[Report published in Astronomy & Geophysics 43, 3.27-3.31 (2002)]
[See below for the report of the UKSP part.]
by N F Arnold (University of Leicester) and G J Bailey (University of Sheffield)
Published in Astronomy & Geophysics 43, 3.27-3.31 (2002)
The magnetosphere, ionosphere and solar-terrestrial physics community gathered at the Tapton Hall of Residence, University of Sheffield from 9-11th April 2002. For the first time MIST was held jointly with the UK Solar Physics meeting.
The first session of the meeting was chaired by the organiser of Steel MIST, Roy Moffett (Sheffield). He introduced Rod Heelis (Dallas, Texas) who had examined ion and neutral drifts in the polar upper atmosphere in response to solar drivers. He reported that ion motions were perturbed significantly faster than the neutrals. These results were consistent with those expected from ion/neutral collision times. Chris Wilford (Sheffield) compared the concentrations of singly charged helium in the plasmasphere, as observed by the Arecibo incoherent scatter radar at Puerto Rico, with data from satellite overpasses and numerical modelling studies. A night-time layer formed at around 800 km that could be reproduced in the model provided realistic thermospheric temperatures were used.
The history of the thermosphere and ionosphere prior to the onset of a magnetic storm was found to be highly significant when examining the response of the upper atmosphere to substorm activity, reported Anasuya Aruliah (University College London). Her study included observations from a Fabry Perot Interferometer and an incoherent scatter radar data in Northern Scandinavia. Henry Rishbeth (Southampton) used AE-C satellite measurements of the O/N2 ratio in the Earth's thermosphere to test the circulation theory that there should be enhanced zones of atomic oxygen concentration at high mid-latitudes in the winter, coinciding with high electron density levels due to upwelling vertical winds. The evidence seemed to be supportive of the theory.
FPIs in the auroral zone and the polar cap were used by Eoghan Griffin (UCL) to measure thermospheric temperatures under a wide range of geomagnetic conditions. Current empirical models were found to be unsatisfactory for disturbed conditions, predicting values several hundred degrees lower than those observed. Michael Denton (University of Wales, Aberystwyth) discussed the phenomenon of the 'tongue-of-ionisation' whereby high density plasma is drawn over the polar cap by ionospheric convection. Asymmetries in the Interplanetary Magnetic Field strongly influence the evolution of such features. Both model and ionospheric tomography measurements agreed well, so hypotheses regarding their generation and development could be tested. Nanan Balan (Aberystwyth) reported simultaneous mesosphere-thermosphere-ionosphere observations of several magnetic storms using various radars, optical imagers and a network of 1000 GPS receivers distributed around Japan. A rare low mid-latitude aurora was observed on 31st March 2001. The storm reversed the direction of the winds at a range of altitudes.
The second session of the first day was chaired by Alan Aylward (UCL). His colleague, George Millward (UCL) presented results from a global three-dimensional model of Jupiter's coupled ionosphere and thermosphere. In particular, the atmospheric response to electron precipitation within the high-latitude auroral region was highlighted. Auroral ionospheric conductivity was strongly non-linear with respect to the incoming electron energy. Scott England (Leicester) suggested that there was evidence of a correlation between indices of solar variability and long-term climate change. By using results from two-dimensional zonally averaged models, and by modulating the effects of solar forcing, the way in which these changes couple into the global climate system were illustrated and briefly discussed.
Chris Davis (Rutherford Appleton Laboratory) presented results from an investigation of the effects of ion velocity variability on the Joule heating using tristatic velocity measurements from the EISCAT UHF radars. A recent study of the fine-scale structures associated with the presence of Noctilucent Clouds and Polar Mesospheric Summer Echoes in the high-latitude summer mesopause region was described by Eivind Thrane (NDRE). It was shown that the observed PMSEs must be caused by small-scale fluctuations and/or gradients in the D-region electron density.
By using the discrete periodic inverse scattering transform method, Julia Rees (Sheffield) presented results from a non-linear spectral analysis of the far-field effects of a simulated disturbance in the auroral region. She showed that the largest wavenumber and dominant TAD (Travelling Atmospheric Disturbance) mode is a soliton. Peter Younger (Bath) investigated the 8-hour mesospheric tide using observations from an all-sky VHF meteor radar in Sweden. The tide was a persistent feature of the Arctic atmosphere and the day-to-day variability of the amplitude of the tide was large with a clear seasonal variability.
