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AR and flare emission above 6 keV as seen by SPP/XIS J.McTiernan 12-feb-2010

AR and flare emission above 6 keV as seen by SPP/XIS J.McTiernan 12-feb-2010. 2) Photon flux for typical active time. T = 8 MK, EM = 1.0e47 cm -3 (RHESSI) Flux is at Minimum distance: 0.045 AU Dashed line is without shield, includes 6.4 cm 2 area. Solid line includes shield transmission.

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AR and flare emission above 6 keV as seen by SPP/XIS J.McTiernan 12-feb-2010

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  1. AR and flare emission above 6 keV as seen by SPP/XIS J.McTiernan 12-feb-2010

  2. 2) Photon flux for typical active time. • T = 8 MK, EM = 1.0e47 cm-3 (RHESSI) • Flux is at Minimum distance: 0.045 AU • Dashed line is without shield, includes 6.4 cm2 area. • Solid line includes shield transmission. • Peaks near 8keV

  3. 3) Photon flux versus distance • Here is plotted the flux in photons/second from 6 to 20 keV, versus distance from the sun. • The peak is at 120 photons/sec.

  4. 4) Solar background emission versus time • This is the background level due to steady-state solar emission for the 7 years of SPP orbit. • T = 8 MK, EM between 1046.5 and 1047.5 cm-3. • The long-term time variation is calculated from the GOES event list from 1996 to 2003. • The blue, red and amber lines are background estimates. INTEGRAL: 1.3 counts/s RHESSI: 1.5 count/s ISEE-3/ICE: 4 counts/s

  5. 5) Number of days above a given photon count • This is the number of days for which the photon count rate is greater than the flux value on the X axis. • The dashed lines are the background estimates from different spacecraft:

  6. 6) Log N – Log S for RHESSI at 1AU • This is the solar flare frequency distribution for flares with emission greater than 6 keV, calculated using the RHESSI flare list. • The currently-being-reprocessed flare list now gives photon fluxes and fluences above 6 keV for all flares. • The slope of the differential distribution shown is approximately 1.5

  7. 7) Log N – Log S scaled by distance. • The effect of the shield*eff_area (6.4 cm2) is to move the dN/dS curve to the left by 0.017. • The effect of changing the distance to the Sun is to move the dN/dS curve to the right. • Since the slope is about 1.5, the number of flares at a given size scales like 1/r3. • E.g., at closest approach, there would be ~100 flares/day at 10 photons/sec.

  8. 8) Flares/day above given photon flux • This is a plot of the expected number of flares/day above fluxes of, 10, 100, 1000, 10000, 100000 photons/sec. • The numbers on the right are the peaks of the curves for each photon flux. • As for the AR case, the solar cycle dependence is obtained from the GOES flare count from 1996 - 2003.

  9. 9) Total number of expected flares. • This is a plot of the total expected number of flares for the 7 year orbit. • This is the cumulative distribution, so the plot is the number of flares observed with photon flux greater than the X value. • The red line includes the AR background estimate (16000 flares total) • The blue line includes the 4.0 photons/sec “high” non-solar background estimate (5500 flares total).

  10. 10) Conclusions: • XIS will see steady-state AR emission at the level of at least 0.2 photons/sec, with levels increasing to a few hundred photons/sec at closest approach. • XIS will see many flares, thousands of flares at the microflare level (10 photons/sec), and when close to the sun, will see hundreds of flares per day. • The largest RHESSI flare scaled to closest approach is 8*109 photons/sec.

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