First session - Chairman: Peter Cargill (IC)
Second session - Chairman: Richard Balthazor (Sheffield)
Third session - Chairman: Ranvir Dhillon (Leicester)
Posters:
Affiliation abbreviations:Aberystwyth: The University of Wales, AberystwythArizona: The University of Arizona, USA BAS: British Antarctic Survey Berkeley: University of California at Berkeley, USA Cambridge: Institute of Astronomy, University of Cambridge 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 IRF: Swedish Institute of Space Physics, Kiruna, Sweden JPL: Jet Propulsion Laboratory, USA Leicester: University of Leicester, Radio and Space Plasma Physics Manchester: School of Physics & Astronomy, University of Manchester MIT: MIT Haystack Observatory, USA MPI: Max-Planck Institute fur Extraterrestrische Physik, Garching, Germany MSSL: Mullard Space Science Laboratory RAL: Rutherford Appleton Laboratory Sheffield: University of Sheffield SWRI: South West Research Institute, USA UCL: University College, London; Atmospheric Physics Laboratory UCLA: University of California at Los Angeles, USA UKAEA: UKAEA Fusion, Culham Warwick: University of Warwick; Space & Astrophysics Group
|
by
Published in
Astronomy & Geophysics 46, 3.36-3.37 (June 2005)
The annual one-day meeting of the MIST (Magnetosphere, Ionosphere and
Solar-Terrestrial) community was held on the 26th November, 2004 at
the Geological Society, Burlington House. The first session of the
meeting was chaired by Peter Cargill (Imperial College). A number of
crossings of Saturn's outer magnetosphere were analysed by Nick
Achilleos (IC) during Cassini's orbit insertion. Models allow the
dynamic variability to be mapping into a global picture of the
magnetosphere. There was evidence of sub-corotation of the
magnetospheric plasma relative to the planet at distances of greater
than 5 Saturn radii. Hazel McAndrews (Mullard Space Science
Laboratory) reported on the initial results from the Cassini electron
detector at the magnetopause of Saturn. It was found that within the
magnetosheath there were episodes where the plasma was intermediate
between being within and outside the magnetosphere. Plasma transfer
could be related to either steady state reconnection or diffusion
across the boundary.
An investigation of upstream waves from the bowshock and the
magnetosheath region of Saturn using the Cassini magnetometer was
presented by Cesar Bertucci (IC). Streams of plasma moving away from
the bowshock created a 'foreshock' that modified the velocity
distribution function. First observations of low frequency waves
connected to the bowshock were achieved. Chris Smith (University
College London) proposed auroral heating and ion drag as possible
mechanisms for the imbalance between radiative transfer estimates of
Jovian thermospheric temperatures and observations. If variable
electric fields were used, then there was an increase in the amount
of energy available without affecting the ion drag, so a net effect
could be achieved.
Chris Arridge (IC) described how a global model of Saturn's
magnetospheric field could be used to help interpret the observed
data and to infer the global structures from in situ observations.
Starting from a model of the internal planetary field and an
azimuthal current disk, magnetopause currents were included to extend
the applicability of the model to higher latitudes and greater
distances from the planet. Observations of magnetic anomaly
signatures in Mars Express data were considered by Yasir Soobiah
(MSSL). In the absence of a strong planetary magnetic field, only
residual crustal forces remain, but these are sufficient to influence
the solar wind close to the planetary surface. The spacecraft could
descend to an altitude of 300 km from a highly elliptical orbit,
which was sufficient to detect ionospheric and sheath plasma. The
fields focused or defocused the plasma population.
In the first of three talks from the University of Warwick, Sandra
Chapman reflected on particle-in-cell simulations of reforming
perpendicular shocks. Reflection of plasma from a shock boundary
resulted in heating of the plasma in front of the shock. It was
found that a fraction of the plasma could undergo significant
accelerations and that going from hydrogen to helium ions could also
increase the energies available to the plasma. Bogdan Hnat
attempted to distinguish between solar wind and internal
magnetospheric processes in determining the short time scale (less
than a few hours) variability of the geomagnetic indices using the
Fokker-Planck scaling approach. Self-similar statistics appeared to
give a good approximation within this time frame regardless of solar
activity levels. Lastly, Tom March described how 'mutual information'
between geomagnetic indices and the solar wind as seen by the WIND
spacecraft could have implications for propagation time estimates.
The method allowed non-linear relationships to be tested. Out of
five schemes for estimating solar wind propagation times were
investigated, the one assuming a fixed orientation consistent the
Parker Spiral orientation gave the best agreement.
