Slitless Solar Spectroscopy
Abstract
Spectrographs provide a unique window into plasma parameters in the solar atmosphere. In the corona and elsewhere spectral line profiles have been used to infer microturbulence velocities, Doppler shifts have been used to measure flows, and line ratios have been used to measure temperatures. In fact spectrographs provide the most accurate measurements of plasma parameters such as density, temperature, and flow speed. However, traditionally spectrographic instruments have suffered from the inability to cover large spatial regions of the Sun quickly. To cover an active region sized spatial region, the slit must be rastered over the area of interest with an exposure taken at each pointing location. The raster process can easily take several minutes or longer to cover an active region sized area on the Sun. Because of this long cycle time, the spectra of dynamic events like flares, CME initiations, or transient brightening are obtained only rarely. And even if spectra are obtained they are either taken over an extremely small spatial region, or the spectra are not co-temporal across the raster. Either of these complicates the interpretation of the spectral raster results. Imagers are able to provide high time and spatial resolution images of the full Sun but with limited spectral resolution. The telescopes onboard the Solar Dynamics Observatory (SDO) normally take a full disk solar image every 10 seconds with roughly 1 arcsec spatial resolution. However the spectral resolution of the multilayer imagers on SDO is of order 100 times less than a typical spectrograph. We suggest an alternate reconstruction approach based on tomographic methods with regularization. Results show that the typical Doppler shift and line width error introduced by the reconstruction method is of order a few km/s at 300 A.
- Publication:
-
American Astronomical Society Meeting Abstracts #220
- Pub Date:
- May 2012
- Bibcode:
- 2012AAS...22020617D