The 1?55 � X-ray emission from an active limb prominence

Abstract

The solar X-ray emission spectrum between 1 and 55 A has been studied for one solar event, using the two X-ray experiments on-board of the ESRO 2 satellite. Although this event fits the description of the class of X-ray events described as gradual rise and fall events there is evidence to show that it is caused by the superposition of a number of events, of which the largest one was correlated with the appearance of an active loop-like prominence on the East limb of the Sun. By assuming the radiation processes in the source region to be thermal, temperatures and emission measures against time for the source region have been derived using the most recent models for free-free continuum and line emission due to thermal plasmas. The temperatures derived have been used to calculate cooling rates due to radiation losses. It is shown from data in the 2.2–3.0 A band that the cooling rate of the excited corona associated with the prominence is compatible with an electron density of 1 × 1011 cm−3 if a single injection of particles is considered to occur in the corona. From data in the 5.8–8.8 A band one finds a value of 2 × 1010 cm−3. An estimate of the total injected energy is made.