HR: 0830h
AN: SH21B-0118    [PDF]
TI: A Statistical Study of Interplanetary Shocks and Pressure Pulses Internal to Magnetic Clouds
AU: Lepping, R P
EM: rpl@leprpl1.gsfc.nasa.gov
AF: NASA, GSFC, Greenbelt, MD 20771 United States
AU: * Collier, M R
EM: mcollier@pop600.gsfc.nasa.gov
AF: NASA, GSFC, Greenbelt, MD 20771 United States
AU: Berdichevsky, D B
EM: xrdbb@lepvax.gsfc.nasa.gov
AF: NASA, GSFC, Greenbelt, MD 20771 United States
AB: We have canvassed the Wind magnetometer data from launch in November of 1994 through May of 2002 searching for cases of interplanetary shocks and pressure pulses internal to magnetic clouds. An internal shock or pressure pulse is defined as an unbalanced (in a pressure sense), sharp (quicker than 12 minutes), large ($\Delta$B/B$>$0.23) change in the magnitude of the magnetic field within the boundaries of a magnetic cloud. We have found nine cases in 68 clouds, so that these shocks and pressure pulses occurred in about 13% of the Wind magnetic clouds. Of those nine cases, six occurred during the 1995-1998 period when the average sunspot number was less than 90 while only three occurred during the 1999-2002 period when the average sunspot number was greater than 90, although roughly equal numbers of magnetic clouds were observed over the two periods (38 versus 30). These ``internal" shocks tend to occur in the latter half of the clouds, i.e., time-wise, about two-thirds of the way through. In every case, the field change is highly compressive at the shock showing little or no change in angle during or after the magnitude jump. In three of the nine cases, potential external sources for these internal shocks and pressure pulses have been identified, but in at least one of these three cases, which identified a flare, no evidence for associated ejecta or shocks could be found [Collier et al., JGR, 106, 15,985, 2001].
DE: 2109 Discontinuities
DE: 2139 Interplanetary shocks
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting