IAGA/
URSI JOINT WORKING GROUP on:
U.S. Inan (Stanford University, USA) began the proceedings with a paper
on observations of Trimpi events from the HAIL array of stations in
central USA. Bursts of electron precipitation from the radiation belts were
detected with increasing time delays at the higher latitude stations,
consistent with an interaction with obliquely propagating whistlers.
Observations which had previously been explained in terms of electron
scattering by ducted whistlers were reinterpreted as being caused by
non-ducted signals. M. Walt (Stanford University, USA) reviewed the
wave scattering of both trapped electrons and trapped protons. The former was
well established, though the relative importance of various types of whistler
mode waves (whistlers, chorus, plasmaspheric hiss, VLF transmissions) in
different L-ranges, and of ducted vs. non-ducted whistlers was still
uncertain, mainly because of the lack of experimental data on wave amplitudes,
etc., for use in models. Experimental evidence for the wave scattering of ions
was much more sparse.
C.J. Rodger (British Antarctic Survey, UK) reported on magnetospheric
line radiation, a spectrally structured VLF emission, possibly related to
power line radiation, and a potential scatterer of trapped electrons.
Occurrence statistics and characteristics of such events, as observed at
Halley station were presented. No convincing evidence was found for any
connection with power line radiation. A report by F. Darrouzet
(Institute for Space and Aeronomy, Belgium) and others highlighted the current
lack of empirical models and maps of VLF/ELF wave distributions throughout the
magnetosphere, analogous to the existing particle models of the radiation
belts. Many satellite wave data exist in various places, but there was a need
to synthesise this information into a model which would be useable for
radiation belt studies. It was proposed that a first step should be
identifying and cataloguing of the various data sources.
J.M. Albert (Air Force Research Lab., USA) described a theory of
cyclotron resonance interactions in the radiation belts using a relativistic
Hamiltonian approach with 1½ degrees of freedom. Adiabatic invariance
breaks down at resonance. Returning to the subject of the experimental wave
intensity data needed for modelling the wave-particle interactions in the
radiation belts, A.J. Smith (British Antarctic Survey, UK) reported a
statistical study of whistler occurrence and characteristics at Halley
station, Antarctica. Subject to some assumptions about the propagation
conditions, it was possible to infer average wave intensities of ducted
whistlers in the magnetosphere.
D. Summers (Memorial University of Newfoundland, Canada) addressed the
topic of the enhanced fluxes of relativistic electrons which appear in the
magnetosphere during magnetic storms and are sometimes known as "killer
electrons" because of the damage they can cause to space engineering systems.
He gave a theory of how these fluxes could be accelerated by wave particle
interactions, by applying relativistic diffusion theory to a "seed population"
of electrons. Finally in the oral session, Y. Zhang (University of
Saskatchewan, Canada) described a survey of whistler mode waves in geospace,
carried out by the GEOTAIL
satellite. The waves intensities are well-correlated with plasma densities. In
the poster session on 19 August, A.G. Demekhov (Institute of Applied
Physics, Russia) reported calculations of the self-consistent modelling of
ring current ions, and D.L. Pasmanik (of the same institute) presented
a model describing localised energetic particle precipitation in the vicinity
of high plasma density gradient regions such as the plasmaspause.
The following were present: Andy Smith (UK), Michel Parrot (France), Elisabeth
Blanc (France), Craig Rodger (UK), Orsolya Ferencz (Hungary), Richard Horne
(UK), Steve Cummer (USA), Vikas Sonwalkar (USA), Umran Inan (USA), Ondrej
Santolik (Czech Republic), Jyrki Manninen (Finland), Antti Oikarinen
(Finland), Tim Bell (USA), Katsumi Hattori (Japan), Yasuhide Hobara (Japan),
Hal Strangeways (UK), Joseph Lemaire (Belgium).
Andy Smith took the chair, and after welcoming those present, presented the
triennial report of the working group for 1996-99 compiled by Michel Parrot
(France), the URSI co-chairman of the group. This report was subsequently
published in The Radio Science Bulletin No. 290 (September 1999), p.
46.
It was agreed to recommend to the relevant Commissions (G and H) that the
VERSIM working group should continue for the next triennium, with Michel
Parrot as URSI co-chairman (this was subsequently agreed at the Commission G
and H business meetings). Several of those present reported on the latest
VERSIM activities and future plans at their institutes or in their countries.
