by M J Laird (King's College, London) and N G J Gazey (Rutherford Appleton Laboratory)
Published in Q. J. R. astr. Soc. (1996) 37, 605-615
The remaining papers of the session were all on auroral topics, the first, entitled `Do auroral arcs move at the plasma convection velocity?', being presented by N.G.J.Gazey (Rutherford Appleton Laboratory), with co-authors P.N.Smith, R.P.Rijnbeek and M. Buchan (Sussex), and colleague M.Lockwood. Using optical and EISCAT data, the authors had studied the apparent velocities of auroral arcs against background convection as a function of substorm phase. Allowing for the error in velocity estimation from both sources, the results showed that most of the features move through the background plasma faster than the speed at which convection would carry them. These features seem to be associated with substorm growth phases.
Next, B.S.Lanchester (Southampton) spoke on time dependent studies of auroral arc elements using optical and radar measurements, work done with colleague M.H.Rees, H.U.Frey (Max Planck Institute for Extraterrestrial Physics) and K.Kaila (Oulu). She described optical studies with high spatial and temporal resolution, accompanied by high-resolution EISCAT measurements. Detailed modelling showed that the bright narrow filaments are produced by monoenergetic electron beams superimposed on a lower energy Maxwellian background. The result has a direct application to the acceleration mechanisms above the ionosphere.
The concluding paper of the session, on sub-auroral electron bursts, was presented by S.J.Gale (British Antarctic Survey), with colleague M.J.Jarvis, and T.J.Rosenberg (Johns Hopkins). Short-lived (15-20 min) bursts in riometer absorption (1.1-2.8 dB) had been observed near dusk at subauroral latitudes. Originally observed in Alaska using an imaging riometer system, these events had also been seen at Halley and on automated geophysical observatories in Antarctica. They appeared to differ from classic absorption spikes in their latitude, timing and motion.
Following tea came a tribute to the late Sir Granville Beynon from P.J.S.Williams (Aberystwyth). After a brief review of Sir Granville's scientific career, and his close association with Appleton, the speaker referred to his role as an international statesman, including his involvement with the IGY and the IYQS, his presidency of URSI and his crucial part in establishing EISCAT. Sir Granville was a warm, human person, who understood people.
The scientific session, on high latitudes, continued with J.Foster in the chair and A.C.Graham (BAS) speaking on the longitudinal width of the cusp, work done with colleague A.S.Rodger. There had been some controversy in the literature: statistical studies of DMSP data suggested a width of ±2 h of noon, whereas theoretical work, and one case study, showed a possible width of ±4 h of noon under certain conditions. However, it had been difficult to obtain suitable data, because radars of great enough range had not been available. But now the SuperDARN HF radars covering a range of more than six hours of longitude are in operation. Preliminary studies of two days, 1995 February 15/16, showed that the cusp completely filled this range at times.
The next paper, on the nightside subauroral current system during great magnetic storms, was given by M.Watanabe (National Institute of Polar Research, Japan), with T.Iijima (Tokyo) as co-author.The three-sheet pattern for the spatial structure of the large-scale field-aligned current (FAC) system in the Harang discontinuity sector is an oversimplified picture, the actual system being highly variable and complicated. The authors had used magnetic field and precipitating particle data from the DMSP-F7 satellite acquired in great magnetic storms (Dst < -100 nT) and had focused on the relationship between FACs and ion precipitation. From a survey of seven magnetic storms, they had found FAC flowing away from the ionosphere equatorward of the inner edge of the ion plasma sheet in the pre-midnight sector, a morphology different from previous studies.
The programme continued with a paper on determining the dayside reconnection voltage presented by M.Pinnock (BAS), collaborative work with colleague A.S.Rodger, K.B.Baker (Johns Hopkins), G.Lu (NCAR, Boulder) and M.Hairston (Texas). In a case study, the authors had tried to determine the dayside reconnection voltage in conjugate hemispheres. The flow across the noon separatrix was determined by the SuperDARN HF radars at Goose Bay and Halley, and the radar data, together with plasma drift data from the {DMSP satellites, had been used in the AMIE model to evaluate the total cross-polar cap potential. In common with earlier studies, the reconnection voltage given by this technique was bursty in nature, and typically 50% of the total cross polar cap potential. Though the technique is flawed, the observed asymmetry agreed with the dipole tilt, and the flow pattern was as expected.
A.Matsuoka (Imperial College/Institute of Space and Astronautical Science, Japan) spoke on characteristics of magnetospheric plasma flow and particle precipitation during northward IMF (interplanetary magnetic field). Ions originating in the magnetosheath had been observed in association with sunward flow in the dayside polar region during northward IMF and were considered to be injected by high-latitude reconnection. From an analysis of the energy dispersion and the energy-pitch angle relation, their entry was estimated to take place at an altitude of about 10 RE.
M.Lester (Leicester) followed with a paper on convection in the vicinity of the ionospheric footprint of the magnetospheric cusp. He began by pointing out that the new bistatic HF radar, CUTLASS, is well placed to make observations in this vicinity. A special operational mode operated on 1995 August 25, when only the Finland CUTLASS radar was operational. Between 0630 and 0800 UT a well-defined flow shear gradually moved poleward. Ground magnetometer data from Svalbard indicated the development of electrojet signatures in association with this flow shear.
J.Schoendorf (University College, London) concluded the session and the day by speaking on modelling electron densities at high latitudes. With her colleague A.D.Aylward, she had investigated the effect of high-latitude forcing on electron densities calculated by the UCL/Sheffield/SEL Coupled Thermosphere Ionosphere Model (CTIM) by comparing EISCAT CP-3 data to four diurnally reproducible model simulations.These simulations differed only in the placement of the energetic particle distribution and convection pattern, and predicted varying degrees of agreement with the data. Modelled high latitude neutral winds varied substantially among the runs.
The first session on Tuesday morning, chaired by C.J.Davis, was on interplanetary topics and geomagnetism. A.R.Breen (Aberystwyth) presented a paper on EISCAT measurements of the solar wind, the result of collaborative work with colleagues P.J.Moran, C.A.Varley, W.P.Wilkinson and P.J.S.Williams, W.A.Coles, R.Grall and M.T.Klinglesmith (UCSD) and J.Markkanen (EISCAT Sodankyla). EISCAT observations of interplanetary scintillation (IPS) had been used to measure the velocity of the solar wind at heliocentric distances of between 15 and 130 solar radii. Away from transients and interaction regions, two distinct components could be identified, a fast stream with a velocity of ~800 km/s and a slow stream at ~400 km/s, with the slow stream dominating at low latitudes and the fast stream dominating at high latitudes. Comparison with white-light coronograph images allowed stream characteristics to be directly associated with coronal features; the fast streams being associated with coronal holes and the slow with areas of closed magnetic field lines. Going on to the interaction between fast and slow streams, the speaker said that compression regions showed up strongly in the IPS data, whereas rarefaction regions caused little scintillation, and could only be inferred. Observations were consistent with theoretical predictions.
A.Lachin (IC) then spoke on dual spacecraft observations of solar wind flow: Galileo - IMP-8 correlations, with co-authors D.J.Southwood (IC) and M.G.Kivelson (UCLA). Simultaneous measurements of magnetic field data from the two spacecraft were presented, together with a cross-correlation analysis, to study the propagation of structures in the IMF. Convection lags of magnetic field structures had been calculated, and were contrasted with predicted solar wind propagation times to study the variability of the IMF over differing length scales.
The next paper, on magnetic signatures of coronal mass ejections (CMEs) observed by Ulysses, was presented by J.Glover (IC), work done with colleague A.Balogh. In a survey of CMEs, identified in the plasma and magnetic field data and located from the ecliptic to near polar regions, the magnitude, variance and field direction rotation of the IMF had been examined. CMEs were associated with low variance and high but declining field strength. In the majority of CMEs examined, the total rotation of the magnetic field seemed to provide a unique signature.
More analysis of Ulysses magnetometer data was presented by R.Kilmurray (IC), who spoke on searches for slow mode shocks, the co-author being A.Balogh. Compared with the number of fast mode shocks seen, very few slow mode shocks had previously been identified, though certain solar wind regimes should be favourable to their formation. The speaker outlined the differences between fast and slow shocks, and what to look for in the data in order to find and distinguish them. As a result of the searches, it was concluded that slow shocks are rare, and that CMEs have the best chance of generating them.
Turning to geomagnetism, A.Thomson (British Geological Survey) described uses of satellite data in modelling the main geomagnetic field, joint work with colleagues D.Barraclough, T.Clark, E.Clarke and S.Macmillan. Techniques commonly applied to satellite data to isolate the internal component of the geomagnetic field were reviewed, and the significance of ionospheric fields in POGS (Polar Orbiting Geophysical Survey) and Magsat data demonstrated. With a view to exploiting vector magnetic data from the Øersted satellite (to be launched in 1997), a study had been made aimed at providing a better characterisation of the spatial and temporal fluctuations in the main and ionospheric fields, with benefits for main-field modelling.
In the next paper, J.K.Wilson (IC) discussed joint work with colleague V.Moore, and with M.A.Hapgood (RAL) on the diurnal and annual variation of the AE index and the Russell-McPherron effect. The semi-annual variation of geomagnetic activity is well established in various geomagnetic indices. Russell and McPherron had suggested that this is due to the modulation of the southward component of the IMF, predicting maxima on April 5 and October 5, whereas the equinoctial hypothesis required maxima at the equinoxes. The authors' study of the AE geomagnetic index over a 22-year period from 1966-88 showed no semi-annual variation at low thresholds, but some at high threshold, with peaks between March 27 and 30, and between September 29 and October 2, between the equinoxes and the Russell-McPherron predictions. There was no distinct summer minimum. The evidence most favoured the Russell-McPherron suggestion.
The final paper of the session, given by M.A.Clilverd (BAS) and co-authored by E.Clarke and T.Clark (BGS), was entitled `Long-term change in the solar-terrestrial climate?'. Modern sunspot observations now cover nearly 250 years, systematic records of magnetic storms are available for 130 years, and ionospheric sounding data for 60 years. Study of the aa index (started in 1868) suggests that long-term changes have taken place in the occurrence of storms, particularly at solar minimum, where there has been an increase. Surveying possible reasons, the authors had concluded that changing solar activity was much the most likely; ionospheric influence was small, and in the opposite sense, and magnetospheric effects, arising from the continuing decrease in the main geomagnetic field strength, though difficult to quantify, were also small.
After coffee, T.Clark took the chair for a session on the thermosphere, the opening paper being on tests with a new Fabry-Perot interferometer (FPI) configuration at Kiruna, presented by I.McWhirter (UCL), joint work with colleagues N.P.Meredith, J.Percival, D.V.P.Wade, A.L.Aruliah and A.D.Aylward. The interferometer included a new type of CCD detector, and initial trials using this instrument for making measurements on the OH layer near the mesopause were very encouraging. Tests also demonstrated the ability to measure neutral temperature as well as neutral winds.
The next speaker, A.L.Aruliah (UCL), discussed problems in the derivation of neutral winds from plasma flows at high latitudes, the co-authors being A.D.Aylward together with C.J.Davis (RAL). The problems, highlighted by disagreement between EISCAT and FPI values for neutral winds, may in part be due to the unfavourable radar viewing geometry at high latitudes, where the large inclination of the geomagnetic field leads to poor resolution of horizontal wind components. In addition, significant vertical winds may be present in the auroral regions, and it was also suggested that the value used for the O+ - O collision frequency may be in error.
There followed a paper on simulations of tides propagating upwards from the mesopause, using a modified version of the UCL/Sheffield/SEL thermosphere-ionosphere model given by I.Mueller-Wodarg(UCL). The model had recently been modified to allow the input of parameterized tidal oscillations at its lower boundary at an altitude of 80 km. The speaker presented details of the changes to the model, together with simulations of semidiurnal tidal modes and their influence on temperatures and winds in the thermosphere and ionosphere.
