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RHESSI Investigations of the Neupert Effect in Solar Flares

RHESSI Investigations of the Neupert Effect in Solar Flares. Brian R. Dennis AAS/SPD Meeting 6 June 2002. The Neupert Effect. The time integral of the hard X-ray emission closely matches the temporal variation of the soft X-ray emission.

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RHESSI Investigations of the Neupert Effect in Solar Flares

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  1. RHESSI Investigations of the Neupert Effect in Solar Flares Brian R. Dennis AAS/SPD Meeting 6 June 2002

  2. The Neupert Effect • The time integral of the hard X-ray emission closely matches the temporal variation of the soft X-ray emission. • Implies that accelerated electrons that produce the hard X-rays also heat the plasma that produces the soft X-rays.

  3. SXR:HXR Ratio vs. Flare SizeA. Veronig et al. A&A, in press (2002)

  4. RHESSI Contribution • RHESSI observes both the soft X-rays (down to ~3 keV) and the hard X-rays with the same detectors. • RHESSI also provides 2 arcsecond imaging capability in both soft and hard X-rays. • RHESSI’s temporal resolution for images is 2 s for a complete set of spatial Fourier components. • The spatially integrated time resolution is limited only by counting statistics.

  5. RHESSI’s Limitations • Suffers pulse pile up when the rates exceed ~10,000 counts per detector per second. • Shutters moved into FOV when dead time reaches ~10%. Limits lower energy response below ~10 keV. • K-escape photons contaminate low energy counts with higher energy emission.

  6. RHESSI/GOES Comparison

  7. RHESSI Light Curves 6 – 12 keV 12 – 25 keV 25 – 50 keV 50 – 100 keV 10 April 2002 GOES 10 1 - 8 Å Time derivative GOES 1 - 8 Å

  8. RHESSI Images 10 April 200219:02:34 – 19:03:03 UT 6 – 12 keV 12 – 25 keV 50 – 100 keV 25 - 50 keV

  9. X1.5 Flare on 21 April 20022650 + 0043 0151 0238 GO8 5 XRA 1-8A X1.5 6.0E-01 9906

  10. X1.5 Flare on 21 April 2002

  11. RHESSI Light Curves 25 – 50 keV 50 – 100 keV 21 April 2002 GOES 1 - 8 Å Time derivative GOES 1 - 8 Å

  12. X1.5 Flare on 21 April 2002

  13. Start of X1.5 Flare on 21 April 2002TRACE images at 195 Å, RHESSI 12 – 25 keV contours 00:42:50 – 00:43:10 UT 00:48:54 – 00:49:14 UT

  14. Start of X1.5 Flare on 21 April 2002TRACE images at 195 Å, RHESSI 12 – 25 keV contours

  15. X1.5 Flare on 21 April 2002TRACE 195Å images and RHESSI contours at times of hard X-ray peaks 12-25 keV 50 – 100 keV 01:15:43 – 01:16:03 UT 01:23:27 – 01:23:47 UT

  16. Conclusions • Neupert Effect is alive and well. • Fraction of flare energy in accelerated electrons • Increases with flare size on average • Decreases with time during 21 April X flare • Additional heating mechanism is required

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