[Report published in Astronomy & Geophysics 45, 3.29-3.32 (2004)]
by N F Arnold (University of Leicester) and A W P Thomson (British Geological Survey)
Published in Astronomy & Geophysics 45, 3.29-3.32 (2004)
The magnetosphere, ionosphere and solar-terrestrial physics community gathered with the UK solar community at the Pollock Halls of Residence, University of Edinburgh from 29th March -1st April 2004. The programme was expanded to four days to cater for a day of joint presentations and to reflect the breadth and depth of the science covered.
The first session of the meeting was chaired by the organiser, Alan Thomson (British Geological Survey). Five presentations from Lancaster started the proceedings. Mike Kosch outlined a proposal for a new artificial aurora experiment using VLF-induced particle precipitation via the European Incoherent Scatter radio wave heater. With the correct heater modulation, cyclotron resonance would be induced along the magnetic field lines. Farideh Honary described some experiments using the EISCAT HF facility. The heater waves were scattered from targets at distances of around 6000 - 16000 km along the magnetic field lines, indicating either plasma wave scattering, cusp precipitation or mode conversion.
Mina Ashrafi compared the characteristic energy of precipitating electrons derived from the IRIS high resolution imaging riometer, observations from all-sky auroral cameras, and satellite data. There was good agreement during stable, moderate geomagnetic activity over a seven year period. Roman Makarevitch also used the imaging riometer to observe the drift of cosmic noise absorption structures near the flow reversal boundaries of the ionospheric convection currents in Northern Scandinavia. A possible explanation for the cause of the motion was given.
A chain of riometers was used by Amin Aminaei to study brief, but intense, 'spikes' in the absorption data during geomagnetic substorm events. A statistical analysis related these events to short period pulsations in the magnetometer data. The spikes were associated with X-ray emissions seen by the Polar spacecraft. Stuart Thom (Sheffield) compared extreme ultraviolet observations of plasmaspheric ions made by the IMAGE satellite with those simulated by the Coupled Thermosphere Ionosphere Plasmasphere (CTIP) model. It was found that the midnight plasmapause location was related to the Dst index of geomagnetic activity.
The second session was chaired by Mark Lester (Leicester). Nigel Meredith (Mullard Space Science Laboratory) presented an analysis of data from the CRRES satellite to determine the variability of plasmaspheric hiss with respect to substorm activity. Measuring acceleration and loss of relativistic electrons during these storms, it was found that equatorial and mid-latitude hiss was strongest during geomagnetically active conditions. Andy Smith (British Antarctic Survey) described ground observations of whistler mode chorus waves before, during and after geomagnetic storms. Using a statistical study over a complete solar cycle, the observations suggested that whistler activity during storms contributed to the acceleration of electrons to relativistic energies.
Looking beyond the confines of the Earth, Simon Child (Imperial College) made use of Ulysses spacecraft data going back to 1990 to study the heliospheric current sheet at solar maximum. The high-latitude data used in conjunction with equatorial observations from the ACE spacecraft, suggested a single highly tilted current sheet at this stage in the solar cycle. James Scuffham (IC) described a new model of Mercury's magnetosphere developed in anticipation of the forthcoming BepiColombo mission. The magnetosphere is small and so would have unusual features relating to the closeness of the magnetopause to the surface during strong solar activity.
Jonathan Nichols (Leicester) showed that the inclusion of precipitation-induced enhancements to Jupiter's ionospheric conductivity improved a model of the planet's ionosphere-magnetosphere coupling currents. The outflow of material from Io was shown to feed the auroral oval. Christopher Arridge (IC) introduced a new three-dimensional global model of Saturn's magnetospheric field in anticipation of the arrival of the Cassini-Huygens spacecraft in July 2004 at the planet. The model will be used to assist data interpretation as early as the orbital insertion phase.
The first session of Tuesday was chaired by Richard Horne (BAS) and results from the four Cluster spacecraft featured prominently. Ian Bates (Sheffield) made use of these space probes to study an interval which contained two distinct crossings of the perturbed magnetosheath. An upstream pressure pulse enabled the magnetosphere to overtake the spacecraft for a second re-entry. From these observations, it was possible to compute the properties of the waves. James Wild (Leicester) described simultaneous in situ observations of the signatures of dayside magnetic reconnection at the high and low latitude magnetopause by Cluster and Geotail respectively. Simultaneous observations at both high and low latitudes constrained the source of the magnetic flux transfer events.
A large number of enhanced Earthward moving plasma events were identified by Adrian Grocott (Leicester) during Cluster crossings of the near-Earth inner central plasma sheet. These events were characterised in terms of the prevailing interplanetary magnetic field conditions and substorm phase. Chris Owen (MSSL) examined Cluster-PEACE measurements of electron distributions in and around magnetotail flux ropes in the Earth's magnetotail near substorm onset. These ropes may be associated with travelling compression regions, which in turn may be related to a bulge in the plasma sheet.
Nanan Balan (Sheffield) examined a structured magnetospheric cusp recorded by the Cluster spacecraft during a geomagnetic storm. Three distinct anti-sunward flow events were observed. Relatively large fluctuations along the magnetic field implied strong field-aligned currents. Atousa Goudarzi (Leicester) reported two flow intervals in the dayside cusp region under differing IMF conditions using a combination of space- and ground-based observations. Initial analysis suggested that the flows responded differently in the two hemispheres due to changes in the solar wind.
After the coffee break, Elizabeth Lucek (IC) was in the chair. Hina Khan (Leicester) described satellite observations of a relationship between charge-exchanged neutral atom emissions from the magnetosheath and the appearance of cusp-like signatures in the ionosphere. During strong southward IMF conditions when emissions were high, the SuperDARN radar chain detected an increase in convection current flow speed and backscattered power. Gareth Chisham (BAS) made use of SuperDARN spectral width boundaries as proxies for the boundary between open and closed magnetospheric field lines and compared the results with satellite-derived particle precipitation observations. There was good agreement over much of the dayside and around midnight, but the picture became very confused in the late afternoon.
In the first of two talks by Leicester speakers, Lisa Baddeley described a long-lived, large scale ULF wave that was observed in the dawn magnetosphere using the SuperDARN HF radars and a chain of magnetometers. The event lasted over half a day and coincided with a protracted period of northward IMF, resulting from a solar wind impulse. Matthew Wilson then reported on a statistical investigation of magnetospheric particle precipitation, as measured by the Polar satellite overlying the location of the new SPEAR radar facility. The aim was to determine the likelihood of experiencing favourable conditions for investigating magnetohydrodynamic waves driven by wave-particle interaction. Iain Coleman (BAS) suggested that the macroscopic structure of reconnection at the magnetopause was conditioned by turbulence in the solar wind and the magnetosheath. Superposed on the perfect draping of the IMF on to the magnetopause, there was a strong likelihood that the turbulent spectrum was fractal in nature.
The first joint session of the meeting was chaired by Chris Owen (MSSL). Alan Hood (St. Andrews) presented a review of waves in the solar corona. He described how missions such as SOHO have transformed our understanding of the Sun and how magnetohyrodynamic (MHD) theory can be applied to infer the properties of these waves. Huw Morgan (University of Wales, Aberystwyth) then presented an investigation of oscillations in coronal structures observed by the SOHO spacecraft using wavelet analysis, a few solar radii from the surface. Periodic oscillations of order of a few seconds were shown to exist in a coronal hole, on the quiet Sun and in a streamer. Hannah Scoffield (Leicester) investigated the field-aligned current associated with a large-scale ULF wave, using a combination of CUTLASS HF radar and FAST satellite data. A simple field line resonance model of the wave was created. A comparison of large and small scale field aligned current signatures was carried out.
Richard Horne (BAS) assessed the timescale for electron acceleration by whistler mode waves in the Earth's radiation belts following a geomagnetic storm. He made use of CRRES satellite data to compute pitch angle diffusion rates and found that the time-scale was of order of a day, in good agreement with observations. Also from BAS, Sarah Glauert complemented the previous talk by describing simulations of electron scattering and loss in the Earth's magnetosphere using a new pitch-angle and energy diffusion code. The ability to include any type of wave mode in a cold, multi-ion plasma, reduced the errors at low energies considerably. Whistler mode chorus waves were found to be most efficient at low densities.
