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VLF plasma wave measurements in the magnetospheric tail — New results from the subsatellite Magion-4 in the INTERBALL mission
A&. Space Res. Vol. 20. No. 3. pp. 505408. 1997 1997 COSPAR. Published by Elsevier Science Ltd. All rights reserved Phted in CheatBritain m73-1177/97 $17.00 + 0.00 Pm s0273-1177(97)00719-9
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Pergamon
ELF/VLF PLASMA WAVE MEASUREMENTS IN THE MAGNETOSPHERIC TAIL -NEW RESULTS FROM THE SUBSATELLITE MAGION- IN THE INTERBALL MISSION J. Bled,* J. Juchniewicz,* P. Triska,** K. Kossacki,* S. A. Romanov,*** S. P. Savin,*** J. Smilauer,** J. Slominski,* J. Vojta** and R. Wronowski* * Space Research Center PAS, 00716 Warsaw, 18A Bartycka, Poland
** Institute of Physics of Atmosphere ASCR, Bocni II, 1401-141 31 Praha 4, Czech Republir ** Space Research Institute RAN, Moscow, Profsoyuznaya 84132, Russia
ABSTRACT The Interball Tail Probe satellite together with its subsatellite Magion- were launched into a highly elliptic orbit with a 3ORe apogee and a 63” inclination on August 3, 1995. The plasma wave analyser on the Magion- performs analysis of the magnetic field fluctuations in the frequency range 32-2000 Hz. The Interball was operating in the magnetospheric tail from October 1995 until February 1996. The results of the Magion- wave measurements of electron cyclotron and lower hybrid electromagnetic modes in the regions of the magnetospheric tail directly 0 1997COSPAR.Publishedby ElsevicrScienceL.td. connected-with aurora1 ionosphere are presented ii this paper.
INTRODUCTION Plasma wave measurements are a basic tool for studying the geospace. Our current knowledge of the processes in space plasma allows us to say that waves give timdamental information about conditions in the different regions of the magnetosphere. Examination of the plasma wave in the space plasma is important for several reasons: (1) Collisionless plasma waves are a source of the anomalous dissipation and they play a crucial role in the energy, mass and momentum transport across magnetospheric boundaries, (2) They can be useful indicators for identification of events and structures, (3) Space plasma gives unique and pure conditions for the study basic processes, and (4) Waves provide information on the microphysics of the processes in plasmas. The Interball -1 satellite with its subsatellite Magion -4 were launched on 3 August 1995 into the orbit with apogee about 200,000 km and a 63” inclination. The wave experiment aboard Magion- gives the information about ELF magnetic field fluctuations from different regions of the magnetospheric tail. In this presentation we focused our attention on three regions directly associated with the polar ionosphere: plasma sheet, polar cup and aurora1 field lines. WAVE EXPERIMENT The wave experiment aboard Magion- subsatellite, with SAS (Spectrum Analyser for Subsatellite) as the central unit, performs the spectrum analysis in the ULF and VLF ranges of the signals obtained from electric and magnetic field sensors and from split langmuir probe, which measured current density. The wave complex is described by Triska et al. (1995). Electric field measurements. The electric antenna is a 1.6 m long dipole made of two spherical carbon ED detectors, each with a preamplifier. The detectors are fixed at the ends of the folding booms of the subsatellite. The frequency range is 0.1 Hz-400 kHz and sensitivity is 5010~*V/m Hztn at 2 kHz.
