1-5 July 2013, St Andrews, UK
By Alex Chartier, SSI Fellow and and PhD Candidate, Invert centre for imaging science, University of Bath
I met Mark Lester (Leicester), Mike Hapgood (Rutherford Appleton Lab) and Herb Carlson (USU). I found out about the CLUSTER mission for studying the plasmasphere, which is relevant to several of my colleagues, and got an insight into the future planning of UK Space Weather.
The National Astronomy Meeting (NAM) is an annual, week-long meeting sponsored by the Royal Astronomical Society. There are around 600 attendees from fields ranging from cosmology to the search for extra-terrestrial intelligence to fireballs and satellite design. This year's meeting was partnered with meetings of the UK Space Agency and the Magnetosphere-Ionosphere Solar-Terrestrial (MIST) group. My primary reason for attendance was to participate in the MIST sessions.
Highlights of the Plenary Talks
Mike Thompson (Director, NCAR HAO) gave an introduction to Solar physical processes. The discussion involved a description of magneto-hydro-dynamics and an explanation of the incredible levels of computing power that would be required to produce an accurate model of the whole Sun.
Catherine Heymans (Edinburgh) gave a talk on observing the dark universe. The Planck satellite has been important for research in this area, confirming that the quantities of dark matter and dark energy are roughly accurate. Dark matter is a theory put forward to explain why the orbits of stars at large distances from the centre of galaxies is faster than could be explained by visible matter. Dark energy is a theory put forward to explain the accelerating expansion of galaxies. We have no idea what dark matter and dark
energy are, but dark energy could be some sort of beyond-Einstein gravity theory.
Mark Lester (Leicester) outlined the SuperDARN program, which is a network of radars for sensing electric fields in the auroral regions. Observations from this network of receivers can provide input drivers to thermosphere-ionosphere models to improve forecasts.
Herb Carlson: Why should thermospheric density/drag double over the cusp? In the auroral cusp region, the thermosphere is very different above and below 200 km. This is odd, but might be caused by plasma velocity shears. Such shears are observed by EISCAT and SuperDARN. Local shears may persist for 15-20 minutes. Frictional drag heating results in far quicker thermospheric response if it occurs at 200 km rather than 120 km because there is far less mass to absorb the change. UCL's physics model responds to an ionospheric forcing as expected.
Ian McCrea: Experiment modes for thermosphere and space weather applications of EISCAT_3D
EISCAT 3D is a proposed instrument for making three-dimensional, time-dependent observations of the upper atmosphere above Scandinavia. The images will be accurate in the middle, but not so good around the outside. There may also be fans of beams and other arrangements aimed at determining physics accurately. The science case is aimed at space weather and atmospheric physics. A new version of the science case will be published each year. Object tracking and space debris will also be explored.
Natasha Jeffrey – X-ray solar flares In a standard solar flare, we get both thermal and non-thermal emissions.
However, some flares have coronal emissions, but basically no X-rays. These events may allow for the study of the acceleration region itself. Reduction in magnetic pressure may explain this. Thermal pressure might balance and overcome this after a while.
Jasmine Sandhu – Plasma Mass Density in the Magnetosphere from Cluster observations WHISPER is an instrument on the CLUSTER mission (run by the European Space Agency) that measures electron density using a resonant sounder. The CIS instrument gives ion mass distribution. The CLUSTER mission has run from 2000, but still continues to operate today. CLUSTER can image the whole plasmasphere over a long period of time. Ion mass distribution roughly matches electron density. It is possible to retrieve ion composition. Cummings has showed a power law form of electron density distribution over field line. This does not give constant electron density values along the field lines. However, reality does not even match that distribution – the ion mass distribution will change things somewhat. This power law distribution works for the main part of the plasmasphere, but not the plasmatrough.
I gave a talk titled “Storm-Time Ionospheric Plasma Density Forecasting”.
This is the abstract of the talk: Data assimilation has been used successfully for real-time ionospheric specification, but it has not yet proved advantageous for forecasting. The most challenging and important ionospheric events to forecast are storms. The work presented here examines the effectiveness of data assimilation in a storm situation, where the initial conditions are known and the model is considered to be correct but the external solar and geomagnetic drivers are poorly specified. The aim is to determine whether data assimilation could be used to improve storm-time forecast accuracy. The results show that, in the case of the storm of Halloween 2003, changes made to the model's initial thermospheric conditions result in improved electron density forecasts for over 24 hours, whilst the effects of changes to the ionospheric fields are completely lost after 12 hours. Further examination shows that the neutral composition is especially important to the accuracy of ionospheric electron density forecasts. Updating the neutral composition gives almost all the benefits of updating the complete thermospheric state. A comparison with globally distributed observations of vertical total electron content confirms that an update of thermospheric composition can result in significantly improved forecast accuracy.