V . E . R . S . I . M

VLF/ELF Remote Sensing of Ionospheres and Magnetospheres

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). 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, and Wave propagation in magnetosphere and ionosphere. There are currently over 100 scientists from 22 different countries on the VERSIM mailing list.

Some VERSIM Research Laboratories

URSI, Toronto, 1999

The 26th URSI General Assembly will be held in Toronto, Canada, 13-21 August 1999. For more details contact the
URSI GA'99 Secretariat, National Research Council Canada, M-19, Montreal Road, Ottawa, Ontario K1A 0R6, Canada; Tel: (613) 993-7271; Fax: (613) 993-7250; email: ursi99@nrc.ca
or see the WWW page: http://www.nrc.ca/confserv/ursi99. The First Announcement and Call for Papers will be issued around 30 June 1998.

Pitch-angle scattering (and acceleration) of trapped particles by waves in magnetospheres

This VERSIM-sponsored session (Session H3) which is 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 is being convened by A.J. Smith, J. Lemaire and U.S. Inan.
Draft Call for papers
It is known that waves propagating though the magnetosphere can interact strongly with trapped particles which can cause a number of important effects including acceleration, pitch-angle scattering, and precipitation into the ionosphere. A particular example is that of whistler-mode waves which undergo transverse cyclotron resonance with energetic electrons trapped in the radiation belts. The waves involved may either be naturally generated in space (e.g. hiss) or may come from powerful ground sources (e.g. transmitters, power lines or lightning). It is still not clear how important wave-particle interactions are as a loss mechanism for trapped populations, compared with other possible loss processes. It is particularly important to quantify the effect of lightning in view of a possible increase in global lightning activity associated with global warming. Papers reporting experimental and theoretical results on these and related topics are invited. We also welcome contributions on comparable processes in planetary magnetospheres other than Earth's.

Other sessions for Toronto

Other sessions schedule for URSI'99 which may be of particular interest to the VERSIM group include:
Active experiments involving space plasmas Convener: W.J. Raitt
Wave-particle interactions: quantitative comparison between observations, theory and simulations Conveners: R.R. Anderson, I. Nagano and D. Nunn
Theory and simulations of nonlinear kinetic processes in space plasmas Conveners: Y. Omura, M.A. Abdalla and S. Ossakow
Wave propagation: observations and data analysis Conveners: F. Lefeuvre, K. Hashimoto and K. Mahajan
Electromagnetic coupling including seismic activity between the ground and the upper ionosphere and magnetosphere Conveners: S. Pulinets, M. Parrot and O. Molchanov
Lightning-ionosphere interaction Conveners: U.S. Inan and D. Nunn
For more information, see: http://terezka.ufa.cas.cz/ursi/hsess.html and http://ulcar.uml.edu/ursi/URSI-98-7.html.

IUGG, Birmingham, 1999

The 22nd General Assembly of the International Union of Geodesy and Geophysics, which encompasses IAGA, will be held at the University of Birmingham, UK, 19-30 July 1999. The programme of symposia, and information on how to register for the assembly and submit an abstract, will be given in the Second Circular to be published in May 1998. The deadline for abstracts will be 15 January 1999. More details may be found on the Web site: http://www.bham.ac.uk/IUGG99/, or contact the organising committee at email: IUGG99@bham.ac.uk or fax: +44 121 414 4942.

Other forthcoming meetings

IAGA, Uppsala, 1997

The 8th Scientific Assembly of IAGA was held in Uppsala, Sweden, 4-15 August 1997.

Localised ionospheric perturbations related to lightning and VLF transmitters

This half-day session (Session 2.14) held on Monday 11 August 1997 was sponsored by VERSIM and convened by D. Nunn and A.J. Smith. It was a good session, attended by about 40 scientists. Although it was a little sparse, owing to a number of papers being withdrawn, this did allow time for some good discussions. The session began with a presentation by A.R.W. Hughes on whistler ghosts; these were faint whistler traces of the same dispersion as the main whistler components but delayed. For 11 events observed during one 2.5-hour interval at Marion Island (L=2.6), this delay was consistently close to 600 ms. An interpretation was given in terms of the triggering of lightning through the precipitation, caused by the leading whistler, of electrons into the ionosphere above a northern hemisphere thunderstorm. An invited paper by M.A. Clilverd dealt with a sharp decline in Trimpi activity with increasing latitude, which had been observed between Faraday and Rothera stations, Antarctica, located at L=2.3 and L=2.8, respectively. Trimpi activity observed on nearly parallel paths from the NPM VLF transmitter in Hawaii, dropped off by about 90% between Faraday and Rothera. D. Nunn discussed numerical modelling of VLF Trimpis on the path NWC (Australia)--Dunedin (New Zealand). Two numerical models were compared: the first due to Nunn was a weak scattering model, rigorous within the Born limit, whilst the second due to Baba and Hayakawa used a finite element approach. R.F. Yeo described modelling the VLF Trimpi Effect with multiple point scatterers.

