UV spectra, bombs, and the solar atmosphere

A recent analysis of UV data from the Interface Region Imaging Spectrograph (IRIS) reports plasma "bombs" with temperatures near 8 × 10⁴ K within the solar photosphere. This is a curious result, first because most bomb plasma pressures p (the largest reported case exceeds 10³ dyn cm⁻²) fall well below photospheric pressures ($>7\times {10}^3$), and second, UV radiation cannot easily escape from the photosphere. In the present paper the IRIS data is independently analyzed. I find that the bombs arise from plasma originally at pressures between ≤ 80 and 800 dyne cm⁻² before explosion, i.e., between ≥ 850 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.