turbulence both below the bottomside critical level and in the topside ionosphere. Results of these and related experiments will be presented and directions for the future will be discussed. ------------------------------------------------ S19-02 SIMULATION STUDY ON UPPER HYBRID AND ELECTROMAGNETIC EMISSIONS IN IONOSPHERIC RADIO MODIFICATION EXPERIMENTS H. O. UEDA (1), Y. Omura (2), and H. Matsumoto (2) (1) Faculty of Engineering, Chiba University (2) Radio Science Center for Space and Atmospheric, Kyoto University E-mail: ueda@cute.te.chiba-u.ac.jp Stimulated electromagnetic emissions (SEE) are nonlinear plasma phenomena observed in the ionospheric modification experiments by means of high-power HF radio waves. The SEE spectrum has a rich structure extending around the pump frequency. The experiments found a close connection between the SEE features and small-scale magnetic field-aligned irregularities thermally generated in the upper hybrid resonance region of the pump wave. Some theoretical models for explaining the formation of the irregularities and the excitation of the secondary electromagnetic emissions are based on ideas of trapped and driven upper hybrid oscillations. The theories suggest the pre-existing irregularity leads to generation of the upper hybrid waves which are trapped in density depletions of the irregularity, and furthermore it causes transformation of the electrostatic waves to the electromagnetic ones due to wave-wave interactions. We performed particle-in-cell (PIC) simulations assuming the ionosperic modification experiments to describe details of the interaction processes. In the simulation model, an obliquely propagating pump wave is continuously injected into the region where a small-scale field-aligned irregularity exists. The simulation results demonstrate the emissions of UH wave, low-frequency and HF electromagnetic waves in the inhomogeneous plasma. We discuss on conditions of the most interesting feature in the SEE spectrum, broad upshifted maximum (BUM), according to proposed theories of parametric four-wave interaction. ------------------------------------------------ S19-03 TRIGGERING OF LOCAL SUBSTORM ACTIVATIONS INDUCED BY THE TROMS\O HEATING FACILITY N. F. BLAGOVESHCHENSKAYA (1), V. A. Kornienko (1), B. Thide (2), M. T. Rietveld (3), and M. J. Kosch (3) (1) Arctic and Antarctic Research Institute, St.Petersburg, Russia (2) Swedish Institute of Space Physics, Uppsala Division, Sweden (3) Max-Plank Institut f\"ur Aeronomy, Katlenburg-Lindau, Germany E-mail: nataly@aari.nw.ru Experimental results from Troms\o HF pumping experiments in the nightside auroral ionosphere are reported. A bistatic HF Doppler radio scattering setup has been used in conjunction with the EISCAT UHF radar, the DASI digital all-sky imager, the IMAGE magnetometer network, the Troms\o dynasonde and IMP 8, 9 satellites to find the evidence that powerful HF radio waves produce the modification of the ionosphere-magnetosphere coupling which can lead to a local substorm activation. Summarising multi-instrument observations one can distinguish the following peculiarities related to this activation: modification of the auroral arc and its break-up above Troms\o; local changes of currents in the vicinity of Troms\o; increase of the electron temperatures and ion velocities at altitudes above the HF pump reflection level; distinctive features in dynamic HF radio scatter Doppler spectra; pump-induced electron precipitation; substorm activation exactly above Troms\o. The possible mechanisms of the local substorm activation through the enhancment of field-alighned currents and excitation of the turbulent boundary layer inside an ionospheric Alfv\'en resonator in the selected magnetic flux tube footprinted on the heater-enhanced conductivity region are discussed. The obtained results prove the active role of the auroral ionosphere in a substorm process and provide a strong evidence that the location and timing of the auroral activation was related to the HF pumping experiment, but its energy source remains the interaction between the solar wind and the magnetosphere. ------------------------------------------------ S19-04 THE STUDIES OF THE IRREGULAR STRUCTURE OF THE LOWER IONOSPHERE BY THE API TECHNIQUE N. V. BAKHMET'EVA, V. V. Belikovich, E. A. Benediktov, and A. V. Tolmacheva Radiophysical Research Institute (NIRFI), Nizhny Novgorod, Russia E-mail: natali@nirfi.sci-nnov.ru The studies of the irregular structure of the lower ionosphere (the E- and D-regions) have been carried out in 1999 (August, 10-12) near Nizhny Novgorod (56.15N, 44.3E) using API technique. As is known, the artificial periodic inhomogeneities (API) are formed in the field of a powerful standing radio wave as a result of the interference of waves incident and reflected from the ionosphere. Experiment was carried out using SURA heating facility at the frequency of 5.69 MHz X-mode. The power transmitter was turned on for three second three times per minute. Amplitudes and times of relaxation of signals back scattered by the API were measured at the same frequency when the power transmitter was turn off. The height step of the sample data was 0.7 km and the repetition frequency of probing pulses was 50 Hz. Range-time-amplitude plots of API echoes were obtained at height range from 60 km (D-region) up to the bottom of the F2-layer. The existence of the ionospheric irregularities and sporadic E-layers which have been observed permanently. The sporadic layers between 80 and 95 km existed during some hours and the irregular structure of these layers was visible.The sporadic layers as lower as above the E-layer maximum were observed and division of the E-layer maximum on two parts took place also.The additional layers in the interlayer E-F valley at the height \sim 140 km were seen during 20-30 minutes. Sometimes descent down to the E-layer maximum was observed. The appearance of the additional layers in the valley was noted in 1998 by Bakhmet'eva et al. Radio Sci., 33, 583--595). The work was supported by RFBR under Grants N 99-05-64464 and N 00-05-64695. ------------------------------------------------ S19-05 ACTIVE EXPERIMENTS WITH HIGH-SPEED INJECTIONS FROM SPACE P. A. BERNHARDT (1), R. E. Erlandson (2), and J. Zetzer (3) (1) Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 USA (2) Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723 USA (3) Institute for Dynamics of Geospheres, Moskow, Russia E-mail: bern@ppdu.nrl.navy.mil High speed injection of neutrals and ions into the upper atmosphere permits the study of processes that occur in nature. Several recent experiments involving the Space Shuttle and sounding rockets have provided new insight into the physics of high-speed ion interactions. The Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) used ground based incoherent scatter radars at Arecibo, Puerto Rico; Jicamara, Peru; and Kwajalein, Marshall Islands to detect non-equilibrium ion distributions in the Space Shuttle exhaust. Dedicated firings of the orbital maneuver subsystem (OMS) engines injected water vapor molecules with kinetic energies of 10 eV. Charge exchange with the ambient atomic oxygen ion produced molecular ion beams moving 10 times the ion sound speed. The relaxation of these beams was detected with incoherent scatter radars and the presence of turbulence from kinetic instabilities was inferred. The ion-line spectra from the radar was similar to that seen in disturbed auroral ionosphere. These experiments were conducted between 1997 and 1999 on Shuttle flights STS-86 and STS-93. During 1997, the FLUXUS I and II experiments released plasma jets parallel to the magnetic field near 150-km altitude. These jets were observed optically with the MSX satellite and with ground sensors. A follow-on experiment called APEX North Star was conducted in early 1999 involving two explosive payloads and two diagnostic payloads. The diagnostics included both plasma sensors (Langmuir Probe, electric field sensor, plasma wave receiver) as well as high-speed optical sensors. The measurements provided the full spectrum of plasma kinetic effects initiated by the injections. ------------------------------------------------ S19-06 BEAM-PLASMA EFFECTS OF ARTIFICIAL ORBITAL INJECTION (OVERVIEW OF APEX MISSION RESULTS) V. Oraevsky, Y. RUZHIN, and V. Dokukin IZMIRAN, Troitsk, Moscow region, 142092 RUSSIA E-mail: ruzhin@izmiran.rssi.ru The main results of Active Plasma EXperiments (project APEX) are presented. For the first time an opportunity of injection of an electron beam was shown under limited conditions to neutralise a charging of spacecraft by environmental plasma. The supervision are executed in a wide range magnetosphere conditions: from equatorial up to high latitude zones, including magnetic force tube extending on many radiuses of the Earth. These supervision show that the modulated electron beam can be used as a effective radiating aerial. For the first time VLF emission of a modulated electronic beam is registered at subsattelite on distances of hundreds km. Series of coordinated active experiments above groundbased radio heating facilities were conducted. An opportunity for tunnelling effect