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RHESSI OBSERVATIONS OF THE 2005 JANUARY 20 SOLAR FLARE

RHESSI OBSERVATIONS OF THE 2005 JANUARY 20 SOLAR FLARE. Gerald Share 1,2 , Ronald Murphy 2 , David Smith 3 , Gordon Hurford 4 , Allan Tylka 2 , and Robert Lin 4. 1 UMD, 2 NRL, 3 UCSC, 4 UCB. Supported by NASA SEC-GI & SR&T. SUMMARY

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RHESSI OBSERVATIONS OF THE 2005 JANUARY 20 SOLAR FLARE

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  1. RHESSI OBSERVATIONS OF THE 2005 JANUARY 20 SOLAR FLARE Gerald Share1,2, Ronald Murphy2, David Smith3, Gordon Hurford4, Allan Tylka2, and Robert Lin4 1 UMD, 2NRL,3UCSC, 4UCB Supported by NASA SEC-GI & SR&T

  2. SUMMARY RHESSI has observed two distinct components of particle acceleration in the 2005 January 20th solar flare. There is a ‘normal’ impulsive component beginning at ~06:42 UT, peaking at ~06:47 UT, lasting about 10 minutes, evidenced by bremsstrahlung and nuclear-line radiation interacting at a footpoint with an ion power-law index of ~-3. A separate component began with a sharp 1-2 min peak at ~06:46 UT, with a spectrum dominated by pion-decay radiation; emission lasted for ~2 hours. No information as yet on how compact this source is. The GLE event commenced at 06:48 UT and was observed at energies >4 GeV. An ~5 min-wide peak was observed at ~06:53 UT.

  3. RHESSI observation of the 2005 January 20 Spectral Accumulations SEPs

  4. …. Bremsstrahlung ___ Narrow Nuclear - - - Broad Nuclear -decay Spectrum dominated by a strong continuum (bremsstrahlung & pi-decay) extending to high energies. Line features are relatively weak, consistent with a hard accelerated-particle spectrum.

  5. Calculated gamma-ray spectra vs flare-accelerated particle power-law index.

  6. RHESSI gamma-ray time line in January 20 flare Neutron-capture line fluxes agree with calculations for an accelerated-particle spectrum following a power-law with index ~3.

  7. 20 January 2005 06:44 - 06:56 128 x 128 arcsec 250-500 keV 250 – 500 keV 2215-2231keV RMC 4-9 RMC 6+9 RMC6+9 12 arcsec 35 arcsec 35 arcsec 35 arcsecond resolution cannot distinguish the footpoints

  8. 20 January 2005 06:44-06:56 TRACE 1600A at 06:52:30 UT 250 – 500 keV 30, 50, 70, 90% contours 2215-2231 keV centroid 1- error circle

  9. Comparison of Imaged and Spatially-Integrated Neutron-Capture Line Counts Demonstrates that particles producing a bulk of the neutron-capture line emission are primarily confined in magnetic loops.

  10. There appears to be a second high-energy component revealed above 10 MeV that can be fit by a pion-decay spectrum. Its time profile is different: sharp peak and long tail. This high-energy radiation produces instrumental annihilation line radiation that contributes to the solar flux in panel 4.

  11. CORONAS (Kuznetsov et al. 2005/6) also observed this high-energy component with a time profile similar to that observed by RHESSI.

  12. 06:43:30 – 06:45:10 UT 06:45:10 – 06:47:25 UT The CORONAS spectra at the peak in the decay phase are consistent with a pion-decay origin.

  13. Good agreement between corrected 511 keV flux and calculation for PL index =3. Nuclear-line flux appears to be produced by one population of accelerated ions interacting in a footpoint while the ‘pion’ and >20 MeV flux is dominated by a second higher-energy particle component.

  14. >20 MeV The high-energy photon emission observed by RHESSI extends up to two hours after the sharp peak.

  15. There is weak 2.223 MeV line emission after 08:00 UT suggesting that the high-energy emission is from ion interactions.

  16. Hi-E gamma peak South Pole neutron monitor flux increased within about 2 min after high-energy gamma-ray peak. The neutron monitor and Milagro rates have relatively narrow peaks at ~06:53 UT

  17. SUMMARY RHESSI has observed two distinct components of particle acceleration in the 2005 January 20th solar flare. There is a ‘normal’ impulsive component beginning at ~06:42 UT, peaking at ~06:47 UT, lasting about 10 minutes, evidenced by bremsstrahlung and nuclear-line radiation interacting at a footpoint with an ion power-law index of ~-3. A separate component began with a sharp 1-2 min peak at ~06:46 UT, with a spectrum dominated by pion-decay radiation; emission lasted for ~2 hours. No information as yet on how compact this source is. The GLE event commenced at 06:48 UT and was observed at energies >4 GeV. An ~5 min-wide peak was observed at ~06:53 UT.

  18. Comparison of accelerated particles interacting at the Sun and observed in space (Mewaldt, priv. comm. 2005) Total number of protons >30 MeV: Solar flare impulsive component: (2.8 ± 0.8) x 1032 Solar flare high-energy component:  0.7 x 1032 Event integrated SEPs: 210 x 1032 Power-law spectral index: Solar flare impulsive component: 3.0 ± 0.05 Solar flare high-energy component: <2.3 Event integrated SEPs: 2.15

  19. Extended emission > 4 GV? Narrow peaks in the Milagro and Climax NM data (Ryan et al. 2005) appear similar to the high-energy gamma-ray peak. Does the GLE event also have an extended high-energy component?

  20. The Tibet Yangbaging neutron monitor also observed such an extended tail. Could some of the counts be due to solar neutrons?

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