Andy Smith passed on a report received from Arthur
Hughes (South Africa) who had chaired a business meeting of VERSIM at the
recent IUGG Assembly in Birmingham (see below). It had been proposed and
agreed that there would be a VERSIM symposium at the next IAGA General
Assembly (Hanoi, August 2001) on Whistlers, particle precipitation and low
latitude VLF phenomena. As regards the next URSI General Assembly in the
Netherlands (2002) it was decided not to propose a specific VERSIM symposium,
as there were already many proposed symposia titles which would satisfactorily
cover the VERSIM field. Finally Joseph Lemaire put forward a recommendation to
support a survey of the spatial distributions of VLF and ELF waves in the
magnetosphere. The VERSIM group endorsed this and it was subsequently put
forward to and agreed by Commission H and the URSI Council. For more details,
see below.
Agreed: That the WG should continue and that Andy Smith be asked to continue
as chairperson. AH indicated that AS was prepared to accept this position.
Division 2 Chairperson made an announcement at the beginning of the meeting
suggesting that symposia proposed for Hanoi should take into account the
possible interests of the local participants. With this in mind it was
proposed that VERSIM request a symposium entitled: Whistlers, particle
precipitation and low latitude VLF phenomena. Andy Smith was proposed as
convenor of this session. AH said he would take the session proposal to the
Business meetings of Divisions 2 and 3. JL announced that the proceedings of
the meeting in honour Don Carpenter at URSI would be published in a Special
Issue of JAS-TP and that the issue would be open to contributors who did not
submit papers to the URSI meeting.
The working group unanimously agreed to support the proposal by J Lemaire and
colleagues to Commission H of URSI that a model be developed of the wave
background in the magnetosphere. JL pointed out that models existed for
particles, the ionosphere and the atmosphere but that no models existed for
the wave environment and that this was a disadvantage to theoretical studies
of the magnetosphere. AH pointed out the need to establish such a model as a
base for EM pollution studies of the magnetosphere. JL and colleagues had
already made a list of satellites that had recorded wave information. AH said
that he had unpublished global maps of the occurrence VLF waves. CR pointed
out that the results from the French micro-satellite, Demeter would contribute
to such a model.
MC reported on the VLF work at BAS and outlined their plans for studying the
effects of the solar eclipse on 11 August 1999. AH reported on the Natal
programme and outlined the studies on whistler ghosts, requesting that workers
keep a look out for ghosts and stressing the value of observations at
different latitudes. JL reported on his polar wind studies. KT reported on the
work being done in Beijing.
A vote of thanks was passed to Andy Smith acknowledging his excellent
contribution to the working group."
A web site has been set up at
http://www.magnet.oma.be/sevem/ which presents a comprehensive documented
catalogue of missions/satellites that surveyed the electromagnetic VLF and ELF
environment in the terrestrial magnetosphere since 1959. The orbital
parameters are given for each satellite, as well as contact persons,
bibliographical references concerning the experiments and preliminary results.
The location where the data are stored is also given. The site is maintained
by Fabien Darrouzet.
Firther details may be on the web site for Special Whistler Mode Experiments with the IMAGE Satellite.
Return to Contents
The working group on VLF/ELF Remote Sensing of the Ionosphere and
Magnetosphere (VERSIM) is an international group of scientists interested in
studying the behaviour of the magnetosphere and ionosphere by means of ELF
(300 Hz - 3 kHz) and VLF (3-30 kHz) radio waves, both naturally and
artificially generated. The group was set up in 1975 by IAGA (International
Association of Geomagnetism and Aeronomy) and URSI
(International Union of Radio Science), see history. Originally the emphasis was on
probing of the magnetosphere by whistlers, but later the scope became somewhat
broader. The group aims to promote research in this field by facilitating the
exchange of ideas, information and experience between active research workers
and other interested scientists. This is done through regular meetings at
IAGA and URSI Assemblies, and via the circulation of a newsletter. The group
has also been active in sponsoring scientific symposia at IAGA and URSI
Assemblies, in areas relevant to its field of interest, and in coordinating
observational campaigns. At present the main subjects of interest include
Plasma structures and boundaries - morphology and dynamics,
Wave-particle and wave-wave interactions, Wave-induced particle
precipitation, Wave propagation in magnetosphere and ionosphere,
Sprites and the effects of lightning on the ionosphere. There are
currently over 100 scientists from 22 different countries on the VERSIM
mailing list.