was demonstrated. Researches of Alfv\'en critical ionisation velocity (CIV) phenomena during a neutral xenon gas injection are executed.Passive measurements of parameters of a plasma in auroral and equatorial zones in a range of heights of 450-3000 km were conducted. ------------------------------------------------ S19-07 STABILITY OF ELECTRODYNAMIC TETHERS M. DOBROWOLNY Istituto Fisica Spazio Interplanetario, CNR, Rome, Italy E-mail: dobrowolny@ifsi.rm.cnr.it Electrodynamic tethers are at present being investigated especially in relation to two applications. The first one is that of obtaining propulsion and the second, important in relation to the problem of accumulation of debris in the near Earth environment, that of using tethers to deorbit LEO objects. For both applications, the relative importance of electrodynamic forces with respect to gravity gradient forces can be much greater than for systems, like TSS, which have already being flown. One main problem, concerning the feasibility of these applications is that of the dynamic stability of the system and the ways to control it when necessary. There are in fact indications, from extensive numerical simulations, that the system may go unstable but the numerical simulations themselves are not capable of illustrating the physical mechanism of the intability and associate that with a critical parameter. In this paper we present initial results of an analytical approach to the problem of stabilty of electrodynamic tethers in the framework of a model where the tether current is assumed to be given with a plausible frequency content.We indeed find possible instabilities of the lateral modes of the tether and obtain thresholds as a function of current. More significantly, the treatment leads to the determination of a dimensionless parameter (a function of the current and the parameters of the given tether system) which controls the tether stability. ------------------------------------------------ S19-08 NUMERICAL SIMULATIONS OF ELECTROMAGNETIC INTERACTION BETWEEN ANTENNA AND SPACE PLASMA H. USUI, H. Matsumoto, and Y. Omura Radio Science Center for Space and Atmosphere, Kyoto University E-mail: usui@kurasc.kyoto-u.ac.jp We studied the electromagnetic interactions between antenna and space plasma by performing EM-PIC (Particle-In-Cell) simulations. We particularly focused on the field and plasma environment of the sheath region formed around antenna. Previous theoretical studies found new modes of electromagnetic wave called sheath waves which propagate along the plasma-metal interface on the assumption that the sheath region is vacuum. To examine the property of the sheath waves, we performed PIC simulations with a two-dimensional model which includes a metal surface of antenna immersed in magnetized background plasma. Due to the difference of thermal velocity between electrons and ions, an ion sheath is created near the antenna surface. We basically could confirm the sheath waves propagating along the metal-plasma interface at the frequencies lower than those of normal wave modes for a uniform plasma. The dispersion relation of the sheath waves is modified in the simulations because the electron density gradually changes at the transition region from the background plasma to the sheath while a sharp boundary is assumed in the theory. We also investigated an active antenna case in which we added high power RF electric field to the antenna. The nonlinear effects to the sheath formation and associated antenna charging were examined by PIC simulations. ------------------------------------------------ S19-09 OF CURRENT INTEREST: PROBES AND ELECTRODES IN SPACE MAGNETOPLASMAS J. G. LAFRAMBOISE York University, Toronto, Canada E-mail: laframboise@quasar.phys.yorku.ca Recent space experiments, including CHARGE-2, SPEAR I, and especially TSS-1 and TSS-1R, have generated increased efforts to improve current-collection theories for large, positively charged objects in space. In all of these experiments, electron collection exceeded substantially that predicted by the theory of Parker and Murphy (1967) for spherical probes in collisionless magnetoplasmas. In all three experiments, breaking of rotational symmetry about the magnetic-field direction was invoked as a cause of this excess current. In CHARGE-2, electron-beam emission was involved, but symmetry-breaking also occurred because of asymmetry of the shape of the spacecraft. In SPEAR I, it was caused by the presence of the oppositely charged rocket body which carried the spacecraft's large electron-collecting spherical probe. In the case of TSS-1 and TSS-1R, orbital speed large compared with the ion thermal speed produced such symmetry-breaking, even though this speed was small compared with the electron thermal speed. It is widely believed that time-averaged current collection may also be increased by effects of plasma turbulence. We review the available evidence for and against this contention, and we also review older steady-state theories and recent developments in theory for electron collection from the space plasma environment. ------------------------------------------------ S19-10 FLOATING POTENTIALS OF CONDUCTORS IN SPACECRAFT DIELECTRICS K. G. BALMAIN, M. G. Serban, G. R. Dubois, P. C. Kremer, and A. A. E. Luttgen Dept.~of Electrical \ Computer Engineering, Univ.~of Toronto E-mail: balmain@waves.utoronto.ca Electrostatic charging continues to be a threat to high altitude spacecraft. On satellites, conductors that are electrically ``floating" represent a special danger, which explains why designers take such pains to provide conductors with DC paths to the satellite-frame ``ground". Measuring the potentials of an array of conducting probes embedded at different depths in a variety of different but relevant dielectrics is clearly a technique that could lead to a useful spacecraft monitor device to warn of a worst-case threat, as well as providing needed insight both into the physics of energetic-electron charging and into better principles of spacecraft electrical design. A 12-channel monitor device based on the above concepts has been built, and then tested in the laboratory under high vacuum. The electron source is a Strontium-90 radioisotope approximately representing a moderate magnetic storm at geosynchronous orbit, and its use has enabled continuous long-term tests up to 3-4 weeks in duration. The results of these tests include the observation of 1) potential-growth time constants at different depths with potentials stabilizing as high as 12 kV negative, 2) discharge events, 3) ion neutralization as a function of depth, and 4) comparative properties of different dielectric materials. To predict such effects, numerical modeling of field-enhanced conduction and charge redistribution in irradiated dielectrics has been done using Monte Carlo and finite-element techniques. The computation is essentially one-dimensional and the dielectric can be multilayered and have metal inserts acting as probes. Such computations have produced results in agreement with experimental data and have shown that, with proper calibration, conducting probes inserted in dielectrics can be used to characterize the charging/discharging state. Further, the computations show that it is necessary to take into account the interactions with external circuits, especially those involving the internal and external capacitances of the probe conductors. ------------------------------------------------ S19-11 COMPUTATION OF CURRENT TO A MOVING BARE TETHER T. ONISHI (1), M. Martinez-Sanchez (1), and D. L. Cooke (2) (1) Space Systems Laboratory, MIT (2) Air Force Research Laboratory, Space Vehicle Directorate, Hanscom AFB E-mail: onishi@mit.edu An electrodynamic bare tether has been considered as an alternative method of propulsion without expenditure of propellant. The object of the work reported here is the development of a numerical method, Particle-In-Cell method, for the calculation of electron current to a positive bare tether moving at orbital velocity in the ionosphere, i.e. in a flowing magnetized plasma under Maxwellian collisionless conditions. The code uses the quasi-neutrality condition to solve for the local potential at points in the plasma which coincide with the computational outside boundary. Given the boundary conditions, Poisson equation is solved in such a way that the presheath region can be captured in the computation. Electrons are assumed to have a Maxwellian distribution at the boundary due to their high mobility, whereas ions are assumed so only in the far upstream region and are also assumed to only decelerate one-dimensionally due to their large mass. The results indicate a stable convergence, and clearly represents a presheath region. Collected currents turn out to be more than that predicted by the Orbital Motion Limit (OML) theory. As a possible cause of the enhanced current collection, particle-field interaction, which may be responsible for the plasma heating, is observed. ------------------------------------------------ S19-12 FIRST RESULTS FROM THE RADIO PLASMA IMAGER ON THE IMAGE MISSION B. REINISCH and the RPI Team University of Massachusetts, Lowell, MA, USA E-mail: reinisch@cae.uml.edu The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission was successfully launched on March 25, 2000. IMAGE was placed into a polar orbit with apogee of about 7 Earth radii (R_E) and inclination of about 45 degrees. The Radio Plasma Imager (RPI) on IMAGE is a radio sounder designed to sweep from 3 kHz to 3 MHz. Radio plasma imaging uses total reflection of electromagnetic waves from plasmas whose plasma frequencies equal the radio sounding frequency and whose electron density gradients are parallel to the wave normals. The RPI has two orthogonal 500-m long dipole antennas in the spin plane for transmission and reception. The spin axis antenna is a 20-m dipole for reception only. Echoes from magnetospheric boundaries and plasma regions have been received on all three orthogonal antennas, allowing the determination of the angle-of-arrival of the echoes. RPI has been operating in three active sounding modes: (1) remote sounding to probe magnetospheric boundaries, (2) local (relaxation) sounding to probe the local plasma, and (3) whistler stimulation sounding. In addition, there is a passive mode to record natural emissions, and to determine the local electron density and temperature by using a thermal noise spectroscopy technique. On the IMAGE mission, RPI is well situated to observe the structure and dynamics of a number of magnetospheric boundaries over periods of several hours during geomagnetic storms. This paper will provide an overview of the early measurements from the RPI instrument during many of its operating modes. ------------------------------------------------ S19-13 PLASMA SOUNDER EXPERIMENT IN THE LOWER ALTITUDE IONOSPHERE (S310-28 ROCKET EXPERIMENT) T. ONO Tohoku Univerisity E-mail: ono@stpp3.geophys.tohoku.ac.jp The sounder experiment (SDR) was carried out onboard the S310-28 rocket which was launched on February 2, 10:30 (JST) in 1998 for the verification test of the function of instrumentation for the Lunar Radar Sounder Experiment (LRS) to be installed on the SELENE satellite. The S310-28 SDR system consists of two sets of the 14 m tip-to-tip dipole antennas and an electronics package including a high power transmitter and receiver in HF frequency range from 800 kHz to 11 MHz. Provisional data analyses showed that power transmitter radiated the designed power of about 60 watts and confirmation has been made for radar sounder function. Sounder experiments were carried out in the low altitude region of ionosphere with in the altitude range from 100 to 180 km. We found a interesting feature of the echo signals near 3 MHz returned from the bottom side F-region ionosphere, however there was no signal from the ground in this frequency range. The echoes found in the altimeter operation at around 10 MHz shows that sounder pulse propagate along the field aligned irregular structures appearing in the E-region ionosphere. ------------------------------------------------ S19-14 SUMMARY OF SYMPOSIUM S19 H. G. JAMES Communications Research Centre, Ottawa E-mail: gordon.james@crc.ca oindent ------------------------------------------------ S19-P01 HF BISTATIC SCATTER OBSERVATIONS OF ARTIFICIAL FIELD-ALIGNED IRREGULARITIES UNDER DIFFERENT ELEVATION ANGLES OF THE TROMS\O HF HEATER ANTENNA BEAM N. F. BLAGOVESHCHENSKAYA (1), M. T. Rietveld (2), and V. A. Kornienko (1) (1) Arctic and Antarctic Research Institute, St.Petersburg, Russia (2) Max-Plank Institut f\"ur Aeronomy, Katlenburg-Lindau, Germany E-mail: nataly@aari.nw.ru Experimental studies of artificial field-aligned irregularities (AFAI) in the nightside auroral F region during quite magnetic conditions on dependence of elevation angles of the Troms\o HF heating facility are reported. They are based on observations from bistatic HF Doppler radio scatter with conjunction with the EISCAT UHF incoherent scatter radar. It was found that the most strong AFAI are generated when HF heater antenna beam was centered along magnetic field-aligned direction. It can be seen from variations of spectral power and spectral broadening of HF scattered signals under different positions of the HF heater antenna beam. A close connection between AFAI and electron temperature T_e enhancements was also observed. The distinctive feature of the modification experiment is the large T_e enhancements during heater-on periods that in 2-4 times exceeded T_e during heater-off periods. The largest T_e enhancements observed in a wide altitude range from 200 to 600 km took place in direction parallel to the magnetic field. The most plausible mechanism that can lead to heating the electron population is the ion-acoustic instability. Another peculiarity accompanied T_e enhancements was increases of the ion temperatures and positive values of the ion velocities at the heights above 350 km that is higher the HF pump wave reflection level. Signatures observed from UHF radar data during the modification experiment under quiet magnetic conditions are indicative for the generation of HF pump-induced upward ion flows, analogous to those occurring naturally in the nightside auroral ionosphere under disturbed magnetic conditions. ------------------------------------------------ S19-P02 INVESTIGATION INTO THE SPORADIC-E LAYER AND ITS ASSOCIATED PHENOMENA L. KAGAN Radiophysical Research Institute, N. Novgorod, Russia E-mail: kagmil@nirfi.sci-nnov.ru We propose to study the sporadic-E layer and its associated phenomena using a new method based on an induced 557.7 nm emission associated with the sporadic-E layer illuminated by the HF transmitter beam [1, 2] and simultaneous diagnostics of the ionosphere and thermosphere either using incoherent scatter radar or artificial periodic irregularities technique. Among those we see, for an example, investigation into phenomena associated with the Es of a patchy type when the Es is compiled from ionization clouds, which may be organized by the neutral turbulence and result in quasi periodic backscatter, which by the moment is believed to be caused by a gravity wave-modulated Es only. ------------------------------------------------ S19-P03 KINETIC EFFECTS RELATED TO HF PUMPING OF THE IONOSPHERE S. M. GRACH Radiophysical Faculty, State University of Nizhny Novgorod E-mail: sg@nirfi.sci-nnov.ru Some kinetic phenomena occurring in the ionospheric F-region modified by HF powerful radio wave are discussed. Particularly, the acceleration of electrons by pump-driven HF plasma turbulence is considered in the quasilinear approximation for the pump wave frequencies close to multiple electron gyrofrequency. In this case the electrons are accelerated mainly across the magnetic field. This leads to the formation of the strongly anisotropic distribution function of the fast electrons. Relaxation of this function due to the Coulomb collisions with charged particles outside the accelerating layer results in the appearance of the maximum in the particle distribution over the transverse velocities in the tail of the distribution function. The cyclotron instability of such a nonequilibrium distribution can result in generation of the plasma waves at frequencies above the pump wave frequency. These plasma waves may be related to generation of the Broad Upshifted Maximum feature in Stimulated Electromagnetic Emissions of the ionosphere. A nonlinear interaction between Upper Hybrid and Bernstein waves is considered outside of the multiple electron gyroresonance frequency regions. In this case, an interaction kernel must be obtained from kinetic theory because wave numbers of Bernstein waves are greater then inverse thermal electron gyroradius. It is shown that nonlinear growth rate of the UH wave induced scattering to Bernstein wave increases essentially when the upper hybrid frequency approaches to an electron gyroharmonic from below in parallel with a decrease of Bernstein wave wavenumber. Thus, the Bernstein waves should represent a sink of the HF energy in the upper part of the pump frequency interval between two successive gyroharmonics. Such an effect can be responsible for the observed decrease of the SEE intensity for the pump frequencies below gyroharmonics. ------------------------------------------------ S19-P04 TEMPORAL BEHAVIOR OF BROAD UPSHIFTED MAXIMUM IN STIMULATED ELECTROMAGNETIC EMISSIONS S. M. GRACH (1), E. N. Sergeev (2), B. Thide (3), T. B. Leyser (3), T. Carozzi(3), V. F. Frolov (2), and G. P. Komrakov (2) (1) Radiophysical Faculty, State University of Nizhny Novgorod (2) Radiophysical Research Institute (3) Swedish Institute of Space Physics, Uppsala Division E-mail: sg@nirfi.sci-nnov.ru It's well known that the powerful HF pump wave transmitted into ionospheric F-region excites Stimulated Electromagnetic Emissions, which is detected on the ground. In the report we present results on the temporal behavior studies with a high frequency and temporal resolution of Broad Upshifted Maximum spectral feature in Stimulated Electromagnetic Emissions. The results were obtained with the use of new baseband system with 20 MHz sampling rate and 23-bit dynamic range at the SURA facility near Nizhny Novgorod, Russia. BUM is present in SEE spectra at the upshifted frequencies (from approximately 20 kHz up to 150 kHz) relatively to the pump wave frequency if the latter varies from slightly below (<10 kHz) till well above (up to roughly 150 kHz) electron gyro frequency harmonic. The experiments were carried out for 4th and 5th gyro harmonics. In view to study the conditions for BUM generation in the modified ionosphere, the low pump diagnostic duty cycles (less then 5) after CW switch off were used. It was found, that characteristic times of BUM relaxation vary from 0.2 till 0.8 s increasing with a pump wave frequency offset from a gyro harmonic, with a decrease of the frequency shift as well as with time after switch off. Such times are much shorter then those for downshifted SEE features and correspond to the decay times of artificial small-scale (of order of 1-3 m) irregularities. ------------------------------------------------ S19-P05 HF DOPPLER RADAR STUDY OF CHEMICAL MODIFICATIONS OF THE IONOSPHERE O. TYRNOV, L. Kostrov, S. Martynenko, V. Pushin, and V. Rozumenko Department of Space Radio Physics, V.