The following events are relevant to VERSIM.
Worldwide Stanford University ELF/VLF measurement activities currently in progress include:
The new South African Antarctic base at Vesleskarvet, at about (71°S; 2°W), is expected to be operational by February 1997. The SHARE radar and a range of experiments including a pulsation magnetometer, a VLF direction finder, an "Omnipal" receiver and all-sky auroral cameras will be reintroduced. An addition to the programme is a proposed telemetry station to be operated for the Royal Institute of Technology, Stockholm, to take data from the Astrid-2 satellite. This will provide fine scale electric field measurements over auroral forms. We will also be measuring ozone column densities and UV fluxes. The new base is 200~km inland from the former South African base at Sanae-3.
Two VLF wave-particle campaigns were conducted in 1996. One was to Marion Island (46°S 38°E) in collaboration with the British Antarctic Survey, in which their VLF Doppler receiver was operated in conjunction with our VLF and Omnipal receivers. Initial comments by the experimenters (Mark Clilverd, BAS; Ken Rice and Andre Larisma, Natal) suggest that good data sets have been obtained. The other campaign was to make wave-particle measurements at three stations in Natal in collaboration with the tethered satellite experiment launched by the US Space Shuttle. Unfortunately the tether broke just before full deployment and no data were obtained. A future campaign is planned in conjunction with particle injection experiments on the MIR space station. Apart from our work in Antarctica we see much of our future in space physics in Natal as making these wave-particle measurements in association with satellite measurements made by other groups.
During the 1995-96 Antarctic summer the third of the four BAS AGOs, A81 ("High Sierra"), was deployed at (81.5°S 3.0°E), with the same instrument payload as A81. Two further instruments, supplied by US collaborators, were added to A80 and A81, namely a LF/MF/HF receiver to study auroral radio noise (J. LaBelle, Dartmouth College) and a pulsation magnetometer (M. Engebretson, Augsburg College). A late-season visit was made to all the AGOs, enabling a good coincident data set for about three weeks to be collected; this is currently being analysed.
As part of an international project with BAS and Stanford University, narrow band recordings have been made at Commandante Ferraz, the Brazilian Antarctic station, of NAA, NPM, NSS, NAU, and NLK for 12 hours per day (00-12 UT) throughout 1995. The data are currently being analysed for Trimpi event activity.
Our VLF receivers have now been installed at the "Futuroscope" site, near Poitiers, and since the beginning of April 1996 we have been monitoring signals from NAA, GQD, and HWU, in order to study the Trimpi effect. Unfortunately so far there has been very little Trimpi activity, possibly because geomagnetic disturbance levels have been low during this time.
Beginning from April 1996, the Eötvös Geophysical Institute and the Department of Geophysics, Eötvös University, Budapest, restarted routine whistler recordings in Tihany, but in digital form. At the moment, two minutes of every half an hour is recorded digitally and analysed offline, but by the end of September a new automatic whistler detector is expected to be set up. This will monitor the received waveform continuously, and only the part of digitised signal that contains whistler(s) will be stored. Trimpi measurements are also made during the night-time hours
During the period 1994-1995 (and to June 1996) VLF/ELF waves studies continued, mainly using satellite data from the ACTIVE and APEX missions. New data on wave phenomena have been recorded since August 1995 at the Panska Ves satellite TC/TM station within the INTERBALL mission. For this mission two MAGION-type satellites have been developed in the Czech Republic (Institute of Atmospheric Physics). The first, MAGION-4, a small satellite weighing 59kg, was launched on August 3, 1995, as a part of the INTERBALL-1 spacecraft, and was separated from this "mother satellite" during the first orbit. The highly eccentric elliptical orbit (apogee 193000km, perigee 793km, inclination 62.9°) enables measurements to be made in different parts of the Earth's magnetosphere and in the solar wind. The scientific payload of MAGION-4 was the result of extensive international cooperation, and includes magnetic field and particle measurements and a set of wave experiments using the following sensors: one double-probe electric dipole 1.7m long for f<400kHz, three search coils for f<2kHz, and one search coil for f<40kHz. The onboard equipment includes a filterbank, ULF waveform digitizer, step frequency analyser and broadband analogue telemetry channels. The MAGION-4 orbit crosses the plasmasphere regularly, which allows us to observe plasmaspheric wave phenomena as LHR hiss, magnetospherically reflected whistlers, ELF auroral emission, etc. Observations of these types of ELF/VLF phenomenon are expected to continue, and to be extended after activation of another small (68kg) Czech satellite, MAGION-5, with a payload similar to MAGION-4. It is to be launched in August 1996 as a part of the INTERBALL-2 project. The proposed orbit is: apogee 20000~km, perigee 800km and inclination 63°.
