Observation of 2011-02-15 X2.2 flare in Hard X-ray and Microwave

TL;DR

This study provides a detailed multi-wavelength analysis of the 2011 X2.2 solar flare, revealing the spatial and temporal behavior of high-energy electrons and their relation to flare models.

Contribution

It offers new insights into the spatial and temporal distribution of accelerated electrons during a major solar flare using combined HXR and microwave observations.

Findings

Seven emission peaks originate from two main sources.

Spatial location changes are observed mainly between the second and third peaks.

The results support the tether-cutting model of solar flares.

Abstract

Previous studies have shown that the energy release mechanism of some solar flares follow the Standard magnetic-reconnection model, but the detailed properties of high-energy electrons produced in the flare are still not well understood. We conducted a unique, multi-wavelength study that discloses the spatial, temporal and energy distributions of the accelerated electrons in the X2.2 solar flare on 2011, Feb. 15. We studied the source locations of seven distinct temporal peaks observed in hard X-ray (HXR) and microwave (MW) lightcurves using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in 50 to 75 keV channels and Nobeyama Radioheliograph (NoRH) in 34 GHz, respectively. We found that the seven emission peaks did not come from seven spatially distinct sites in HXR and MW, but rather in HXR we observed a sudden change in location only between the second and the third peak, with the same pattern occurring, but evolving more slowly in MW. Comparison between the HXR lightcurve and the temporal variations in intensity in the two MW source kernels also confirmed that the seven peaks came predominantly from two sources, each with multiple temporal peaks. In addition, we studied the polarization properties of MW sources, and time delay between HXR and MW. We discuss our results in the context of the tether-cutting model.