OXFORD MIST 31 March - 2 April 1998
St Edmund Hall

Queens Lane, Oxford

[Report published in Astronomy & Geophysics 39, 3.31-3.33 (June 1998)]

A. Programme B. Report

OXFORD MIST 31 March - 2 April 1998

Tuesday 31 March 1998

Arrival and Registration
M Lockwood (RAL) Opening Remarks

Session 1: - Chairperson: Ian McCrea (RAL)

C J Davis, I W McCrea (RAL) and J Schoendorf (UCL/Boston), An EISCAT investigation of O+ -O collision-cross section using heat balance methods
J Schoendorf (UCL/Boston), Deriving thermospheric oxygen from incoherent scatter measurements
M H Denton, Y Z Su, G J Bailey (Sheffield), K -I Oyama (ISAS) and T Abe (Aoyama Gakuin), High altitude observations of electron temperature and a possible north/south asymmetry
B S Lanchester, M H Rees, K J F Sedgemore, J R Palmer (Soton), H U Frey (Berkeley) and K U Kaila (Oulu), Ionospheric response to variable electric fields in small scale auroral structures
B S Lanchester (Soton), A Otto (Alaska), D Lummerzheim (Alaska), I W McCrea (RAL), K J F Sedgemore and M H Rees (Soton), Patterns of electric fields associated with structured auroral arcs
K J F Sedgemore, B S Lanchester, M H Rees (Soton), T S Trondsen (Calgary), M Lockwood, I W McCrea (RAL), D Lorentzen and J Moen (UNIS), ESR and optical observations of small-scale auroral structure: preliminary results from the January 1998 campaign

Session 2: - Chairperson: Francis Sedgemore (Soton)

P N Smith (Sussex), The Sussex auroral TV Database: An update
M Buchan (Sussex), J V Bogdanova ,V S Semenov (St Petersburg), R P Rijnbeek, P N Smith (Sussex), I W McCrea (RAL), B Holmeslet (Tromsø) and J Kultima (Sodankyla), Characteristics of equatorward and poleward moving arcs in the nightside auroral ionosphere
C F del Pozo P J S Williams (Aberystwyth), K S C Freeman (RAL), P N Smith (Sussex), M Kosch (Lindau), and F Honary (Lancaster), Electrodynamics of auroral arcs from a multi-instrument campaign on 13/14 February 1996
J Semeter (Garching), R Doe (SRI) and D Lummerzheim (Alaska), Auroral energetics inferred from tomographically reconstructed emission profiles
M J Birch (Central Lancashire) and J K Hargreaves (Central Lancashire/Lancaster), Estimation of GPS satellite biases by comparing slant and zenithal observations
K S C Freeman, R F Rosser (RAL), R E Webster (Hallam) and P J S Williams (Aberystwyth), Application of a full profile technique for the determination of the ion-neutral collision frequency from the EISCAT data
R A Bamford and C J Davis (RAL), Ionospheric radio and the UK total eclipse of the sun in 1999
G H Millward, R J Moffett (Sheffield) and A S Rodger (BAS), Modelling the ionospheric response to ion and electron precipitation in the cusp with the Sheffield high latitude model
S E Pryse, L Kersley, A M Smith, I K Walker (Aberystwyth) and J Moen (UNIS), Spatial distribution of the ionospheric plasma in the cusp region

Special Discussion Session

P Cargill (ICSTM), E C Thomas (Leicester) and T Naylor (Keele), The PPARC Astronomical Computing Panel, followed by a group discussion on the implications of the panel for the STP community

Wednesday 1 April 1998

Session 3: - Chairperson: Anasuya Aruliah (UCL)

