HR: 15:00h
AN: SM43A-04 INVITED     [Abstracts]
TI: On Field-aligned Ion Beams in the Earth's Foreshock Region
AU: * Kucharek, H
EM: Harald.Kucharek@unh.edu
AF: University of New Hampshire, 39 College Road, Durham, NH 03824, United States
AB: The foreshock global morphology is organized by the interplanetary magnetic field direction, the bow shock shape, and, crucially, by particle dynamics. All physical processes at and around the Earth's bow are collisionless and the ion dynamic is determined by the wave-particle interactions. Particles are reflected and energized at the shock and some with high speeds are able to propagate upstream against the solar wind. Therefore, the generation of gyrating ions by reflection as well as the formation of field-aligned ion beams are essential parts of this dynamic. First, field-aligned ion beams, predominately found at the quasi-perpendicular bow shock, propagate into the distant foreshock region and may create wave activity. Secondly, ion reflection is most likely the first interaction of ions with the shock before they undergo the downstream thermalization or reflected upstream. These processes are fundamental and may be found at other astrophysical settings such as the termination shock. Recent observations at the Earth's bow shock with Cluster spacecraft provide new insights into time the evolution of particle distributions and the reflection properties of the oblique Earth's bow shock. Field-aligned ion beams appear to emerge from the gyrating ions in the shock ramp created by the same reflection process. In fact, effective scattering in pitch angle within the shock ramp during the reflection seems to be the basic production mechanism of field-aligned ion beams. We revisit ion reflection, the source and basic production mechanism of field-aligned ion beams and their dynamics in the foreshock region, by using multi- spacecraft measurements, and contrast these observations with existing theories.
DE: 7811 Discontinuities (2109)
DE: 7845 Particle acceleration
DE: 7851 Shock waves (4455)
DE: 7863 Turbulence (4490)
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly