The Relationship Between Wave Energy and Cool Regions in the Solar Chromosphere

Principal Investigator / Institution: Frank Hill, NSO
Co-Investigators: Thomas Ayres, CASA, Douglas Rabin, NSO

Recent spectroscopic imaging of the carbon monoxide (CO) band system 
near 4.7 (m (Ayres and Rabin 1996, Astrophys. J. 460, 1042) directly supports 
a new picture of the low solar chromosphere that had been suggested by earlier 
observations of CO and other diagnostics.  In this new picture, the classical 
chromosphere does not exist over 50-90% of the surface at heights below 
about 1000 km.  The volume is instead mostly filled by a "COmosphere" as 
cool as 3000 K.

The proposed study will investigate the physical processes that create a 
thermally inhomogeneous chromosphere.  Specifically, we will seek to 
determine the detailed relationship between the spatio-temporal
distribution of mechanical wave energy in the photosphere, examine the
interaction of the p-mode compressions and rarefactions with the
CO radiative cooling mechanism at high altitudes, and 
follow the evolution of high-frequency disturbances from propagation in the 
photosphere to possible shock waves in the low chromosphere.

The investigation will employ the SOI/MDI instrument on SOHO in both high- 
and moderate-resolution mode to obtain about 5-10 time series of Doppler 
velocity images, with each series lasting several hours.  Simultaneously, 
images of the temperature distribution in the low chromosphere will be 
obtained in the CO bands with the Near Infrared Magnetograph (NIM) at the
National Solar Observatory McMath-Pierce Telescope on Kitt Peak, as
well as intensity in the Ca K line with 
the High-L Helioseismometer (HLH) at the Kitt Peak Vacuum Telescope.  The 
Doppler velocity images will be decomposed into spatial maps of mechanical 
wave power filtered into broad temporal frequency bands.  These maps will be 
correlated with the CO and Ca K images to provide four-dimensional (three 
spatial and one temporal) maps of the velocity and temperature fields in the 
photosphere and low chromosphere.

The proposed study will contribute to the understanding of the physical origins 
of the solar atmospheric thermal structure, enhance the scientific return 
of the MDI/SOI investigation on SOHO, and develop new data analysis techniques 
(such as four-dimensional Fourier analysis) that will be generally useful for 
the NASA Space Science program.