~Karazin Kharkiv National University E-mail: Oleg.F.Tyrnov@univer.kharkov.ua A set of chemical release experiments and associated ground diagnostics have resulted in fair agreement between the data and the models. The chemical releases performed at an altitude of approximately 150 km were observed on frequencies of about 3.7 MHz at distances of 30 to 80 km at the ground using a portable HF Doppler radar. Its specifications are as follows. Operational frequency band of 3 -- 30 MHz at 0.01 Hz intervals, pulse length of 500 ms, pulse repetition rate of 100 -- 200 per second, receiver dynamic range of 80 dB, system bandwidth of 10 Hz, master oscillator of 10 -- 9 stability, instrument error of 0.01 Hz at the maximum Doppler frequency shift of `5 Hz. During the releases of gas clouds of barium, caesium, and lithium, three types of echoes were observed: from the clouds, from the F region, and from the clouds rebound through the F region. For masses of released chemicals of a few tens of kilograms, the echoes were observed during up to 405 min, and the Doppler shifts of the signals reflected from the clouds attained a maximum value of .5 to .0 Hz. When in Doppler modeling allowance is made for cloud drift and relaxation, the agreement between the data and the calculations is reasonable, and the analysis of signal mode structure provides further improvements. For masses of released chemicals of less than 1 kg, the drift observations have showed electric field intensities of 2 -- 10 mV/m, and electron density changes by a factor of several times the ambient values. ------------------------------------------------ S19-P06 ARTIFICIAL IONIZED REGION IN THE ATMOSPHERE AND ITS APPLICATIONS N. BORISOV (1) and A. Gurevich (2) (1) Institute of Terrestrial Magnetism, Ionosphere and Radio Waves Propagation (2) Lebedev Physical Institute E-mail: borisov@td.lpi.ac.ru It is suggested to create Artificial Ionized Region (AIR) in the atmosphere at the heights of several of tens km in crossed beams of microwaves. To maintain ionization in AIR for a long time breakdown pulses should be sent periodically. Optimal conditions to achieve maximum ionization in AIR are discussed theoretically. It is shown that plasma concentration in AIR can exceed maximum concentration in the ionosphere by orders of magnitude. Several important applications of AIR creation are discussed. First, AIR can serve as an artificial ``mirror" for radio and telecommunication in HF, VHF and UHF ranges. Second, each breakdown pulse is accompanied by stimulated optical emission from AIR. It means that powerful N_2 laser is formed in the atmosphere with the help of AIR. Third, AIR can be used for the investigation of complicated chemical processes with minor atmospheric constituents and for direct local action on ozone layer. The main theoretical results are confirmed in the laboratory experiments with strong microwaves. ------------------------------------------------ S19-P07 INFLUENCE OF THE LONGITUDINAL INHOMOGENEITY ON INTERACTION OF WAVES IN STRIATIONS N. BORISOV Institute of Terrestrial Magnetism, Ionosphere and Radio Waves Propagation E-mail: borisov@td.lpi.ac.ru The existence of elongated small-scale plasma inhomogeneities (striations) causes substantial influence on waves interaction and formation of the spectrum of the stimulated electromagnetic emission (SEE). Up to now in the theory of high frequency (HF) heating of the ionosphere only transversal plasma inhomogeneity in striations was taken into account. Such inhomogeneity causes trapping of upper hybrid (UH) waves in striations. We analyse analytically propagation of UH waves in the resonator (single striation) taking into account inhomogeneity along the magnetic field line and in the transversal plane. It is found that the interaction of each UH eigen mode with the electromagnetic pump wave occurs only in a very restricted range of heights. Due to it the amplification of UH waves takes place at a rather low level. It means that the electron temperature in striations is not too high as it was predicted before. The obtained results allows us to esimate the intensity of lower hybrid (LH) oscillations, the spectrum and the intensity of UH waves that contribute to SEE spectrum and the influence of the discussed mechanism on the formation of superthermal electrons. ------------------------------------------------ S19-P08 GENERATION OF INTERNAL GRAVITATIONAL WAVES BY PERIODIC HEATING OF AN IONOSPHERE BY USING ``SURA" FACILITY N. A. Mityakov, V. O. Rapoport, and F. I. VYBORNOV Radiophysical Research Institute (NIRFI) E-mail: vybor@ nirfi.sci-nnov.ru Results of two serials (May 1998 and August 1998) of ionospheric modification experiments on investigation of wave disturbances of upper atmosphere are presented. Heating facility Sura (N. Novgorod, Russia) was used for modification ionosphere. At these experiments the antenna array dipoles phases were chosen in such a way that the antenna pattern was split in two beams inclined by 18^\circ from zenith at the East West direction with width of each about 8^\circ. The ordinary mode for the pump wave was used. The frequency of the pump was 5.75 MHz, the power of transmitters were 750 kW. Probe pulse transmitter was located at Zimenki, (130 km to the west from the Sura facility). Probe frequency was 5.68 MHz. Signals of pump and probe frequencies were recorded at Zimenki. Artificial IGW parameters are determined by variations of Doppler shift of received signal. Heating on off period was 10 min at May session and 15 min at August session. Doppler shift period was 20 min at May session (twice of heating period) and 15 min at August session (equal to heating period). The experiments have shown, that the perturbed area of an ionosphere is a source IGW. If the frequency of the pump wave turning on and off was lower than Brund-Vaisala frequency, IGW were as result of heating the ionosphere by powerful radio waves. If the frequency of turning the power on and off of the facility ``Sura" was above than Brund-Vaisala frequency, parametric generation way of IGW had a place. ------------------------------------------------ S19-P09 INVESTIGATION OF THE ELECTRON AND PLASMA BEAMS INTERACTION WITH IONOSPHERE: THE EXPERIMENT ONBOARD THE MIR STATION S. I. KLIMOV (1), V. A. Grushin (1), I. A. Dobrovolskyi (1), Y. V. Lissakov (1), M. N. Nozdrachev (1), A. A. Petrukovich (1), S. A. Romanov (1), S. P. Savin (1), A. A. Skalsky (1), O. R. Grigoryan (2), E. A. Grachev (2), O. V. Lapshinova (3), A. V. Markov (3), B. A. Mednikov (3), S. B. Ryabukha (3), I. V. Tchurilo (3), F. L. Dudkin (4), V. E. Korepanov (4), G. Berghofer (5), W. Magnes (5), W. Riedler (5), K. Schwingenschuh (5), H. U. Auster (6), K.-H. Fornakon (6), W. W. L. Taylor (7), W. E. Pine (8), N. N. Antropov (9), A. S. Mashkov (10), and N. M. Pushkin (10) (1) Space Research Institute, Russian Academy of Sciences, Moscow (2) Institute of Nuclear Physics, Moscow Sate University (3) Rocket-Space Corporation ENERGIYA, Korolev, Moscow region (4) Lviv Centre of the Institute of Space Research (5) Institut fur Weltraumforschung Austrian Akademie der Wissenschaften, Graz (6) Institut fur Geophysic und Meteorologie, Technische Universitat Braunschweig (7) Raytheon ITSS and INSPIRE, Washington, DC (8) Chaffrey High School, Ontario, CA, and INSPIRE, Upland, CA (9) RIAM, Moscow, Russia (10) NPO IT, Korolev, Moscow region E-mail: sklimov@mx.iki.rssi.ru For the International Project INTMINS (INTerball-Mir-INSpire), plasma and electron beams are injected from the space station MIR into the surrounding plasma. The plasma-wave phenomena resulting from the injection are observed with the SPRUT-VI experiment and the Zond-Zaryad instrument flown onboard the MIR. The simultaneous ground-based observations of waves caused by electron and plasma injections are carried out by the INSPIRE network. During the first phase of the INTMINS Project (1995-1999) electron and plasma injections were performed when the MIR was above the sites of the INSPIRE network. The second phase start on August, 1999 after the installation of the SPRUT-VI on outer surface of the MIR and include the experiment in the frame September 1999 Space