M.J.Jarvis (BAS) then discussed QBO effects in the Antarctic lower thermosphere. After 38 years of continuous operation by the UK, the operation of Argentine Islands Geomagnetic Observatory at Faraday Research Station has been passed over to the Ukraine. In this long term dataset, a quasi-biennial oscillation (QBO) in the semidiurnal component of the SQ range had been observed, indicative of modulation of the upward propagating semidiurnal tide by the QBO in stratospheric zonal winds. The 27-month peak could be compared with the 27-month periodicity reported near the equator.
The next speaker, H.F.Parish (Leicester) provided evidence of gravity wave structures in CUTLASS radar measurements, joint work with colleagues T.R.Robinson, T.B.Jones and A.J.Stocker. Initial studies of ground backscatter measurements from the CUTLASS and other SuperDARN radars had shown that waves with large spatial scales and periods in the range 1-3 h were frequently present in the data. These periods and spatial scales were consistent with TIDs caused by thermospheric gravity waves. The strongest effects were at times of low geomagnetic activity.
To end the morning, R.L.Balthazor (Sheffield) presented results of an investigation of the effects on the low-latitude ionosphere due to the interaction of atmospheric gravity waves (AGWs) propagating equatorially from both hemispheres, the co-author being colleague R.J.Moffett. The Sheffield/UCL/SEL coupled ionosphere-thermosphere-plasmasphere model had been used to simulate the production and propagation of AGWs created simultaneously at magnetically conjugate latitudes, the waves crossing at the equator. It was found that AGWs drive TIDs towards the equator, that the waves interfere as they cross, and that the AGW passes underneath and `loses' the TID.
M.A.Clilverd took the chair for the first session of the afternoon, the topic being the ionosphere. C.J.Davis (RAL) talked about the latest developments with the EISCAT Dynasonde data archive at RAL. Dynasonde data from 1992 November are available on-line, and this facility, together with the required analysis software, enables EISCAT users to analyze dynasonde data remotely. Examples shown included mesospheric echoes observed with the Halley Dynasonde.
To follow, R.Stamper (RAL) spoke on improved prediction of the I(F2) and I(G) ionospheric indices. Since 1982, the World Data Centre C1 for Solar-Terrestrial Physics has predicted these indices using an adaptation of the McNish-Lincoln technique for predicting sunspot numbers, but these predictions are sometimes inaccurate. The speaker showed how significantly more accurate predictions could be obtained using artificial neural networks, in which past data is used to provide iterative training from a random initial state.
P.R.Field (Southampton), with colleague H.Rishbeth , spoke on the response of the ionospheric F2-layer to geomagnetic activity, using 20 years' data from 53 ionosondes. The disturbed/quiet ratio of NmF2 shows consistent latitudinal patterns, NmF2 being enhanced in winter as compared to equinox and summer. The results compare well with ESRO-4 data, and with atomic/molecular ratios from the MSIS-90 model, and with results from the CTIM computational model; they support the `composition change' theory of F2-layer storms. There is however a long-term effect, in that the disturbed/quiet ratios have different mean levels in different sunspot cycles.
There followed two papers on ionospheric tomography. The first, on ionospheric tomography in Antarctica: first results and comparison with dynasonde observations, was given by J.A.T.Heaton (Aberystwyth), joint work with colleague L.Kersley, and with G.O.L.Jones (BAS). Two receiving systems had been deployed, at Faraday and Halley, to monitor NNSS signals. In spite of the poor geometry, the receivers not being at the same longitude, tomographic images showed reasonable agreement with independent observations of the vertical electron density profile measured by the dynasonde at Halley. An example of a deep trough imaged by the technique illustrated the potential of tomography for studying an extended spatial region of the ionosphere over inhospitable terrain.
In the second, M.J.Williams (Aberystwyth) spoke on the polar cap ionosphere in mid-winter imaged by tomographic techniques, the co-authors being L.Kersley and S.E.Pryse. Images were presented from an experimental campaign carried out in 1994 December on Svalbard. Measurements of the ionospheric electron content had been made using the differential carrier phase technique by monitoring NNSS signals at Ny Ålesund and Longyearbyen. A second campaign, involving additional stations, had taken place in 1995 November. In the polar cap, convective flow dominates, and the large-scale structures of the images were interpreted in the light of convective flow patterns.
