Direct Detection of a CME-Associated Shock in LASCO White Light Images

TL;DR

This paper presents the first direct imaging evidence of a CME-associated shock in LASCO white light images, combining observations and MHD simulations to confirm the shock's density enhancement and streamer interactions.

Contribution

It introduces a novel analysis linking LASCO white light features with a CME-driven shock through combined observations and MHD modeling.

Findings

Identification of a clear white light signature of a CME shock

Confirmation of shock-related density enhancement via simulation

First direct imaging of streamer deflection by a CME shock

Abstract

The LASCO C2 and C3 coronagraphs recorded a unique coronal mass ejection on April 2, 1999. The event did not have the typical three-part CME structure and involved a small filament eruption without any visibile overlying streamer ejecta. The event exhibited an unusually clear signature of a wave propagating at the CME flanks. The speed and density of the CME front and flanks were consistent with the existence of a shock. To better establish the nature of the white light wave signature, we employed a simple MHD simulation using the LASCO measurements as constraints. Both the measurements and the simulation strongly suggest that the white light feature is the density enhancement from a fast-mode MHD shock. In addition, the LASCO images clearly show streamers being deflected when the shock impinges on them. It is the first direct imaging of this interaction.