Neil Arnold (Leicester) provided observational evidence of a systematic reduction in gravity wave fluxes in the mesosphere and lower thermosphere from solar minimum to solar maximum. Three-dimensional model simulations suggested that this change could significantly enhance the coupling that exists between the solar variability and the winter stratosphere due to planetary wave activity. Using observations of tides made in the mesosphere/lower thermosphere region, Nick Mitchell (Bath) presented results of comparisons with the tides obtained by the Global Scale Wave Model. The results showed good agreement with the amplitude and phase of the 24-hour tide, but significantly larger amplitudes than predicted in the case of the 12-hour tide in summer at high latitudes. Modulation of the tides by planetary waves was strong for the 10-day and 16-day waves in summer.
High-power microwaves were used to generate artificial ionised regions (AIRs) in the atmosphere according to Nicholas Borisov (Lancaster/IZMIRAN). The plasma concentration in these regions could be several orders of magnitude greater than the maximum natural plasma concentration. Several applications of AIR were described. Martin Jarvis (BAS) reported how an iron resonance lidar, designed to study the summer mesopause region, was being prepared for deployment in Antarctica early next year. The lidar's capabilities and objectives were described.
The chairman of the first session of the second day was Hugo Alleyne (Sheffield) and he introduced seven papers related to the four CLUSTER spacecraft. Ian Bates (Sheffield) investigated the properties of magnetosheath waves observed by CLUSTER. Previous estimates of the wave dispersion relationship obtained essentially linear measurements. Now it was possible to use minimum variance analysis. It was found that the waves propagated almost parallel to the bulk ion velocity and at similar speeds, indicating the presence of mirror waves. Malcolm Dunlop (Imperial College, London) examined magnetopause crossings to study the structure of the boundary layer and the dynamical response to external forcing. Using data from the CLUSTER discontinuity analyser, it was possible to determine the thickness of the boundary, its orientation and the behaviour of trapped waves. Jonathan Eastwood (IC) also used minimum variance analysis to study the direction and orientation of Ultra Low Frequency waves in the terrestrial foreshock. The velocity, wavelength, field alignment and relationship between magnetic field and plasma density were consistent with magnetosonic waves.
Attempts using CLUSTER to find large scale structures within quasi-parallel shocks were described by Elizabeth Lucek (IC). It was found that when the orbital configuration resulted in separations of 100 km, then spatial correlations were high but this agreement deteriorated markedly out to 600 km. Ian Krauklis (Mullard Space Science Laboratory) used data from the PEACE particle detectors on board CLUSTER to identify the different regions of the magnetosphere and their variations with changing Interplanetary Magnetic Field conditions. It was found that the peak velocity of the plasma motions was taking place in the boundary layer rather than the cusp.
Matthew Taylor (MSSL) combined observations from a number of particle detectors on CLUSTER to perform a case study of a magnetospheric cusp crossing. The orbit took the spacecraft along the magnetosheath boundary for some time, resulting in multiple transitions into different particle energy population regions of the magnetopause. CLUSTER observations of quasi-electrostatic subshocks during a shock front crossing in March 2001 were analysed by Misha Balikhin (Sheffield). He found that spikes in the electric field corresponded to ramps in the magnetic field during these shocks, suggesting that this spike induced the non-linear change in the magnetic field.
Ulysses results were reported by the final two speakers of the session. Adam Rees (IC) studied the magnetic clouds that were sometimes associated with coronal mass ejections (CMEs). During the fast part of the spacecraft's orbit, Ulysses travelled between the two heliospheric poles in a year to obtain a 'snapshot' of the heliosphere. There was a clear hemispheric dependence on the East / West orientation of the magnetic cloud axis that was confirmed at high latitudes. Jonathan Gloag (IC) was interested in the characteristics of weak interplanetary shocks. Unlike strong shocks, the theory of magnetohydrodynamics appeared to be less applicable. The shocks' behaviour in terms of high frequency wave distributions could often resemble non-shock disturbances.
After coffee, Ian Mann (York) took over the chair. Observations from IMAGE satellite data and a Northern European magnetometer network were combined by Zoë Dent (York) to study the magnetospheric plasma and electron densities during a magnetic storm. It was possible to examine the plasmaspheric dynamics of depletion and refilling and the local variations in the heavy ion production during a storm. Lisa Baddeley (Leicester) made use of the Doppler shift of the ionospheric reflection layer measured by HF radar to resolve high wavenumber ULF waves. These disturbances were related to wave-particle interactions, and distinct population enhancements at particular energies in satellite ion detectors made it possible to infer the resonance mechanism.
Three more papers from York began with Louis Ozeke. He described how one quarter wavelength harmonic resonances in the Earth's magnetic field could be sustained provided that asymmetric conductivities existed in the nodes within the ionosphere. Such conditions have been shown to occur when only one node is in daylight. An example of such a phenomenon was presented using two conjugate magnetometers. David Milling described a rare observation of a long duration, quasi-monochromatic disturbance recorded by a magnetometer station at an exceptionally low latitude. Normally, such phenomena are associated with the auroral zone and the possibility of drift-bounce resonant driving with energetic ions was considered. Paul Abernethy combined coherent VHF radar observations of ion flows in the E-region of the ionosphere with Northern European magnetometer network data to monitor the development of travelling convection vortex current systems. Several theories that related this ionospheric footprint to disturbances deep in the magnetosphere via upward and downward field aligned currents were discussed.
Emma Woodfield (Leicester) assessed the effectiveness of the Doppler spectral width parameter generated by the SuperDARN HF radar network as an ionospheric proxy for the open/closed magnetic field line boundary. From three years of data it was noted that there were distinct seasonal and magnetic local time variations in the regions with enhanced spectral widths. Sophie Cash (Leicester) described how ULF waves that were generated by artificially heating the ionosphere could be observed by the FAST satellite. Numerical calculations revealed that a linear process of electron acceleration by parallel electric fields was sufficient to account for the observed energy-dispersed downward electron fluxes.
Throughout the last two days of the meeting a number of posters were displayed. Iain Coleman (BAS) presented results from a multi-spacecraft study of the draping of the Interplanetary Magnetic Field lines around the Earth's magnetosphere. Northward IMF leads to much more variability, especially at high latitudes but also in the flanks. A multi-instrument study of the dynamics of auroral forms and absorption patches during substorm activity was described by Carlos Del Pozo (Lancaster). Optical features tended to be narrow and followed the magnetic field lines closely, whilst riometer absorption was more patchy. There was also a time delay between optical and absorption features. Observations of the formation of artificial aurora using the EISCAT HF heater were outlined by Mike Kosch (Lancaster). Atomic oxygen emissions were field-aligned and well below the reflection height of HF waves.
Mike Pinnock (BAS) displayed a study of the location and rate of dayside reconnection during an interval of southward IMF. The total cross-polar cap potential during the event was observed to be in the region of 150 kV. Martin Jarvis (BAS) described the use of riometers to observe gravity waves in the mesosphere. These waves were found to be well correlated with data from the Halley airglow imager. The former had the advantage of working during day time.
After lunch a joint session between the MIST and solar physics communities took place. Three invited review papers were chaired by Alan Rodger (BAS) to introduce each community to the work of the other. Shadia Habbal (Aberystwyth) discussed the solar wind at solar maximum and its origin at the Sun. Ian Mann (York) described magnetohydrodynamic waves in the magnetosphere and their role in energy transport and dynamics. Andy Breen (Aberystwyth) explained how radio scintillation measurements could be used to untangle structures in the inner heliosphere.
A session on the Grid and its application to MIST and Solar research preceded "Where do we go from here?" - a discussion session chaired by Peter Cargill (IC). Alan Rodger introduced the ongoing ten-year solar system review that will report back to PPARC this year to recommend future priorities and highlight excellence in current science. Len Culhane (MSSL) outlined solar aspects of the International Living with a Star programme and its links to ESA. Mark Lester (Leicester) focussed on MIST aspects of ILWS.
Andy Smith (BAS) was in the chair at the start of the third day of the meeting. Gary Abel (BAS) described how high-energy electrons injected into the Earth's magnetosphere during a substorm can transfer energy to VLF/ELF waves. These waves can then propagate towards the ionosphere along magnetic field lines, where they could be observed by a network of detectors in Antarctica. A gap in the wave spectral intensity at half the equatorial gyrofrequency was noted and linked to electric field effects. Satellite observations of the October 1990 geomagnetic storm were examined by Nigel Meredith (MSSL). It was found that the population of energetic electrons increased for the following three days in association with prolonged substorm activity and enhanced levels of whistler-mode chorus waves. A localised stochastic acceleration mechanism was proposed associated with Doppler shifted cyclotron resonance.
