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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L12103, doi:10.1029/2005GL022777, 2005

Downstream structures of interplanetary fast shocks associated with coronal mass ejections

R. Kataoka

National Institute of Information and Communications Technology, Tokyo, Japan


S. Watari

National Institute of Information and Communications Technology, Tokyo, Japan


N. Shimada

National Institute of Information and Communications Technology, Tokyo, Japan


H. Shimazu

National Institute of Information and Communications Technology, Tokyo, Japan


K. Marubashi

National Institute of Information and Communications Technology, Tokyo, Japan


Abstract

We investigate 17 coronal mass ejection (CME) events identified by the ACE spacecraft during solar cycle 23, focusing upon the fine structures of the sheath region between the CME and its associated shock to find their dependence on the shock parameters. We observe the planar magnetic structure (PMS) downstream of a quasi-perpendicular shock when the Alfvén Mach number >2.0. Here, the PMS is characterized by the magnetic fields changing directions abruptly and intermittently within a plane parallel to the shock plane. The downstream PMS does not form when a magnetic cloud with β value <0.05 exists just upstream of a shock with Alfvén Mach number <2.0. The sheath magnetic fields become highly turbulent when the shock angle is <60 and/or the upstream β value is >0.5 and the upstream is dominated by Alfvenic fluctuations.

Received 21 February 2005; accepted 20 May 2005; published 18 June 2005.

Index Terms: 2101 Interplanetary Physics: Coronal mass ejections (7513); 2109 Interplanetary Physics: Discontinuities (7811); 2134 Interplanetary Physics: Interplanetary magnetic fields; 2139 Interplanetary Physics: Interplanetary shocks; 2149 Interplanetary Physics: MHD waves and turbulence (2752, 6050, 7836).

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Citation: Kataoka, R., S. Watari, N. Shimada, H. Shimazu, and K. Marubashi (2005), Downstream structures of interplanetary fast shocks associated with coronal mass ejections, Geophys. Res. Lett., 32, L12103, doi:10.1029/2005GL022777.