Double discontinuity: A compound structure of slow shock and rotational discontinuity
Y. C. Whang, J. Zhou, R. P. Lepping, A. Szabo, D. Fairfield, S. Kokubun, K. W. Ogilvie, and R. Fitzenreiter
Department of Mechanical Engineering, Catholic University of America, Washington, D. C.
This paper reports the observations of a compound structure in space plasma composed of a slow shock layer and an adjoining rotational discontinuity layer on the postshock side. The compound structure looks like a new kind of MHD discontinuity; it may be called a double discontinuity. Two dual-spacecraft observations of double discontinuities using high-resolution magnetic field data were made in interplanetary space in 1995. The first one observed from Wind and IMP 8 is composed of a reversed slow shock and a rotational discontinuity. The second one observed from Wind and Geotail is composed of a forward slow shock and a rotational discontinuity. A double discontinuity is a stable, large-scale solar wind structure. The thickness of the slow shock layer is of a few ion inertial lengths. The flow in the preshock region has a low b i value and a large shock angle.
J. Geophys. Res., 103, A4, 6513-6520, 1998