High Resolution Temporal and Spatial Structure of a White Light Flare

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Revision as of 08:59, 28 April 2017

Introduction

The New Solar Telescope (NST) at Big Bear Solar Observatory currently has the largest aperture (1.6 m) of any solar telescope in the world, and thus has the best resolution at its diffraction limit. Solar flares are obvious targets for such a telescope: they exhibit tiny spatial scales and have rapid time variation. In this Nugget we describe the white-light continuum emission from three homologous flares, SOL2014-10-29 (C6.8, M1.3, and M1.2 by their GOES classifications. In Ref. [1] we describe these flares as observed by NST, making reference to AIA images in the EUV and high-energy observations from RHESSI and from Fermi/GBM

Fine Spatial Structure of TiO Continuum Enhancement

The three consecutive flares of were impulsive, confined, and short-duration two-ribbon flares (4-5 min). They had plasma ejection and no detectable ribbon separation. All of them produced detectable enhancement in HMI intensity images. At the NST the white-light observations are made in a spectral band at 7057Å due to the TiO molecule. In these three flares we found that the two M-class flares produced TiO emission and hard X-rays above 50 keV, whereas the C-class flare did not. In Figure 1 we plot RHESSI hard and soft X-ray contours over the 18:49:44 UT NST/TiO original image and a 18:49:44-18:49:14 UT difference image taken at the flare peak. While RHESSI shows one compact hard X-ray source, the TiO images clarify that there were actually three well-separated compact bright patches. These had >15% enhancement above the quiet-Sun brightness level over a dimension of about 0.2 Mm, with areas of order 10¹⁴ cm². White-light flares often show fine structure, but because of NST's resolution these are among the finest features yet reported.

Figure 1: RHESSI X-ray contours (green 25-50 keV and blue 50-100 keV) plotted over the 18:49:44 UT NST TiO image (left) and a TiO difference (18:49:44-18:49:14 UT) (right) images of the M1.3 flare. RHESSI contour levels are plotted at 30%, 50%,70%, and 90% of the corresponding peak intensity. Numbers 1, 2a, 2b, 3, and 4 indicate enhanced the TiO patches discussed in the study.

References ===

[1] "High-resolution Observations of a White-light Flare with NST"