Thinkshop12

On the Nature of Ellerman Bombs and Microflares as Observed with the 1.5m GREGOR Telescope

Christoph Kuckein (Leibniz-Institut fuer Astrophysik Potsdam (AIP))

Abstract. Ellerman bombs (EBs) are conspicuous small-scale (~1 arcsec) brightenings visible in the hydrogen Balmer lines and observed in complex and developing active regions. EBs are especially well seen in both wings of the H alpha line from approximately 0.05 nm on outwards of the line center, while the inner H alpha core is not affected. The scenario of magnetic field reconnection taking place in the lower layers of the solar atmosphere is widely accepted as the triggering mechanism of Ellerman bombs. On the other hand, solar flares are believed to have their origin in magnetic reconnection processes in the corona, depositing part of their released energy in the transition region and chromosphere where the plasma is heated to temperatures above 10e7 K. Microflares (and nanoflares) are defined after the fraction of thermal plasma energy they contain compared with the largest observed flare events. Observations show that microflares have a similar nature as large flares in terms of their spectral and X-ray properties. In August 2014, the following polarity of active region NOAA 12139 was observed with the GREGOR Fabry-Perot Interferometer (GFPI) at the 1.5 m GREGOR telescope (Tenerife). Time-series of filtergrams scanning along the H alpha line provided two-dimensional spectroscopic information of two solar phenomena taking place simultaneously within the observed field of view: (1) Ellerman bombs clearly visible in the wings of the H alpha line, and (2) a microflare only visible in the higher chromospheric layers where the H alpha inner-core forms. We investigate the nature and (dis-)similarities of these two events from the analysis of the H alpha profiles and, by comparison with AIA/SDO data, we speculate about the simultaneous occurrence of magnetic reconnection processes taking place at the same spatial location at both photospheric and coronal layers.

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