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Remote spacecraft observations of waves excited by the pulse electron beam injected into ionosphere
Adv. Space Res. Vol. 15, No. 12, pp. (12)25-(12)28, 1995 Copyright 8 1995 COSPAR Printedin Great Britain. All ri hts reserved. 0273-I 1771pf $9.50 + 0.00
0273-l 177(95)00005-4
REMOTE SPACECRAFI’ OBSERVATIONS OF WAVES EXCITED BY THE PULSE ELECTRON BEAM INJECTED INTO IONOSPHERE H. Rothkaehl,* 2. Klos,* V. S. Dokukin** and P. Triska*** * Space Research Centre, PAS, Bartycka 18A, 00-716 Warsaw, Poland ** Izmiran, Troitsk, Moscow Region 142092, Russia *** Institute of Atmospheric Physics, CiiU, Bocni 2, 14131 Prague, Czech Republic ABSTRACT
In the Apex project the modulated electron beam (pulses of 2 micro see duration, E=8 keV, 1~0.1 A and 25 micro set repetition) was emitted from a main satellite. The RP emissions were observed in parallel on the mother satellite as well as on Magion- s&satellite. The paper discusses the case when the s&satellite was separated about 200 km from the main object and the electron gun was operated. Together with strong electrostatic emission at the upper hybrid plasma frequency on the main spacecraft, selected spikes in RP frequency range on Magion3, were simultaneously detected, which can be related to pulse electron beam emission. INTRODUCI’ION Disturbances of the ionospheric plasma by electron gun have been made by a large number of spacecraft beginning from the sixties/l/. The basic goal of those investigations, beside the examination of basic plasma properties was to explain the ionospheric events during the precitipitation of particles in polar regions. The main part of the experiments was conducted using rockets with particle and waves diagnostics on the board, in the low part of the ionosphere. In recent years research progressed by technique on such satellite as EXOS-B/2/, and new technical possibility like space shuttle STS3 flight/3/, Spacelab-l/4/. Several processes produced by charged electron beams in space plasma have been already well identified and examined including the nonlinear phenomena and interaction between electron beam and spacecraft body/5/. Usually the theoretical approach and experimental data consider the vicinity of gun operations. During the rocket Echo-4 experiment/6/ together with electron gun the payload contained a photometer, Langmuire probe and particle analayzer, as well as the radio wave receivers were located on the ground. The authors detected at the ground based receiver the enhancement of radiation in megahertz band associated with downward gun injection into the ionosphere at the altitude of 190 km. The APEX experiment was composed of two independent satellites to examine the plasma behavior during the electron beam injection simultan~usly in the vicinity of electron source as well as far away. INSTRUMENTATION The Apex spacecraft and subsatellite Magion- was launched with initial perigee 43Okm, apogee 3100 km and inclination 82.5 deg. The main Apex spacecraft contained the electron gun with acceleration voltage of 8 keV and current of 100 mA. The gun had a few possible modes of work, 2 ps pulses with 100% of gun power and 23 ps rest between is one of them. Two sweeping radiospectrometers provided by Space Research Center in Warsaw, were located on the board of APEX spacecraft together with the other plasma diagnostic instruments. The synthesizer radiospectrometer on board of the mother satellite was operated in the frequency band 0.1-10 MHz with dipole electric antenna 15 m long from tip to tip. The individual spectrum has been detected with time resolutions from 2s to 64 s in 80 dB dynamic range of the signal. The superheterodyne double sweeping frequency radiospectrometers on the board of Magion- was
(12)25
operated in the same frequency range was supplied by the smaller dipole 3 m long from tip to tip. The subsatellite receiver had the same level of sensitivity and better time resolutions from 0.1 s to 1 s depend on the telemetry speed. While the mother spacecraft had 3-axis stabilization, Magionlost it and somersaulted during the experiment. The subsatellite manueavet system allowed to control the relative position of the spacecrafts. Thus, the relative distance between the satellites changed from tens up to tens thousand kilometers. THE OBSERVED
SPECTRAL
PROPERTIES
On the boatd of Apex satellite sevetal experiments with injection of pulsed electron beam into the ionosphere were carried out. During the flight only in one case on 23.01.1992 when the gun was operated with 100% power the emission associated with electron injection simultaneously on board of two independent spacecrafts was detected.
Fig 1. The sequence of dynamic spectra observed along the Apex orbit on 23.01.1992. Emissions intensity are marked from black 0 dB/pVto white 50 dB/pV. The gun was operating from 12:18 to 12:24 UT. It is well know that during the electron beam injection into plasma significant excitation of electrostatic plasma waves is observed. Along the beam the interaction between beam electron and the ambient plasma is very strong. The sequence of dynamic spectra detected by radiospectrometer along the orbit of Apex spacecraft in northern hemisphere are presented in Firure 1. The time resolution between two neighbouring spectra is 8 s while the gun was operated with 2~s pulse repetcd every and 25 pm. The correlation between the gun shot and enhancement of waves radiation at the local upper hybrid resonance and its harmonics is well manifested. At the same time the radiospectrometer located on the board of remote subsatellite Magion- detected the selected spikes emission in the range of HF band, Fig 2. Along the orbit the local plasma density and electron gyrofrequency change but the observed events had a constant frequency emission. The first spike occurs at a frequency around 2.15 MHz and the next ones are harmonics of them. The half width of emission line is equal 50 KHz which is corelated with repetition time of the electron gun pulses. The relative distance of the spacecrafts during that active experiment was around 200 km, Fig 3, the subsatellite Magionat the beginning at shell L=2.99, a little bit over the main satellite which passed L-3.27. The satellites moved to higher altitude with nearly the same relative configuration after the termination of electron injection Magion- reached L= 1.53 while Apex L= 1.50, respectivly.
(12)27
Waves Excited by Pulsed Electron Beam
Fig 2. The upper panel presents the sequence of radio spectra observed along orbit of Magionsatellite. Emissions intensity are marked from black 0 dB /pVto white 30 dB/pV with nine equidistant level. During the electron beam injection the selected spikes emission are well manifested. The bottom panel represents a single spectrum (12: 19:37 UT) detected during electron injection into the ionosphere.
H
ldw
LON
s
57.2 35.7
:;:z
ma 1075
A
68.1
:tt
714 1044
37.4
Fig. 3. The plot displays the relative position of APEX spacecraft (A) and subsatellite Magion(S) in the space. The axis x corresponds to geographic latitude, y to geographic longitude in deg, z-to altitude in km. The relative distance during injection was about 200 Km. The dotted line presents the geomagetic field line. The injection started at the altitude 714 km, 12:18 UT and finished at 1044 km, 12:24 UT.
(12)28
H. Rothkaehl er al.
CONCLUSION The spikes detected along the orbit of Magion- are electromagnetic in origin. All observed facts force us to the conclusion that when the receiver is far away from the electron beam we observe the electromagnetic emission of the oscillating current created by the injected electron beam. The beam parameters like: shape of a beam, current intensities, pulse time, arc correlated with some characteristics of the generated emission in the background plasma. It seems that the observed base frequency around 2 MHz can be related to the characteristics of electron beam current while the half width of the spikes corresponds to beam pulse time. Future modelling and investigations will clarify the physical properties of the observed phenomena. REFERENCES 1. J.R.Winckler, The aplication of artificial electron beams to magnetospheric and Space Phys., 18 # 3, p. 659 (1980). 2. H.Matsumoto,
research, Rev.
ofGeophys.
Electron beam injection into space plasma, J.A.T.P., 47,# 12, p. 1303 (1985).
3. SD. Shawhan, G.B. Murphy, P.M. Banks, P.R. Williamson, W.J. Raitt, Wave emissions modulated electron beams on STS3, Radio Sci., 19, p. 471 (1984).
from dc and
4. D. Mourenas, C. Beghin, J.P. Lebreton, Electron cyclotron and upper hybrid harmonics electron beam injection on Spacelab-1, Ann. Geophysic. 7, p. 519 (1989).
produced by
5. Z. Klos, Z. Zbyszynski,G.G. Managaze, T.I. Gugala, N.A. Leonov, HF emission of one-dimensional electron beam emitted from body subject to neutralization curtent, Adv. Space Res. lO,# 7, p. 155 (1990). 6. S.J. Monson, P.J. Kellogg, Ground observations of waves at 2.96 MHz generated electron beam in the ionosphere, J. Geophys. Res. 83, # Al, p. 21 (1978).