`Butterflies and sunspots: non-linear dynamical control of the atmosphere' was the intriguing title of the last paper of the session, by N.Arnold (Goddard Space Flight Center) and the presenter, T.R.Robinson (Leicester). The influence of a butterfly's wings on the weather in New York has become a common-place, due to the work of Lorenz. What is less well understood is how solar activity might affect climate. The direct impact on the thermosphere can be very large, but this has been found to tail off rapidly as one goes to the surface. The speaker presented some new three-dimensional models which suggested that tropospherically generated planetary waves may have a role to play in transmitting the information about the thermosphere to the rest of the atmosphere.
The final session of the day, chaired by D.M.Willis, began with short discussions of the relationship between MIST and the R.A.S. and between MIST and the Joint Association for Geophysics, introduced respectively by P.J.S.Williams and R.B.Horne. The first scientific paper of the session was given by D.J.Southwood (IC), who presented new results from Jupiter, obtained from the Hubble Space Telescope and from Galileo. From the telescope, aurora could be seen and, well equatorward, a patch of activity identified as the magnetic footprint of Io. Galileo magnetometer measurements could be compared with those made by Pioneer 10 in 1974. There were considerable similarities in the data, except that the outer Jovian magnetosphere as observed by Galileo was much bigger.
More features of Jupiter were presented by N.F.Laxton (IC) in a paper on the first-order anisotropy of ~1 MeV ions in the Jovian magnetosphere during the Ulysses flyby: flux gradients and plasma flows, joint work with colleagues A.Balogh, R.J.Forsyth, R.J.Hynds and K.Staines, and S.W.H.Cowley (Leicester). The first-order anisotropies can originate either from plasma flows or flux gradients transverse to the ambient magnetic field; their relative contributions can be estimated by examining the energy dependence, yielding separate measurements of bulk flows and flux gradient scales. Anisotropy Telescope data obtained during the Ulysses flyby of Jupiter showed that at ~1 MeV, flow anisotropies dominate in the outer magnetosphere, while gradient anisotropies dominate in the middle magnetosphere current sheet.
Magnetic field signatures resulting from the sudden expansion of a flux shell in a rapidly rotating magnetosphere were discussed in the next paper, by the presenter, C.F.A.Lofting, M.K.Dougherty and D.J.Southwood (all IC). The time variation of the signatures had been investigated by means of a model developed from first principles. The development of azimuthal lag of the field lines from corotation at the equator, as well as the provision of torque transmitted by an Alfvén wave from the planet to accelerate the field lines back to corotation, had been examined.
The day's proceedings concluded with a discussion of the current and future programmes, facilities and data needs of UK ground-based STP research, chaired by T.R.Robinson.
The first session on Wednesday, on balloon and radar studies of the high latitude ionosphere and chaired by A.Brekke, was devoted to polar cap convection with many new CUTLASS/SuperDARN results from the Leicester team. To begin, A.Kadokura (NIPR) reported collaborative work, with nine co-authors, on measurements of convection velocity enhancements measured with antarctic stratospheric balloons and magnetometers at the conjugate points along the west coast of Greenland. These occurred in response to a southward turning and strengthening of the IMF.
J.R.Taylor (Leicester) presented some of the first SuperDARN convective flow results, joint work with colleagues M.Lester and T.K.Yeoman. In two cases they showed how strong anti-sunward convection surges across the northern pole established noticeable convection patterns after periods when no obvious flow pattern was discernable. In the first case, during southward IMF, a two cell convection pattern was induced following a sudden impulse, and in the second, a three-cell pattern followed a northward turning in the IMF.
T.K.Yeoman (Leicester), with H.Luehr (Braunschweig) as co-author, continued with SuperDARN/CUTLASS images, which showed up short (4 min) equatorward flow bursts during a substorm growth phase, well correlated with increases in local By. The flow pattern fitted a scheme wherein two FACs spaced several hundred kilometres apart give rise to a `Hall vortex'. The bursts of flow may be due to bursty reconnection although discussion revealed that such signatures have been seen outside of a substorm interval.