Swapping roles briefly, Andy Smith (BAS) examined ground-based evidence for whistler wave acceleration of electrons to relativistic speeds. He compared the large 'Bastille day storm' event ELF/VLF observations at Halley with the quiet pre-storm data. There was a drop out in signal during the storm followed by a massive enhancement later. Absorption extended to unusually low latitudes. Jonathan Nichols (Leicester) considered the effect of the jovian ionospheric Pedersen conductivity and iogenic plasma mass outflow rate on the main jovian auroral oval. The former was found to dominate in the region of Io, whilst the latter became increasingly important at large distances. Voyager I data provided empirical estimates of the magnitudes of these quantities.
Gareth Chisham (BAS) described how spectral widths from the SuperDARN radars were used to measure the location of the boundary between open and closed field lines in the magnetosphere. He demonstrated how a new technique for determining the boundary between two regions with different statistical characteristics could be applied successfully to this problem. F-region auroral arcs above Sondrestrom were monitored by Joshua Semeter (SRI International) using a multi-spectral imager and an incoherent scatter radar to determine the production and loss of singly charged oxygen atoms on auroral flux tubes. It was found that vertical upwelling of these ions was required to account for the observations.
Lyman-a measurements from the IMAGE satellite in conjunction with convection flows from the SuperDARN radars were analysed by Katie Throp (Southampton) to investigate the ionospheric response to magnetospheric reconnection processes in the cusp. Proton precipitation follows newly opened magnetic field lines and the location and intensity of the resulting aurora depends on the strength and orientation of the solar wind with respect to the magnetosheath boundary. Tim Stubbs (IC) compared the total ion signature in the magnetosphere observed by the POLAR spacecraft with precipitating ion fluxes measured in the topside ionosphere seen by the DMSP satellites. The total ion distributions were found to be consistent with earlier studies of alpha particles which had been used to infer ion injection and ion transport characteristics from the solar wind into the magnetosphere. Steve Morley (Southampton) described a model that predicted the structure of field-aligned currents associated with the ionospheric signatures of transient magnetopause reconnection for a variety of orientations of the interplanetary magnetic field, satellite geometry and amplitude of the reconnection pulse rate. The presence of these field-aligned structures may affect the UV/green-line auroral forms that are believed to be associated with regions of upward field-aligned current flow.
The final session of the meeting was chaired by Farideh Honary (Lancaster). She introduced four papers from her group. Mike Kosch described the first observations of mesospheric ozone destruction from the ground using the Slow-scan CCD All-Sky Imager in combination with an Imaging Riometer (IRIS) at Skibotn, Norway. A solar proton event in November 2000 significantly enhanced OH emissions. Satellite measurements of total atmospheric ozone indicated a substantial reduction at this time. Steve Marple explained how the IRIS riometer could be used to monitor variations in solar activity at 38.2 MHz. There was good agreement with other solar indices such as f204 MHz and X-ray emissions. Absorption can be attributed to electromagnetic radiation and particle precipitation and in conjunction with these, other measurements components of solar activity can be identified.
A multi-instrument study of substorm-related changes in precipitation in the dayside auroral zone was conducted by Andrew Kavanagh. The data raised questions about the ability of gradient-curvature drifting electrons to account for the enhanced electron density at event onset. A large change in the precipitation spectrum in the latter half of the event indicated that ion precipitation dominated over electrons. Andrew Senior presented observations of large period pulsations from the IRIS riometer that were consistent with magnetometer data. The occurrence of these pulsations increased during episodes of high solar wind speed. The riometers imaging array made it possible to resolve the azimuthal wavenumber and was sufficiently sensitive to detect a class of pulsations that could not be resolved by magnetometers.
Going back in time, Nasser Al-Hatmi (Sheffield) described a wavelet based spectral analysis of atmospheric temperatures from 1600 BC to the present using variations in the thickness of tree rings. There were notable signals at a number of time periods, but inter-comparison of data from three disparate locations indicated no strong global trends. David Willis (Warwick) examined ancient East Asian texts between 20 - 1918 AD to attempt to reconstruct evidence for the identification of historical geomagnetic storms. A positive result required unusual sunspot activity to have taken place within a week of low-latitude auroral observations. Some ten to twenty such storms have been observed over two millennia, consistent with modern predictions.
