February 15, 2011: sun-quakes produced by flux rope eruption

TL;DR

This study analyzes the 2011 solar flare, confirming two sunquake sources linked to a flux rope eruption, with seismic activity occurring before the main X-ray emissions, challenging previous assumptions about sunquake timing.

Contribution

It presents the first detailed analysis of sunquakes associated with a flux rope eruption, revealing that seismic signals can precede X-ray peaks, and proposes a new model for sunquake triggering mechanisms.

Findings

Two seismic sources at flux rope ends confirmed by acoustic holography.

Seismic emissions occur minutes before major X-ray peaks.

Sunquakes are triggered at flux rope footpoints during eruption onset.

Abstract

We present an analysis of the 15 February 2011 X-class solar flare, previously reported to produce the first sunquake in solar cycle 24 (Kosovichev 2011). Using acoustic holography, we confirm the first, and report a second, weaker, seismic source associated with this flare. We find that the two sources are located at either end of a sigmoid which indicates the presence of a flux rope. Contrary to the majority of previously reported sunquakes, the acoustic emission precedes the peak of major hard X-ray (HXR) sources by several minutes. Furthermore, the strongest hard X-ray footpoints derived from RHESSI data are found to be located away from the seismic sources in the flare ribbons. We account for these discrepancies within the context of a phenomenological model of a flux rope eruption and accompanying two-ribbon flare. We propose that the sunquakes are triggered at the footpoints of the erupting flux rope at the start of the flare impulsive phase and eruption onset, while the main hard X-ray sources appear later at the footpoints of the flare loops formed under the rising flux rope. Possible implications of this scenario for the theoretical interpretation of the forces driving sunquakes are discussed.