Magnetic-Reconnection Generated Shock Waves as a Driver of Solar Surges

Abstract:

We found that a surge consists of multiple shock features. In our high spatio-temporal spectroscopic observation of the surge using Fast Imaging Solar Spectrograph of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory, each shock is identified with the sudden appearance of an absorption feature at the blue wings of the Ca II 8542 Å line and Hα line that gradually shifts to the red wings. The shock features are overlapped with one another with an time interval of 110 s, which is much shorter than the duration of each shock feature 300 – 400s. This finding suggests that the multiple shocks may not have been originated from a train of sinusoidal waves generated by oscillations and flows in the photosphere. As we found the signature of the magnetic flux cancellations at the base of the surge, we conclude that the multiple shock waves in charge of the surge were generated by the magnetic reconnection in the low atmosphere associated with the flux cancellation.