Hot Prominence Cavities

Multiwavelength observations of the solar corona made during the total solar eclipses of 2006 March 29 and 2008 August 1, are used to study the thermodynamic properties of prominence cavities. Historically, cavities have been associated with the base of streamers where the white light intensity is reduced compared to their surroundings. The exceptional high spatial resolution close to 1 arcsec in the white light eclipse images, show that they consist of arch-like envelopes, extending from 0.1 to 0.3 solar radii above prominences. They are invariably bright in coronal emission lines, with their brightness varying with temperature. For most of the cases observed, the cavities are dominated by emission from the hotter, 2 MK Fe XIII 1074.7 and Fe XIV 530.3 nm lines, although examples of cavities which were bright in the cooler 1 MK Fe X 637.4 and Fe XI 789.2 nm lines, and dim in the hotter lines, were also found. These observations resolve the long-standing ambiguity associated with the temperature of cavities.