Conveners:
Bill Peterson (Bill.Peterson@lasp.colorado.edu)
Co-Chair of GEM WG-1 on Plasma Outflow in the Magnetosphere-Ionosphere
Coupling (MIC) Campaign
and Josh Semeter (jls@bu.edu) Chair GEM MIC WG-2 and CEDAR Representative
2005 Wednesday 29 June 0130-0330 PM
The Magnetosphere-Ionosphere Campaign WG 1 on plasma outflow co-sponsored with CEDAR a tutorial by Dr. Gang Lu, HAO/NCAR, entitled, "Auroral boundaries: finding them in data and models" (Wednesday 0800-0850 AM) and a joint GEM/CEDAR workshop on the same topic (Wednesday 29 June 0130-0330 PM).
The Lu tutorial, available on the web at the CEDAR website http://cedarweb.hao.ucar.edu/workshop/tutorials/2005/lu05.pdf and at the GEM website http://www-ssc.igpp.ucla.edu/gem/tutorial/index.html set the tone for a joint GEM/CEDAR workshop that followed. She discussed the physics associated with boundary formation and reviewed the work that has been done to use in-situ plasma observations, high frequency and incoherent scatter radar observations to elicit boundary locations. She also discussed techniques used to identify boundaries in MHD code outputs and gave a brief introduction to the enhanced boundary finding abilities of the new AMISER radar.
The lively joint GEM/CEDAR session had 11 speakers and quite a bit of discussion. Mervin Freeman (British Antarctic Survey) discussed the spectral width features in the SuperDarn radar that can be used boundary identifications. He showed that, except between 02 and 06 LT the agreement between boundaries identified by SuperDarn and DMSP plasma agree well. Josh Semeter (BU) discussed various representations of the polar cap boundary over Sondrestrom, Greenland, using IMAGE, FAST, ISR, and spectral imagery. In particular, comparisons between sheared plasma flow in the ionosphere and optical auroral boundaries agree very well.
Dan Weimer (Mission Research Corp) showed pathological examples of open and closed boundaries with structure to illustrate that automatic boundary identification is a very challenging task indeed. Bob Strangeway (UCLA) made the same point using data from the FAST satellite.
Michelle Thomsen (LANL) noted that the success that Kp has in organizing magnetospheric phenomena follows from the locations of the magnetometer stations used to construct Kp being at latitudes near the auroral boundary where they are very sensitive to changes in the convection electric field which drives magnetopsheric processes. Karen Remick (USGS) made the same point but with the very extensive set of magnetometer data she has accumulated.
Joe Borovsky (LANL) made two major points, one unintended. First: he showed comparisons of all sky camera images at/near the magnetic foot points of geosynchronous satellites. Comparisons of plasma observed at geosynchronous altitude and auroral arcs showed that the diffuse aurora is associated with the displacement of the ion and electron plasma sheets. He unintended point was that the chairperson was so used to electronic projection, that old-fashioned view graphs were difficult to accommodate!
Erika Harnett (U of Washington) presented multi-stream MHD results demonstrating change in auroral boundary, field aligned currents, and outflow with increasing southward IMF - currents enhance and move to nightside. H+ outflow increases in area while O+ outflow increases particularly more on the dayside. Lutz Rastaetter (CCMS/GSFC) presented a polar cap metric study for Feb. 18, 1999 event using the BATSRUS, Weimer-2K and OpenGGCM. The results showed substantial deviation of all models from data. He noted that field line tracing produced better results than using field-aligned currents.
Thomas Sotirelis (JHU/APL) showed examples of nightside boundary identifications using automated procedures on DMSP plasma data. He noted that the interval selected by the conveners did not have believable boundaries until instrumental degradation was accounted for. He noted that there are limits to correlations involving Dst and the stretching index because of relatively long magnetopsheric response times
Bill Peterson (CU/LASP) argued that dynamic coordinates derived from plasma data provide better ordering that geomagnetic coordinates of invariant latitude and magnetic local time, but that their definition is instrument and platform dependant.