M Pinnock (BAS), A D M Walker (Natal), K B Baker (JHU/APL), J R Dudeney (BAS), J Rash (Natal), R A Greenwald (JHU/APL), S Kokubun (STEL), D Fairfield (GSFC), J Scudder (Iowa) and N Maynard (Nashua), Nightside ionospheric flow bursts observed during quiet solar wind conditions
M Lester and S Milan (Leicester), Nightside convection during magnetically quiet conditions
D A Neudegg (Leicester), U Auster (Braunschweig), W Baumjohann (Garching), S W H Cowley (Leicester), K -H Fornacon (Braunschweig), E Georescu (Brunswick), G Haerendel (Garching) and T K Yeoman (Leicester), Coordinated SuperDARN and Equator-S observations of the cusp
G Provan, T R Yeoman and S Milan (Leicester), CUTLASS Finland radar observations of the ionospheric signatures of flux transfer events and the resulting plasma flows
H Khan and S W H Cowley (Leicester), Investigation of dayside and nightside ionospheric response delays to changes in the IMF conditions using simultaneous satellite and EISCAT data
J R Taylor, S W H Cowley, T K Yeoman, M Lester, T B Jones (Leicester), R A Greenwald (JHU/APL), G Sofko (Satskatchewan), J -P Villain (CNRS/LPCE), R P Lepping (GSFC) and M R Hairston (Texas), SuperDARN studies of the ionospheric convection response to a northward turning of the interplanetary magnetic field

Session 4: - Chairperson: Mervyn Freeman (BAS)

J Wild and T R Yeoman (Leicester), Eastward propagating transient features in substorm electrojets as observed by the CUTLASS Iceland radar
T K Yeoman (Leicester), T Mukai and T Yamamoto (ISAS), Simultaneous ionospheric and magnetospheric observations of azimuthally propagating transient features during substorms
J K Gauld, T K Yeoman (Leicester), and F Honary (Lancaster), Riometer and HF radar studies of a period of substorm-associated enhanced ionisation
R Balthazor (Sheffield), Magnetic substorms and global circulation patterns
A Aruliah (UCL) and J Schoendorf (UCL/Boston), Substorms and other things, seen through a neutral perspective
H Rishbeth (Soton), I Mueller-Wodarg (UCL) and L Zou (Soton), Vertical circulation and thermospheric composition
A D Aylward (UCL), J Schoendorf (UCL/Boston) and C F del Pozo (Aberystwyth)A new EISCAT-based high-latitude electric field model
D M Willis and R W Norris (Warwick), Fractal dimensions of solar and geomagnetic activity

Session 5: - Chairperson: Tim Yeoman (Leicester)

D M Wright, T R Robinson, P Eglitis and A J Stocker (Leicester), Saturation and hysteresis in CUTLASS backscatter from heater induced plasma density irregularities
T R Robinson (Leicester), Heater generated ULF oscillations at large ranges
T R Robinson (Leicester), SPEAR: Space plasma exploration by active radar
S D Walker and C J Davis (RAL), Automated calibration of EISCAT radar data using the Tromsø Dynasonde
R J Forsyth and A Balogh (ICSTM), The return of Ulysses to equatorial latitudes
G H Jones, A Balogh and R J Forsyth (ICSTM), Radial heliospheric magnetic fields detected by Ulysses
E A Lucek and A Balogh (ICSTM), The identification and characterisation of Alfvénic fluctuations in Ulysses data at mid-latitudes
R I Kilmurray and A Balogh (ICSTM), Examination of the conditions for slow mode shock formation in the heliosphere and an investigation into discontinuities bounding CMEs
A J Smith (BAS), MIST Announcements

Session 6: - Chairperson: Darren Wright (Leicester)

A R Breen (Aberystwyth), W Coles (UCSD), R Fallows, P Moran, C Varley, W Wilkinson and P J S Williams (Aberystwyth), Irregularity scales derived from simultaneous IPS measurements of the solar wind using EISCAT
P Cargill and J Schmidt (ICSTM), Overexpanding CMEs: magnetic field models
P A Chaizy, M A Hapgood (RAL), L J Lanzerotti (Bell Labs), R P Lepping (GSFC), S Kokubun (STEL), R P Lin (Berkeley), J M Bosqued (CNRS/CESR), T R Sanderson (ESTEC), T Yamamoto (ISAS), Influence of spatial variations of the injection and transport conditions on measured scattering strength of measured energetic solar electrons
D R Nunn (Soton), K Baba (Chubu) and M Hayakawa (Chofu), Numerical modelling of VLF Trimpis by 3D Born codes and 2D FEM method - a comparison
A J Smith, M P Freeman, M G Wickett, B D Cox and S Hunter (BAS), On the relationship between the magnetic Pi2 and VLF signatures of the substorm expansion phase
K J Mills, A N Wright and I R Mann (St Andrews), Oscillations in the magnetosphere due to the flow in the magnetosheath
A N Wright (St Andrews), W Allan (NIWA), R D Elphinstone and L L Cogger (Calgary) Phase mixing and phase motion on tail-like auroral field lines
R B Horne (BAS) and R M Thorne (UCLA), Potential wave modes for electron scattering and stochastic acceleration to relativistic energies during magnetic storms
T Clark (BGS), Edmond Halley, the first MIST scientist?
End of Session
Conference Dinner

