A Very Small and Super Strong Zebra Pattern Burst at the Beginning of a Solar Flare

TL;DR

This paper reports an extremely intense, short-lived zebra pattern burst at the start of a solar flare, indicating rapid particle acceleration and energy release in a small region.

Contribution

It presents the first observation of a super strong, brief ZP burst coinciding with EUV flash at flare onset, revealing a new aspect of flare initiation processes.

Findings

ZP burst intensity exceeds several times the broadband continuum.

The burst lasts only 18 seconds, occurring at flare start.

Associated EUV flash indicates rapid energy release.

Abstract

Microwave emission with spectral zebra pattern structures (ZPs) is observed frequently in solar flares and the Crab pulsar. The previous observations show that ZP is only a structure overlapped on the underlying broadband continuum with slight increments and decrements. This work reports an extremely unusual strong ZP burst occurring just at the beginning of a solar flare observed simultaneously by two radio telescopes located in China and Czech Republic and by the extreme ultraviolet (EUV) telescope on board NASA's satellite Solar Dynamics Observatory on 2013 April 11. It is a very short and super strong explosion whose intensity exceeds several times that of the underlying flaring broadband continuum emission, lasting for just 18 s. EUV images show that the flare starts from several small flare bursting points (FBPs). There is a sudden EUV flash with extra enhancement in one of these FBPs during the ZP burst. Analysis indicates that the ZP burst accompanying EUV flash is an unusual explosion revealing a strong coherent process with rapid particle acceleration, violent energy release, and fast plasma heating simultaneously in a small region with short duration just at the beginning of the flare.