506
J. Blecki ef al
Magnetic field measurements. The magnetic field is measured in two frequency ranges: ULF (lHz-2kHz) -3 components B,, By, B, and VLF (l-5OkHz), one component B,. Sensitivities of these measurements are 10“ nT/HzlR at 2 kl-lz for VLF range and 30 l@’ nT/Hzln at 100 Hz for ULF range. Current density measurements. The current probe consists of two hemispheric collectors separated by a thin (-mm) insulator (Kozlov, 1969, Bering ef al., 1973). The frequency range of the measured fluctuations is 0.1 Hz-40 kHz. The sensitivity is lo-” A/cm2Hz’n. Suectrum analvser. The SAS is a two channel step frequency spectrum analyser. Each channel can be switched on and off by telecommands. The additional part of SAS is SASTRA -the time transjbrmer a device expanding the possibility of the analysis in the low frequency band; signals coming in the 32 Hz - 2000 Hz (or 32 - 20000 Hz) band are transformed to 4000 -266144 Hz (or 400 - 262544 Hz) band and then analysed by SFA. OBSERVATIONS The number of available measurements from the subsatellite is very limited. There is no memory for the scientific data in the telemetry system on the subsatellite. It means that only the measurements performed during direct transmission are available. The telemetry station is located in Panska Ves in the north part of Czech Republic and measurements are performed during visibility of MAGION- from this station (Triska et al, 1995).The regular measurements by SAS began in October 1996. The satellite INTERBALL 1 and subsatellite Magion- were then in the magnetospheric tail. We will present the results of the wave measurements from the magnetotail. This work is the continuation of our studies using data of Prognoz-8 (Blecki, 199.5) which had a similar orbit to Interball’s orbit. The results presented in this paper are very preliminary and our aim is to use them only as an example of the possibilities for wave measurements by the SAS instrument onboard of the subsattelite Magion- in different regions of the magnetosphere. The Plasma Sheet. The spectra taken within the plasma sheet are presented in Figures 1 and 2. The vertical axis represents the spectral density of the magnetic field fluctuations in telemetric units, and the horizontal ones correspond to frequency and time.
Fig. 1. The panoramic view of magnetic field fluctuations spectra in the frequency range 32-2000 Hz within the plasma sheet on 23.02.1996 during disturbed time (Kp=3). The co-ordinates: geocentric distance, magnetic local time and magnetic latitude, ofthe satellite are 10.5RE, 18.57, 3.3”.
507
ELF/VLFPlasmaWaveMea.suremen~~
In Figure 1 the increases of the intensity just above 250 Hz and 500 Hz at 19:37 UT and at the end of interval are associated with harmonics of the electron cyclotron frequency. The characteristic maxima appear at frequencies of about 25OHz,5OOHz and 7OOHzand are likely associated with harmonics of the electron gyro-frequency. These modes of plasma waves can be generated by microinstabilities of the temperature anisotropy of electrons (Mikhailovsky, 1974). This type of electron distribution function is often observed in the near plasma sheet. Plasma wave measurements with highest time resolution onboard Magion- can give additional information on the structures of the studied magnetospheric regions. The measurements of the electron cyclotron modes can be a signature of presence of the special type of electron populations- anisotropy of the temperature or ring distribution. ULF Spectrum 0.030_
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0.025
-
0.020
-
0.015
-
0.010
-
0.005
-
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.
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.
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19:38:42
1.. 500
23 Febwory
I996
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.
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0.. 1500
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.2500
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Fig. 2. Single spectrum taken at 19:38 UT during the same event as in Figure 1. Five harmonics of the electron
cyclotron ii-equency are seen. The value of the electron gyrofrequency is about 250 Hz. Aurora1 Zone. It is a very well known fact that the aurora1 zone is very dynamic and turbulent region of the magnetosphere (Gumett, 1991). Figure 3 shows the spectra of the magnetic field fluctuations taken during entry of Magion- into aurora1 zone. Geomagnetic co-ordinates of the satellite at this moment were r=6RE , LMT=12 and GLat=55”.