Thursday 2 April 1998

Session 7: - Chairperson: Chris Davis (RAL)

M J Jarvis (BAS), F -J Lübken (Bonn), G O L Jones (BAS), D C Fritts (Colorado Research), R F Woodman (Peru) and B B Balsley (Colorado), Observing the summer mesosphere at Rothera, Antarctica
V St C Howells, N J Mitchell (Aberystwyth) and H G Muller (Shrivenham), A climatology of gravity waves and gravity-wave/tidal interactions in the mesopause region
N Arnold and T R Robinson (Leicester), Dynamos, dominoes and depletions - the influence of the ionosphere on the Arctic ozone layer
K Stevens (Oaklands), Global Warming: Reality
D Idenden (Sheffield), Modelling the dynamic plasmapause: A preliminary study

Session 8: - Chairperson: Mike Lockwood (RAL)

M A Hapgood and M Lockwood (RAL), Ordering of electron anisotropy in the low-latitude boundary layer
S Szita (MSSL/UCL), Comparison of the magnetic field direction inferred from geosynchronous energetic (40-300 keV) electron data with the Tsyganenko 89 model
G A Abel and A D Johnstone (MSSL), Observations of field aligned electron events in the energy range 100eV to 10keV with the LEPA instrument on CRRES
M W Dunlop, T I Woodward (ICSTM), C J Farrugia (New Hampshire) and H Luhr (Potsdam), Identification of non-planar magnetic structure: use of dual-spacecraft data
N P Meredith, A D Johnstone (MSSL) and R B Horne (BAS), Butterfly electron distributions in the outer radiation belts
I Krauklis, A N Fazakerley, A D Johnstone, A J Coates, G A Abel (MSSL), W K Peterson and S A Fuselier (Lockheed) Preliminary study of the modulation of the O+/He++ density ratio by the IMF Bz component
R Mist and C Owen (QMWC), A statistical analysis of observations of reconnection flows and slow flows in the magnetotail
M K Dougherty and D J Southwood (ICSTM), Magnetic nulls/plasma enhancements in the Jovian and Saturnian magnetospheres
Close and Lunch

Special Discussion Session - Chairperson: Tudor Jones (Leicester)

Open Meeting for users of STP Ground-Based Facilities All researchers using the data from CUTLASS, EISCAT/ESR, IRIS, Ionosondes, SAMNET and WDC are encouraged to attend. Further details will be circulated in advance of this meeting.

