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


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