MIST meeting
28 November 2003

Geological Society Lecture Room, Burlington House, London (enter from Piccadilly); map. (AV facilities)

A. Programme B. Report C. Abstracts

MIST meeting, London, Autumn 2003

Coffee (served in the Library)

First session - Chairman: Anasuya Aruliah (UCL)

N Achilleos, M K Dougherty (IC), D T Young and F Crary (SWRI), Cassini magnetic observations of Jupiter's bow shock
A M Rymer, A J Coates, N P Meredith (MSSL), M F Thomsen (LANL) and M K Dougherty (IC), Correlation of plasma and magnetic field transitions with distance and with solar wind Mach numbers down the dusk flank of the Jovian bow shock
C G A Smith (UCL), I C F Mueller-Wodarg (IC), S Miller and A D Aylward (UCL), Auroral heating of gas giant thermospheres
T Moffat, A D Aylward (UCL) and I Mueller-Wodarg (IC), Three dimensional modelling of the Martian thermosphere and ionosphere at UCL
I V Alexeev (MSSL) and V S Semenov (St Petersburg), Self-consistent model of the reconnection rate dynamics
N C Draper, M Lester, J A Wild, S E Milan, G Provan, A Grocott, S W H Cowley (Leicester), A N Fazakerley, Y Bogdanova, J P Dewhurst (MSSL), J A Davies (RAL) and J-M Bosqued (CESR), Preliminary Cluster observations of a magnetic field cavity in the plasma sheet
A Grocott, S V Badman, S W H Cowley, T K Yeoman and P J Cripps (Leicester), The influence of IMF By on the nature of the nightside high-latitude ionospheric flow during intervals of positive IMF Bz
G Provan and M Lester (Leicester), Pulsed flow signatures observed during an interval of prolonged northward interplanetary magnetic field
A J Smith (BAS), MIST announcements
Lunch (available in the Library)

Second session - Chairman: Jason Dewhurst (MSSL)

H R Middleton, S E Pryse (Aberystwyth), G Bust (Texas) and E J Fremouw (NWRA), Dayside plasma structure under IMF Bz>0: a hemispheric view
P T Younger and N J Mitchell (Bath), Tides in the equatorial mesosphere and lower thermosphere over Ascension Island
N J Mitchell, P T Younger and D Pancheva (Bath), The meteor radar on Ascension Island and Kelvin waves in the equatorial mesosphere and lower thermosphere
S England (Leicester), A Dobbin (UCL), N Arnold (Leicester) and A Aylward (UCL), A new gravity wave parameterisation for the UCL Couple Middle Atmosphere Thermosphere general circulation model
A L Aruliah, E M Griffin, A D Aylward, E A K Ford (UCL), M J Kosch (Lancaster), C J Davis (RAL/UCL) and V S C Howells (RAL), First direct evidence of meso-scale variability on ion-neutral dynamics using co-located tristatic FPIs and EISCAT radar in Northern Scandinavia
H Vo (Aberystwyth), Observations of sub-auroral electric fields: its behavior and implications
N P Meredith (MSSL), R B Horne (BAS), R M Thorne (UCLA) and R R Anderson (Iowa), Favoured regions for chorus-driven electron acceleration to relativistic energies in the Earth's outer radiation belt
Tea (served in the Library)

Third session - Chairman: Nick Mitchell (Bath)

N Balan, H Alleyne, S Walker (Sheffield), P M E Decreau (LPCE), M Andre (IRFU), A Balogh (IC), A N Fazakerley (UCL), H Reme (CESR), N Cornilleau (CETP/CNRS) and D C Gurnett (Iowa), A structured magnetospheric cusp observed by Cluster
K Nykyri, P J Cargill, E A Lucek, T S Horbury, A Balogh (IC), B Lavraud, I Dandouras and H Reme (CESR), Ion cyclotron waves in the high-altitude cusp: Cluster observations at varying spacecraft separations
R C Fear, A N Fazakerley, C J Owen (MSSL) and A Balogh (IC), Cluster PEACE observations of a boundary disturbance near the cusp magnetopause
Y V Bogdanova, A N Fazakerley, C J Owen (MSSL), B Klecker (MPI), P Cargill, A Balogh (IC), M Andre, D Sundkvist (IRFU), N Cornilleau-Wehrlin, B Grison (CETP), H Reme and J M Bosqued (CESR), The ion outflow from the cleft-cusp: Cluster results
S Dalla (UMIST) and S Krucker (Berkeley), Solar energetic particle propagation to widely separated spacecraft
M Owens and P Cargill (IC), Non-radial solar wind flows induced by the motion of interplanetary coronal mass ejections
J P Dewhurst, C J Owen, A N Fazakerley (MSSL) and A Balogh (IC), Cluster PEACE observations of flow shears in the plasma sheet

