Plasma and magnetic field structure of a slow shock: Wind observations in interplanetary space

Y. C. Whang, D. Larson, R. P. Lin, R. P. Lepping, and A. Szabo

Catholic University of America, Washington, D. C. 20064

Abstract:

This paper reports on the observation of an interplanetary slow shock on May 23, 1995 using 3-s plasma and magnetic field data from the Wind spacecraft. Since the time to traverse the shock (~ 15 s) is much greater than the 3-s temporal resolution of the data, this observation can reveal the plasma and magnetic field structure through the interior of the shock. The 3-s data also provide accurate preshock and postshock conditions immediately outside the shock layer. The flow speeds in the shock frame of reference Un < a cos Q on both sides of the shock, Un1 > CS1, and Un2 < CS2. Here a and CS are, respectively, the Alfven speed and the slow speed, Q is the acute angle between the magnetic field vector and the shock normal, and the subscripts 1 and 2 denote the preshock and the postshock conditions. Q 1 ~ 47 and Q 2 ~ 39 . The jump conditions B2/B1, N2/N1, and (Ti + Te)2/(Ti +Te)1 of the observational result are in good agreement with the Rankine-Hugoniot solution. The thickness of the shock is of the order of 36 times of the preshock ion inertial length.

Geophys. Res. Lett., Vol. 25, No. 14, 2625-2628, 1998