Toby Clark (BGS) discussed the reliability of the historical geomagnetic aa index between 1868 and 2000. This quantity has been related to the total solar magnetic flux and so may be a useful indicator of solar activity. Whilst the instruments, located in the United Kingdom and Australia, have been relocated a number of times, meticulous record keeping and quality control limit the errors to a small fraction of the total change in the data. Mervyn Freeman (BAS) introduced computational mechanics as a means of analysing geomagnetic data. Taking three hours geomagnetic index data and applying a threshold, it is possible to perform a statistical analysis of the repeat occurrence of various pattern combinations. By this means the diurnal cycle was readily identified but also using 40 minute data, the 'Poisson switch-like' substorm interval was seen.
by R. Erdelyi (University of Sheffield)
Published in Astronomy & Geophysics 43, 3.27-3.31 (2002)
The solar and solar-terrestrial physics community gathered at the Tapton Hall of Residence, University of Sheffield from 10-12th April 2002. For the first time the annual UKSP was held jointly with the MIST meeting and has started with a Welcome Address by Prof Colin Whitehouse (Pro-Vice-Chancellor for Research, Sheffield University).
The joint MIST/UKSP sessions on Wednesday, 10 April 2002, were already reported above, so we start here with solar session which started on Thursday. Helen Mason (Cambridge) has chaired the first session on current and future missions which included updates on the satellite missions where there is a considerable UK involvement. First Richard Harrison summarised the latest news on SOHO, STEREO and Solar Orbiter. SOHO has been in operation for over six years and has had a tremendous impact on our knowledge of the Sun. The announcement that SOHO's operation has been extended up to 2007 was in particular welcomed by the community. The STEREO mission is due for launch in 2005. STEREO carries camera systems and an instrument from the UK (RAL and Birmingham). The objective of STEREO is the observation and investigation of coronal mass ejections from out of the Sun Earth line. Further in the future is the recently selected ESA F-mission, Solar Orbiter, which was proposed by a team with a heavy UK involvement. Louise Harra (MSSL) gave a summary on Solar-B which is due for launch in 2005 on an ISAS (Institute of Space and Astronautical Science) M V rocket. It will be placed in a polar sun-synchronous orbit. The instrument payload consists of the Solar Optical Telescope (SOT), X-ray Telescope (XRT) and the EUV Imaging Spectrometer (EIS). Mike Thompson (IC) addressed the key science questions of SDO (due lunch 2007) with a goal to observe the Sun's dynamics to increase understanding of the nature and sources of solar variability. The focus area of SDO studies are the changes in the solar magnetic field and the relationships between the Sun's magnetic field and mass and energy releases. George Simnett (Birmingham) updated on the SMEI (Solar Mass Ejection Imager) which is an instrument designed to detect the transient clouds of hot ionized plasma - which from time to time are emitted by the sun. Of particular interest are those clouds that are coming towards the earth, as they can have a serious effect on earth-orbiting satellites and electrical power distribution networks, not to mention interfering with normal long-distance radio communication. Finally Andrew Conway (Open University) a reported on the successful launch of RHESSI (High Energy Solar Spectroscopic Imager) to observe high energy emission from solar flares (photon energies ~3 keV to 20 MeV). It was amazing to see the very first images of this new mission.
After a coffee break Len Culhane (MSSL) took over the chair and run the next session on trends in the solar-terrestrial system which started with a review by Mike Lockwood (RAL) on long-term variations in solar magnetic fields and potential effects on terrestrial climate. The second perihelion pass of Ulysses confirms the constancy of the radial component of the heliospheric field. Recent paleoclimate studies have shown that cosmogenic isotopes, produced in the atmosphere by cosmic ray bombardment, show a strong correlation with climate indicators throughout the Holecene. These results imply that either cosmic rays can directly influence climate (presumably via the proposed modulation of low-altitude cloud cover) or that the total solar irradiance is highly correlated with the open solar flux. Studies over the last three solar cycles reveal that the latter may indeed be the case and a model developed to explain the open flux variation offers a potential explanation. Robert Forsyth (IC) discussed another Ulysses observations of the heliospheric magnetic field from pole to pole at solar maximum by giving a detailed view of the structure of the heliospheric magnetic field close to the maximum of solar activity. R. Fallows showed a reconstruction of the structure of heliosphere using interplanetary scintillation arising from the scattering of radio waves by density irregularities. Matthew Owens (IC) embarked on examining the relationship between the magnetic field intensity and speed of solar wind events using approximately three years of data from the ACE spacecraft which was followed by a theoretical talk by Lorraine Allen (Aberystwyth) describing a 16-moment, three-fluid description of the solar wind consisting of electrons, protons, and alpha particles. The last talk of this session was another theoretical approach by Youra Taroyan (Sheffield) on resonant flow instabilities at the outer magnetospheric boundary to explain substorms or Pc5 wave activities.
