HR: 09:10h
AN: SM51D-05    [Abstracts]
TI: What Supports Parallel Electric Fields in Birkeland Current Regions?
AU: Jasperse, J R
EM: John.Jasperse@hanscom.af.mil
AF: Air Force Research Laboratory, 29 Randolph Rd., Hanscom AFB, MA 01731, United States
AU: Basu, B
EM: Bamandas.Basu@hanscom.af.mil
AF: Air Force Research Laboratory, 29 Randolph Rd., Hanscom AFB, MA 01731, United States
AU: * Lund, E J
EM: Eric.Lund@unh.edu
AF: University of New Hampshire, Space Science Center, Morse Hall, 39 College Rd., Durham, NH 03824, United States
AB: Quasi-steady electric fields parallel to the background magnetic field exist in both upward and downward Birkeland current regions above the aurora. These electric fields, together with the turbulence found in the auroral region, energize ionospheric plasma as it flows upward into the magnetosphere. These parallel electric fields are split among one or more double layers, a transition region above the double layer, and a long-range potential region. Recently, we have developed a new kinetic and multimoment fluid theory for the Birkeland current system which includes the effect of plasma turbulence [1,2]. Using that theory, we derive a generalized Ohm's law for the Birkeland currents and find that these parallel electric fields are supported by some combination of (1) anomalous resistivity, (2) pressure gradients, and (3) the mirror force. Most theoretical efforts have focused on anomalous resistivity as the dominant supporting factor in parallel electric fields. Applying this theory to observations in the long range potential region of the downward Birkeland current, however, we show that the anomalous resistivity accounts for only a small portion of the parallel electric fields (<10%) and that the contributions of the other two terms are much more important. This result has important implications for other regions of space, such as reconnection sites and near solar flares, where parallel electric fields are likely to exist in inhomogeneous plasmas. [1] J. R. Jasperse et al. (2006), Phys. Plasmas 13, 072903 [2] J. R. Jasperse et al. (2006), Phys. Plasmas 13, 112902
DE: 2451 Particle acceleration
DE: 2704 Auroral phenomena (2407)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 7863 Turbulence (4490)
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting