Coronal hard X-ray sources and associated decimetric/metric radio emissions N. Vilmer D. Koutroumpa (Observatoire de Paris- LESIA) S.R Kane G. Hurford (Space Sciences Laboratory Berkeley)

 YOHKOH/HXT  coronal above the loop top > 30 keV X-ray sources in impulsive flares (Masuda, 1994; Masuda et al., 1998) (< 6 events) Compact above the loop top source together with double footpoint sources 10’’ above the SXR loop apex Relatively hard spectrum Located at slightly higher altitudes at higher X-ray energies. 1 event (Sato, 2001) without footpoints Extended source above 30 keV at h> km  HXR in solar flares  acceleration and propagation of energetic electrons interacting at the Sun  Bulk of HXR emission from footpoints of flaring B loops by electrons accelerated in the low corona ( cm -3 ) near the loop top From Masuda et al 1998

energization of electrons in the reconnection site itself or at the place where the downward hot plasma from the reconnection site collides with underlying closed B loops  Different types of interpretation for reconnection sites:  Loop with a cusp configuration (Masuda)  Emerging flux type configuration  Loop-loop reconnection Interpretation in the scheme of magnetic reconnection above (outside the bright soft X-ray loop) the loop top: cartoon from Masuda et al, 1998  Here observations of coronal above the loop top HXR sources with RHESSI and time evolution in the flare

GOES M2.5 AR 9893 AR 9893 N21 W81 large part behind the limb H  N23 W88 SF AR 9893 < N19 W67 SF AR9901 Coronal HXR source from 13:07 UT H  8 days earlier

RHESSI images keV  10’’ above the limb after 1307 UT

movie_trace+hessi1225.html movie_trace+hessi2550.html Comparison of RHESSI images with TRACE images at 195 Å =flare plasma at 15 MK  TRACE and RHESSI keV images before 13:07 UT (no coronal HXR sources) movie_trace+hessi1225_ html  TRACE and RHESSI keV and keV images after 13:07 UT (coronal HXR of the event sources with most of the time no footpoints Most energetic part )

RHESSI keV images

Associated radio emissions??  Gyrosynchrotron emission from energetic flare associated electrons in the cm/mm domain Observations at 3 from Bern Similarity between durations of 30 keV HXR and cm emissions from energetic electrons (as usually observed) RHESSI 6-12 keV keV keV 19.6 GHz 11.8 GHz 8.4 GHz

Coherent radio emissions in dm/m wavelengths Spectrum ETH Zürich Radio type III bursts e beams in the corona limited range (< 350 MHz) limited time range (30 s) Flux at 3  in the flare region from the Nançay Radioheliograph + Images at 327 MHz NRH 327 MHz NRH 236 MHz NRH 164 MHz

3-6 keV 6-12 keV keV keV 327 MHz Limited duration of Associated dm emissions Consistent with the observations that 10 to 15 % of HXR producing electrons have no detectable emission at decimeter and longer wavelengths (e.g. Simnett and Benz, 1986). t

NRH 327 MHz during 4 bursts Between and RHESSI keV

NRH 327 MHz during 4 bursts Between and RHESSI keV

Summary/discussion In the most energetic part of the HXR event, coronal HXR sources with no (permanent) footpoints Coronal HXR sources (> 10’’ ) above the limb, displaced (above) the hot magnetic structures seen with TRACE keV coronal sources above keV sources Consistent with the previous (~ 6 ) observations with YOHKOH/HXT More dynamic behaviour: from TRACE observations, suggestion of loop-loop interactions between 2 loop systems with one system apparently connected to parts of the AR behind the limb. Appearance of the coronal sources and of the most energetic part of the event at the time of the interaction. No footpoints: most of the loop structures connected to parts behind the limb. Only the emission from the region close to the reconnection sites(s) but rather loop-loop reconnections.

Simple 2D sketch More complex at 3D with several loop systems as suggested by TRACE e-beams X-rays  cm and HXR emission: gyrosynchrotron emission from electrons in low-lying B loops  Most of the event: no dm/m emissions  No electron access to high or open B field lines seen from the earth  Energetic electrons are only present in small scale loops as seen from the earth  After abrupt reformation of low lying B field lines through sequence of loop-loop interactions, the B field reconfiguration may extend over larger distances and reach overlying open field lines seen from the earth : possible acceleration sites for radio emitting electrons Radio dm/m emissions at the time of appearance of second component of keV source indicating displacement of energy release site and possible electron access to new B lines.