We began the meeting with a general discussion about recent changes at the
NASA Advisory Counsel (NAC). To rehash, Gene Levy, Wes Huntress, and Charlie Kennel chose
to resign from the NAC several months ago. At this point, it appears most productive to point
out that any division between exploration and science is artificial. This has been the position of
the Heliophysics Subcommittee (HPS). There is definitely a ramp up of activities to prepare for NASA's
lunar program. This has a scientific component and Heliophysics will participate. Attached is an excel
spread sheet (draft form) describing potential lunar scientific activities. Any recommendations for
additions or changes should be provided to Jim Spann (
).
George Siscoe pointed out the similarity between a popular model of CMEs and the expulsion of plasmoids in the magnetotail. In both cases the acceleration can be described by a simple bouyancy model, and both require reconnection in pretty much the same way. He also showed a plot of X-ray luminosity vs magnetic flux that suggests a common process over a huge range of scales from magnetic bright points to very active young stars. George then raised the possibility of a joint paper on the commonality of eruptive magnetic processes as a useful step toward IHY and a general application of heliospheric physics to astrophysics. Steve Kahler brought up comet tail disconnection events as another example analogous to the CMEs and plasmoids.
I presented an analysis of X-ray and UV data that points toward a dominance of energetic particles in the energy partition in the reconnection region during an X-class solar flare. One wants to know how much of the dissipated magnetic energy ends up as kinetic, thermal or energetic particle energy. There are many parameters, such as plasma beta, Alfven Mach number, density, current sheet length, or E field that might be important. (Note that in discussing energy partition, one can consider just the gas and field passing through the current sheet, as I did here, or one can include the kinetic energy of the CME. The first is local energetics, and the latter is a large scale problem that depends on field topology. Both are important for astrophysical applications, but it's important to be clear which you mean.)
Kathy Reeves presented results from her extension of the Lin & Forbes model of CME eruption starting with loss of equilibrium of a flux rope. For rapid reconnection, kinetic energy of the expanding CME dominates over thermal energy of the gas that passes through the current sheet by over an order of magnitude, while for slower reconnection they are comparable. It should be possible to make analogous calculations for plasmoids in the magnetotail.
Jun Lin presented an analysis of current sheets associated with solar flares. The spacing between successive plasmoids gives a scale that can be related to the current sheet thickness, assuming that the plasmoids are formed by the tearing mode. The thickness turns out to be far larger than expected from ordinary or anomalous resistivity. This suggests that a much larger effective resistivity results from the breakup of the current sheet into magnetic islands and turbulence.
The attached power point slide is a draft of the program that IHY program managers are putting together for a 2007 summer school. You will see "Universal Processes" in many places. The program answers in part the question that Steve Kahler asked at yesterday's meeting: why we should undertake at this time a project to write a joint review paper that develops the theme of comparitive explosive energy converions? The IHY summer school program indicates that the topic now seems to be timely. George
Nathan Schwadron
Boston University
Dept. of Astronomy
725 Commonwealth Avenue
Boston, Massachusetts 02215
phone: (617) 358-4365
fax: (617) 353-5704