New Light on the Heart of Darkness of the Solar Chromosphere
S. K. Solanki 1,
W. Livingston 2, and
T. Ayres 3
1 Institute of Astronomy, ETH-Zentrum, CH-8092 Zürich, Switzerland
2 National Solar Observatory, National Optical Astronomy Observatories, Tucson, AZ 85726
3 Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0391
Solar carbon monoxide spectra indicate the existence of a cool (less than 4000 kelvin) component to the solar chromosphere coexisting with the hot, bright gas at 6000 to 7000 kelvin. However, both the existence and the location of the cool component have been controversial. New high-resolution spectra show that carbon monoxide goes into emission just beyond the limb, allowing it to be probed without photospheric contamination. The cool component has temperatures as low as 3000 to 3500 kelvin and appears to cover 50 to 85 percent of the quiet solar surface. There is a steep temperature rise to normal chromospheric temperatures at a height of 900 to 1100 kilometers. Large horizontal velocities are seen, suggesting that the cool component is maintained by the supersonic adiabatic expansion of upwelling gas in overshooting granules.
Submitted on November 5, 1993
Accepted on November 24, 1993
