Synthetic analysis of a two-ribbon microflare

Abstract

High-resolution Stokes spectral data of Hα, Ca II 8542 Å, and Fe 16302.5 Å lines for a two-ribbon microflare (TRMF) were simultaneously obtained by the THEMIS telescope on 2002 September 5. We derive the intensity, velocity, and longitudinal magnetic field maps. The hard X-ray emission observed by RHESSI provides evidence of nonthermal particle acceleration in the TRMF. Using Hα and Ca II 8542 Å line profiles and a non-LTE calculation, we obtain semi-empirical atmospheric models for the two brightest kernels of the TRMF. Our result indicates that the temperature enhancement in the chromosphere is more than 2500 K. The kinetic and radiative energies at the kernels are also estimated, resulting in an estimate of the total energy of the TRMF of about 2.4 ×1029 erg. Observations indicate that the TRMF results from the low coronal magnetic reconnection following the eruption of a small filament. However, the local temperature “bump" in the chromosphere presents a puzzle for such a standard flare model. A possible solution to this is discussed.