Future Imaging/Spectroscopy Approaches to High Energy Solar Science

G.J. HurfordSpace Sciences Lab

University of California, Berkeley

Annapolis 5-August 2010

Some Key Science Issuesto which Imaging/Spectroscopy

might be relevant

• Directivity – Are accelerated electrons and ions beamed?

• Coronal Sources – What are the properties of the acceleration site?– What is the role and properties of trapping in the corona?

• Ions– What are the spatial characteristics of ion acceleration

and propagation?

Three Approaches to measuring Directivity

• Imaging Polarimetry– Requires high sensitivity and well-conceived instrumentation

• Directivity– Requires cross-calibrated measurements with good spectral

resolution from 2 or more vantage points– At least one measurement should be imaging/spectroscopy– Instrumentation does not require exceptionally high angular

resolution or sensitivity

• Albedo– Requires good image quality and high spatial resolution at hard

x-ray energies– Yields directivity and footpoint height

Coronal Sources

• Requires ability to cleanly separate coronal sources from bright footpoint sources

• Requires ability to measure multiple size scales

• Good quality imaging spectroscopy is essential

• Options– High dynamic range– Limb occultation

Ion Imaging

• Priorities:– Neutron capture line (2.2 MeV)– Electron bremsstrahlung continuum (<100 t o > 300keV)– Annihilation line (511 kev)– Prompt lines

• Requires much more sensitivity• Requires low background• Excellent spectral resolution is highly desirable but may

not be essential• Needs moderately good (~10”) spatial resolution• ENA imaging

– High sensiivity required– Moderate spatial resolution (~1 arcminute)

Wish List• Maintain current strengths

– Excellent absolute and co-location accuracy– High spectral resolution and uniformity of response

• Hard X-rays– Much better dynamic range– Somewhat higher angular resolution (~1”)

• Gamma-rays– Much better angular resolution (<10”)– MUCH better sensitivity and background suppression

• ENA imaging capability

• Sensitivity to Magnetic fields

Enabling Technologies for New Flare Observations

• Focusing optics– Direct imaging - Christe will discuss

• Digital correlators enable radio imaging/spectroscopy -Steven White discussed

• Ge detectors with 3-D positioning

• Grid technology subarcsecond HXR imaging compact collimators

• CZT and other pixelated detector capability

• TRL of booms – Albert Shih will discuss application

• Advances in on-board and ground data systems

• Steady progress in polarization instrumentation - McConnell

• Etc, etc

Enabling Technologies for New Flare Observations

• Focusing optics– Direct imaging - Christe will discuss

• Digital correlators enable radio imaging/spectroscopy -Steven White discussed

• Ge detectors with 3-D positioning

• Grid technology subarcsecond HXR imaging compact collimators

• CZT and other pixelated detector capability

• TRL of booms – Albert Shih will discuss application

• Advances in on-board and ground data systems

• Steady progress in polarization instrumentation - McConnell

• Etc, etc

3D-Germanium Detectors• Germanium detectors• 7.5cm × 7.5cm × 1.5cm• Orthogonal strips on

opposite faces• 0.5-mm pitch • Locate each energy

deposition to ~0.1 mm3

• Compton-scatter track reconstruction

• Gives time, energy, location and directional information on each photon 9

GRIPSGamma-Ray Imaging Polarimeter for Solar flares

P.I. Bob Lin, UCB

Multi-pitch rotating modulator

Spectrometer/polarimeterwith 0.5mm spatial resolution

Energy range ~20 keV to >~10 MeV

Angular resolution 12.5 to 162 arcsec First balloon flight: spring 2012

Shih will discuss adaptation to s/c

8 m boom length

Detector provides time, energy, location and a polarization signature of each photon with low background

Two Perspectives on GRIPS Imaging

• Each photon identifies a set of ‘probability stripes’ on Sun from which it could have originated

• Observations of many photons image

1 3 10

30 100 1000

Time sequence of counts beneath each mask location/orientation measures one visibility

Continuous set of gid pitches measures solid annulus in uv plane

uv plane

Radial profile of PSF

Adaptation to HXR Energies

• Could combine MPRM approach with pixelated CZT detectors to achieve subarcsecond, high-dynamic range imaging spectroscopy in a ~3m long package

Detector and Grid Technology Implications

Feasible to put such instruments on heliocentric orbits

Directivity Occultation of limb sources

Can simultaneously follow the spectral and temporal evolution of coronal and footpoint sources from 3-200 keV with no dynamic range limitations

•High resolution X-ray imaging spectroscopy can be done with small insturments

~10^2 of resources of RHESSI

Examples of Compact HXR Instrumentation

Solar Orbiter / STIX

Selected

7” 4-150 keV

Solar Probe / XIS

Proposed

35” 4-150 keV

Sentinels / Studied

18” 4-150 keV

LEO

opportunities

Adaptations of above

Thank you