by 8-to-40 keV
0273-l 177(95)00005-4
REMOTE SPACECRAFI’ OBSERVATIONS OF WAVES EXCITED BY THE PULSE ELECTRON BEAM INJECTED INTO IONOSPHERE H. Rothkaehl,* 2. Klos,* V. S. Dokukin** and P. Triska*** * Space Research Centre, PAS, Bartycka 18A, 00-716 Warsaw, Poland ** Izmiran, Troitsk, Moscow Region 142092, Russia *** Institute of Atmospheric Physics, CiiU, Bocni 2, 14131 Prague, Czech Republic ABSTRACT
In the Apex project the modulated electron beam (pulses of 2 micro see duration, E=8 keV, 1~0.1 A and 25 micro set repetition) was emitted from a main satellite. The RP emissions were observed in parallel on the mother satellite as well as on Magion- s&satellite. The paper discusses the case when the s&satellite was separated about 200 km from the main object and the electron gun was operated. Together with strong electrostatic emission at the upper hybrid plasma frequency on the main spacecraft, selected spikes in RP frequency range on Magion3, were simultaneously detected, which can be related to pulse electron beam emission. INTRODUCI’ION Disturbances of the ionospheric plasma by electron gun have been made by a large number of spacecraft beginning from the sixties/l/. The basic goal of those investigations, beside the examination of basic plasma properties was to explain the ionospheric events during the precitipitation of particles in polar regions. The main part of the experiments was conducted using rockets with particle and waves diagnostics on the board, in the low part of the ionosphere. In recent years research progressed by technique on such satellite as EXOS-B/2/, and new technical possibility like space shuttle STS3 flight/3/, Spacelab-l/4/. Several processes produced by charged electron beams in space plasma have been already well identified and examined including the nonlinear phenomena and interaction between electron beam and spacecraft body/5/. Usually the theoretical approach and experimental data consider the vicinity of gun operations. During the rocket Echo-4 experiment/6/ together with electron gun the payload contained a photometer, Langmuire probe and particle analayzer, as well as the radio wave receivers were located on the ground. The authors detected at the ground based receiver the enhancement of radiation in megahertz band associated with downward gun injection into the ionosphere at the altitude of 190 km. The APEX experiment was composed of two independent satellites to examine the plasma behavior during the electron beam injection simultan~usly in the vicinity of electron source as well as far away. INSTRUMENTATION The Apex spacecraft and subsatellite Magion- was launched with initial perigee 43Okm, apogee 3100 km and inclination 82.5 deg. The main Apex spacecraft contained the electron gun with acceleration voltage of 8 keV and current of 100 mA. The gun had a few possible modes of work, 2 ps pulses with 100% of gun power and 23 ps rest between is one of them. Two sweeping radiospectrometers provided by Space Research Center in Warsaw, were located on the board of APEX spacecraft together with the other plasma diagnostic instruments. The synthesizer radiospectrometer on board of the mother satellite was operated in the frequency band 0.1-10 MHz with dipole electric antenna 15 m long from tip to tip. The individual spectrum has been detected with time resolutions from 2s to 64 s in 80 dB dynamic range of the signal. The superheterodyne double sweeping frequency radiospectrometers on the board of Magion- was
(12)25
operated in the same frequency range was supplied by the smaller dipole 3 m long from tip to tip. The subsatellite receiver had the same level of sensitivity and better time resolutions from 0.1 s to 1 s depend on the telemetry speed. While the mother spacecraft had 3-axis stabilization, Magionlost it and somersaulted during the experiment. The subsatellite manueavet system allowed to control the relative position of the spacecrafts. Thus, the relative distance between the satellites changed from tens up to tens thousand kilometers. THE OBSERVED
SPECTRAL
PROPERTIES
On the boatd of Apex satellite sevetal experiments with injection of pulsed electron beam into the ionosphere were carried out. During the flight only in one case on 23.01.1992 when the gun was operated with 100% power the emission associated with electron injection simultaneously on board of two independent spacecrafts was detected.