Weather Month. The third phase have made in 2000 when the MIR and the INTERBALL-1 were on the same magnetic field line. The observations from the SPRUT-VI and the Zond-Zaryad, and the result of the INSPIRE network observations will be presented. ------------------------------------------------ S19-P10 MODELLING OF OZONE PRODUCTION BY POWERFUL ELECTRON BEAM INJECTION AT STRATOSPHERE V. N. Oraevsky, Y. Ruzhin, and N. BORISOV IZMIRAN, Troitsk, Moscow region, 142092 RUSSIA E-mail: ruzhin@izmiran.rssi.ru The balloon active experiment with electron beam injection in stratosphere is discussed. The results of modelling of injected beam behaviour and active action of it on ozone density evolution are presented. The main parameters of beam injection is varied to estimate more effective conditions for ozone regeneration and degradation processes. It is shown that the balloon payload for powerful electron pulse injection at stratosphere is prospective instrument for solving of modern ozone regeneration problems. ------------------------------------------------ S19-P11 GENERATION OF ALFV\'EN WAVE BY ORBITAL CRRES INJECTION OF BARIUM CLOUD IN MAGNETOSPHERE V. Oraevsky, Y. Ruzhin, V. Badin, and M. DEMINOV IZMIRAN, Troitsk, Moscow region, 142092 RUSSIA E-mail: ruzhin@izmiran.rssi.ru The results of analyses of Alfv\'en wave generation by magnitosphere Barium cloud injection during CRRES mission are presented. The experimental data obtained by means of simultaneous optical and radiophysical observations from Cuba during winter and summer 1991 campaigns. We examine the possible substorm triggering from data of HF radiotelescope measurements during substorm simulation G-8 experiment (geostationary injection). The significance of Alfv\'enic wave generation during artificial injection is discussed in context of current ideas based on artificial cloud - magnetosphere plasma interaction. It is shown that efficiency of Alfv\'en wave generation reach the MAX at time when the radius of expanding barium cloud is more than Larmor radius of background plasma ions but less than barium ions one. A variety of geophysical conditions is encountered. ------------------------------------------------ S19-P12 RADIATION BELT PARTICLES MIRRORING BY PLASMA BEAM INJECTION IN BMA IONOSPHERE REGION Y. RUZHIN, V. Korobeinikov, and V. Skomarovsky IZMIRAN, Troitsk, Moscow region, 142092 RUSSIA E-mail: ruzhin@izmiran.rssi.ru The results of rocket experiment with dense caesium plasma beam injection to ionosphere plasma in Brazilian Magnetic Anomaly (BMA) are discussed. The effects of disappearing of energetic particles with energy more than 2 MeV are analysed. It means that dense beam plasma injection can be like umbrellafor rocket payload during such active action on energetic component of radiation belt population. It is shown that pulse of magnetic field from neutralisation current along geomagnetic field line during beam injection may be an effective mirroring of quasi trapped or precipitated energetic particles in BMA region. The practical advantage of this effect for protection of manned spacecraft is discussed. ------------------------------------------------ S19-P13 THE MULTIPROBING ONBOARD MEASUREMENTS OF MAGNETIC FIELD VARIATIONS DUE TO XENON PLASMA JET INJECTION (APEX PROJECT) Y. RUZHIN, V. Dokukin, and V. Korobeinikov IZMIRAN, Troitsk, Moscow region, 142092 RUSSIA E-mail: ruzhin@izmiran.rssi.ru During the APEX mission with high energy electrons injections the effective spacecraft neutralisation was registered even without plasma jet operation. It was found that the main neutralisation current flows along magnetic field line or parallel to injected electron beam. The magnetic field cavity generation observed by two spaced onboard magnetometers during xenon plasma jet injection is investigated (in full altitude range of 450-3000 km) and the disturbance sometimes more than 2000 nT is found. The model of magnetic cavity or magnetic field anomaly generation is proposed and discussed. ------------------------------------------------ S19-P14 DISTANT CORONA PLASMA PROBING ON 30 R_\odot BY ELECTRON GUN OPERATION ONBOARD OF INTERHELIO-PROBE MISSION V. Oraevsky, Y. RUZHIN, V. Kuznetsov, and V. Dokukin IZMIRAN, Troitsk, Moscow region, 142092 RUSSIA E-mail: ruzhin@izmiran.rssi.ru The programme of active experiments with electron beams injection at Solar corona plasma (INTERHELIOS project) is presented and discussed. Based on APEX mission data it is shown that by appropriate choice of beam parameters it is possible to measure the plasma density and magnetic field at some distance from spacecraft. The distant plasma probing by means of energetic electron beam injection is proposed as independent method of plasma diagnostic in INTERHELIOS mission. The possibilities to model the generation of different types of Solar radiobursts which are observed during active events on the Sun are also discussed. ------------------------------------------------ S19-P15 TRANSITIONAL RADIATION OF THE MODULATED ELECTRON BEAMS IN THE ACTIVE BEAM-PLASMA EXPERIMENTS IN THE IONOSPHERE I. O. ANISIMOV, O. I. Kelnyk, I. Y. Kotlyarov, Y. E. Kovalyov, S. M. Levitsky, Y. V. Maruda, and I. M. Voronov Kyiv Taras Shevchenko National University, Radiophysics Faculty E-mail: ioa@rpd.univ.kiev.ua Waves excitation in the ionosphere by the modulated electron beams was observed in some active beam-plasma experiments. Transitional radiation due to the plasma inhomogeneities is one of the possible mechanisms of this radioemission. The frequency of this sort of radioemission is determined by the beam modulation; it can lie in the whistler band or in the high frequency band (more than electron plasma frequency). It can be also caused by the beam fronts. The role of the inhomogeneities can be played by the spacecraft surface, by the plasma jet, injected from the spacecraft board for its neutralization, by the ion-acoustic waves that perturb the background plasma density and by the accidental inhomogeneities of the background plasma (their level is especially high in the aurora regions). The radioemission characteristics (directivity diagram and total radiated power) are calculated for all these cases. The mechanisms that can amplify the radiated power are the resonant waves excitation in the local plasma resonance region, local Cherenkov resonance region and local Doppler resonance region, the transitional scattering of the modulated electron beam into electromagnetic waves in the stratified plasma, the excitation of the eigenmodes of the spatially restricted plasma. Estimations show that the radiated power is high enough to be detected. ------------------------------------------------ S19-P16 INHOMOGENEOUS PLASMA DIAGNOSTICS VIA TRANSITIONAL RADIATION OF THE CHARGED BUNCHES I. O. ANISIMOV, I. A. Blazhko, and K. I. Lyubich Kyiv Taras Shevchenko National University, Radiophysics Faculty E-mail: ioa@rpd.univ.kiev.ua Diagnostics of the density profile and other parameters of the inhomogeneous plasma objects using the transitional radiation of the modulated electron beams or charged bunches moving through this objects is proposed. The model of a cold planarly stratified plasma was treated. The electron bunch was considered to move along the plasma concentration gradient. The high frequency (non-resonant) and low frequency (resonant) components of the transitional radiation were studied. For the non-resonant radiation the magnetic field parallel to the electron bunch velocity was taken into account. The possibility to find out the plasma concentration profile from the measurement of the non-resonant transitional radiation of the relativistic modulated electron beam or charged bunch was shown analytically and using the computer simulation. For anisotropic plasma the magnetic field can be also found out. The measurement of the resonant transitional radiation of the charged bunch (this component is stronger than the non-resonant one) gives the information about the profile function of the concentration profile, i.e. the part of the plasma concentration profile where concentration grows along the bunch trajectory. The wake waves excitation in the inhomogeneous plasma was also studied for the simplest one-dimensional model. Consequently the conditions when the plasma object was not deformed by the wake field were found out. ------------------------------------------------ S19-P17 DYNAMICS OF THE ELECTRON BEAM-PLASMA INTERACTION IN THE SPACECRAFT VICINITY G. LIZUNOV (1), A. Volokitin (2), and I. Blazhko (1) (1) Kyiv Shevchenko University, Physics Dept., Glushkova 6, Kyiv, 252022, Ukraine (2) IZMIRAN, Troizk, Moscow region, 142092, Russia E-mail: liz@galaxy.ups.kiev.ua We report the results of analytical consideration and computer simulation of the process of electron beam injection from spacecraft into ionosphere. The real structure of injected electron beam is quite complicated: beam appears as a thick helix gradually spreading into a hollow cylinder. Thus artificially injected beam forms a hydrodynamic flow along and, as a result of Larmor gyration, across the magnetic field lines. We reveal that the scenario of generation of beam driven turbulence differs from the ``classical", previously described ones. The most important difference is the fact that the ionospheric plasma experience the quick (in times 0.01 ms) and strong turbulent heating. The further behavior beam-plasma system is determined by the coupling of the three fundamental processes: (1) emission of the primary Langmuir wave by injecting beam (beam-plasma instability), (2) parametric decay of the primary wave to the secondary one and ionic sound fluctuations (L \ge L+IS), and (3) the thermal damping of Langmuir waves. ------------------------------------------------ S19-P18 TRANSIENT RESPONSE OF IONOSPHERIC PLASMA TO DISCHARGE ON SPACECRAFT SURFACE M. CHO (1), R. Raju (2), M. Hikita (1), K. Tanaka (3), and S. Sasaki (3) (1) Department of Electrical Engineering, Kyushu Institute of Technology (2) Satellite Venture Business Laboratory, Kyushu Institute of Technology (3) Institute of Space and Astronautical Sciences E-mail: cho@ele.kyutech.ac.jp The use of high power in future space missions calls for high voltage power generation and transmission, typically >100 V. The use of high voltage, however, causes serious interactions, such as electrical discharge, between space plasma and spacecraft whose potential generally becomes highly negative with respect to the plasma. Laboratory experiments and computer simulations are carried out to investigate the transient plasma response to the discharge on spacecraft surface in simulated Low Earth Orbit plasma environment. Once a discharge occurs, the positive current into the spacecraft body circuit drives the spacecraft potential positive. Part of spacecraft surface is covered by electrical insulator. The insulator potential is nearly zero before the discharge and stores positive charge from the surrounding plasma. Once a discharge occurs, the jump of spacecraft body potential drives the insulator surface potential highly positive. The positively charged insulator surface is exposed to the space plasma and electrons are rapidly attracted to the surface. A current path is formed between the discharge point and remotely located insulator surface through the plasma whose density is highly enhanced due to ejection of discharge plasma. Once the current path is formed, the insulator surface charge is provided as the discharge current. Therefore, the scale of discharge depends on whether the discharge path is connected to nearby insulator surface which serves as a capacitance. The measurement by a moving probe revealed that there is electric field between the discharge point and the insulator. Computer simulations show that the sudden increase of the spacecraft insulator surface induces ionization inside the positive sheath surrounding the surface. The sheath boundary expands outward and once the sheath meets the discharge point, the current path is formed and the discharge current keeps flowing until all the stored charge on the insulator surface is released through the path. ------------------------------------------------ S19-P19 EXPERIMENTS WITH SIMULATED BARE ELECTRODYNAMIC TETHERS IN A DENSE FLOWING, HIGH-SPEED PLASMA B. E. GILCHRIST (1) and S. G. Bilen (2) (1) The University of Michigan, Ann Arbor, MI 48109-2143 (2) The Pennsylvania State University, University Park, PA 16802 E-mail: brian.gilchrist@umich.edu It has been proposed that operating in the orbital-motion-limited (OML) regime is especially beneficial for electron current collection to thin, bare electrodynamic tethers (EDTs) with dimensions on the order of a Debye length [1]. Predictions indicate that a bare tether will be a highly efficient collector of ionospheric electrons (per unit area) when compared to other current collection geometries at equal bias. This prediction of high efficiency is due to the result that the OML regime provides the highest possible current density. NASAs Advanced Space Transportation Programs mission called Propulsive Small Expendable Deployer System (ProSEDS), which is set to fly in Fall 2000, will be the first to use the bare-tether concept and will demonstrate high current and measurable thrust; the technology is also being considered for other future missions. However, a small, thin cylinder is not necessarily the best tether design when considering other practical factors such as tether lifetime. For example, to increase tether lifetime a tether based on ribbon-like geometry e.g., flat and wide) or more sparse structures of equal series resistance may be preferred; hence, these tethers would have dimensions exceeding a Debye length. These new geometries pose several questions that must be answered. For example, how will the current collection performance change as a function of geometry and Debye length when in an ionospheric plasma at orbital velocities? Does the orientation of the ribbon with respect to the direction of flowing plasma have an impact on collection efficiency? In this presentation we describe chamber tests of simulated EDTs of different geometries operating in a dense, high-speed plasma. The geometries tested were cylinder, flat-ribbon, and a mesh (similar to the so-called Hoytether). For these tests, the 6-m ~ 9-m chamber operated by Michigans Plasmadynamics and Electric Propulsion Laboratory (PEPL)was used along with a PEPL/USAFdesigned Hall thruster for the plasma source. These tests were done, in part, to support design efforts for the follow-on mission to ProSEDS called STEP-Airseds which will demonstrate multiple boost/deboost and inclination change operations over a period of a year and covering from below 400 km to above 700 km altitude. [1] Sanmartin et al., J. Prop. Power, 9, 353--360, 1993. ------------------------------------------------ S19-P20 COMPUTER SIMULATION OF SPACECRAFT CHARGING AT THE CONDITIONS OF CHARGED PARTICLES INJECTION IN MAGNETOSPHERE K. Krupnikov, A. Makletsov, V. MILEEV, and L. Novikov Nuclear Physics Institute, Moscow State University E-mail: kkk@nsrd.npi.msu.su The methodology of computer simulation of high-orbit spacecraft charging occurring under the condition of electron and ion injection into magnetosphere from the spacecraft is considered. The brief descriptions of developed computation algorithms and programs are given. The results of spacecraft charging simulation for various magnetosphere plasma environment and electron and ion injection parameter values are presented. Computations of the injected electron and ion trajectories in the spacecraft electric field were done. In terms of the computation data and GEO experimental results, the opportunities of the spacecraft charge neutralization by the electron and ion fluxes injection were analyzed. The methodology of on-board electron and ion spectrometer data interpretation for space plasma parameter measurements under the spacecraft charging conditions is discussed. ------------------------------------------------ S19-P21 MATHEMATICAL MODEL OF SPACECRAFT CHARGING IN LOW-EARTH ORBIT K. Krupnikov, A. MAKLETSOV, V. Mileev, L. Novikov, and V. Sinolits Nuclear Physics Institute, Moscow State University E-mail: kkk@nsrd.npi.msu.su Principle points of mathematical model of spacecraft charging under the conditions of cold ionosphere plasma and high-energy auroral electron impact are presented. The model includes the developed technique of effective ram ion capture surface construction in the vicinity of the charged spacecraft. The case of differential spacecraft charging is investigated in the model in terms of the analysis of various plasma component current balance for every spacecraft surface element. The simulation of charge accumulation processes on the surface enables to analyze the spacecraft charging dynamics. Examples of the electric potential distribution on the spacecraft surface for various charging conditions, and of the potential variations on the spacecraft design elements in cases of abrupt changes of environmental plasma parameters are presented. Various methods of the simulation result visualization are discussed. ------------------------------------------------ S19-P22 EFFECTS OF INJECTED ELECTRON FLOW ON A MAGNETIC FIELD GENERATION IN THE NEARSATELLITE PLASMA V. V. AFONIN (1), N. V. Baranets (2), and B. A. Ryabov (2) (1) Space Research Institute of RAS, 117810 Moscow, Russia (2) IZMIRAN, 142190 Troitsk, Moscow region, Russia E-mail: baranets@izmiran.rssi.ru A set of quasihydrodynamic equations to describe an interaction of injected field-aligned electron flow with slightly collisional ionospheric plasma is considered in terms of Alfv\'enic and magnetosonic perturbation quantities. Excitation of linearly polarized Alfv\'en waves (AW) in quasilateral-to-B0 direction by the slowly varying charged plasma column is studied in a frame of well-known problems with injected electron helicity. When the fluid velocity is equal to the Alfv\'en velocity, the most meaningful goals of the problem may be summarized as follows: (i) resonant/slowly-growing generation of the quasistatic magnetic fields (Alfv\'en wave packet envelopes); (ii) transformation of AW into ion-cyclotron modes in the range of ion hyrofrequencies and followed by strong absorp-tion by the ion plasma components. There are arguments to believe that in both cases the