On formation of a shock wave in front of a coronal mass ejection with velocity exceeding the critical one

Abstract

[1] It is shown that in front of a coronal mass ejection, having a velocity u lower than the critical u C relative to the surrounding coronal plasma, there is a disturbed region expended along a direction of the CME propagation. The time difference brightness (plasma density) in the disturbed region smoothly decreases to larger distances in front of the CME. A discontinuity forms at u higher than u C in the disturbed region front part in radial distributions of the difference brightness. Since the u C value is close to the local fast-mode MHD velocity, which in corona approximately equal to the Alfven one, the formation of such a discontinuity when u C is exceeded may be identified with the formation of a shock wave. Citation: Eselevich, M. V., and V. G. Eselevich (2008), On formation of a shock wave in front of a coronal mass ejection with velocity exceeding the critical one, Geophys. Res. Lett., 35, L22105,

Magnetic Field Strength in the Upper Solar Corona Using White-Light Shock Structures Surrounding Coronal Mass Ejections

“…To compare with Alfven speed, we added the Alfven speed profile obtained using the models of magnetic field and plasma density (Dulk & McLean 1978;LeBlanc et al 1998;Mann et at. 1999;Gopalswamy et al 2001;Eselevich & Eselevich 2008). As shown in the figure, all events have speeds faster than the Alfven speeds and hence can form shocks.…”

Coronal Mass Ejections: Models and Their Observational Basis

“…It is still on debate whether such a piston-driven shock may show up at metric wavelengths (Vršnak and Cliver, 2008). The white-light imaging signature of this piston-driven shock should be the so-called "CME forerunner" found by Jackson and Hildner (1978), which was later inferred based on the streamer deflections and clearly detected by Vourlidas et al (2003) and Eselevich and Eselevich (2008), as shown by Figure 33. The spectroscopic properties of the CME-driven shock are well documented by Raymond et al (2000), Mancuso et al (2002), and Ciaravella et al (2006).…”

A possible mechanism of energy dissipation in the front of a shock wave driven ahead of a coronal mass ejection

“…Notably, calculations for a simple geometric model of quasi-spherical shock [Eselevich and Eselevich, 2008] show that the observable brightness profile width δ F was close to width δ N for the density jump in the shock wave.…”

“…Eselevich M. and V. [Eselevich and Eselevich, 2008] revealed that there is a disturbed region extended along the direction of coronal mass ejection (CME) propagation in front of the CME, when its velocity u relative to the ambient coronal plasma is below a certain critical velocity u C . Given u > u C , a discontinuity in the difference brightness distributions is formed in the frontal part of the disturbed region.…”