Affiliation abbreviations

Aberystwyth: University of Wales, Aberystwyth
Alaska: University of Alaska; USA
Aoyama Gakuin: University of Aoyama Gakuin; Japan
BAS: British Antarctic Survey
Bell Labs: AT&T Bell Laboratories, New Jersey; USA
Berkeley: University of California, Berkeley; USA
BGS: British Geological Survey
Bonn: University of Bonn; Germany
Boston: Boston University; USA
Braunschweig: Technical University of Braunschweig; Germany
Brunswick: ISS Brunswick; Germany
Calgary: Calgary University; Canada
Central Lancashire: University of Central Lancashire
Chofu: University of Electro-Communications, Chofu; Japan
Chubu: Chubu University, Nagoya; Japan
CNRS/CESR: Space Radiation Centre, Toulouse; France
CNRS/LPCE: Laboratory of the Physics and Chemistry of the Environment; France
Colorado: University of Colorado; USA
Colorado Research: Colorado Research Associates; USA
ESTEC: ESA/ESTEC/SSD, Noordwijk; Netherlands
Garching: Max Planck Institute for Extraterrestrial Physics, Garching; Germany
Hallam: Sheffield Hallam University
GSFC: NASA Goddard Space Flight Centre; USA
ICSTM: Imperial College of Science, Technology and Medicine, London
Iowa: University of Iowa; USA
ISAS: Institute of Space & Astronautical Sciences; Japan
JHU/APL: Johns Hopkins University/Applied Physics Laboratory; USA
Keele: Keele University
Lancaster: University of Lancaster
Leicester: University of Leicester
Lindau: Max Planck Institute for Aeronomy, Lindau; Germany
Lockheed: Lockheed-Martin Palo Alto Research Laboratory; USA
MSSL: Mullard Space Science Laboratory
Nashua: Mission Research Corporation, Nashua; USA
Natal: Natal University; South Africa
New Hampshire: University of New Hampshire, USA
NIWA: National Institute of Water and Atmospheric Research; New Zealand
Oaklands: Oaklands Observatory, Derby
Oulu: University of Oulu; Finland
Peru: Institute of Geophysics; Peru
Potsdam: GEC, Potsdam; Germany
QMWC: Queen Mary and Westfield College, London
RAL: Rutherford Appleton Laboratory
Satskatchewan: University of Satskatchewan; Canada
Sheffield: University of Sheffield
Shrivenham: Royal Military College of Science, Shrivenham
Sodankyla: Sodankyla Geophysical Observatory; Finland
Soton: University of Southampton
SRI: SRI, Menlo Park; USA
STEL: Solar Terrestrial Environment Laboratory; Japan
St Andrews: University of St Andrews
St Petersburg: St Petersburg State University; Russia
Sussex: University of Sussex
Texas: University of Texas; USA
Tromsø: University of Tromsø
UCL: University College, London
UCLA: University of California, Los Angeles; USA
UCSD: University of California, San Diego; USA
UNIS: UNIS, Longyearbyen; Svalbard
Warwick: University of Warwick

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OXFORD MIST 31 March - 2 April 1998
Meeting Report

by M J Laird (King's College, London) and N F Arnold (University of Leicester)

Published in Astronomy & Geophysics 39, 3.31-3.33 (June 1998)

With over 100 participants and 60 papers, the 1998 spring meeting, hosted by Rutherford Appleton Laboratory, testified to the continuing health and vitality of the MIST community. In this report, we can do no more than refer to the individual contributions, and endeavour to pick out some of the highlights.

Making use of EISCAT data, Chris Davis had attempted to derive values for the O+-O collision cross-section by equating the heat flowing into F-region ions from hot electrons with that lost to colder neutrals, while Jackie Schoendorf presented a new method, using the ion momentum budget, for measuring atomic oxygen. The EXOS-D (Akebono) satellite had observed electron temperatures at low latitudes at altitudes between 2000 and 4000 km. According to Mick Denton, analysis showed a north-south asymmetry, with higher relative temperatures in the northern hemisphere in the day time and in the southern hemisphere at night.

There followed a number of papers on auroral arcs. In a video-illustrated talk, Betty Lanchester showed how high resolution optical and radar measurements had revealed the presence of large electric fields adjacent to auroral filaments produced by monoenergetic electron fluxes. She went on to present a three-dimensional simulation, whose predictions fitted well with the observations. Further up-to-the minute radar and optical data from a 1998 January campaign, again exhibiting small-scale auroral structure, were shown by Francis Sedgemore. Peter Smith described and illustrated the Sussex auroral TV database, comprising summary data files created by digitising the original video recordings arising from over 1100 hours of observation. Via MATLAB programs, `keograms' can be viewed interactively, and digital `movies', created from the original videos, are also available. Maria Buchan talked about the relative motion between arcs and the background plasma during substorms. Poleward-moving arcs, which occur only during the expansion and recovery phases, often move substantially faster than the plasma, particularly at substorm onset, while equatorward-moving arcs, which may be seen at any time, may move faster or slower. From similar optical and radar data, together with riometer measurements, Carlos del Pozo found a very good correspondence with the E-region ionosphere. On a slightly different tack, but still with the aurora, Josh Semeter introduced a tomographic technique whereby the height distribution of photon emission could be inferred from a set of ground-based monochromatic images.