perturbations in the beam-plasma system may be stimulated by the presence of baroclinic effect. To explore these effects under plasma parameters measured in the point of injec-tion, we adopt a technique closed to ``modified guiding center's loading" (MGCL) by Naitou et al. J.Comp.Phys., 38, 265, 1980). The MGCL-technique is applied to Fourier-components of e beam density and temperature perturbations, in which the slowly vary-ing amplitudes are corrected by in situ plasma measurements. For different growth rates of AW, wave excitation frequencies and resonance detuning, this complex approach al-lows us to evaluate the low-frequency and time-averaged values of current density fluctua-tions. Comparison of active experiment measurements and model MGCL-approximation shows that for considered cases small parameters fluctuations in the beam-plasma system can cause the significant magnetic field perturbations. ------------------------------------------------ S19-P23 ANALYSIS OF SPACECRAFT CHARGING ACCOMPANYING ION ENGINE OPERATION I. FUNAKI (1), H. Kuninaka (1), and Y. Nakayama (2) (1) Space Propulsion Division, Institute of Space and Astronautical Science (2) National Defense Academy E-mail: funaki@ep.isas.ac.jp An ion engine that exhausts high velocity positive ions by an electrostatic acceleration always requires an electron source called a neutralizer that supplies the same amount of electron current as the ion beam to maintain the charge neutrality of the spacecraft. One of the severe problems for the ion engine is an abrupt failure of the neutralizer because the ion beam emitted from the ion engine without neutralizing electrons will drive the spacecraft to a negative potential of several kilovolts in a very short period of about an order of micro second, which will be determined by the capacitance of the spacecraft and the ion beam current density. As a result, when the failure of the neutralizer occurred, the spacecraft potential will be highly negative before any inhibit sequences of the engine by a controller becomes effective. In this paper, a one-dimensional ion flow emitted from the spacecraft was analyzed by the particle-in-cell plasma code, and both the transient plasma and corresponding spacecraft potential behavior was discussed. ------------------------------------------------ S19-P24 REAL TIME OBSERVATION OF CHARGE ACCUMULATION IN PMMA UNDER ELECTRON BEAM IRRADIATION Y. TANAKA, H. Tanaka, N. Tomita, M. Murooka, and T. Takada Department of Mechanical Systems Engineering, Musashi Institute of Technology E-mail: tanaka@me.musashi-tech.ac.jp Real time charge accumulating process in PMMA under electron beam irradiation was observed using the PIPWP method. In space environment exposed to radioactive rays, discharging phenomena sometimes cause unexpected serious damages of spacecraft controlling system. The discharging process seems to be closely related not only to charge accumulating process on surface but also in bulk of dielectric materials. Therefore, it is necessary to investigate the charging process in the bulk of dielectric materials under radioactive ray irradiation. To apply the charge distribution apparatus to this theme, the PIPWP method has been modified. Using the improved system, the real time measurement of charge distribution in PMMA was carried out under electron beam irradiation. The increase of the electrons injected into PMMA was clearly observed with increase of the irradiation time. From the results of the charge distribution, the change of the electric fields and potential were also calculated. Furthermore, the decay of the charge distribution after irradiation was observed. From these results, it is proved that the real time measurement during irradiation is possible. In other words, a monitoring system of electron beam irradiation in spacecraft can be developed in near future. ------------------------------------------------ S19-P25 TOTAL DOSE MEASUREMENT BY SMALL DOSIMETERS FOR SPACECRAFT Y. KIMOTO (1), H. Ohira (2), H. Koshiishi (1), H. Matsumoto (1), and T.Goka (1) (1) Office Of Research And Development, National Space Development Agency of Japan (NASDA) (2) Ryoei Technica Corporation E-mail: kimoto.yugo@nasda.go.jp The tolerance of the total dose from the space high-energy radiation environment is one of the concerns for spacecraft design. Some simulation models have ever evaluated the total dose effects. But the real total dose of the spacecraft in orbit hasn't understood. The satellites, which have small dosimeter sensors in several points, will be launched. This mission measures the total dose environment in spacecraft. The sensor design, calibration test results, and pre-simulation results are presented. The total dose model will be reconstructed from the acquired data and analysis. ------------------------------------------------ S19-P26 ARTIFICIAL IONOSPHERIC DISTURBANCE STUDY BY RADIO PULSES SOUNDING G. I. TERINA Radiophysical Research Institute (NIRFI), Nizhny Novgorod, Russia E-mail: ter@nirfi.sci-nnov.ru The experimental results of artificial ionospheric turbulence studies by its sounding by short probing pulses are presented. Different types of scattered signals were discovered: ``caviton" (CS), ``plasma" (PS) and ``aftereffect" signals. In this paper the latest results of CS studies are considered. CS appeared under the operation of the heating and probing transmitters at both O- and X- modes. Sounding by X-mode pulses allows to study the time and spatial CS evolution without PS influence. The time dependence of CS amplitude was mostly a series of maxima with periods, decreasing with the increase of the heater power and with the decrease of the difference of the probe and the heater frequencies. With the heater turning on CS period increased in some time, and then it fluctuated. The results of the experiments showed that the strong Lengmuir turbulence was excited, that qualitatively agreed with the numerical simulation of strong turbulence effects. This work is supported by RFBR (grant N 99-02-16642). ------------------------------------------------ S19-P27 SIMULATION OF POWERFUL EMISSION ACTION ON IONOSPHERIC PLASMA G. I. TERINA (1), A. V. Kochetov (2), and B. A. Mironov (2) (1) Radiophysical Research Institute, N.Novgorod, Russia (2) Institute of Applied Physics RAS, N.Novgorod, Russia E-mail: ter@nirfi.sci-nnov.ru The results of simulation of nonlinear dynamic effects arising in the ionospheric plasma under the action of the disturbing wave using the numerical solution of nonlinear Schredinger equation for linear inhomogeneous plasma layer are presented. The spatial soliton structures of the field and plasma, their formation and penetration into the overdense plasma, their time evolution and spectra were studied. The periodic and chaotic stages of soliton emission were considered. The period of the soliton generation decreased with the increase of the amplitude of the incident wave. The soliton period increased in time for the periodic stage, and it fluctuated for the chaotic one. At the relaxation stage the soliton amplitude increased, and its width decreased. The numerical simulation shows the excitation of strong Langmuir turbulence and qualitatively interprets signals, scattered by the disturbed ionosphere. This work is supported by RFBR (grant N 99-02-16642). ------------------------------------------------ S19-P28 RF-INDUCED GLOW PATTERNS AROUND SPACECRAFT DIPOLE ANTENNAS: LABORATORY SIMULATION A. A. E. Luttgen (1), K. G. BALMAIN (1), and H. G. James (2) (1) Electrical \ Computer Engineering, University of Toronto (2) Communications Research Centre, Ottawa E-mail: balmain@waves.utoronto.ca During the early phase of the OEDIPUS-C tethered sounding rocket experiment, the payload was separated into two parts connected by a conducting tether. Both sub-payloads carried a crossed-dipole antenna each; the antenna on the aft sub-payload received signals transmitted from the forward sub-payload's antenna. The aft sub-payload also carried a video camera for attitude measurement, which recorded the view of the forward sub-payload during the entire flight. Argon thrusters on the forward sub-payload drove the separation of the two sub-payloads. The Earth's magnetic field was directed almost perpendicular to the dipole antenna plane. While the thrusters were still running, the transmitter was turned on and luminous RF discharges were observed as the high fields close to the antenna accelerated the ambient electrons, which then caused light emission on collision with the Argon atoms. The observed light pattern consisted of glows both around the antenna and between the monopoles. For laboratory simulation of the RF discharges, a scaled-down model of the OEDIPUS-C antenna has been built, consisting of two V-shaped monopoles. With this setup placed in the center of an axially magnetized laboratory plasma and transmitting an amplified signal, a similar glow pattern is observed. The shape and intensity of the glow pattern depends on the transmitted frequency and is strongest for frequencies close to the electron cyclotron frequency. In order to explain this glow, calculations of the fields in the magnetized plasma using quasistatic theory