Spectral analysis of Ellerman bombs

By use of the high-resolution spectral data obtained with THEMIS on 2002 September 5, the characteristics of 14 well-observed Ellerman bombs (EBs) have been analyzed. Our results indicate that 9 of the 14 EBs are located near the longitudinal magnetic polarity inversion lines. Most of the EBs are accompanied by mass motions. The most obvious characteristic of the EB spectra is the two emission bumps at the two wings of both H alpha and Ca II lambda 8542. For the first time both thermal and nonthermal semiempirical atmospheric models for the conspicuous and faint EBs are computed. In computing the nonthermal models, we assume that the electron beam resulting from magnetic reconnection is produced in the lower chromosphere. The reasons are that it requires much lower energies for the injected particles and that it gives rise to a more profound absorption at the H alpha line center, in agreement with our observations. The common characteristic is the heating in the lower chromosphere and the upper photosphere. The temperature enhancement is about 600 - 1300 K in the thermal models. If the nonthermal effects are included, then the required temperature increase can be reduced by 100 - 300 K. These imply that the EBs could probably be produced by the magnetic reconnection in the solar lower atmosphere. The radiative and kinetic energies of the EBs are estimated, and the total energy is found to be 10(26) to 5 x 10(27) ergs. According to the characteristics of EBs, we tentatively suggest that EBs could be called "submicroflares.''