Some VERSIM Research Laboratories
VLF Data on the Web
IAGA, Hanoi, 2001
The 9th Scientific Assembly of
IAGA will be held in
Hanoi, Vietnam, 18-30 August 2001. It will be a combined meeting with IASPEI. Contact: IAGA-IASPEI 2001
Secretariat, Institute of Geophysics, Box. 411 Buu Dien Bo Ho, Hanoi, Vietnam;
fax: +84 4836 4696; phone: +84 4756 2802; email: IAGA-IASPEI@fpt.vn. See also details
about the venue given in IAGA News,
No. 38 (October 1998).
Whistlers, Particle Precipitation and Low-latitude VLF Phenomena
This session was orignally proposed and approved at the VERSIM meeting in Birmingham (see report below) as a joint Division II/II session. It is now the half-day session G2.07 in the Division II programme, convened by
A.J. Smith (British
Antarctic Survey, UK) and A.R.W.
Hughes (Natal
University, South Africa), and is on the subject of whistlers (including
ion whistlers) in the magnetosphere and ionosphere, their propagation and
interaction with particle populations, and the induced effects in the
ionosphere, particularly precipitation. The submission deadline was 1 March 2001. The programme will be published soon.
VERSIM Business meeting
There will be a VERSIM business meeting arranged during the assembly; more
details will be provided nearer the time.
URSI, Maastricht, 2002
The 27th General Assembly of URSI
will be held in Maastricht, the Netherlands in August 2002. There will be
no specifically VERSIM session, but the following topics have been proposed
for symposia at Maastricht, which, together with the Open Sessions, should
cover all areas of interest to VERSIM:
There will be a VERSIM business meeting arranged during the assembly; more
details will be provided nearer the time.
Other forthcoming meetings
URSI, Toronto, 1999
The 26th General
Assembly of URSI
was held in Toronto, Canada, 13-21 August 1999.
Pitch-angle scattering (and acceleration) of trapped particles by waves in
magnetospheres
This VERSIM-sponsored session (Session H3) which was a follow-up to the
successful "waves and the radiation belts" session at Lille, broadened to
include waves other than whistler mode and radiation belts other than Earth's,
was convened by A.J. Smith, J. Lemaire and U.S. Inan; see
programme. The oral session was held on
Friday 20 August 1999, and the posters on Thursday 19 August 1999.
The Plasmasphere rediscovered: a tribute to Donald Carpenter
This special workshop, convened by {J. Lemaire and L.R.O. Storey
was be held in Toronto on Saturday 14 August 1999 in honour of Don Carpenter
and his achievements in helping to discover and understand the plasmasphere
and plasmapause using whistlers. Don was instrumental in founding the VERSIM
group, originally known as the working group on Passive Electromagnetic Probing of the
Magnetosphere. The report of the workshop by the conveners is to be
found on the web at
http://www.magnet.oma.be/ws-h/index.html. In the evening, a banquet was
held in Don's honour, attended by his family, friends and colleagues. Various
speeches were made, culminating in a most amusing speech by Owen Storey
on whistlers, including demonstration of their dispersion and echoing using a
slinky.
Other sessions at Toronto
Other sessions held in Toronto also contained contributions of interest to the
VERSIM group: Terrestrial Electromagnetic Environment,
Electromagnetic coupling including seismic activity between the ground and
the upper ionosphere and magnetosphere, Lightning-Ionosphere
interaction, Active experiments involving space plasmas,
Wave-particle interactions: quantitative comparison between observations,
theory, simulations and modelling, Theory and simulation of nonlinear
kinetic processes in space plasmas, Wave propagation: observation and
data analysis, and a tutorial lecture by L.R.O. Storey on The
Measurement of Wave Distribution Functions.
VERSIM Business meeting
There was a meeting of the VERSIM working group during the Toronto Assembly,
on Tuesday 17 August 1999.
IUGG, Birmingham, 1999
The 22nd General Assembly of the International Union of Geodesy and
Geophysics, which encompasses IAGA, was held at the University of
Birmingham, UK, 19-30 July 1999.
VERSIM Business meeting
There was a meeting of the VERSIM working group during the Birmingham
Assembly, on Tuesday 20 July 1999. In the absence of the IAGA co-chairman,
A.J. Smith, the meeting was chaired by A.R.W. Hughes (South Africa). Here is
his report: "Those present: A. Hughes (chair), J. Lemaire, M. Clilverd, C.
Rodger, K. Tang.
SEVEM (Survey of ELF and VLF Experiments in the Magnetosphere)
At the VERSIM meeting held during URSI General
Assembly in Toronto, a Recommendation was put forward by Joseph Lemaire
(Belgium) to support a modelling effort to survey and map the ELF and VLF wave
environment in the magnetosphere. The first stage would be to identify and
catalogue the many satellite data sets of VLF/ELF waves. The recommendation
was subsequently approved by URSI Commission H and the URSI Council. The text
is available on the web at
http://www.magnet.oma.be/sevem/URSI-Recommendation.html. It was agreed
that VERSIM would support the development of comprehensive empirical global
3-D models/maps for the distribution of ELF and VLF waves in the
magnetosphere.
VLF/LF/MF transmitter now operating at high altitudes near Earth
The IMAGE spacecraft was successfully
launched on 25 March 2000. Don
Carpenter sent the following information about the radio sounder, dated 15
June 2000. "A transmitter capable of radio sounding as well as whistler mode
wave injection is now operating on the IMAGE satellite in an elliptical polar
orbit, with apogee at about 7 Earth radii altitude and perigee about 1000 km.
The interest of ground and satellite radio observers is solicited in
experiments to determine conditions under which signals from the satellite can
be received at ground stations or on satellites of opportunity. The radio
sounder, or Radio Plasma Imager
(RPI) on IMAGE, for which the principal investigator is Bodo Reinisch of U. Mass. Lowell, is capable of transmitting
in the range 3 kHz - 3 MHz. Present plans call for conventional radio sounding
in free space modes during satellite operations at high altitudes outside the
plasmasphere. Within the plasmasphere and at low altitudes over the Southern
Polar Cap it is will be possible to operate so as to excite the whistler mode,
using frequencies from 3 kHz to 500 kHz, depending upon satellite position. An
initial program would involve transmission of a sequence of 0.5 second pulses
at 3, 5, 7, 9, 11, 13, and 15 kHz, at a pulse rate of 1 Hz. These experiments
are not yet scheduled, but are expected to begin by July 2000 so as to take
advantage of winter conditions in the southern hemisphere ionosphere. Further
information when available will be posted on the Web at http://image.gsfc.nasa.gov. If you are
interested in recording during RPI transmissions, please advise Don Carpenter regarding the location
of your station(s), so that you may be advised of upcoming schedules by email.
For the present, only transmissions in the 3-5 kHz range are envisaged.
However, transmissions in the 400-500 kHz range are also under consideration."
DEMETER
DEMETER is a
low altitude micro-satellite (800 km) mainly aimed the study of
electromagnetic signals generated by seismic or volcanic events, to be
launched in 2002. CNES (the French National
Space Agency) will issue a call for Guest Investigators by the end of 2000.
Anyone interested should contact Michel Parrot who has provided the
following information about DEMETER:
The wave experiment will record in:
News from the Czech Republic
Pavel Triska sends the following report,
dated 19 October 1999. "Our activities in magnetospheric wave phenomena
research continue. At the present time we continue (since May 1998) to record
VLF broadband up to 20 kHz the E and B components using the
Czech micro-satellite (68 kg) MAGION-5 in RTT
regime. This S/C was launched together with INTERBALL-2 on 29 August
1996, perigee 750 km, apogee 19300 km, inclination 65°. We have got many
interesting records from the equator plane to the polar magnetosphere, most
data belong to the plasmasphere region."
VLF summary plots from BAS stations
VLF/ELF summary plots from British Antarctic Survey at Halley,
Antarctica (65°S, 27°W, L=4.3), and the
Automatic Geophysical Observatories (AGOs) poleward of Halley, are now
available for browsing via the world-wide-web. Go to:
http://www.nerc-bas.ac.uk/public/uasd/data/dataserv.html and select the
link to "VLF summary plots".
VERSIM bibliography
Please send any additions or corrections to Michel Parrot.
Obituaries
Previous editions of this page
VERSIM Newsletters
The VERSIM Newsletter (and its predecessor, the PEPM Newsletter) has been published about 1-2 times per year. The
latest issue (No. 14) was published in June 2000. Newsletters up to No. 13 were distributed on paper. From No. 14 onwards they will be distributed electronically, either via the VERSIM electronic mailing list or through this web page. Here is an archive of past VERSIM Newsletters:
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 M. Parrot; email
mparrot@cnrs-orleans.fr
This document is maintained by A.J. Smith and was last updated 6 March 2001.
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