Peter Cargill (IC) took the reins for the second joint session of the afternoon. Mervyn Freeman (BAS) carried out a review of magnetic reconnection research into the Earth's magnetosphere and its applicability to solar studies. He highlighted the ability to perform observations both remotely and in situ. As there is no electrical resistance in geospace, sophisticated explanations are needed to account for how reconnection takes place. David Pontin (St. Andrews) followed this up with a presentation on how simulations of magnetic reconnection differ considerably from two dimensional studies with the inclusion of the third spatial dimension. The absence of a unique field line velocity in three dimensions resulted in field lines splitting and reconnecting everywhere within the reconnection region.
Panagiota Petkaki (BAS) considered the relative importance of various kinetic scale effects to magnetic reconnection in addition to MHD processes as wave-particle interactions make an important contribution. The non-linear evolution of the ion-acoustic instability was investigated and found to be three orders of magnitude larger than quasi-linear solutions. Valery Zharkova (Bradford) considered the relative importance of proton versus electron heating in solar flares. Particle-particle interactions were considered for electrons and wave-particle interactions for protons. Heating was found to occur at different altitudes for the two classes of particles.
The first session on Wednesday was chaired by Farideh Honary (Lancaster). Mathew Beharrell (Lancaster) used EISCAT, IRIS riometer and satellite data to examine the ionospheric impact of two large solar flares around Halloween, 2003 on the ionospheric electron density profile. The IRIS instrument detected a strong negative deviation in absorption before a doubling of the electron density occurred. Kathryn Dewis (UWA) discussed the dayside, high-latitude F-region trough under quiet geomagnetic conditions, using a combination of the UWA tomography experiment in Northern Scandinavia and simulations from the CTIP model. Competing processes of solar photo-production, ionospheric convection and particle precipitation under winter conditions were considered.
Henry Rishbeth (Southampton) reflected on the long-standing question of why there is more 'ionosphere' in January than in July. Variations in the Earth's orbit around the Sun were not sufficient to account for the difference. He concluded that conditions in the lower atmosphere may have an important role to play. Martin Jarvis (BAS) presented the first observations of polar mesospheric summer echoes from Halley, Antarctica. An improved dynasonde was deployed just in time to capture the end of the austral summer. The PMSEs observed had similar properties to those seen in the Northern Hemisphere. Martin Füllekrug (Bath) described how networks of magnetometers could be used for remote sensing of the atmospheric electrodynamic environment. Variations in propagation speeds of Earth-ionosphere standing waves related to changes in the conductivity of the global electric circuit.
The session after coffee was chaired by Nigel Meredith (MSSL). Chris Davis (RAL) investigated the possible connection between thunderstorms and enhancements in sporadic E. Such a link would provide important evidence for energy flow between the lower and upper atmospheres and a gradual decrease in sporadic E may be a pointer to changes in the global electric circuit. David Nunn (Southampton) described an ionospheric chemistry relaxation model of the electron density profile that was consistent with observed VLF 'Trimpi' signals. The results compared favourably with satellite-derived electron precipitation estimates, suggesting that these waves can be used as a tool for remote sensing the ionosphere.
David Kerridge (BGS) introduced INTERMAGNET, the worldwide near-real-time magnetic observatory dataset for space weather research and services. Approximately eighty stations provide high quality inputs to the determination of the Earth's magnetic field and inputs to geomagnetic indices. Mark Clilverd (BAS) described efforts to reconstruct the long-term geomagnetic index referred to as 'aa'. To test the robustness of an apparent trend that has seen a doubling of this quantity over the past hundred years, independent stations on continental Europe were used instead of the UK station. The analysis supported the original findings. Susan Macmillan (BGS) explained how a spherical harmonic model of the Earth's magnetic field for 2001 was constructed using ground-based geomagnetic observatory data and measurements from the Řrsted satellite. A clear 26-day periodicity was observed that was linked to variations in the solar wind.
Richard Harrison (RAL) was in the chair for the second afternoon of joint presentations with the solar community. Peter Cargill (IC) conducted a review of Cluster science, three years after launch. He described a number of important breakthroughs relating to the solar wind and the magnetosphere-ionosphere system. Progress had also been made in understanding a number of fundamental plasma physical processes. Andrew Fazakerly and Len Culhane (MSSL) described the evolution of a coronal mass ejection as it made its way from the Sun to the Earth. It was first observed by a fleet of spacecraft including SOHO, TRACE and GOES and radio emissions made it possible to study the shock as it propagated through the interplanetary medium. The shock encountered Cluster and the newly launched Chinese DoubleStar spacecraft and a pressure pulse was experienced for several hours. Both of the spacecraft observed a displaced magnetopause and bowshock.
Richard Jones (UWA) presented EISCAT observations of interplanetary coronal mass ejections using the interplanetary scintillation technique. This data made it possible to determine the solar wind parameters relating to CMEs over a range extending from the Sun to interplanetary space. Cathryn Mitchell (Bath) described ionospheric scintillations at high latitudes as seen by total electron content measurements from Global Positioning Satellites passing over Northern Scandinavia. During the storm of October 2003, an enhanced region of plasma travelling across the polar cap suggested convection from a source at much lower latitudes.
After the interval Alan Rodger was in the chair. Richard Horne (BAS) discussed satellite vulnerability to geomagnetic storms. As total failures are rare, a statistical analysis was carried out on data going back a number of years. The highest risk was found to occur for the six days following a storm and that some manufacturers were more prone to problems than others. Richard Harrison (RAL) discussed the forthcoming International Heliophysical Year in 2007 to mark the 50th anniversary of the highly successful International Geophysical Year. The aim will be to encourage and facilitate large-scale international collaboration to co-ordinate space and ground-based observations.
Robert Bentley (MSSL) introduced the work of the European Grid of Solar Observations. This initiative was set up to provide enhanced access to solar and related datasets from around the world. Barbara Bromage (University of Central Lancashire) reviewed our current state of knowledge about solar cycles and our ability to predict future activity. This work is important for the planning of future satellite missions. An observed lengthening of the cycle indicated a weakening in the intensity in the near future. Nick Walton (Cambridge) updated the community on developments related to Astrogrid - the UK's virtual observatory - and described new capabilities that would be of interest to the MIST and UKSP communities.
In the MIST poster session, Robert Fear (MSSL/UCL) described how the combination of instruments onboard Cluster allowed a range of Flux Transfer Events to be identified and studied from a catalogue of data in 2002-2003. These FTEs are signatures of transient magnetopause reconnection near the cusp region. Tommi Karhunen (University of Leicester) presented a Cutlass multi wavelength frequency study of atmospheric waves in the high and mid latitudes. Using a new mode for the Cutlass radars, atmospheric waves were seen over a thousand kilometres of ionosphere. Scott England (University of Leicester) presented a study of the impact of two different gravity wave parameterisations on tides and background winds in the equatorial middle atmosphere in the UCL CMAT model. Chris Smith (UCL) examined the discrepancy between predicted and measured temperatures in Saturn's thermosphere. A polar heat source representing magnetospheric sources and a global circulation model of the thermosphere were used to investigate the global temperature distribution.
Allan McKay (BGS) described the surface electric field in the UK that results from measured magnetic storm variations. This field drives geomagnetically induced currents (GIC) in the power grid. Electric field and GIC modelling techniques and results were described. Gert Botha (University of Leeds) presented a study into the twenty-seven different interactions between Alfvén, fast and slow magnetosonic waves in a compressible, polytropic, low-beta plasma and defined the sets of resonant wave vectors. Andrew Buckley (University of Sussex) studied short time scale electron behaviour observed by Cluster near magnetic reconnection sites in the tail and at the magnetopause. Beam properties, acceleration, diffusion and electron-wave interactions were examined using measures of the strength of particle interactions and the index of dispersion.
