On Formation Of A Shock Wave In Front Of A Coronal Mass Ejection With Velocity Exceeding The Critical One

TL;DR

This paper investigates the formation of shock waves ahead of coronal mass ejections, confirming that shock formation occurs when CME velocity exceeds a critical threshold, with observable plasma density discontinuities.

Contribution

It provides empirical evidence for the velocity threshold at which shock waves form in front of CMEs, extending previous findings from 2008.

Findings

Shock wave forms at CME velocities above the critical threshold.

Discontinuity in plasma brightness indicates shock formation.

Disturbed region behavior varies with CME velocity.

Abstract

New study confirms conclusions made in [M. Eselevich, and V. Eselevich, 2008]; according to it, there is a disturbed region expended along the CME propagation direction in front of a coronal mass ejection whose velocity $u$ is lower than the critical $u_C$ relative to the surrounding coronal plasma. The time difference brightness (plasma density) in the disturbed region smoothly decreases to larger distances in front of CME. A shock wave forms at u higher than $u_C$ in the front part of the disturbed region manifested as a discontinuity in radial distributions of the difference brightness.