rhessi observations of lde flares – extremely long persisting hxr sources
DESCRIPTION
RHESSI observations of LDE flares – extremely long persisting HXR sources Mrozek, T., Kołomański, S., Bąk-Stęślicka, U. Astronomical Institute University of Wrocław. Questions. How long? Spatial scale Where?. After the maximum of the flare; not during the impulsive phase. - PowerPoint PPT PresentationTRANSCRIPT
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RHESSI observations of LDE flares – extremely long persisting HXR sources
Mrozek, T., Kołomański, S., Bąk-Stęślicka, U.
Astronomical InstituteUniversity of Wrocław
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Questions
How long?
Spatial scale
Where?
After the maximum of theflare; not during the impulsive phase
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YOHKOH results - SXR
Kołomański, S., 2007:
>6h duration
>3 orbits of YOHKOH starting from the maximumof the flare
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YOHKOH results - SXR
Different sources observed at the same time suggest that the energy reales takes placein different locations
Typical sizes of the SXR sources are 1.0-1.5x104 km
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YOHKOH results - HXR
HXR emission in the L channel (14-23 keV) was observed up to 40 minutesafter the maximum of the flare
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YOHKOH results - HXR
Rise phase – coronal and footpoint sources
Decay phase - HXR source observed 40 minutes after the maximum of the flare. It is 10 times longer than characteristic cooling time of such source – indirect proof for the energy release long after the maximum of the flare.
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RHESSI & LDEs - motivation
Better spatial resolution – more detailed investigation of sources
Better sensitivity - weak, coronal sources could be detected long after the maximum of the flare
Better energy resolution – more detailed analysis of LDEs spectra, searching for different types of sources (very hot thermal, non-thermal)
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RHESSI & LDE
Feb. 2002 – Feb. 2008
~ 160 LDE flares foundwith the use of GOESlightcurves
~ 50 which last longer than 3 hours in RHESSI observations
30 July 2005X1.3>10 h
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Method
2-minutes intervals:
-with attenuators out
- outside the radiation belts
- far from the SAA
Thus, for 10 hours decay we have only three time intervals for imaging and spectroscopy (for this flare, in other cases we can have up to 9-10 intervals)
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Method
Images:
Time interval: 11:38 – 11:40Grids: 3,4,5,6,8,9Pixel size: 1”
4-6 keV 10-12 keV 15-23 keV
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Method
The signal in the 12-25 keV interval is observed (11:40 UT – 6 hoursafter the maximum) - why we can’t obtain images?
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Method
Because of the size of sources?
gridnumber
time
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Method
We have to choose detectors in more flexible way – sources are large, but the result is realiable
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30 July 2005 - images
Comparison with EIT 195 Å
RHESSI images reconstructed with the use of PIXON method
Red contours – 6-7 keVBlue contours – 15-25 keV
6 hours after the maximum of the flare
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30 July 2005 - spectra
double thermal
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30 July 2005 - spectra
thermal + thin target
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30 July 2005 - spectra
thermal + thick target
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30 July 2005 - spectra
thermal + broken power-law
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30 July 2005
How long?
HXR emission in 15-25 keV is observed 6 hours after the maximum - we need an energyrelease existing for such long time
To balance the thermal and conductive losses we need a heating of the order of 1 erg s-1cm-3
(1028 erg s-1 from the whole volume)
Spatial scale:
the order of 104 km
Where?
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7 Nov 2003
B4.7S29W90
30-40 degrees behind the limb
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Extremely weak
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Conclusions
LDEs are observed by RHESSI however the analysis is very complicated due to attenuators, radiation belts, SAA and other
HXR sources (above 15 keV) are visible even 6 hours after the maximum of the flare.
Long-lasting HXR sources are located above structures seen in different wavelengths andhave large sizes.
For long-lasting HXR sources located far above the solar limb we do not detect significantnon-thermal or hot components.