A.G.Hart (Leicester) presented a statistical study of high latitude patches, joint work with T.K.Yeoman. These are seen to occur predominantly in the morning sector (0600-0700 in the winter; 0500-0600 in the spring and autumn; none in the summer). This distribution may be skewed by unknown HF propagation effects. The presence of patches seems to require a definite IMF By orientation and a prior period of southward IMF Bz.
G.P.Holdsworth (Leicester) reported on a study of 13 years of EISCAT CP-3 data aimed at determining useful latitudinal length scales in the auroral zones, the co-author being M.Lester. They obtained the following results for a scale length (SL) defined as the latitude over which NmF2 changed by 10%: SL is largest between 68 and 70° Lat, falling towards the pole; SL is largest around midday (6-10 UT); and larger in the winter than the summer due to a solar zenith dip angle dependence; the summer increase on SL is modulated by sunspot number. SL ranges between 0.5° Lat (winter) and 2.5° Lat (summer).
D.W.Idenden (Sheffield) described results from the time-dependent high-latitude Sheffield/UCL/SEL convection model, joint work with colleagues R.J.Moffett and S.Quegan. Simulated density patches formed around local noon by the application of rapid electric field changes at the `throat' of the convection pattern drift across the polar cap towards the nightside leaving a density depletion in their wake. The patches begin to lag behind the flux tubes on which they began their journey. Taking all terms of the diffusion equation into account there is net upward diffusion out of the tube.
To end the session, S.E.Milan (Leicester) discussed the seasonal variation in the first 10 months of CUTLASS data from 65-89° N. During the winter, autumn and spring, backscatter is obtained from farther ranges than during the summer. In all cases, increased magnetic activity leads to reduced HF backscatter.
The second session, A.R.Breen in the chair, was on waves and plasmas, and followed a description by A.Brekke (Tromsø) of UNIS on Svalbard where university students can spend a year studying atmospheric/space physics and gain credit in `EU equivalent points'. He concluded with a call for those in the audience to consider spending periods of time at UNIS as teachers or visiting scientists.
Extending previous work showing that electromagnetic ion cyclotron (EMIC) waves can heat O+, R.B.Horne (BAS), in work done with R.M.Thorne (UCLA), discussed how heated He+ distributions observed in the outer magnetosphere by AMPTE may also be the result of heating by EMIC waves, either at the H+-He+ bi-ion resonance frequency or at the second harmonic of the He+ gyrofrequency. Energy gained by the wave from the H+ population is dumped into the He+ population over a very small range of latitudes.
M.A.Balikhin (Sheffield) presented a paper on LF turbulence at quasi-perpendicular shock fronts, collaborative work with T.Dudok de Wit (CNRS), S.N.Walker and L.J.C.Woolliscroft (Sheffield), W.Mier-Jedrzejowicz (IC) and W.Baumjohann (MPI-XTP). Ruling out instabilities related to reflected ions, he instead invoked non-linear waves, also observed in AMPTE data, propagating upstream and downstream from the shock region.
D.J.Southwood (IC) discussed Alfvén waves and turbulence in the magnetosheath. After the discovery of distinct regions of pure uni-directional Alfvén waves in the flanks of the magnetosheath at 2 min resolution, he reported similar Alfvén structure on much shorter time scales (12 s) propagating away from the Sun.
A.J.Smith (BAS) and co-authors M.P.Freeman (BAS) and G.D.Reeves (LANL), using VLF Substorm-related Chorus events (SCEs), which are produced at about L=4 on the nightside (2300-0600) and are associated with substorms, find that they can infer substorm frequency values similar to those previously quoted by Kamide and Borovsky, allowing for the small longitudinal viewing window of the antarctic station. However, the distribution of inter-substorm times is different to that measured via particle injections at geostationary orbit, with the mode lying nearer 1 h than 2-3 h.
