UV spectra, bombs, and the solar atmosphere

Abstract

A recent analysis of UV data from the Interface Region Imaging Spectrograph {\em IRIS} reports plasma "bombs" with temperatures near \hot{} within the solar photosphere. This is a curious result, firstly because most bomb plasma pressures $p$ (the largest reported case exceeds $10^3$ dyn~cm${}^{-2}$) fall well below photospheric pressures ($>7\times 10^3$), and secondly, UV radiation cannot easily escape from the photosphere. In the present paper the {\em IRIS} data is independently analyzed. I find that the bombs arise from plasma originally at pressures between $\lta80$ and 800 dyne~cm${}^{-2}$ before explosion, i.e. between $\lta850$ and 550 km above ${\tau }_{500}=1$. This places the phenomenon's origin in the low-mid chromosphere or above. I suggest that bomb spectra are more compatible with Alfvénic turbulence than with bi-directional reconnection jets.

Accepted for publication in the Astrophysical journal

References in corpus (1)

• Hot Explosions in the Cool Atmosphere of the Sun

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