In August 1992 our whistler station at Grocka (Lambda=43.8°, Phi=102.27°) was badly damaged during a thunderstorm. At the end of last year we finished reconstructing it. During 3 minutes every hour, broadband (1-10 kHz) observations are recorded and analysed by a 486 PC-based digital acquisition system. The main problem now is that during last winter whistlers were recorded very rarely at our station, because of the high level of noise. However, some very unusual (and as yet unexplained) rising tone events in the range 2-5kHz were recorded on 8 April 1996, at 1450-1452UT, during quiet geomagnetic conditions.
A specific precipitation zone of energetic electrons has been observed on the evening/ afternoon side after sufficiently strong magnetic storms. This zone has some remarkable features investigated using the data of low-altitude (h~103km) NOAA satellites. In particular, the moderate pitch-angle diffusion regime with a filled loss cone is evident, the precipitated electron fluxes being of the same order as the fluxes of trapped electrons, and the precipitation event having a specific cliff-like form along the satellite trajectory as it crosses L-shells. These quasi-steady events are often accompanied by the precipitation of protons located in the same LT sector but at higher latitudes. We suggest a theoretical model based on cyclotron resonant interactions to explain these observed phenomena. We consider that this electron precipitation zone is formed by energetic electrons which interact via the whistler wave cyclotron resonance instability with a region of relatively large cold plasma density. This region is caused by a restructuring of the plasmasphere during the magnetic storm. The source of energetic electrons is situated on the night side and they enter the interaction region by the process of magnetic drift. The isotropisation of the distribution function during the process of pitch angle diffusion is accompanied by the redistribution of the energetic electrons along the magnetic flux tube. This can lead to a large (by almost an order of magnitude) increase of the trapped electron flux measured at low altitudes. Based on self-consistent equations for the whistler cyclotron instability we obtained quantitative estimates for the parameters of the energetic electron precipitation zone which are in agreement with the observations.
For comparison of theoretical results with experimental data, it is obviously fruitful to employ simplified models for quickly estimating parameters that provide the best agreement with experiment. We considered the simplest dynamic model of the whistler cyclotron instability based on the so-called multi-level set of equations for the cyclotron maser, taking into account nonlinear modulation of the pitch-angle distribution of trapped particles. We tried to simulate two precipitation events for which satellite trapped energetic electron data and EISCAT data on the electron precipitation were available (Manninen et al., J. Atmos. Terr. Phys., 58, 97, 1996). We showed that the different precipitation time patterns in these events can be consistently related to the recorded plasma parameters.
These investigations are a part of a joint project coordinated by Dr. T. Turunen, Director of the Sodankylä Geophysical Observatory, and funded by INTAS.
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Some VERSIM Research Laboratories
XXV General Assembly of URSI
The next URSI General Assembly will be held in Lille, France, 28 August to 5 September 1996. For more details, contact the Local Organising Committee at agursi@univ-lille1.fr.
Session H1 - Whistler-mode waves and their effects on the radiation belts
A VERSIM half-day session (convenors A.J. Smith, U.S. Inan and J. Lemaire) will be held on the morning of Thursday 29 August, 0830-1230 (oral session). The posters for all URSI sessions will be displayed on the afternoon of Tuesday 3 September.
The provisional H1 programme is:
Oral session
Poster session
Other relevant sessions
Some of the sessions to be held at the Assembly, of relevance to VERSIM, are:
VERSIM business meeting
There is planned to be a meeting of the VERSIM working group during the Lille Assembly; the exact time and venue are to be announced (at the Assembly, or check the VERSIM WWW page shortly beforehand). The draft agenda is: 1. Chairman's Report; 2. Future of the working group; 3. Reports from VERSIM research groups; 4. Symposia at future IAGA and URSI Assemblies; 5. Election of IAGA Co-chairman for 1995-99; 5. Any other business. With respect to item 4, the following have already been suggested for the 1999 URSI General Assembly: Thunderstorm-Ionosphere Coupling and Whistler-mode Wave-Particle Interactions (the latter with particular reference to high latitude phenomena studied using data from the POLAR satellite and the new AGO networks in Antarctica).