M.A.Clilverd (BAS), in joint work with R.B.Horne, showed data and simulation results that indicate that whistler absorption is much stronger at high L-values than at low ones. This absorption can be attributed to cyclotron resonance of the waves with energetic plasmaspheric electrons. Ground based observations therefore can be used to estimate plasma density in the plasma sphere between 1 and 40 keV.
G.E.Bond (Leicester) presented the results of an ionospheric heating experiment in which CUTLASS was used as an additional diagnostic to the EISCAT radar and a local TX/RX pair, work done with colleagues T.R.Robinson, A.J.Stocker and P.Eglitis. No diagnostic measured the signature of an X-mode heating wave, only O-mode waves. CUTLASS backscatter was observed over the heater beam in a cone of about 20°.
In the last paper of the session, R.J.Moffett (Sheffield) compared results from the Sheffield circulation model with O+, H+, He+, and electron and ion temperature profiles up to 2000 km from Arecibo, collaborative work with colleagues B.MacPherson and G.J.Bailey, and S.Gonzales (AIO). While photoelectron heating is well modelled up to about 600 km, there is as yet little way of simulating the observed structure above that.
P.R.Field took the chair for the final session, on the high-latitude magnetosphere and ionosphere. P.N.Smith (Sussex), stressing the need for coordinated optical observations in future, presented details of a sensitive new all-sky camera combining fast `telecentric' optics and state-of-the-art intensifier technology. The instrument includes narrow band interference filters for observing at different wavelengths.
G.R.Lawrence (Sussex) presented a simulation code that models reconnection using a `reconnection' coordinate transformation in which flux tubes can be simply represented as strings, the co-authors being R.P.Rijnbeek, and V.Semenov (St Petersburg). Resistivity, which ultimately allows for reconnection, is included only on very local scales so as to maintain simplicity in the representation.
K.J.F.Sedgemore (Aberystwyth) presented plasma velocity estimates obtained by combining Doppler velocities from digital ionosondes, work done with colleague P.J.S.Williams, G.O.L.Jones (BAS), and J.W.Wright (U Wales). The estimates give good agreement with EISCAT estimates when conditions are not active, even down to gravity wave signatures. The agreement in eastward component of Vperp is much better than that in the northward component due to complicating structure that moves preferentially in the NS plane.
C.F.del Pozo (Aberystwyth) presented results of a comparison of (hard, >25 keV) electron fluxes measured by the low-altitude satellite SAMPEX and electron fluxes derived from EISCAT-measured electron density profiles, collaborative work with I.W.McCrea and D.M.Willis (RAL) and M.Looper, J.B.Blake and P.Anderson (Aerospace). The agreement is reasonable above 95 km where ion dynamics are less complicated. Uniformity of precipitation seems to be more important than the closeness of the satellite.
D.M.Willis, with co-authors M.Beech, V.N.Davda, K.S.C.Freeman and I.W.McCrea (all RAL), discussed his code for calculating the error envelope when tracing along the Earth's field. In this talk, he focussed on field line mapping from low-altitude satellites, which find themselves within the domain of the Earth's internal field, back to the Earth. He concluded that the major sources of error are the specification of the Earth's field itself and the uncertainty in the satellite's position.
A.M.Hall (RAL/Leicester), with co-workers C.H.Perry and M.Grande (RAL), M.Lester (Leicester) and B.Wilken (MPAe), had investigated whether substorm onset depended on plasma sheet composition by examining the variation in composition of substorm injections measured by the CRRES satellite. Injections ranged from L=5 to L=8. The numbers of those dominated by solar wind He2+ depended on the time spent in a region by the satellite. This was not the case with the smaller number of O+ dominated injections which were spread over a smaller latitude range centred on the magnetic equator.
K.S.C.Freeman (RAL) discussed measurements of ionospheric electric current and joule heating using EISCAT data and employing various models of the neutral atmosphere and the ion-neutral collision frequency, joint work with colleagues S.Williams and S.Crothers, and P.J.S.Williams (Aberystwyth). Inclusion of FPI neutral wind velocities was discussed.
The meeting ended with thanks to all speakers and contributors, session chairmen (most of whom had past or present associations with Southampton), the local organizer, H.Rishbeth, and the MIST co-ordinator A.J.Smith.