The first Thursday afternoon session on large-scale energy releases in the solar atmosphere was chaired by Philippa Browning (UMIST). The session was kicked off by a talk by Sarah Matthews (MSSL) on the origin of solar white-light flares which problem is still unresolved in spite of the decades long research. Comparing the characteristics of all of the white-light flares observed by Yohkoh in the period 1991-1992 - a total of approximately 30 events - with a group of non-white-light flares from the same period one may identify the factors that lead to the production of enhanced white-light emission. Extending such studies to other X-ray Yohkoh flares, as presented by Ken Phillips (RAL), one can estimates electron temperatures (satellite/resonance line ratios), Doppler temperatures or turbulent velocities (line widths), and emission measures. Data from the SOHO spacecraft's SUMER instrument suggest that turbulent velocities are very small an hour or so after the start of a long-duration flare, yet Yohkoh BCS Ca and S spectra indicate turbulent velocities of 40 km/s or more. It seems possible that the explanation is slightly incorrect wavelengths for the high-n satellites, giving a resonance line profile that is too large. Over one third of all flares imaged by Yohkoh's Hard X-ray Telescope show a single hard X-ray source in multiple channels. Chris Goff (MSSL) studied, by combining Yohkoh, SOHO and Nobeyama Radio Observatory data, single source events in detail to try to determine whether they represent unresolved double footpoint emission, asymmetric electron deposition due to magnetic mirroring or a genuine departure from the standard model. Next, Martin Birch (UCLAN) discussed how energetic solar flares are the source of the solar energetic particle (SEP) events which result in polar cap absorption (PCA) conditions in the Earth's ionosphere during solar cycle 23. This was followed by the last talk of this session by Chris Brockwell (OU) on the application of cellular automata modelling of flaring events in the solar atmosphere. Specifying only very general initial conditions, a variety of interesting energy reslease properties, subject to interpretation, were produced.
After a swap of the chair to Robert Erdelyi (Sheffield) the last session of this afternoon on how many ideas have we got for coronal heating started with the enthusiastic review talk by Eric Priest (St Andrews) flux tube tectonics modelling for coronal heating. Since the photospheric flux is concentrated into many small sources, the overlying coronal magnetic field will be highly complex and will contain myriads of separatrix surfaces, dividing the flux from each source. A consequence of this is that large coronal loops should exhibit enhanced heating near their feet in the carpet and that the upper parts of the loops should be heated rather uniformly but less strongly. Philippa Browning (UMIST) argued that observations suggest that solar coronal heating may be the result of a superposition of transient heating events, over a range of energies with nanoflares perhaps at the lower end. She presented a model where an energy releasing event is triggered by an ideal MHD instability such as a kink, with the energy dissipation occurring due to reconnection in the nonlinear phase. This was followed by an alternating idea, explained by Cesar Mendoza (Sheffield), who studied the possibility of coronal loop heating by impulsive sources at the base of the loop. The idea of nanoflare heating was probed by a test carried out by Grisha Vekstein (UMIST). Since individual nanoflares may be too small to be recognised individually it was demonstrated how to consider statistical characteristics of active regions to test the nanoflare scenario of coronal heating. Danielle Bewsher (St. Andrews) presented another statistical investigation of small-scale energy releases called blinkers and explosive events. She arrived to the conclusion these two phenomena may not seem to be related. On contrary, Daniel Marik (Sheffield) argued that numerical simulations of explosive events may be visible in CDS images as blinkers in unipolar regions. This debate will be decided by further more detailed high-resolution observations. Focusing on one single energy release in the form of an Alfvenic pulse David Tsiklauri (Warwick) showed in a numerical study how these MHD fluctuations generate by linear coupling compressible (magnetoacoustic) fluctuations. Another Warwick-talk, by Valery Nakariakov, picked up again the possibility of coronal heating by wide spectrum slow waves. This long and exhausting session was finished by a presentation given by Xing Li (Aberystwyth) on the dissipation of ion cyclotron waves by minor ions and plasma heating in coronal funnels. Ion cyclotron waves are able to heat the corona from 50000 to above 1 million degrees by directly heating alpha particles only. The strong Coulomb coupling between alpha particles and protons, and protons and electrons makes it possible that protons and even electrons are heated to above 1M degrees even though only alpha particles dissipates the waves.