Fig. 3. The same as in Figure 1 but for the aurora1 zone. The strong enhancement is seen just at the boundary. The spectrum has broad band character, and the maxima changes rapidly from spectrum to spectrum.
so8
J. Bledi EI al.
Polar Can. This region of the magnetosphere being connected with the magnetospheric lobe is rather more quiet than the aurora1 zone. Also plasma wave in this region are rather weak, but some times “spikes” of intensity can be observed. Figure 4 shows the spectra of magnetic field fluctuations during the time interval, when Magion- was on the field lines connected with polar cap (rx8RE, MLTz21, Glat=‘lO“).At the lowest frequencies some spikes can be seen and at the end of the interval of measurements sudden enhancement in the whole frequency range appears.
Fig. 4. The same as in Figure 1 for the region associated with the polar cap.
CONCLUSIONS Presented in this paper are preliminary results of the wave measurements performed aboard Magion- and identification of the discussed regions is also preliminary. This first analysis of wave data from the project Interball, the wave experiment aboard Magion, suggests that waves are a useful tool for identifjkg boundaries, electron population with anisotropy of the tempera~re, or ring dist~bution. The data will be interpreted more carefully together with plasma data from Promics, MPS and Electron instruments. ACKNOWLEDGEMENTS This work has been supported by grant KBN 2 PO3C 009 08
Bering, E.A., M.C.Kelley, F.C.Mozer, and U.V.Fahleson, Theory and operation of the split Langmuir probe, Planet.Space.Sci., 21, 1983 (1973).
Blecki J., ULF/ELF plasma waves in the magnetosperic tail as observed by Prognoz-8, E&Xp-371, 247 (1995). Gumett, D.A., Aurora1 Plasma Waves, in Aurora1 Phystcs, edit& by Ch-IMeng, M.J.Rycroft and L.A.Frank, pp. 241-254, Cambridge University Press, Cambridge, New York, Port Chester, Melbourne, Sydney (1991). Kozlov O., Probe in Plasmas, Atomizdat, Moscow (1969). (in Russian) Mikhailovsky A.B., Theory ofPlasma Instabilities, Consultant Bureau, New York (1974). Triska P.,Vojta J., Agafonov Yu., The INTERBALL subsatellites S2-A and S2-T, in JNTERBALL Mission and Payload”, pp 100-l 13, Russian Space Agency, IKI, CNES (1995).
0
Pergamon
ELF/VLF PLASMA WAVE MEASUREMENTS IN THE MAGNETOSPHERIC TAIL -NEW RESULTS FROM THE SUBSATELLITE MAGION- IN THE INTERBALL MISSION J. Bled,* J. Juchniewicz,* P. Triska,** K. Kossacki,* S. A. Romanov,*** S. P. Savin,*** J. Smilauer,** J. Slominski,* J. Vojta** and R. Wronowski* * Space Research Center PAS, 00716 Warsaw, 18A Bartycka, Poland
** Institute of Physics of Atmosphere ASCR, Bocni II, 1401-141 31 Praha 4, Czech Republir ** Space Research Institute RAN, Moscow, Profsoyuznaya 84132, Russia
ABSTRACT The Interball Tail Probe satellite together with its subsatellite Magion- were launched into a highly elliptic orbit with a 3ORe apogee and a 63” inclination on August 3, 1995. The plasma wave analyser on the Magion- performs analysis of the magnetic field fluctuations in the frequency range 32-2000 Hz. The Interball was operating in the magnetospheric tail from October 1995 until February 1996. The results of the Magion- wave measurements of electron cyclotron and lower hybrid electromagnetic modes in the regions of the magnetospheric tail directly 0 1997COSPAR.Publishedby ElsevicrScienceL.td. connected-with aurora1 ionosphere are presented ii this paper.
