Triggering an eruptive flare by emerging flux in a solar active-region complex

TL;DR

This study investigates how flux emergence in a solar active-region complex triggered an eruptive flare and coronal mass ejection through non-standard magnetic interactions, involving reconnection and destabilization of overlying flux.

Contribution

It reveals a novel mechanism where flux emergence triggers eruptions without typical polarity or location conditions, emphasizing the role of large-scale magnetic interactions.

Findings

Flux emergence triggered the eruption via interaction with overlying flux.

Reconnection with emerging flux caused jet emissions and loop system rise.

Destabilization of sheared flux led to the flare and CME.

Abstract

A flare and fast coronal mass ejection originated between solar active regions NOAA 11514 and 11515 on July 1, 2012 in response to flux emergence in front of the leading sunspot of the trailing region 11515. Analyzing the evolution of the photospheric magnetic flux and the coronal structure, we find that the flux emergence triggered the eruption by interaction with overlying flux in a non-standard way. The new flux neither had the opposite orientation nor a location near the polarity inversion line, which are favorable for strong reconnection with the arcade flux under which it emerged. Moreover, its flux content remained significantly smaller than that of the arcade (approximately 40 %). However, a loop system rooted in the trailing active region ran in part under the arcade between the active regions, passing over the site of flux emergence. The reconnection with the emerging flux, leading to a series of jet emissions into the loop system, caused a strong but confined rise of the loop system. This lifted the arcade between the two active regions, weakening its downward tension force and thus destabilizing the considerably sheared flux under the arcade. The complex event was also associated with supporting precursor activity in an enhanced network near the active regions, acting on the large-scale overlying flux, and with two simultaneous confined flares within the active regions.