Mapping the Sound Speed Structure of the Sun's Atmosphere
Abstract
We describe an instrument for seismically probing the acoustic properties of the Sun's lower atmosphere. The instrument, which is based on magneto-optical filter technology, acquires full-disk Dopplergrams simultaneously in the K D1 (770 nm) and Na D2 (589 nm) Fraunhofer lines. The Dopplergrams have a spatial resolution of ~5 arc secs and are recorded at a cadence of one frame every 10 seconds, average from 16 frames per second. These data allow us to use acoustic waves with frequencies beyond the cut-off frequency for the solar atmosphere (~5mHz) to map the spatial and temporal changes in the vertical wave travel time between the mid-chromosphere and the low-photosphere. These types of maps will provide a strong constraint for models of the solar atmosphere and possibly study early warnings for explosive phenomena. We present some preliminary results from observations made at the geographical South Pole during the 2002/2003 Austral summer. We also discuss our program for the next campaign with instrumental improvements as far as a third level Dopplergram and magnetographic capability. We also consider cloning the instrument for Dome C in order to further minimize atmospheric noise and gaps in the data string due to bad weather.
- Publication:
-
Memorie della Societa Astronomica Italiana Supplementi
- Pub Date:
- 2003
- Bibcode:
- 2003MSAIS...2..190C
- Keywords:
-
- MOF;
- Time distance analysis;
- Helioseismology;
- Solar Atmosphere Diagnostic