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: AU Dashed line is without shield, includes 6.4 cm 2 area. Solid line includes shield transmission. Peaks near 8keV

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) 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 and cm -3. The long-term time variation is calculated from the GOES event list from 1996 to 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) 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) 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) Log N – Log S scaled by distance. The effect of the shield*eff_area (6.4 cm 2 ) is to move the dN/dS curve to the left by 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/r 3. E.g., at closest approach, there would be ~100 flares/day at 10 photons/sec.

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, 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

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) 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*10 9 photons/sec.