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First Results of Joint OVSA and HESSI Observations

First Results of Joint OVSA and HESSI Observations. Dale E. Gary 1 , Edward J. Schmahl 2 1 New Jersey Institute of Technology 2 University of Maryland. Joint Observations of Five Solar Bursts.

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First Results of Joint OVSA and HESSI Observations

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  1. First Results of Joint OVSA and HESSI Observations Dale E. Gary1, Edward J. Schmahl2 1New Jersey Institute of Technology 2University of Maryland

  2. Joint Observations of Five Solar Bursts We present 5 solar bursts observed jointly in microwaves with Owens Valley Solar Array (OVSA) and in hard X-rays with the Ramaty Hi-Energy Solar Spectroscopic Imager (RHESSI). A spectral comparison of the 5 bursts in both microwaves and hard X-rays is presented in the accompanying figures. We examine one event, 2002 Mar 18, in more detail, both spectrally and spatially.

  3. 2002 Feb 20

  4. 2002 Feb 23

  5. 2002 Feb 25

  6. 2002 Mar 18

  7. 2002 Mar 29

  8. Ask to see this animation of the RHESSI spectrum for the 2002 Mar 18 burst on a laptop computer!

  9. OVSA Radio Spectra (2002 Mar 18)

  10. Spectral Results (2002 Mar 18) • Thermal part of X-ray emission rises and falls relatively smoothly. • > 25 keV X-rays vary in several acceleration episodes, apparently independently of the thermal emission. • In first acceleration episode, > 25 keV X-rays progressively harden (from d ~ 7.5-4.7) . • At the same time, the OVSA spectral peak increases monotonically. • Spectral peak can increase due to three effects: increase in NL, increase in B, or decrease in d (Dulk 1985).

  11. RHESSI Images (2002 Mar 18) 12-25 keV 25-50 keV

  12. BBSO Context (2002 Mar 18)

  13. Spatial Results (2002 Mar 18) • Thermal part of X-ray emission fills a small loop, about 20” long. • > 25 keV X-rays come from a smaller source at one end of the loop. • OVSA source is compact, and all frequencies appear to be nearly cospatial.

  14. Conclusions • After only four months OVSA and RHESSI have jointly observed at least a dozen events. • We have presented some preliminary comparisons of 5 events. • The outstanding spectral resolution of RHESSI allows detailed comparison with OVSA microwave spectra. • The thermal components seen by RHESSI are only weakly detected with OVSA. • Comparisons of spatial source structure have not yet been done, but will be done as soon as possible.

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