Thursday concluded with an excellent conference dinner in Firth Court.
The last day of the meeting started with a session (chaired by Ken Phillips, RAL) on atmospheric magnetic fields. There were three talks from St. Andrews. Clare Parnell investigated the nature of the Magnetic Carpet as small-scale magnetic concentrations on the solar surface are important (i) for providing indications as to how the magnetic fields are generated in the solar interior and (ii) for probing the behaviour of the magnetic field and energy release in the solar atmosphere. Duncan Mackay showed simulations to study the evolution of the Sun's open magnetic flux. For single magnetic bipoles he showed how the open magnetic flux can vary depending on the initial tilt angle of the bipole. Full solar cycle simulations for a few cycles have revealed how the open flux varies as many bipoles interact. Finally, Daniel Brown introduced the fundementals and the notions of magnetic topology theory. Applications to coronal structures as seen by the TRACE and SOHO instruments were presented. Next Lucy Green (MSSL) embarked on coronal mass ejections (CMEs) by studying magnetic helicity within the approximation of linear force-free assumption in AR 8100. The results showed that the main source of helicity needed to account for the CME activity is not found in differential rotation, but must come from the inherent twist of the flux tube in the portions below the photosphere. The last talk of this session by Nicolas Labrosse (Aberystwyth) was on NLTE modelling of helium lines in quiescent solar prominences. New non-LTE computations considering Partial Redistribution in Frequency for the formation of the main EUV resonance lines of helium were shown and results compared with SUMER and CDS observations.
Next Eric Priest took over the chair of a session on magnetic waves and oscillations. Ineke de Morteel gave a nice and compact overview of the geometric and physical parameters of propagating disturbances in coronal loops clearing off some previous debates on well-published TRACE observations. The following two Sheffield-talks concentrated on the theory of MHD waves. Istvan Ballai discussed compressional waves in the magnetosphere in the framework of the double-adiabatic approximation. Misha Ruderman shedded light on, by using the idea of resonant absorption, some previous controversial results on TRACE observations of damped oscillations in coronal loops. Next Fenwick Cooper (Warwick) discussed MHD modes of a current sheet by taking into account the effects of oblique propagation and a magnetic field shear. The relevance of the results to understanding of stability of current sheets and to MHD seismology of solar coronal streamers was demonstrated. Miguel Homem (Sheffield) discussed the effect of steady states on MHD modes in magnetic fluxed tubes. He also pointed out the importance of negative energy character of the MHD surface and body modes in solar magnetic flux tubes. Finally Temury Zaqarashvili (St. Andrews) suggested a mechanism of energy transformation from fast magnetosonic waves propagating across a magnetic field to Alfven waves propagating along the field based on the mechanism of swing wave-wave interactions. Large variety of solar applications were covered.
The last session of the meeting was chaired by Bill Chaplin (Birmingham) who reported on four papers on the frontiers of helioseismology. Mike Thompson (IC) gave an excellent review on the latest results in helioseismology including both the observational and theoretical aspects and future possible developments. Balazs Pinter (Sheffield) discussed the rotational splitting of helioseismic modes in a magnetic solar model with steady state interior. Stephen Hughes (IC) showed a case-study of the rapidly emerging technique of time-distance helioseismology of subsurface flows. The last talk of the meeting by Graham Verner (Birmingham) discussed the solar cycle variation of the He II ionization signature. The sharp variation in the adiabatic exponent at the second helium ionization zone creates a characteristic signal in the solar p-mode eigenfrequencies. This signal carries information regarding the properties of the region and has been used to map changes in the acoustic depth and width of the zone with solar activity. This has been undertaken using data from both the BiSON and GONG observational programmes.