Other forthcoming meetings
IAGA, Uppsala, 1997
The 8th Scientific Assembly of IAGA will be held in Uppsala, Sweden, 3-15 August 1997. For more details, contact the local organising committee [tel: +46-18-303600; fax: +46-18-403100; email: iaga@irfu.se].
There will be a half-day VERSIM session (Session 2.14) on Localised ionospheric perturbations related to lightning and VLF transmitters, conveners: D. Nunn, A.J. Smith. This session will be concerned with the scattering of VLF radiation from D region ionospheric irregularities. Papers are invited on observations of VLF `Trimpis', and on the theory and modelling of VLF scattering. A topic of particular interest is that of VLF holography, in which particle precipitation may be mapped by multi-site observations of VLF Trimpis. Papers are also solicited on scattering due to direct heating of the ionosphere and on Trimpis caused by Sprites and Blue Jets.
COSPAR, Birmingham, 1996
The 31st COSPAR Scientific Assembly will be held in Birmingham, UK, 14-21 July 1996.
News from the VERSIM Community
USA
From: U.S. Inan, Stanford University
South Africa
From: A.R.W. Hughes, University of Natal, Durban.
UK
From: A.J. Smith and M.A. Clilverd, British Antarctic Survey.
Rothera (67.6°S 68.1°W)
No further VLF recordings have been made since 8 October 1995, and the receiving system has now been removed.
Faraday (65.3°S 64.3$°W)
The 2 narrow-band VLF experiments (OMSK and VLF Doppler receivers) and VLF broadband recordings finally stopped on 15 December 1995, prior to handover of the station to the Ukraine. The OMSK and broadband equipment has remained on the station (now known as Vernadsky) although operational schedules are unknown.
Halley (75.6°S 27.3°W)
VLF broadband (recording to DAT tape), OMSK narrowband (`trimpi'), VELOX (filterbank), and VLF Doppler observations continued through 1995. The OMSK programme closed in November 1995 but it is planned to replace it with a new and more flexible OmniPAL receiver in 1997. The other observations are continuing during 1996. Key parameters from VELOX and other experiments at Halley are routinely transferred into the ISTP database as part of the SESAME investigation of GGS (Global Geospace Study). For 1997, it is planned to enhance the VELOX with an additional tunable narrow-band channel capable of receiving signals from the proposed South Pole VLF beacon, and also an impulse counter for measuring spheric rates from global lightning at frequencies of 3 kHz and 10 kHz. For more information, consult the BAS Upper Atmospheric Sciences Division World Wide Web pages.
Automatic Geophysical Observatories
The first AGO-VELOX (AGO-based VLF/ELF receiver) was installed in the A80 AGO (80.9°S 22.3°W) when it was deployed on the Recovery Glacier 600~km south of Halley in January 1995. The power in frequency bands at 0.5, 1, 2, 3, 6 kHz is recorded every second, and other parameters every 10s. A 0-6 kHz spectrogram is recorded every 15 minutes. The AGO instrument complement also included a magnetometer and riometer. Although all the instruments worked well, a fault in the main computer meant that no data were recorded after 26 February 1995. Nevertheless, 40 days of excellent data were taken, and provide an interesting comparison with simultaneous data from identical instruments at Halley. First results will be reported at the Western Pacific Geophysics meeting in Brisbane in July 1996.
Brazil
From: L.R. Piazza, INPE.
France
From: Y. Corcuff, Signal Image Communications Laboratory, Université de Poitiers.
Hungary
From: J. Lichtenberger, Eötvös University.
Czech Republic
From: F Jirícek,and P Tríska, Institute of Atmospheric Physics of the Czech Academy of Sciences, Prague.
Yugoslavia
From: D. Sulic, Geomagnetic Institute, Belgrade.
Russia
From: A.G. Demekhov, Institute of Applied Physics, Nizhny Novgorod.
Newsletter
The VERSIM Newsletter is published about 1-2 times per year. The current issue (No. 9) was published in June 1996. Any material for the next newsletter, or requests to subscribe, should be sent to A.J. Smith, a.j.smith@bas.ac.uk.
Further information
Contact one of the VERSIM working group co-chairmen:
IAGA Co-chairman A.J. Smith; email
a.j.smith@bas.ac.uk
URSI Co-chairman U.S. Inan; email
inan@nova.stanford.edu
This document is maintained by A.J. Smith and was last updated 2 July 1996. Thanks to all who have contributed.
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