Radial Evolution and Turbulence Characteristics of a Coronal Mass Ejection

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Abstract

We investigate a coronal mass ejection (CME) associated with an X3.9 solar flare that occurred on 1992 June 25. This long-duration event showed a system of large postflare loops at the activity site throughout the period of the enhanced X-ray emission. The drift rate of the metric type IV radio burst observed near the X-ray maximum suggests the speed of the ejecta to be ~350 km s-1 at heights ≤2 solar radii. The solar proton intensities, in the energy range 1-100 MeV observed in the interplanetary medium, show gradual-decay profiles lasting for more than two days and suggest CME-driven acceleration near the Sun. The inference on the spatial and kinematical characteristics of the propagating CME in the inner heliosphere (0.2-1 AU) is primarily based on the interplanetary scintillation observations at 327 MHz, obtained from the Ooty Radio Telescope and the Solar-Terrestrial Environment Laboratory. The scintillation data show the deceleration of propagating disturbance speed, VCME ~ R-0.8, in the interplanetary medium. The speeds obtained from the radio and scintillation measurements also suggest that the coronal shock may not be directly related to the interplanetary shock. The size of the CME in the interplanetary medium seems to follow a simple scaling with distance from the Sun, indicating the pressure balance maintained between the ejecta and the ambient solar wind. The density turbulence spectrum of the plasma carried by the propagating disturbance seems to be flat, Φ ~ κ-2.8, also having a small dissipative scale length, Si(IPD) ≤ 5 km. The spectrum is significantly different from that of high-speed flow from coronal holes and low-speed wind originating above closed-field coronal streamers.

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