1 / 15

RHESSI Microflares

RHESSI Microflares. Steven Christe 1,2 , S ä m Krucker 2 , Iain Hannah 3 , R. P. Lin 1,2 1 Physics Department, University of California at Berkeley 2 Space Sciences Lab, University of California at Berkeley 3 Physics Department, University of Glasgow, Scotland, UK.

cybil
Download Presentation

RHESSI Microflares

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. RHESSI Microflares Steven Christe1,2, Säm Krucker2, Iain Hannah3, R. P. Lin1,2 1Physics Department, University of California at Berkeley 2Space Sciences Lab, University of California at Berkeley 3Physics Department, University of Glasgow, Scotland, UK

  2. RHESSI Microflare Observations • Provides unique sensitivity in the 3 to15 keV energy range. • Effective area ~100 times larger then HXIS (SMM) at 10 keV. • An energy resolution of 1 keV can give a better handle on how to interpret spectra. • RHESSI can provide new information on low-level energy releases.

  3. Dataset Overview • Period considered : January 27-30, 2004May 1-5, 2004 • These periods were chosen because of extremely low solar activity. • Number of Events : 230 • GOES Range : A0.01 - C • Flaring rate : 2.5 per hour

  4. Flare examples Size - S

  5. Flare examples Size - XS

  6. Flare examples Size - XSS

  7. CGRO/BATSE Lin et al. 2001 8-13 and 13-20 keV Peak Rate • We see a clear correlation since larger flares have more emission in all channels. • The spread in the correlation gives information on the steepness of the flare spectra. down to 3 keV 300x smaller *define peak rate : photons s-1 cm-2 keV-1

  8. 8-13 and 13-20 keV Peak Rate

  9. Distribution of g and Temp. • Superhot components with T>20 MK do occur though usually only associated with large flares (Hudson & Nitta 1996). • For small bursts, a typical temperature is 10 MK. • Therefore emission is most likely nonthermal.

  10. 4-7 and 7-10 keV • Interpretation of emission is unclear.

  11. Full Spectra Results • Finer energy bins can be used on the spectra of larger flares (> 1000 total counts, 25% of events). • These larger flares show only thermal emission below 10 keV and confirm ratio estimations.

  12. Conclusions • The transition from thermal to nonthermal must occur between 7 - 13 keV for small flares if small flare are not “superhot”. • Interpreting thermal and nonthermal emission in the smallest flares will be difficult. • Using these results we find the smallest events have energies of 1027 ergs (1023 ergs if the cutoff is set to 25 keV).

  13. RHESSI Microflares Steven Christe1,2, Säm Krucker2, Iain Hannah3, R. P. Lin1,2 1Physics Department, University of California at Berkeley 2Space Sciences Lab, University of California at Berkeley 3Physics Department, University of Glasgow, Scotland, UK

  14. The End.

  15. Flare Search Criteria • Events were selected if a 5s increase was detected between adjacent time bins. Time bins from 4 s. to 3 mins. were considered. • Periods considered: May 1-5 and Jan 27-30, 2004 • Non-solar event were individually rejected. • Each event is also associated with a post or pre-event background.

More Related