Affiliation abbreviations:

Aberystwyth: University of Wales, Aberystwyth
BAS: British Antarctic Survey
Bath: Bath University
Berkeley: University of California at Berkeley, USA
CETP: Centre d'etude des Environnements Terrestre et Planetaires, France
CESR: Centre d'etude Spatiale des Rayonnements, Toulouse, France
IC: Imperial College, London; Space & Atmospheric Physics Group
Iowa: University of Iowa, USA
IRFU: Swedish Institute of Space Physics, Uppsala, Sweden
Lancaster: University of Lancaster
Leicester: University of Leicester, Radio and Space Plasma Physics
LANL: Los Alamos National Laboratory, Los Alamos, New Mexico
LPCE: Laboratoire de Physique et Chimie de l'Environnement, France
MPI: Max-Planck Institute fur Extraterrestrische Physik, Garching Germany
MSSL: Mullard Space Science Laboratory
NWRA: North West Research Associates, USA
RAL: Rutherford Appleton Laboratory, Oxfordshire, UK
St Petersburg: St Petersburg State University, Russia
Sheffield: University of Sheffield
SWRI: South West Research Department, USA
Texas: University of Texas at Austin, USA
UCL: University College, London; Atmospheric Physics Laboratory
UCLA: University of California at Los Angeles, USA

MIST meeting, 28 November 2003
Meeting Report

Neil Arnold (University of Leicester)

Published in Astronomy & Geophysics 45, 1.27-1.28 (February 2004)

The annual one-day meeting of the MIST (Magnetosphere, Ionosphere and Solar-Terrestrial) community was held on the 28th November, 2003 at the Geological Society, Burlington House. The first session of the meeting was chaired by Anasuya Aruliah (UCL) and started with four talks on the outer environments of the outer planets. Nick Achilleos (Imperial College) reported on magnetic field observations at Jupiter's bow shock as the Cassini spacecraft flew by on the way to its rendezvous with Saturn. The solar wind pressure varied by an order of magnitude in the space of a few days, making it possible to observe a wide range of angles between the wind and the bow shock normals over a range of distances from the planet, greater than were possible during the Voyager and Pioneer encounters. During this passage, Abigail Rymer (Mullard Space Science Laboratory) examined the electron temperature and density variations that accompanied the magnetic field fluctuations. She found that the relationship between distance from the planet, solar wind Mach number and solar wind Alfven number agreed well with magnetohydrodynamic (MHD) models out to 600 Jupiter radii. The electron heating depended on the solar wind bulk flow and magnetosheath speed.

A three-dimensional model of the thermosphere of the gas giants was introduced by Chris Smith (University College London). Previous models underestimated the observed temperatures by up to 400 Kelvin, so it was necessary to consider the contribution from auroral plasma current heating and the conditions that would be required to ensure that this extra energy was transported effectively to the rest of the planet. A similar approach was taken by Tracy Moffet (also UCL), but this time for Mars. The introduction of an ionosphere made it possible to carry out inter-comparisons with observations from the Radio Science experiment on board the Mars Global Surveyor spacecraft of the free electron density profile. The agreement was good above 150 km, but additional processes will need to be included to improve the representation below this height.

Ilya Alexeev (MSSL) described his research into magnetic reconnection. In order to investigate time varying phenomena, it was necessary to develop a self-consistent numerical model that allowed a non-steady state solution. This allowed feedback structures to evolve. It was found that pulsation rates with a period that was proportional to the diffusion region size were obtained, thereby possibly accounting for the bursty nature of reconnection. Natalie Draper (Leicester) examined Cluster observations of a magnetic field cavity in the Earth's plasma sheet. She took advantage of the unique four spacecraft configuration to isolate unusual events where field and particle data indicated levels consistent with entry of the Central Plasma Sheet, but the spacecraft geometry and time histories suggested that this was not possible. Alternative explanations appear to be required to account for this behaviour.

Two more talks from Leicester examined the impact of the Interplanetary Magnetic Field on the resulting plasma flows in the Earth's ionosphere. Adrian Grocott examined an event where the vertical component of the IMF was northward. Normally, reconnection does not occur under these conditions, but open flux production was maintained by the existence of a strong tangential component. It was believed that the reconnection was linked to a reconfiguration of the asymmetric tail associated with convective transport in the distant tail, rather than being directly related to substorms. Gabrielle Provan had identified a second period where signatures of reconnection were evident in the ionosphere under similar IMF conditions. She described how the changing nature of the IMF resulted in a major reconfiguration of the global ionospheric convection pattern, from the classical twin cell to a multi-cell circulation.

