| Observations of solar chromosphere-corona transition region plasma show evidence of small-scale, short-lived dynamic phenomena characterized by extreme nonthermal broadening and asymmetry in the wings of spectral line profiles. These impulsive mass motions ("explosive events") are thought to be the product of magnetic reconnection and to be similar in driving mechanism (though larger in size) to nanoflares, the small-scale events proposed by Parker (1988) to heat the corona.; The nonthermal broadening and asymmetry associated with explosive events led to speculation that they were significant to the energy balance of the solar atmosphere, yet initial estimates of the energy flux contribution of these events suggested that the energy released was not sufficient to heat the corona and chromosphere. However, these previous estimates were based on characteristic velocities of the plasma (found from the average shift and width of the spectral line profile) and so did not adequately describe the energy flux.; To further establish the energetic significance of explosive events, the differential distribution of the number of events as a function of their energy, dNdE∼E-a , must be evaluated. If the index, a , of this distribution is greater than 2, the total power released by the events is dominated by the smallest events. Hence, if such a distribution continued to small enough energies, these small events (e.g., nanoflares) would be significant in coronal and chromo-spheric heating. |