Moving on to other ionospheric topics, Martin Birch said that, while GPS satellite transmissions offer an opportunity to measure total electron content, uncertainty due to `biases' is a problem. Ken Freeman then described a technique for determining ion-neutral collision frequencies by an iterative technique. Considerable interest was aroused by Ruth Bamford, as she described likely ionospheric effects of the 1999 August 11 solar eclipse, whose path of totality will cross Cornwall. The eclipse `nighttime' will cause the collapse of the D-region, with effects on radio reception, such as increase in signal strength of short wave stations, and at medium wave, intrusion of transmissions from (mainly) Spain. There will be considerable scope for collaboration with the radio communication community, and, indeed, with the general public.

The cusp region is always of great interest, and George Millward presented results from the Sheffield high-latitude ionospheric model, in which the convection path of a single magnetic flux tube was followed. Both electron and ion precipitation were important, with the latter particularly significant at lower altitudes. Eleri Pryse followed with tomographic images, which showed features such as the cusp, and revealed ionospheric signatures of magnetopause reconnection.

The following morning, the emphasis of many of the talks was on results from the SuperDARN network of radars. Mike Pinnock started the proceedings with some observations from the radar at Halley Bay in Antarctica. He showed that during geomagnetically quiet conditions, strong flow bursts, possibly due to a radial orientation of the Interplanetary Magnetic Field (IMF) resulted in a parallel shock condition. Mark Lester, the first of eight speakers from Leicester University, reported an increase in ionospheric scatter in 1997 CUTLASS data compared with the previous year. On 27 November 1997, a clearly defined flow reversal at around 75°N geomagnetic latitude was observed, indicating the boundary of the plasma sheet and the presence of a narrow westward electrojet.

Dave Neudegg provided some early results from the Equator-S satellite magnetometer and was able to map flux transfer events near the magnetopause down to the ionosphere where they were observed by the CUTLASS Finland radar. The energy input from the magnetosphere resulted in the creation of high poleward plasma flows. Gabrielle Provan followed with a statistical study of the distribution of flux transfer events as seen by CUTLASS Finland. The disturbances had a period of around 7-8 minutes with a predominantly westward flow direction, and tended to occur in the pre-noon sector during positive IMF By and post-noon during negative By.

Attention was temporarily transferred to EISCAT radar data by Hina Khan. Measurements of the ionospheric response to changes in the IMF that were first detected by spacecraft stationed sunward of the Earth were used to obtain a daytime delay time between the two instruments of 3-5 minutes. Delays of 6 and 10 minutes were obtained around dawn and dusk respectively. Nighttime delays were of a similar duration but may have been biased by the presence of substorms and related changes in the position of the polar cap. Stan Cowley presented a combination of CUTLASS radar and satellite data to study a flow reversal occurring within a few minutes of a northward turning of the IMF. Recovery to the initial state took place around twenty minutes later, in agreement with earlier theoretical predictions.

Jim Wild continued the Leicester presentations with an examination of an eastward propagating transient disturbance in the plasma convection flow within the CUTLASS Iceland field of view. The observed response of the ionosphere to the expansion phase of the substorm was consistent with that seen by the ground-based magnetometer network. Tim Yeoman went on to discuss this event in the context of processes observed by the GEOTAIL satellite in the magnetotail. Pulsed equatorward flows were measured at the satellite around 150 seconds before the radar signal, while the on-board magnetometer indicated a rotation of the magnetic field rather than a compression. The final CUTLASS presentation came from Jon Gauld. He made use of the riometer at Kilpisjärvi to determine whether observed fade-outs in the backscatter power of CUTLASS were attributable to D-region absorption as expected. However, this explanation was not consistent with the findings of the riometer; re-focussing of the radio waves appeared to be a more likely explanation.