INTRODUCTION Plasma wave measurements are a basic tool for studying the geospace. Our current knowledge of the processes in space plasma allows us to say that waves give timdamental information about conditions in the different regions of the magnetosphere. Examination of the plasma wave in the space plasma is important for several reasons: (1) Collisionless plasma waves are a source of the anomalous dissipation and they play a crucial role in the energy, mass and momentum transport across magnetospheric boundaries, (2) They can be useful indicators for identification of events and structures, (3) Space plasma gives unique and pure conditions for the study basic processes, and (4) Waves provide information on the microphysics of the processes in plasmas. The Interball -1 satellite with its subsatellite Magion -4 were launched on 3 August 1995 into the orbit with apogee about 200,000 km and a 63” inclination. The wave experiment aboard Magion- gives the information about ELF magnetic field fluctuations from different regions of the magnetospheric tail. In this presentation we focused our attention on three regions directly associated with the polar ionosphere: plasma sheet, polar cup and aurora1 field lines. WAVE EXPERIMENT The wave experiment aboard Magion- subsatellite, with SAS (Spectrum Analyser for Subsatellite) as the central unit, performs the spectrum analysis in the ULF and VLF ranges of the signals obtained from electric and magnetic field sensors and from split langmuir probe, which measured current density. The wave complex is described by Triska et al. (1995). Electric field measurements. The electric antenna is a 1.6 m long dipole made of two spherical carbon ED detectors, each with a preamplifier. The detectors are fixed at the ends of the folding booms of the subsatellite. The frequency range is 0.1 Hz-400 kHz and sensitivity is 5010~*V/m Hztn at 2 kHz.
506
J. Blecki ef al
Magnetic field measurements. The magnetic field is measured in two frequency ranges: ULF (lHz-2kHz) -3 components B,, By, B, and VLF (l-5OkHz), one component B,. Sensitivities of these measurements are 10“ nT/HzlR at 2 kl-lz for VLF range and 30 l@’ nT/Hzln at 100 Hz for ULF range. Current density measurements. The current probe consists of two hemispheric collectors separated by a thin (-mm) insulator (Kozlov, 1969, Bering ef al., 1973). The frequency range of the measured fluctuations is 0.1 Hz-40 kHz. The sensitivity is lo-” A/cm2Hz’n. Suectrum analvser. The SAS is a two channel step frequency spectrum analyser. Each channel can be switched on and off by telecommands. The additional part of SAS is SASTRA -the time transjbrmer a device expanding the possibility of the analysis in the low frequency band; signals coming in the 32 Hz - 2000 Hz (or 32 - 20000 Hz) band are transformed to 4000 -266144 Hz (or 400 - 262544 Hz) band and then analysed by SFA. OBSERVATIONS The number of available measurements from the subsatellite is very limited. There is no memory for the scientific data in the telemetry system on the subsatellite. It means that only the measurements performed during direct transmission are available. The telemetry station is located in Panska Ves in the north part of Czech Republic and measurements are performed during visibility of MAGION- from this station (Triska et al, 1995).The regular measurements by SAS began in October 1996. The satellite INTERBALL 1 and subsatellite Magion- were then in the magnetospheric tail. We will present the results of the wave measurements from the magnetotail. This work is the continuation of our studies using data of Prognoz-8 (Blecki, 199.5) which had a similar orbit to Interball’s orbit. The results presented in this paper are very preliminary and our aim is to use them only as an example of the possibilities for wave measurements by the SAS instrument onboard of the subsattelite Magion- in different regions of the magnetosphere. The Plasma Sheet. The spectra taken within the plasma sheet are presented in Figures 1 and 2. The vertical axis represents the spectral density of the magnetic field fluctuations in telemetric units, and the horizontal ones correspond to frequency and time.
Fig. 1. The panoramic view of magnetic field fluctuations spectra in the frequency range 32-2000 Hz within the plasma sheet on 23.02.1996 during disturbed time (Kp=3). The co-ordinates: geocentric distance, magnetic local time and magnetic latitude, ofthe satellite are 10.5RE, 18.57, 3.3”.
