HR: 1340h
AN: SH53A-1261    [Abstracts]
TI: Observations of Large Amplitude Electrostatic Waves Associated with Magnetic Ramp Substructure at Earth's Bow Shock by Polar
AU: * Hull, A J
EM: ahull@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, 7 Gauss Way, Berkeley, CA 94720
AU: Larson, D
EM: davin@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, 7 Gauss Way, Berkeley, CA 94720
AU: Mozer, F
EM: fmozer@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, 7 Gauss Way, Berkeley, CA 94720
AU: Wilber, M
EM: wilber@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, 7 Gauss Way, Berkeley, CA 94720
AU: Bale, S
EM: bale@ssl.berkeley.edu
AF: Space Sciences Laboratory, UC Berkeley, 7 Gauss Way, Berkeley, CA 94720
AU: Scudder, J
EM: jds@space-theory.physics.uiowa.edu
AF: Dept. of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242
AU: Russell, C
EM: ctrussel@igpp.ucla.edu
AF: IGPP, 3845 Slichter Hall, Los Angeles, CA 90095
AB: We present Polar-EFI observations of electrostatic (ES) waves at high frequency (100 Hz < f < 4000 Hz) at Earth's bow shock under extreme solar wind conditions. Polar-EFI provides the first 3-axis measurements of electric fields across the shock layer, allowing for a better evaluation of the electric field properties than previous missions. The ES waveforms are of large amplitude (as large as 20-100 mV/m), and have both parallel and perpendicular components. Although we have observed solitary waves, the most prevalent structures in the magnetic ramp are large amplitude ES wave packets usually lasting from 10-30 cycles. These structures have wavelengths of a few hundred meters (e.g., ~ 10 Debeye Lengths) and are convecting by the spacecraft at speeds from 50 km/s to > 800 km/s. In the events presented, the ES wave power is generally well correlated with maxima in the magnetic ramp substructure, suggesting that these local maxima are important sites for the generation of these waves. These waveforms are not consistent with the classical ion acoustic wave description, since they occur under conditions where T_e~ T_i at local magnetic field maxima as opposed to the gradient and they propagate at oblique angles to the magnetic field. The fact that these waves are collocated with magnetic maxima is suggestive that the free-energy source of these waves may be from phase-space holes in the electron distribution, as a result of the acceleration of the low energy part of electron phase space by the shock DC electric field.
DE: 2139 Interplanetary shocks
DE: 2154 Planetary bow shocks
DE: 7851 Shock waves (4455)
DE: 7863 Turbulence (4490)
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005