Richard Balthazor presented the effects of magnetic substorm activity on the global circulation at spring equinox during solar minimum as seen by the Sheffield/UCL Coupled Thermosphere Ionosphere Plasmasphere (CTIP) model. Considerable changes to the temperature and wind structure were reported, with perturbations still present 10 hours after the initial disturbance. Anasuya Aruliah then presented observed changes in the thermosphere during and after a magnetic storm. It was clear that the neutral atmosphere was strongly coupled to the plasma through ion drag and ion frictional heating. Also, the thermosphere responded differently to the inputs depending on the extent of the recovery from the previous storm forcing, indicating a measure of inertia in the atmosphere-ionosphere system.

Henry Rishbeth had made use of the CTIP model to study vertical air motions and their impact on the ratio of atomic oxygen to molecular nitrogen and on the NmF2 parameter. At equinox, there was up-welling in the day time and down-welling at night. During solstice, there was a bulk flow of 30 m/s from the summer thermosphere to the winter. Significant departures from diffusive equilibrium raise questions about the reliability of the MSIS empirical model.

A new, EISCAT-based, high latitude electric field model, incorporating fifteen years of observations, was discussed by Alan Aylward. David Willis explained how fractal analysis of time series could provide insights into the underlying physical phenomena under consideration. The technique had been applied to a study of all-sky TV summary data; the typical duration of bursts of auroral intensity for this data-set was 3±1 minutes.

The EISCAT heater in Norway generates field-aligned plasma irregularities using high-power radio waves. Darren Wright described recent experiments in which the heater power was varied: backscatter from the irregularities demonstrated both saturation and hysteresis. Terry Robinson reported that heater-generated ULF oscillations had been observed 1800 km away at Wick. The answer to how they got there might lie in the excitation of resonating field lines. He went on to outline a new proposal named SPEAR (Space Plasma Exploration by Active Radar), with techniques based on the experience from the EISCAT heater. In a final paper on EISCAT, Chris Davis discussed the calibration of data.

After a very successful exploration of the high latitude heliosphere in 1994 and 1995 at solar minimum, the Ulysses spacecraft reached aphelion at 5.4 AU in 1998 April. André Balogh, after a brief survey, reported that during the return from high northern latitudes, the heliospheric current sheet was first encountered at the unexpectedly high latitude of 30°. This was associated with a long-lived active coronal region. At solar maximum in 2000 and 2001, Ulysses will again be in the polar regions. According to Geraint Jones, another feature of the mission has been the observation of nearly radial magnetic fields, whose direction was thus far from that corresponding to the Parker spiral; duration was typically several hours, the maximum being six days. Coronal Mass Ejections (CMEs) had been suggested as a possible cause, but only one case followed a CME. Elizabeth Lucek had used a wavelet analysis of magnetic field and plasma observations to investigate Alfvénic fluctuations, and to relate their occurrence to the location of co-rotating interaction regions. Finally in this group of Ulysses papers, Richard Kilmurray had examined the conditions necessary for the formation of slow shocks, and had found that they were not usually favourable: hence the rarity of such events. As for fast shocks, of 64 CMEs seen, about half had a fast shock at the beginning, about half had one at the end and about one third had fast shocks at both.

Continuing on the inter-planetary theme, Craig Varley reported on scintillation measurements using EISCAT, which had earlier established the existence of both fast and slow streams in the solar wind. He had calculated scale sizes, and found significant differences between the two streams. Peter Cargill had developed magnetic field models for overexpanding CMEs, showing that results consistent with Ulysses observations can be produced by CMEs that have the form of a high density flux rope near the sun. The relatively intense magnetic fields arise because of the different ways poloidal and toroidal fields expand, as found by Parker in 1974. According to Patrick Chaizy, measurements made by the GEOTAIL and WIND spacecraft support the idea that spatial variations of the flux time profile of energetic solar flare electrons can influence significantly the flux time profile measured at one spacecraft and, therefore, the estimation of the scattering strength.

The next topic to be taken up was waves, and David Nunn began by discussing numerical modelling of VLF Trimpis by three-dimensional Born codes (assuming Born scattering) and by two-dimensional finite-element methods. Andy Smith reported a superposed epoch study of four years of Substorm Chorus Events observed at Halley, providing conclusive evidence of their association with the substorm expansion phase onset. The median magnetic field variations with respect to the SCE epoch could be interpreted in terms of the DP1, DP2 and SQ equivalent current systems.

Katie Mills presented an ideal MHD model for the excitation of magnetospheric oscillations by the plasma flow in the magnetosheath. Results suggested that increased solar wind velocity should lead to increased Pc5 power. Andrew Wright then discussed phase mixing and phase motions on tail-like auroral field-lines, making use of a one-dimensional model. Adiabatic processes cannot account for the acceleration of electrons to the relativistic energies observed during magnetic storms. Richard Horne had examined the energies at which different wave modes resonated with electrons, and had identified several possibilities, both inside and outside the plasmapause, for stochastic acceleration.

Toby Clark concluded the day with an historical study of `Edmond Halley, the first MIST scientist?' whose observatory in Oxford was close to the meeting venue. Although best known for his comet, Halley also estimated the height of the atmosphere, and made the first recorded use of contour lines in his chart of the geomagnetic field; the tercentenary of his Atlantic voyages is being celebrated this year by the `Wake of the Paramore' expedition.

To begin the final day, Martin Jarvis spoke on a rocket campaign at Rothera, Antarctica, in which observation of the descent of an ejected sphere gave the density, from which the mesospheric temperature could be deduced. Vikki Howells presented results of a statistical study of the horizontal wind velocity variance in the mesopause region, which showed up the presence of gravity waves. Seasonal effects included minimum activity at the equinoxes, and spectral analysis showed modulation by tides and by planetary waves. Neil Arnold discussed the influence of the ionosphere on the Arctic ozone layer, via modelling studies of changes in the upper mesosphere/lower thermosphere and the extent of the weakening of the upper air jet. During solar minimum, unusually low stratospheric temperatures and ozone concentrations were observed. Long-time MIST supporter Ken Stevens spoke on solar radiation.

Moving on to the magnetosphere, David Idenden described modelling the dynamic plasmapause. Using a time-dependent electric field, he had calculated the paths of a large number of flux tubes backwards in time. Results indicated that structure produced by a disturbance could persist for many days. Mike Hapgood presented an analysis of data from low-latitude boundary layer crossings by the AMPTE-UKS spacecraft, which showed that counter-streaming electrons are well-ordered by the Magnetopause Transition Parameter, and that strong counter-streaming is seen only at energies above magnetosheath electron energies. Sarah Szita showed how data from the geostationary satellite Meteosat P2 could be used to find the symmetry axis of the electron distribution, and hence by inference the direction of the magnetic field. Comparison with model fields indicated that the method is valid, though persistent differences, depending on local time and season, had been identified. More electron observations, this time at the CRRES satellite, were discussed by Gary Abel. Bursts of field-aligned electrons often followed substorm onset and a dipolarisation of the magnetic field, and were associated with oscillatory field-aligned currents and magnetic field perturbations.

Malcolm Dunlop had studied non-planar structures in AMPTE-IRM/UKS data in terms of their characteristic geometrical properties. Statistical methods had been developed which could be compared with the minimum-variance analysis widely used to identify planar structures. A butterfly electron distribution is one which, for given energy, has minima parallel and perpendicular to the ambient magnetic field. Nigel Meredith reported that such distributions were commonly observed at the CRRES satellite, and were correlated with electron cyclotron harmonic rather than whistler-mode wave activity. Ian Krauklis presented a study, using data from a number of satellites, of the modulation of the O+/He++ number density ratio by the interplanetary magnetic field. Three days after a southward turning of the field, an enhancement of He++ had been observed.

Rosalind Mist had compared plasma sheet flow speeds observed at ISEE-3 with the predictions of two models of reconnection, concluding that even at large downtail distances, the flow is more often driven by processes other than reconnection. With a switch to other planets, magnetic null events had been observed by Ulysses in the outer Jovian magnetosphere. Michelle Dougherty had examined earlier Pioneer and Voyager Jupiter and Saturn flybys and found similar events. The nulls were generally associated with large enhancements in plasma pressure, and identified with material breaking off the outer edge of the current sheet, which is a feature of the magnetospheres of fast-rotating planets.

Mike Lockwood drew the meeting to a close by thanking all who had contributed, and especially Janet Foster, the local organiser.

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