1. The Focusing Optics X-ray Solar Imager (FOXSI) Steven Christe 1, S. Krucker 2, L. Glesener 2, S. Ishikawa 3, B. Ramsey 4, T. Takahashi 3, R.P. Lin 2 1 NASA GSFC, Greenbelt, MD 2 Space Sciences Lab, UCB, Berkeley, CA 3 Dept. of Physics, U. of Tokyo, Japan 4 NASA MSFC, Huntsville, AL

2.  Basic flare model. Basic Flare Model Upward beams Acceleration site Downward beams Chromospheric evaporation

3.  HXR observations of flare-acceleration electrons  Provide quantitative measurements  Depend on ambient density  Strongest from footpoints  Very faint emission from corona  RHESSI does not have high enough sensitivity or dynamic range  HXR focusing optics can provide it. HXR observations of Flare Model Upward beams Acceleration site Downward beams Chromospheric evaporation HXR n = 10 9 cm -3 n = 10 11 cm -3 n = 10 11-12 cm -3 SXR

4.  HXR observations of flare-acceleration electrons  Provide quantitative measurements  Depend on ambient density  Strongest from footpoints  Very faint emission from corona  RHESSI does not have high enough sensitivity or dynamic range  HXR focusing optics can provide it. HXR observations of Flare Model Upward beams Acceleration site Downward beams Chromospheric evaporation HXR n = 10 9 cm -3 n = 10 11 cm -3 n = 10 11-12 cm -3 SXR HXR

5.  HXR observations of flare-acceleration electrons  Provide quantitative measurements  Depend on ambient density  Strongest from footpoints  Very faint emission from corona  RHESSI does not have high enough sensitivity or dynamic range  HXR focusing optics can provide both HXR observations of Flare Model Upward beams Acceleration site Downward beams Chromospheric evaporation HXR n = 10 9 cm -3 n = 10 11 cm -3 n = 10 11-12 cm -3 SXR HXR

6.  Present day observations show mostly footpoints. HXR observations of Flare Model Upward beams Acceleration site Downward beams Chromospheric evaporation n = 10 9 cm -3 n = 10 11 cm -3 n = 10 11-12 cm -3 SXR RHESSI HXR Obs. HXR 60 arcsec

7.  HXR focusing optics provides imaging of the acceleration region  And track electrons in the corona. HXR observations of Flare Model Upward beams Acceleration site Downward beams n = 10 9 cm -3 n = 10 11-12 cm -3 SXR HXR Chromospheric evaporation n = 10 11 cm -3

8. HXRs from up and down beams HXR Flux Acceleration site Height above the photosphere [arcsec]  ratio of footpoint to coronal emission depends on:  coronal density  electron spectrum  photon energy  trapping time  but it is generally large Dynamic range: ~400

9. HXRs from up and down beams HXR Flux Height above the photosphere [arcsec] ? emission from acc. region? trapping? Acceleration site Dynamic range: ~400  ratio of footpoint to coronal emission depends on:  coronal density  electron spectrum  photon energy  trapping time  but it is generally large

10. Optics Performance -100-50050100150 arcsec FWHM 10’’ HPD 25’’ Point Spread Function (PSF)  Current Tech: slumped glass optics, replicated metal optics  Best resolution currently available by B. Ramsey (NASA MSFC)  Individual shell resolution: 7 arcsec (FWHM)  Telescope module resolution: 10-12 arcsec  Dynamic range: 30 arcsec: ~100 50 arcsec: ~500 Metal optics 0 -2 -3 -4 -5 Log(relative flux)

11.  Dynamic range will allow us to image coronal HXR emission in the presence of HXR footpoints  Footpoints will be unresolved, but can be separated for larger flares Basic Flare Model Upward beams Acceleration site Downward beams n = 10 9 cm -3 n = 10 11 cm -3 n = 10 11-12 cm -3 SXR 5000 3000 1000 700 250 100 20 90” 78” 66” 54” 42” 30” 18” 6” Dynamic Range 60 arcsec HXR

12. HXRs from escaping electrons Assuming 100 cm 2  t=1 s  t=30 s Assuming 100 cm 2 2-4 kg/cm 2 (e.g. 50 kg of optic = 100-200 cm 2 )

13. Jets Quiet Sun network flares (coronal heating) Active Region Flares Radio bursts from shocks Energetic Electrons Type III radio bursts CME

14.  Position sensitive solid state (Si, CdTe, CZT)  Energy resolution 0.2 to 2 keV (1-100 keV)  Current Technology Focal Plane Detectors TypePixelsPitchRangeHeritage Si (strips)128 x 12875 um1-20 keVAstro-H HXI, FOXSI CdTe (strips)128 x 128250 um5-80 keVAstro-H HXI, FOXSI2 CZT64 x 64600 um5-80 keVNuSTAR CdTe256 x 256250 um2-80 keVHEXITEC

15. ParameterValue Focal length10 m Energy Range1-80 keV Energy resolution~1 keV Spatial resolution7 arcsec Dynamic RangeUp to 100 x RHESSI Sensitivity100 x RHESSI CostSMEX-like FOXSI Mission Concept This mission concept is based on existing technology. Currently FOXSI is a sounding rocket (launch Oct. ‘12). HEROES balloon launch in Sept ’13. The future may bring better spatial resolution, lighter optics, etc. FOXSI will observe electrons as they are being accelerated in the corona, along which field line they travel away from the acceleration site, where they are stopped, and how some electrons escape to be detected as SEPs at Earth.

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