The second session of the meeting was chaired by Jason Dewhurst (MSSL). The first talk by Helen Middleton (Aberystwyth) continued the theme of IMF influences on the Earth's ionosphere. She made use of three chains of Global Positioning Satellite receivers in Scandanavia, Alaska and Greenland to reconstruct tomographically the large scale plasma distributions in near real time. She provided an example of a secondary peak in the electron density that was isolated from the auroral oval.

There then followed two presentations from Bath University on observations from a new meteor radar that has recently been deployed on Ascension Island in the Equatorial Atlantic Ocean where it can measure winds in the upper mesosphere and lower thermosphere. Nick Mitchell reported on several years' worth of data which showed a significant signal from 3-day waves, that were thought to be Kelvin waves which appeared to be depositing large amounts of momentum and energy into the background flow at these altitudes. Peter Younger then discussed the tides that were observed by this radar. A strong 24-hour tide was present in the data with a clearly defined seasonal cycle. However, considerable variability on timescales of a month or less indicated that coupling with planetary scale waves was an important factor.

Scott England (Leicester) described recent efforts to improve the ability of the UCL Coupled Middle Atmosphere Thermosphere general circulation model to reproduce the equatorial winds that have been observed by satellites and radars such as the one described above. It was found that accurate representations of the impact of sub-grid scale waves, such as gravity waves brought the model much closer to the observed upper mesosphere and lower thermosphere. The first direct evidence of meso-scale variability on ion-neutral dynamics was provided by Anasuya Aruliah (UCL) using co-located tristatic Fabry-Perot Interferometers and the three receiver configuration of the European Incoherent Scatter radar in Northern Scandinavia. Winds and temperatures on a scale of tens of kilometres were recorded, indicating that the thermosphere is considerably more dynamic than had been previously assumed and that the neutral wind dynamo made a significant contribution to the heating rate.

Hien Vo (Aberystwyth) described some observations of the sub-auroral electric field as seen by the Millstone Hill incoherent scatter radar over two complete solar cycles. A broad region of ring current induced electric field was seen equatorward of the normal two-cell ionospheric convection pattern and this feature corresponded well to the plasmaspheric tail seen by the extreme ultraviolet images from the IMAGE spacecraft. The session was brought to a close by Nigel Meredith (MSSL). He described a statistical search for the more favoured regions for chorus-driven electron acceleration to relativistic energies in the Earth's outer radiation belt and the conditions most likely to induce these forces. It was found that enhanced chorus waves, active geomagnetic conditions and particular magnetic local times were the most conducive.

The third and final session of the day, chaired by Nick Mitchell, was dominated by Cluster science presentations. Nanan Balan (Sheffield) presented observations of a structured magnetospheric cusp crossing during a moderate geomagnetic storm. Three distinct anti-sunward ion flow events aligned roughly parallel to the magnetopause surface were detected in the presence of strong field-aligned currents. Katarina Nykyri (IC) examined ion cyclotron waves in the high altitude cusp and took advantage of the four spacecraft with varying separations to attempt to observe correlations between them. The absence of any positive correlations indicated that the waves appeared to be in highly filamented shear flows with spatial scales much less than 100 km.

Robert Fear (MSSL) looked at data from the PEACE particle detectors when the four spacecraft were aligned in a line along the magnetopause boundary near the cusp. They observed a series of transient bursts of magnetosheath-like plasma. A flux transfer like event was found to be more consistent with motion around a moving boundary caused by a pressure pulse. Yulia Bogdanova (MSSL) examined the ion outflow from the cleft-cusp. This flow is one of the main contributors of ionospheric ions in the magnetosphere. Three such crossings were identified and the location of the region with the most intense ion heating was well correlated with uni- and bi-directional soft (< 500 eV) electron beams, presumably from magnetopause reconnection.

Silvia Dalla (UMIST) examined the propagation times of solar energetic particles at a range of heliospheric latitudes. Is was found that Coronal Mass Ejections were observed near the Earth by the WIND spacecraft much earlier than at the high latitudes observed by Ulysses. One possible interpretation is that the particles were delayed by scattering in the interplanetary medium. Matthew Owens (IC) described attempts to predict the time of arrival at the Earth of these CMEs. Up to half of the events were found to exhibit smooth magnetic field rotations and that twice as many propagated in the westward direction, rather than the eastward, due to the distortions of the Sun's rotation.

Jason Dewhurst (MSSL) concluded the meeting with a paper on Cluster PEACE observations of flow shears in the plasma sheet. He derived electron velocity and magnetic field moments using high resolution data from the four spacecraft. The effect of flow shears on field-aligned flows within the plasma sheet was discussed. There was some evidence of twisting of the flux tubes related to field-aligned current generation with reconnection occurring at the Near Earth Neutral Line.

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