After the lunch break, Richard Balthazor (Sheffield) took over the
chair. Simon Child (IC) considered two years of Ulysses observations
of the heliospheric current sheet at solar maximum to help understand
the topology of the heliospheric magnetic field. Heliospheric
current sheet encounters distributed across a wide range of latitudes
indicated that there was an enhanced spread in the observed elevation
angle of the orientations with increasing latitude. This result was
consistent with a single highly tilted HCS. Ranvir Dhillon
(Leicester) described the first EISCAT Svalbard Radar observations of
SPEAR enhanced ion and plasma lines. There was clear evidence for the
excitation of the parameteric decay instability as well as the so-
called purely growing mode. There was no clear evidence of the ion
line overshoot that was a recurrent feature of the Tromso heater
facility. Balazs Pinter (Sheffield) modelled the sub-auroral
polarization streams using the Coupled Thermosphere Ionosphere
Plasmasphere (CTIP) model in the mid-latitude ionosphere. These
features may raise the peak free electron concentrations by an order
of magnitude, with a considerable impact on TEC measurements and
radio wave propagation directions.
A study of the geometry of artificial plasma irregularities produced
by RF heating was presented by Harmaninder Shergill (Leicester), in
order to test the upper hybrid resonance theory of heater
irregularity generation. The CUTLASS HF radar provided the patch
size determination as a function of frequency and ionospheric
conditions. Atousa Goudarzi (Leicester) described how the SuperDARN
radar and DMSP satellites could be used to identify the location of
the open-closed field line boundary of the Earth's magnetic field in
response to magnetic reconnection. When the IMF was northward, the
boundary moved polewards compared to southward conditions. During
transitions, the response was found to be much quicker in the
northern hemisphere.
Stuart Thom (Sheffield) used the CTIP model to study the refilling of
the plasmasphere following a geomagnetic storm. The model results
were compared with IMAGE light intensity maps of scattering from
helium ions. Density variations were found to be strongly related to
solar wind changes. Silvia Dalla (Manchester) updated the community
on progress in building a grid of inter-operating data archives and
software tools by the AstroGrid consortium. Several examples of
usage relevant to the UK MIST community were presented.
The chairman of the third and final session was Ranvir Dhillon
(Leicester). Tim Yeoman (Leicester) announced the first observations
of SPEAR-induced coherent backscatter. High power HF radio waves
from this facility generated artificial irregularities that could be
observed by the CUTLASS radars several thousand kilometres away.
These irregularities provided a means of accurately measuring the
winds in the ionosphere, providing evidence of ULF waves. Richard
Balthazor (Sheffield) presented evidence of transonic neutral wind
flows in the thermosphere that had been observed by the Dynamics
Explorer 2 satellite. Using the CTIP model, large electric fields
were shown to be able to create strong ion drift flows. The process
was highly non-linear but it was found that neutrals could propagate
at velocities greater than the speed of sound.
Jim Wild (Leicester) revised time-of-flight calculations for high
latitude geomagnetic pulsations using a realistic magnetospheric
magnetic field model. The Cluster spacecraft observed standing
Alfvèn waves with speeds dependant on the strength of the magnetic
fields and the plasma density and from this the time-of-flight
between conjugate points could be calculated. The period of the
pulsations was found to increase towards higher latitudes. Nigel
Meredith (British Antarctic Survey) had carried out a preliminary
investigation of PEACE particle data during Cluster perigee passes.
This data had been highly contaminated with electrons from the outer
radiation belt in spite of a high thickness of shielding. However,
using data from a higher energy detector and given geometric factors
from the second detector, it was possible to remove much of the
contamination.
The meeting ended with three presentations from MSSL. Yulia
Bogdanova presented a possible mechanism for the formation of the
stagnant cusp observed by Cluster at high-altitudes at a time close
to noon. Stagnant conditions were found to last for approximately
one hour during a period of stable lobe flux reconnection.
Continuous particle injections were observed at dawn from IMAGE
satellite data, whilst the SuperDARN radar network showed two
reconnection sites at dawn and dusk. Aurelie Marchaudon described
observations of flux transfer events by the Double Star spacecraft
and injections by Cluster on the dawnside flank of the magnetosphere.
Many of these events were observed and their impact on the ionosphere
using the SuperDARN network was discussed. There was a good
agreement between the two, aiding an understanding of the injection
mechanism. Ilya Alexeev presented Cluster observations of plasma
sheet electrons during a substorm. Multiple crossings during
substorm onset revealed a possible wave propagating across the plasma
sheet. Parallel electric currents were investigated. The
anisotropy was believed to be related to the electron temperature.
The electron distribution was not consistent with a simple adiabatic
theory of electron heating during the substorm.
Throughout the duration of the meeting there was an opportunity to
view three posters. Nanan Balan (Sheffield) described Cluster
southern magnetospheric cusp crossings during geomagnetic storms.
Ion densities increased by more than two orders of magnitude, ion
temperatures increased by a factor of ten whilst the ion velocities
turned strongly southwards. Brigid Cooling (Queen Mary and Westfield
College) modelled the magnetosheath at the magnetopause to allow for
a prediction of the motion of open flux tudes along the magnetopause
during dayside reconnection events. The model hadbeen tested across
a wide range of IMF orientations. Oleg Pokhotelov (Sheffield)
discussed halo instabilities in space plasmas. A fully kinetic
theory of mirror-type modes accounting for finite ion Larmor radius
effects in non-Maxwellian space plasmas had been developed. From
this a dispersion relationship may be obtained, revealing two
different instabilities.
Return to MIST home page
Meeting Report
Neil Arnold (University of Leicester)