Ultraviolet and Hα emission in Ellerman bombs

We present the first high-cadence time profiles of Ellerman bombs (EBs) at two wavelengths, 1.3 Å in the blue wing of the Hα line and the UV continuum at 1600 Å, and study their temporal correlation. Our results demonstrate that 46 out of 75 EBs exhibit a good correlation at the two wavelengths with a correlation coefficient greater than 50%, suggesting that a common energy release produces emission at the two wavelengths. We also find that the EBs with strong Hα emission tend to show a good Hα-UV correlation but that the weakly correlated or noncorrelated EBs are usually weak in Hα emission. More than half of the Hα-UV well-correlated EBs are located at the boundaries of unipolar magnetic areas; the others are located at, or close to, the magnetic inversion lines. However, the majority of the weakly or noncorrelated EBs are located at the magnetic inversion lines. Our results suggest that the physical mechanisms and the energy distributions are quite different in different types of EBs and that heating in the photosphere and temperature minimum region is very important for producing EBs. The high-cadence observations of EBs also confirm unambiguously that the light curves of EBs generally demonstrate a fast rise and a fast decay, with an average e-fold rising/decaying time of about 1 minute, which distinguishes EBs from the flare phenomenon.