Fig 1. The sequence of dynamic spectra observed along the Apex orbit on 23.01.1992. Emissions intensity are marked from black 0 dB/pVto white 50 dB/pV. The gun was operating from 12:18 to 12:24 UT. It is well know that during the electron beam injection into plasma significant excitation of electrostatic plasma waves is observed. Along the beam the interaction between beam electron and the ambient plasma is very strong. The sequence of dynamic spectra detected by radiospectrometer along the orbit of Apex spacecraft in northern hemisphere are presented in Firure 1. The time resolution between two neighbouring spectra is 8 s while the gun was operated with 2~s pulse repetcd every and 25 pm. The correlation between the gun shot and enhancement of waves radiation at the local upper hybrid resonance and its harmonics is well manifested. At the same time the radiospectrometer located on the board of remote subsatellite Magion- detected the selected spikes emission in the range of HF band, Fig 2. Along the orbit the local plasma density and electron gyrofrequency change but the observed events had a constant frequency emission. The first spike occurs at a frequency around 2.15 MHz and the next ones are harmonics of them. The half width of emission line is equal 50 KHz which is corelated with repetition time of the electron gun pulses. The relative distance of the spacecrafts during that active experiment was around 200 km, Fig 3, the subsatellite Magionat the beginning at shell L=2.99, a little bit over the main satellite which passed L-3.27. The satellites moved to higher altitude with nearly the same relative configuration after the termination of electron injection Magion- reached L= 1.53 while Apex L= 1.50, respectivly.
(12)27
Waves Excited by Pulsed Electron Beam
Fig 2. The upper panel presents the sequence of radio spectra observed along orbit of Magionsatellite. Emissions intensity are marked from black 0 dB /pVto white 30 dB/pV with nine equidistant level. During the electron beam injection the selected spikes emission are well manifested. The bottom panel represents a single spectrum (12: 19:37 UT) detected during electron injection into the ionosphere.
H
ldw
LON
s
57.2 35.7
:;:z
ma 1075
A
68.1
:tt
714 1044
37.4
Fig. 3. The plot displays the relative position of APEX spacecraft (A) and subsatellite Magion(S) in the space. The axis x corresponds to geographic latitude, y to geographic longitude in deg, z-to altitude in km. The relative distance during injection was about 200 Km. The dotted line presents the geomagetic field line. The injection started at the altitude 714 km, 12:18 UT and finished at 1044 km, 12:24 UT.
(12)28
H. Rothkaehl er al.
CONCLUSION The spikes detected along the orbit of Magion- are electromagnetic in origin. All observed facts force us to the conclusion that when the receiver is far away from the electron beam we observe the electromagnetic emission of the oscillating current created by the injected electron beam. The beam parameters like: shape of a beam, current intensities, pulse time, arc correlated with some characteristics of the generated emission in the background plasma. It seems that the observed base frequency around 2 MHz can be related to the characteristics of electron beam current while the half width of the spikes corresponds to beam pulse time. Future modelling and investigations will clarify the physical properties of the observed phenomena. REFERENCES 1. J.R.Winckler, The aplication of artificial electron beams to magnetospheric and Space Phys., 18 # 3, p. 659 (1980). 2. H.Matsumoto,
research, Rev.
ofGeophys.
Electron beam injection into space plasma, J.A.T.P., 47,# 12, p. 1303 (1985).
3. SD. Shawhan, G.B. Murphy, P.M. Banks, P.R. Williamson, W.J. Raitt, Wave emissions modulated electron beams on STS3, Radio Sci., 19, p. 471 (1984).
from dc and
4. D. Mourenas, C. Beghin, J.P. Lebreton, Electron cyclotron and upper hybrid harmonics electron beam injection on Spacelab-1, Ann. Geophysic. 7, p. 519 (1989).
produced by
5. Z. Klos, Z. Zbyszynski,G.G. Managaze, T.I. Gugala, N.A. Leonov, HF emission of one-dimensional electron beam emitted from body subject to neutralization curtent, Adv. Space Res. lO,# 7, p. 155 (1990). 6. S.J. Monson, P.J. Kellogg, Ground observations of waves at 2.96 MHz generated electron beam in the ionosphere, J. Geophys. Res. 83, # Al, p. 21 (1978).
by 8-to-40 keV