Hard X-rays associated with CMEs H.S. Hudson, UCB & SPRC Y10, Jan. 24, 2001

Yohkoh observational goals, as of 1991 White-light flares correlated with hard X- rays (Mathews poster) Direct coronal observations of Type II bursts (Shibata presentation) Coronal non-thermal sources (this talk)

Prototype event of March 30, 1969 (Frost and Dennis, 1971; Enome et al., 1971) Metric-decimetric radio observations from an X-ray point of view The Masuda event The event of April 18, 2001 Hard X-rays associated with CMEs

Background Hard X-rays come from bremsstrahlung in the non-thermal tail of the electron distribution function Limb occultation allows us to see hard X- rays from the middle corona With hard X-ray imaging, it is sometimes possible to see disk events

A very few other related events The Hinotori event of May 13, 1981, notable because seen on disk via hard X-ray imaging See Cliver et al., ApJ 305, 920 (1986) for a general review

Masuda’s event Masuda et al. found a non-thermal source located above the soft X-ray loop tops in a limb flare This source suggests electron trapping in an unusual mirror geometry favoring magnetic reconnection Occurrence in the impulsive phase

Event of April 18, 2001 Distinguished by non-Neupert behavior Highly occulted source ( Mm altitude) Overlay with microwave source Motion at about 1,000 km/s outward Movies

How many electrons? Thin-target peak ~10 36 electrons > 20 keV Source density 4 x 10 9 cm -3 Tail fraction > 0.2% > 20 keV Electrons dominate gas pressure and energy

Conclusions Coronal hard X-ray sources occur within the volumes forming CMEs Non-thermal electrons may be dynamically important in some cases The observational situation is far from satisfactory, but HESSI should help