Chromopheric Jets Powered by Sunspot Oscillations (Invited)

Abstract:

It still remains mysterious how the solar chromosphere can stand high
above the photosphere. The dominant portion of this layer must be dynami-
cally supported as evident by the common occurrence of jets such as spicules
and mottles in quiet regions, and fibrils and surges in active regions. Hence
revealing the driving mechanism of these chromospheric jets is crucial for the
understanding how the chromosphere itself exists. Here we report our obser-
vational finding that fibrils surrounding a sunspot are powered by the oscil-
lations of the sunspot. The fibrils are dynamically connected to the umbra
by the shock waves apparently originating from the umbral oscillations. The
predominant period of these shock waves increases with distance: from three
minutes to ten minutes. This short-to-long period transition is attributed to
the selective suppression of shocks by the falling material of their preceding
ones. These results suggest that the photospheric or sub-photospheric
excitation of a magnetic flux tube is responsible for the maintenance
of the chromosphere permeated by the field lines of the flux tube.