VERSIM business meeting

This was held on Wednesday 6 August 1997. The following were present: Andy Smith (UK) in the chair, Marina Goncharova (Russia), Arthur Hughes (South Africa), Umran Inan (USA), Wladlislav Lyatsky (Russia), Jyrki Manninen (Finland), Alexander Sukhorukov (Germany), Keyun Tang (China), Pavel Tríska (Czech Republic). The chairman reported on VERSIM activities in the preceding two years, including VERSIM meetings and symposia, Newsletters circulated, and additions to the VERSIM WWW site, including a VERSIM bibliography and an email directory. Several of those present gave a brief report.

Maninnen described two recent VLF recording campaigns in Finland, one in winter to study auroral phenomena, and one in summer in connection with the Tromsö ionospheric heater. In the latter, effects were observed 400 km away from the heater. He also described the development of a new digital VLF broadband receiver system capable of measuring the azimuth and polarisation of incoming signals. Current collaborations were with Barr (ionospheric heater), Parrot (Freja satellite), and an INTAS collaboration with Nunn, Rycroft and Russian colleagues.

Inan described current activities by the Stanford VLF group. There were now 6 AGOs (Automatic Geophysical Observatories) deployed in Antarctica. The VLF receiver comprised 3 hiss channels (1-2, 2-4, and 30-40 kHz) together with narrowband transmitter channels. Additional hiss channels were being added in the frequency range 0.5-40 kHz. At Palmer station, Antarctica, broadband (300 Hz to 20 kHz) and narrowband Trimpi recordings were made daily during 00-10 UT, whilst at South Pole two 3-h long recordings were made each day in the frequency range 0.3-20 kHz. In the USA there was a holographic array (HAIL) located in Colorado and Arkansas to study sprites and lightning. The data were now available on the Web, and high schools were involved in this project.

Hughes talked about the VLF direction-finding observations currently in progress by the University of Natal group at Sanae, Antarctica, and also the Trimpi event recordings being made using "OmniPal" receivers. He also discussed the whistler ghost events observed at Marion Island (see preceding report of Session 2.14).

Tang reported that VLF observations were continuing at Zhongshan station, Antarctica (L~14) but had ceased at Great Wall station. There were also two temporary station operating in Chain itself for special events e.g. solar eclipses. A new project was the development and deployment of a new whistler receiver.

Tríiska noted that ground-based VLF measurements in the Czech Republic, which had been in progress since the International Geophysical Year, had now ceased. However, his group was actively researching on interesting wave data from the receiver on MAGION-4, the subsatellite of Interball, which was still working well two years after launch. He showed some interesting data on magnetospherically reflected (MR) whistlers observed in the L-range 2.4-2.8, and presented evidence for whistler ducts about 1000 km in width at L~3).

Smith described current VERSIM activities of the British Antarctic Survey group, including the operation of a variety of different broadband and narrowband VLF receivers at the manned station of Halley, and the British AGOs located to the south.

It was agreed not to propose a VERSIM session for the 1999 IUGG Assembly in Birmingham, because of overlap with the URSI Assembly to be held the same year. However, it perhaps would be appropriate to propose one for the following IAGA Assembly in Vietnam in 2001. The chairman undertook to canvas suggestions from the group about this prior to the Birmingham meeting.

VERSIM bibliography

Please send any additions or corrections to
Michel Parrot


Previous editions of this page


The VERSIM Newsletter is published about 1-2 times per year. The latest issue (No. 12) was published in March 1998. 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 M. Parrot; email mparrot@cnrs-orleans.fr

This document is maintained by A.J. Smith and was last updated 31 July 1998.

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