507
ELF/VLFPlasmaWaveMea.suremen~~
In Figure 1 the increases of the intensity just above 250 Hz and 500 Hz at 19:37 UT and at the end of interval are associated with harmonics of the electron cyclotron frequency. The characteristic maxima appear at frequencies of about 25OHz,5OOHz and 7OOHzand are likely associated with harmonics of the electron gyro-frequency. These modes of plasma waves can be generated by microinstabilities of the temperature anisotropy of electrons (Mikhailovsky, 1974). This type of electron distribution function is often observed in the near plasma sheet. Plasma wave measurements with highest time resolution onboard Magion- can give additional information on the structures of the studied magnetospheric regions. The measurements of the electron cyclotron modes can be a signature of presence of the special type of electron populations- anisotropy of the temperature or ring distribution. ULF Spectrum 0.030_
t
0.025
-
0.020
-
0.015
-
0.010
-
0.005
-
‘.
“.
.
”
”
‘.
.
I’.
1 “,
”
‘_
z 2 2 % ‘h % p E
o.ooo
. 0
19:38:42
1.. 500
23 Febwory
I996
1..
.
2 000
0.. 1500
FrcquenCy
1.. 2000
.2500
[HZ]
Fig. 2. Single spectrum taken at 19:38 UT during the same event as in Figure 1. Five harmonics of the electron
cyclotron ii-equency are seen. The value of the electron gyrofrequency is about 250 Hz. Aurora1 Zone. It is a very well known fact that the aurora1 zone is very dynamic and turbulent region of the magnetosphere (Gumett, 1991). Figure 3 shows the spectra of the magnetic field fluctuations taken during entry of Magion- into aurora1 zone. Geomagnetic co-ordinates of the satellite at this moment were r=6RE , LMT=12 and GLat=55”.
Fig. 3. The same as in Figure 1 but for the aurora1 zone. The strong enhancement is seen just at the boundary. The spectrum has broad band character, and the maxima changes rapidly from spectrum to spectrum.
so8
J. Bledi EI al.
Polar Can. This region of the magnetosphere being connected with the magnetospheric lobe is rather more quiet than the aurora1 zone. Also plasma wave in this region are rather weak, but some times “spikes” of intensity can be observed. Figure 4 shows the spectra of magnetic field fluctuations during the time interval, when Magion- was on the field lines connected with polar cap (rx8RE, MLTz21, Glat=‘lO“).At the lowest frequencies some spikes can be seen and at the end of the interval of measurements sudden enhancement in the whole frequency range appears.
Fig. 4. The same as in Figure 1 for the region associated with the polar cap.
CONCLUSIONS Presented in this paper are preliminary results of the wave measurements performed aboard Magion- and identification of the discussed regions is also preliminary. This first analysis of wave data from the project Interball, the wave experiment aboard Magion, suggests that waves are a useful tool for identifjkg boundaries, electron population with anisotropy of the tempera~re, or ring dist~bution. The data will be interpreted more carefully together with plasma data from Promics, MPS and Electron instruments. ACKNOWLEDGEMENTS This work has been supported by grant KBN 2 PO3C 009 08
Bering, E.A., M.C.Kelley, F.C.Mozer, and U.V.Fahleson, Theory and operation of the split Langmuir probe, Planet.Space.Sci., 21, 1983 (1973).
Blecki J., ULF/ELF plasma waves in the magnetosperic tail as observed by Prognoz-8, E&Xp-371, 247 (1995). Gumett, D.A., Aurora1 Plasma Waves, in Aurora1 Phystcs, edit& by Ch-IMeng, M.J.Rycroft and L.A.Frank, pp. 241-254, Cambridge University Press, Cambridge, New York, Port Chester, Melbourne, Sydney (1991). Kozlov O., Probe in Plasmas, Atomizdat, Moscow (1969). (in Russian) Mikhailovsky A.B., Theory ofPlasma Instabilities, Consultant Bureau, New York (1974). Triska P.,Vojta J., Agafonov Yu., The INTERBALL subsatellites S2-A and S2-T, in JNTERBALL Mission and Payload”, pp 100-l 13, Russian Space Agency, IKI, CNES (1995).