coronal hard x-ray sources and associated decimetric/metric radio emissions
DESCRIPTION
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). HXR in solar flares acceleration and propagation of energetic electrons interacting at the Sun - PowerPoint PPT PresentationTRANSCRIPT
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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)
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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> 5104km
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 (109-1010 cm-3) near the loop top
From Masuda et al 1998
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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 configurationLoop-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
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GOES 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
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RHESSI images 12-25 keV10’’ above the limbafter 1307 UT
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movie_trace+hessi1225.htmlmovie_trace+hessi2550.html
Comparison of RHESSI images with TRACE images at 195 Å =flare plasma at 15 MK
TRACE and RHESSI 12-25 keV images before 13:07 UT (no coronal HXR sources)movie_trace+hessi1225_125500.html
TRACE and RHESSI 12-25 keV and 25-50 keV images after 13:07 UT(coronal HXR of the event sources with most of the time no footpoints Most energetic part )
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RHESSI 25-50 keV images
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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
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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)
Flux at 3 in the flare regionfrom the Nançay Radioheliograph+Images at 327 MHz
NRH 327 MHz
NRH 236 MHz
NRH 164 MHz
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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). t
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NRH 327 MHzduring 4 burstsBetween 131120 and 131140
RHESSI25-50 keV
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NRH 327 MHz
during 4 bursts
Between 131120 and 131140
RHESSI25-50 keV
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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
• 25-50 keV coronal sources above 12-25 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.
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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 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 electronsRadio 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.