GEM workshop, Wednesday breakout sessions

This afternoon I went to the breakout sessions on the proposed solar wind structure from L1 to Earth focus group and the diffuse auroral precipitation focus group.

Speakers in the solar wind structure focus group were Joe Borovsky (Los Alamos) introducing the topic, Nicholeen Viall (Boston University) on periodic structures in the solar wind and magnetosphere, Dan Weimer (Solana Scientific) on tilted phase surfaces in the interplanetary magnetic field, Benoit Lavraud (Los Alamos) on the response of the magnetosphere to solar wind variations, Bob McPherron (UCLA) on why it is important to know the structure of the solar wind at 1 AU, and Dan Baker (Colorado) on the effect of quiet space weather conditions on the Aeronomy of Ice in the Mesosphere satellite's transmitter. This is a proposed focus group, so science definition is in progress. The most interesting talk was McPherron's; he noted that the magnetosphere's response to the solar wind is nonlinear and has histeresis; he also listed the different possible magnetospheric response modes including substorms, steady magnetospheric convection, magnetic storms, pseudobreakups, poleward boundary intensifications, and sawtooth events.

Speakers in the first session of the diffuse auroral precipitation focus group (there will be two more sessions on Thursday) were Harald Frey (UC Berkeley) on ground signatures of localized wave-particle interaction in diffuse aurora, Jay Johnson (PPPL, on behalf of Simon Wing of APL) on a magnetotail assimilation model, Michelle Thomsen (Los Alamos) on observations of plasma sheet electrons at geosynchronous orbit, Sarah Jones (UNH, on behalf of Marc Lessard) on the evolution of diffuse particle precipitation to inverted V precipitation, Emma Spanswick (Calgary) on optical and riometer signatures of diffuse aurora, Tom Sotirelis (APL) on the global character of diffuse electron aurora, and Jacob Bortnik (UCLA) on scattering of electrons by chorus waves. Highlights were Frey, who asked the key question, "What is diffuse aurora, anyway?"; Thomsen's demonstration of strong pitch angle diffusion in the geosynchronous particle data, Lessard's speculation that the latitudinal width of the substorm onset arc is determined by the overlap of precipitating plasma sheet ions and electrons, and Sotirelis's demonstration that characteristic precipitating electron energy is highest near noon--the same region where Bortnik showed the strongest off-equatorial chorus, especially at low frequencies.