Towards Understanding the Solar Atmosphere

G. A. Doschek

In this talk I will discuss the connectivity between different temperature regions of the solar atmosphere. Most of the talk will concern the connectivity between the lower (< 2 x 105 K) and upper transition regions (> 2 x 105 K, < 1 x 106 K). In particular, I focus on work in progress on investigating dynamical connections between these two different temperature regimes based on analysis of SUMER spectra from SOHO. I investigate flows observed in two lower transition region lines (C IV, 1548 A, S V 2 x 786 A) observed simultaneously and co-spatially with an upper transition region line (Ne VIII, 2 x 770 A). The spectra were obtained in raster mode and are assembled into images with a spatial resolution of about 1 arcsec. Exposure times were about 20 s. The spectral line profiles are fit with Gaussian distributions from which the radial flows can be determined from the Doppler shifts of the lines. I discuss results obtained to date. I also discuss the connection between the chromosphere and the multi-million degree gas that produces the soft X-ray emission in solar flares. I show that a multi-thermal thread model can resolve the long-standing disparity between high resolution X-ray spectroscopic observations and predictions based on 1D numerical simulations of flaring loops.

Correspondence

G. A. Doschek (george.doschek@nrl.navy.mil)