The Focusing Optics X-ray Solar Imager (FOXSI)Steven Christe1, S. Krucker2, L. Glesener2, S. Ishikawa3, B. Ramsey4, T. Takahashi3, R.P. Lin2

1 NASA GSFC, Greenbelt, MD2 Space Sciences Lab, UCB, Berkeley, CA3 Dept. of Physics, U. of Tokyo, Japan4 NASA MSFC, Huntsville, AL

Basic flare model.

Basic Flare ModelUpward beams

Accelerationsite

Downward beams

Chromospheric evaporation

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

Accelerationsite

Downward beams

Chromospheric evaporation

HXR

HXR

n = 109 cm-3

n = 1011 cm-3

n = 1011-12

cm-3

SXR

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

Accelerationsite

Downward beams

Chromospheric evaporation

HXR

HXR

n = 109 cm-3

n = 1011 cm-3

n = 1011-12

cm-3

SXR

HXR

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

Accelerationsite

Downward beams

Chromospheric evaporation

HXR

HXR

n = 109 cm-3

n = 1011 cm-3

n = 1011-12

cm-3

SXR

HXR

Present day observations show mostly footpoints.

HXR observations of Flare Model

Upward beams

Accelerationsite

Downward beams

Chromospheric evaporation

n = 109 cm-3

n = 1011 cm-3

n = 1011-12

cm-3

SXR

RHESSI HXR Obs.

HXR

HXR

60 arcse

c

HXR focusing optics provides imaging of the acceleration region

And track electrons in the corona.

HXR observations of Flare Model

Upward beams

Accelerationsite

Downward beams

n = 109 cm-3

n = 1011-12

cm-3

SXR

HXR

HXR

Chromospheric evaporation

n = 1011 cm-3

HXRs from up and down beamsHX

R Fl

ux

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

HXRs from up and down beamsHX

R Fl

ux

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

Optics Performance

-100

-50 0 50

100

150arcsec

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:

~10050 arcsec:

~500

Metal optics-

1

0

-2-3-4-5

Log(

rela

tive

flux)

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 ModelUpward beams

Accelerationsite

Downward beams

n = 109

cm-3

n = 1011 cm-3

n = 1011-12

cm-3

SXR

5000

3000

1000

70025010020

90”

78”

66”

54”

42”

30”

18”6”

Dynamic Range

60 arcs

ec

HXR

HXR

HXRs from escaping electrons

Assuming 100 cm2

Dt=1 s

Dt=30 s

Assuming 100 cm2

2-4 kg/cm2 (e.g. 50 kg of optic = 100-200 cm2)

Jets

Quiet Sun network flares(coronal heating)

Active Region Flares

Radio bursts from shocks

Energetic Electrons

Type III radio bursts

CME

Position sensitive solid state (Si, CdTe, CZT) Energy resolution 0.2 to 2 keV (1-100 keV) Current Technology

Focal Plane Detectors

Type Pixels Pitch Range HeritageSi (strips) 128 x

12875 um 1-20 keV Astro-H HXI,

FOXSICdTe (strips) 128 x

128250 um 5-80 keV Astro-H HXI,

FOXSI2CZT 64 x 64 600 um 5-80 keV NuSTARCdTe 256 x

256250 um 2-80 keV HEXITEC

Parameter ValueFocal length 10 mEnergy Range 1-80 keVEnergy resolution ~1 keVSpatial resolution 7 arcsecDynamic Range Up to 100 x

RHESSISensitivity 100 x RHESSICost SMEX-like

FOXSI Mission ConceptThis 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.

Fin