are carried out. It can be shown that a rotational current is induced in the plasma, resulting in circular electron trajectories at frequencies where no glow is observed, and in spiral trajectories with the spiral axis almost aligned with the external magnetic field at frequencies where a strong glow is observed. This suggests that accelerated-electron ionization of the ambient gas causes the glow. ------------------------------------------------ S19-P29 NON-RECIPROCAL SHEATH WAVES ALONG STRUCTURES IN A MAGNETOPLASMA A. A. E. Luttgen and K. G. BALMAIN Electrical and Computer Engineering, University of Toronto E-mail: balmain@waves.utoronto.ca When a metal structure is immersed in plasma there exists a region of low electron density, called the ion sheath, adjacent to its surface. This sheath can act as a waveguide supporting a family of surface waves known as sheath waves. In the case of a cylindrical antenna, sheath waves strongly influence the antenna impedance. Also, they provide a mechanism for electromagnetic waves to propagate between widely separated points on ionospheric spacecraft. The latter has been demonstrated strikingly in the tethered sounding rocket experiments OEDIPUS A and OEDIPUS C, where propagation of sheath waves has been observed along a thin, cylindrical conducting tether oriented almost parallel to the magnetic field. For a cylindrical structure in a plasma, oriented with its axis parallel to the ambient magnetic field, it is known that sheath waves can propagate along it and parallel both to its axis and to the magnetic field. Also, the case of propagation perpendicular to the magnetic field has been solved before and validated experimentally involving azimuthal propagation around the cylinder. There is also the possibility that a sheath wave can follow a spiral path around the cylinder. This would involve propagation at an arbitrary angle with the magnetic field. For the present theoretical study of these waves, a planar geometry is used with the ambient magnetic field parallel to the conducting surface and propagation at an arbitrary angle to the magnetic field. The results presented show two sheath wave modes propagating in opposite directions for each orientation of the magnetic field. These modes are non-reciprocal, exhibiting different passbands, different characteristic frequencies, and different cutoff frequencies. A scheme for their laboratory experimental validation is presented. A key feature is discussed, namely the degree to which the electron cyclotron frequency is visible in the theory and the laboratory and space experiments. ------------------------------------------------ S19-P30 CONTROLLED EXPERIMENTS ON HF DUCTING AT AURORAL LATITUDES H. G. JAMES Communications Research Centre, Ottawa E-mail: gordon.james@crc.ca The bistatic digital sounder on the sounding-rocket double payload OEDIPUS C (OC) has been used to investigate wave ducting in density irregularities of the auroral ionosphere. The OC Receiver for Exciter (REX) was positioned below the High-frequency EXciter (HEX), their separation direction within a few degrees of the axis of the earth's magnetic field. Because the separation distance of about 1200 m was just sufficient to place the REX in the radiation zone of the HEX, the REX can be used to calibrate the radiated output of the HEX. The directly propagating pulse first arrives at and is recorded by the REX. Wave energy continues past the REX to a total reflection in the ionosphere below it and then back to the REX, thus adding an ionospherically reflected pulse to the record. The comparison of the direct and reflected pulse levels by the two-point OC sounder provides unique information about duct dimensions and density depletions. An analysis based on the radiation properties of the transmitter dipoles and on ray optics in cylindrical field-aligned density-depletion ducts shows that very shallow depletions of less than 1 % of the ambient density can explain the magnitudes and fluctuations observed in the reflected pulses. Duct density models with steep isodensity contours produce more realistic predictions of signal levels and their fluctuations with frequency than models with gently sloping contours. The finding of steep walls in ducts may help to identify the primary processes that create and sustain density depletions in the auroral topside ionosphere. ------------------------------------------------ S19-P31 AMPLITUDE OF ELECTROMAGNETIC SIGNALS IN A PLASMA UNDER OBLIQUE RESONANCE CONDITIONS IN THE TWO-POINT OEDIPUS-C EXPERIMENT Y. V. CHUNGUNOV (1), E. A. Mareev (1), V. Fiala (2), and H. G. James (3) (1) Institute of Applied Physics, Nizhny Novgorod (2) Institute of Atmospheric Sciences, Prague (3) Communications Research Centre, Ottawa E-mail: chugun@appl.sci-nnov.ru It was reported recently that observed levels of radiated whistler-mode signals in the two-point OEDIPUS-C experiment were about a hundred times greater than theoretical predictions. We have analyzed the features of a transmitter-receiver system under resonance conditions and have concluded that the experimental results can be explained taking into account both the resonance radiation of quasi-electrostatic waves by a transmitting antenna, and the resonance reception of these waves at the observation point. The voltage induced on the receiving antenna has been calculated using the fluctuation-dissipation relation for a nonequlibrium system consisting of the radiation field and receiving unit, as well as the reciprocity relation in a magnetized plasma (generalized Nyquist theorem for quasi-stationary systems). As a result we have found that the voltage induced on the receiving antenna is proportional to the length of the receiving dipole, the electric field in the incident wave and the receiving pattern in plasma. The latter is calculated in terms of the electric field radiated into the given direction, close to the resonance cone direction. The radiation field for an electric dipole with a triangular current distribution has been considered and compared with the theory of a point source. Corrections were made for thermal motion, whistler-mode diffraction and finite spatial scale of the transmitting antenna when estimating the level of radiating signal. An approach developed for the calculation of the voltage induced on the receiving antenna shows that under resonance conditions the effective length of a dipole antenna in plasma can be substantially greater than the vacuum effective length. This conclusion is of great importance for different applications connected with the recording of electromagnetic emissions in plasmas. ------------------------------------------------ S19-P32 LARGE-SCALE WAVE DISTURBATIONS, ARISING IN MIDDLE LATITUDE IONOSPHERE AFTER FLIGHT OF A ROCKET P. M. NAGORSKY, Y. E. Taraschuk, and B. B. Tscibikov Siberian Physical and Technical Institute at Tomsk State University E-mail: nagorsky.rff@elefot.tsu.ru oindent 1. Are analyzed of wave indignation registered during start of the pilotage ships ``Souz", cargo ships ``Progress", interplanetary stations and other objects. All objects are started through rockets ``Souz", ``Proton" and ``Energy" with of Baikonur under a corner of an inclination of a plane of an orbit to a plane of equator \sim 51.6 deg. The experimental material ( \sim 150 rocket starts) is received at multi channel inclined doppler sounding in the period with 1975 on 1999 years on HF - radio lines of Ashchabad-Tomsk, Tashkent-Tomsk, Dushanbe-Tomsk, Alma-Ata-Tomsk. 2. Characteristic post flight of feature of display wave disturbances, formed by rockets in area F ionosphere, in a spectrum of signals of inclined multi frequency multi line sounding, are considered. Two groups disturbances in the response of a signal are revealed. The connection of the revealed effects with helio-geophysical conditions and conditions of sounding are discussed. 3. A source of the first group disturbances in the response of a signal are of indignation of electronic density formed by a shock waves of torch of rocket in neutral gas of area F of the top atmosphere. The effect in a spectrum of a signal begins after crossing by a rocket of a plane of a radio line with occurrence an additional mode (modes). The time of existence of effect is insignificant and makes from tens seconds up to one - three minutes. The form of variations of frequency has asymmetric M - figurative kind. The variations of frequencies connected to passage through area of reflection sounding of a radio signal of internal gravitational and low-frequency acoustic waves are simultaneously registered. 4. The wave variations of frequency concern to the second group disturbances which occur in the response of a signal through some tens minutes after start. On the periods they concern to low-frequency acoustic disturbances (LAD) and internal gravitational waves (IGW). The periods of waves, connected with IGW, do not fall below than 10 minutes. The cases of consecutive arrival several wave packets LAD and IGW are registered. The time of registration of these processes depends on geophysical conditions and makes units -- tens minutes for LAD and tens -- hundred minutes for IGW.