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STEREO & RHESSI observations of the December 31, 2007 solar flare

STEREO & RHESSI observations of the December 31, 2007 solar flare. Säm Krucker University of California, Berkeley Space Sciences Laboratory J.-P. Wuelser, S. White, A. Vourlidas, R.P. Lin. hard X-ray (HXR) observations. this presentation.

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STEREO & RHESSI observations of the December 31, 2007 solar flare

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  1. STEREO & RHESSI observationsof the December 31, 2007 solar flare Säm Krucker University of California, Berkeley Space Sciences Laboratory J.-P. Wuelser, S. White, A. Vourlidas, R.P. Lin

  2. hard X-ray (HXR) observations this presentation • flare-accelerated electrons produce HXR emission by the bremsstrahlung mechanism • partially disk occulted flares: RHESSI statistical results • December 31, 2007 flare

  3. X-rays from partially disk-occulted flares Standard flare scenario: high density chromosphere  HXR footpoints low density corona  very weak HXR emission HXR footpoints

  4. X-rays from partially disk-occulted flares for flares occurring behind the solar limb, footpoint emission is occulted  purely coronal emission can be studied solar disk HXR footpoints Statistical studies: Roy & Datlowe 1975, McKenzie 1975, Mariska et al. 1996, Tomzcak 2001, Krucker & Lin 2008

  5. X-rays from partially disk-occulted flares Possible coronal sources: for flares occurring behind the solar limb, footpoint emission is occulted  purely coronal emission can be studied HXR emission from flare loop above-loop-top source (Masuda flare) solar disk HXR footpoints Statistical studies: Roy & Datlowe 1975, McKenzie 1975, Mariska et al. 1996, Tomzcak 2001, Krucker & Lin 2008

  6. X-rays from partially disk-occulted flares typical spectrum of partially occulted flare shows 2 components: -) thermal -) faint emission at higher energies for flares occurring behind the solar limb, footpoint emission is occulted  purely coronal emission can be studied thermal additional component power law (g~5) solar disk HXR footpoints Statistical studies: Roy & Datlowe 1975, McKenzie 1975, Mariska et al. 1996, Tomzcak 2001, Krucker & Lin 2008 background

  7. X-rays from partially disk-occulted flares different time profiles! thin target emission from flare-accelerated electrons typical spectrum of partially occulted flare shows 2 components: -) thermal -) faint emission at higher energies thermal thermal additional component power law (g~5) additional component power law (g~5) solar disk Statistical studies: Roy & Datlowe 1975, McKenzie 1975, Mariska et al. 1996, Tomzcak 2001, Krucker & Lin 2007 background Krucker & Lin 2008, ApJ

  8. solar disk HXR footpoints X-rays from partially disk-occulted flares HINODE/XRT thick Be (image) RHESSI (contours) emissions from loop 4-8 keV (thermal) image ~2 keV (thermal) SXR peak time: 4-8 keV 4-8 keV (thermal) 18-30 keV (non-thermal) SXR peak Krucker, Hannah, & Lin, ApJL, 2007

  9. solar disk HXR footpoints X-rays from partially disk-occulted flares HINODE/XRT thick Be (image) RHESSI (contours) Thermal loop at SXR peak time is earlier seen in non-thermal emission. emissions from loop 4-8 keV (thermal) image ~2 keV (thermal) SXR peak time: 4-8 keV HXR peak time: 18-30 keV 4-8 keV (thermal) 18-30 keV (non-thermal) HXR peak SXR peak Krucker, Hannah, & Lin, ApJL, 2007

  10. X-rays from partially disk-occulted flares:flare with above-the-loop-top source occulted by 20” Some events are different with an above-the-loop-top source, similar as Masuda flare. Rarely seen. Main thermal source never reaches 25-50 keV source.

  11. RHESSI and STEREO observations of a partially disk-occulted flare STEREO A C8 class flare on December 31, 2007

  12. STEREO B (flare is on disk) Start of impulsive phase: flare ribbons about 1 hour later: post flare loops

  13. STEREO B (flare is on disk) Start of impulsive phase: flare ribbons about 1 hour later: post flare loops flare ribbons are NOT visible in RHESSI images!

  14. 6-9 keV 20-40 keV Hard X-ray observations: Non-thermal emission above 20 keV up to ~80 keV unusually intense (for occulted event) spectral slope between 3.5 and 4.5 2 1 17 GHz

  15. 6-9 keV 20-40 keV Hard X-ray observations: Non-thermal emission above 20 keV up to ~80 keV unusually intense (for occulted event) spectral slope between 3.5 and 4.5 Radio observations: microwave emission with decreasing spectrum (non-thermal) 2 1 17 GHz

  16. RHESSI imaging: HXR peak HXR peak time; loop? above flare arcade? for comparison: STEREO post flare loops

  17. RHESSI imaging: HXR peak HXR peak time; loop? above flare arcade? thermal loops are below for comparison: STEREO post flare loops

  18. RHESSI imaging: HXR peak HXR peak time; loop? above flare arcade? thermal loops are below for comparison: STEREO post flare loops rare case of above-the-loop-top source (along flare arcade)? low ambient density before flare.

  19. later peak 6-9 keV 20-40 keV Hard X-ray observations: Non-thermal emission above 20 keV up to ~80 keV unusually intense (for occulted event) spectral slope between 3.5 and 4.5 Radio observations: microwave emission with decreasing spectrum (non-thermal) 2 1 17 GHz

  20. RHESSI imaging: later, faint emissions elongated HXR source above thermal loops? for comparison: STEREO post flare loops

  21. Comparison with EUV imaging STEREO B 171A: difference image EIT 195A difference image: flare site dimming enhanced emission above HXR source

  22. Summary • great diagnostic potential of multi-view solar flare observations with STEREO • 2007 Dec 31 event: unusually intense coronal HXR emission • similar to Masuda flare? • late phase emission related to CME?

  23. fast (2000 km/s) backside CME. flare site 40 degrees behind limb. HXRs from CMEs size small soft X-ray emission, but large HXR burst! motion RHESSI 15-25 keV flare 40o Earth Kane et al. 1992 Hudson et al. 2001 Krucker, White, & Lin, ApJL, 2007

  24. HXRs from CMEs size very large source (>200 arcsec) expanding and rising motion HXR emission from electrons in magnetic structures related to coronal mass ejections. speed of CME front ~ 2000 km/s ~400 km/s 300” ~800 km/s filament ~ 1000 km/s Krucker, White, & Lin, ApJL, 2007

  25. EIT 195A (flare 12o behind limb)

  26. STEREO B 171A (flare on disk)

  27. STEREO A 171A (flare 33o behind limb)

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