Coronal hard X-ray sources and associated radio emissions

N. Vilmer

D. Koutroumpa(Observatoire de Paris- LESIA; Thessaloniki University)

S.R Kane

G. Hurford(Space Sciences Laboratory Berkeley)

Background: CORONAL ABOVE THE LOOP TOP SOURCES 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 • Located at slightly higher altitudes at higher X-ray energies.

From Masuda et al 1998

cartoon from Masuda et al, 1998

Do we have such observations with RHESSI? Are they consistent with such a cartoon?A complementary view of one of the event presented here by Sui

Coronal HXR sourcesGOES M2.5 AR 9893AR 9893 N21 W81 large part behind the limbH 1310-1320-1332 N23 W88 SF AR 9893 < 1323- 1338 N19 W67 SF AR9901

Coronal HXR source from 13:07 UT

H 8 days earlier

Vilmer, Koutroumpa, Kane, Hurford, EGS

RHESSI images 12-25 keV(30%,50%,70%,90%)10’’ above the limbafter 1307 UT

RHESSI 25-50 keV images grids from 7’’

Steep non-thermal emissionAbove > 10 keV(-6.7)

Comparison of RHESSI images with TRACE images at 195 Å =flare plasma at 15 MK(coalignment between EIT and Trace during the flare)

TRACE and RHESSI 12-25 keV images before 13:07 UT (no coronal HXR sources)

TRACE and RHESSI 12-25 keV

images after 13:07 UT(coronal HXR

sources with most of the time no

footpoints Most energetic part of the

event)

TRACE and RHESSI 25-50 keV images after 13:07 UT(coronal HXR sources with most of the time no footpoints Most energetic part of the event)

•Coronal HXR sources (> 10’’ ) above the limb, displaced from the hot magnetic structures seen with TRACE?•25-50 keV predominant coronal sources above 12-25 keV sources (faint footpoints close to max)•(see previous YOHKOH/HXT obs but more dynamical and more complicated fields?)

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

12-25 keV

25-50 keV

19.6 GHz

11.8 GHz

8.4 GHz

Coherent radio emissions in dm/m wavelengths

Spectrum ETH ZürichRadio type III burstse beams in the coronalimited range(< 350 MHz)limited time range (30 s)

No emission in the IP Medium(no electron escape)

Flux at 3 in the flare regionfrom the Nançay Radioheliograph+Images at 327 MHz

NRH 327 MHz

NRH 236 MHz

NRH 164 MHz

3-6 keV

6-12 keV

25-50 keV

12-25 keV

327 MHz

Limited duration ofAssociated dm emissions

Consistent with the observations that10 to 15 % of HXR producing electrons have no detectable emission at decimeter and longer wavelengths (e.g. Simnett and Benz, 1986).

RHESSI25-50 keV

NRH 327 MHzduring 4 burstsBetween 131120 and 131140

Double source at the Time of the radio peak

Coronal HXR source for the 16/04/02 flare • In the most energetic part of the HXR event, predominant

coronal HXR sources above 25 keV with no (permanent) footpoints

• Coronal HXR sources (> 10’’ ) above the limb, with 25-50 keV displaced (above) the hot magnetic structures seen with TRACE

• 25-50 keV coronal sources above 12-25 keV sources

• Consistent with the previous (~ 6 ) observations with YOHKOH/HXT but• 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 permanent footpoints: confined energetic electrons?

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 emissionsNo electron access to high or open B field lines seen from the earth Energetic electrons are only present in low lying loops as seen from the earth

At the time of the radio burst the B field reconfiguration may reach overlying open field lines seen from the earth : possible acceleration sites for dm radio emitting electrons

Radio dm/m emissions at the time of appearance of second component of 25-50 keV source indicating displacement of energy release site and possible electron access to new B lines.

10/04/02 GOES M8.8

Radio 4 GHz to 1 MHz

WIND

PHOENIX

OSRA

RHESSI50-100 keV

spectrograms

RHESSI 40-65 keV 432 MHz (black) 327 MHz (dashed-dotted white) 164 MHz (dotted white)

No emission below 327 MHz before 122753 UTExtension towards 164 MHz at 122843 UT

New radio positions after 123048 UT 2nd HXR peak Extension to 12 MHz (electron path to high corona)