Evangelos Evangelidis (Demokritos University, Greece) considered a thermalised plasma interacting with Alfvén waves and determined the direction of energy flow, given by the wave polarisation, plasma state and relative levels of thermal energy density. David Simpson (University of Sheffield) described the absolute and convective instabilities of a circularly polarised Alfvén wave propagating parallel to an ambient magnetic field using analytical methods. The results were used to interpret measured data from space plasmas. Adam Rees (IC) presented a study on sheath region data formed ahead of fast magnetic clouds in interplanetary space. Some examples of the cross-sectional morphology of fast clouds were given. Nick Achilleos (IC) described magnetic field data obtained from Cassini in Jupiter's magnetosheath, including signatures of field draping about the magnetopause and dynamical magnetosheath plasma downstream of the planet.
Nigel Meredith (MSSL) presented evidence for electron acceleration to relativistic energies by VLF/ELF whistler mode chorus waves during prolonged substorm activity. The most significant electron flux enhancements occurred outside of the plasmapause for long duration events. Mervyn Freeman (BAS) provided a statistical description of magnetic storm re-occurrence, using the Dst index below a certain threshold for a certain length of time. The probability density function was shown to have a dependence on solar cycle phase. Extreme storms were also shown to have no characteristic recurrence time for durations between 1 and 100 hours.
Len Culhane (MSSL) described the development of Grid-compatible tools for handling Solar Dynamics Observatory data, supported by the Astrogrid e-science initiative. Chris Nicholas (IC) presented a time series study of Dopplergrams containing sunspots produced by the Michelson Doppler Imager onboard SOHO. Results were presented that showed the modulation of acoustic power by the magnetic field in the vicinity of sunspots.
The final MIST session of the meeting was chaired by Allan McKay (BGS). Steve Milan (Leicester) presented a simple model of the flux content of the distant magnetotail. The model enabled the profile of open flux within the magnetotail lobes to be determined from the current size of the polar cap and the past-history of low-latitude dayside reconnection. Thus hysteresis in the far tail may be an important determinant for reconnection. Steve Morley (BAS) carried out a comparison of observed statistical properties of substorms with those predicted by a minimal substorm model. The model considered the energy input from the solar wind, the ideal energy state for all boundary conditions and the threshold at which the magnetotail must cross to return to this state. Gary Abel (BAS) described some additional tests of the minimal substorm model. It was found that the distribution of substorm onset times compared favourably with the distribution of a thousand inter-substorm intervals, the question of how the energy accumulated by the magnetospheric system relates to the solar wind state at the time of onset remained.
Kaido Kaal (Lancaster) studied the variations in energetic particle cut-off energies from several polar cap absorption events using data from the IRIS riometer and the SGO magnetometer chain. The results were compared with those predicted by the Tsyganenko model of the Earth's magnetosphere. Alexandra Cran (St. Andrews) considered electron acceleration in the downward auroral current region. Ionospheric electrons were accelerated by a field aligned component of the electric field related to global magnetospheric Alfvén waves. Ohm's law in the form of a current-voltage relationship was determined from the quasi-neutral Vlasov equation.
Peter Damiano (St. Andrews) discussed 2-D hybrid simulations of an Alfvén wave pulse using a self-consistent hybrid MHD-kinetic model. Observations suggested that shear Alfvén waves on the Earth's magnetic field were linked to the formation of auroral arcs. The structure of the electric field in the pulse and plasma frames was discussed with respect to the evolution of the electron distribution function. Finally, Misha Balikhin (Sheffield) presented a fully kinetic theory of magnetic mirror instabilities in a high-beta uniform space plasma, including finite ion Larmor radius effects. This latter term strongly influenced the instability growth rate and threshold. This was due to wavelengths of order the ion Larmor radius affecting the effective elasticity of the magnetic field lines.
The report of the UKSP-only part of the meeting by Lyndsay Fletcher (University of Glasgow) and Robert Erdelyi (University of Sheffield) was published in Astronomy & Geophysics 45, 3.33-3.35 (2004)