Kinematical analysis of flare spray ejecta observed in the corona

Abstract

The mass ejection event on 17 January 1974 was a classsic spray associated with a flare from an over the limb region. The structure of the accompanying coronal transient was typical of well-observed mass ejections, with coronal loops and a forerunner racing ahead of the rising prominence. Observations in Hα, soft X-ray, white light and radio wavelengths allowed us to track both cool (T _e∼10⁴ K) and hot (T _e>10⁶ K) material from limb de-occultation to 6R _⊙. We determined the kinematics and thermodynamics of the internal material, and the overall mass and energy budget of the event. The majority of the mass and energy was linked with coronal material, but at least 20% of the ejected mass originated as near-surface prominence material. We conclude that the upper part of the prominence was being continuously heated to coronal temperatures as it rose through the corona. Above ∼2R _⊙ nearly all of the material was completely ionized. The primary acceleration of the prominence occurred below 3.5 × 10⁴ km with all of the material exhibiting constant velocity above 1.5R _⊙. We found evidence that a moving type IV burst, indicative of strong magnetic fields, was associated with the upper part of the prominence. Our observations suggest that both the cool and hot material were acted upon by a similar, continuous force(s) to great heights and over a long time interval. We find that the observations are most consistent with magnetic propulsion models of coronal transients.