ISSN:
1573-093X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract A survey of soft X-ray images from Skylab has revealed a class of large-scale transient X-ray enhancements in the lower corona which are typically associated with the disappearance of Hα filaments away from active regions. Contemporary with the Hα filament disappearance, X-ray emitting structures appeared at or near the filament location with shape and size resembling the filament. Eventually these structures faded, but the filament cavity was no longer obvious. Typically the peak of the X-ray event lagged the end of the filament disappearance by tens of minutes. The durations of the coronal X-ray enhancements were considerably longer than the associated Hα filament disappearances. Major flare effects, such as chromospheric brightenings, typically were not associated with these X-ray events. One event analyzed quantitatively had a peak temperature between 1.8 and 2.7 × 106 K, achieved a peak density of ≈109 cm−3 and resulted in an enhancement in the plasma pressure over the conditions of the preexisting coronal cavity of at least a factor of 7. The mass of the coronal X-ray emitting material was about 10% that of the preexisting filament and the thermal energy of the coronal event was on the order of 1029 erg, about 10% of the mechanical energy of the Hα filament eruption. The event appeared to cool by radiative losses and not by thermal conduction. It is likely that the coronal enhancements are caused by heating of an excess of previously cooler material, either from the filament itself, or by compression of coronal material by a changing magnetic field.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00153342
