HESSI Science Facts Technical Facts

Solar:

	Determine the frequency, location, and evolution of impulsive energy release in the corona
	Study the acceleration of electrons, protons, and heavier ions in flares
	Study the heating of plasma to tens of millions of degrees and determine its relationship to particle acceleration
	Study the propagation and evolution of energetic particles in flares
	Determine the relative abundances of accelerated and ambient ions in flares

Non-Solar:

	Obtain images and spectra of the Crab Nebula with 2 arcsecond spatial resolution and ~1 keV spectral resolution
	Detect and obtain high resolution spectra of gamma-ray bursts and cosmic and terrestrial transient sources over a large fraction of the sky
	Search for cyclotron line features in gamma-ray bursts and cosmic transient sources
	Obtain high resolution spectra and search for line features in steady X-ray and gamma-ray sources

Primary Observations:

Simultaneous, high resolution imaging and spectroscopy of solar flares from 3 keV X-rays to 17 MeV gamma rays with high time resolution

Expected Numbers of Flares:

	Tens of thousands of microflares
	Over a thousand X-ray flares with crude imaging and spectra to >100 keV
	Hundreds of flares with >1000 counts per second above 20 keV, allowing spatial changes to be followed on timescales of 0.1 seconds.
	Tens of flares sufficiently intense to allow the finest possible imaging spectroscopy
	Up to 100 flares with the detection of gamma-ray lines
	Tens of flares with detailed gamma-ray line spectroscopy and the location and extent of the source determined to ~40 arcseconds

HESSI "Firsts":

	Hard X-ray imaging spectroscopy
	Hard X-ray and gamma-ray imaging above 100 keV
	Imaging in narrow gamma-ray lines
	Determination of solar gamma-ray line shapes
	Combination of spatial, spectral, and time resolution that is commensurate with physically relevant scales for energy loss and transport of >10 keV electrons
	Dynamic range to both detect microflares and make quantitative spectral measurements of the largest flares
	High resolution X-ray and gamma-ray spectra of cosmic sources
	Hard X-ray images of the Crab Nebula with 2 arcsecond resolution

Complementary Observations:

	SOHO EUV images and spectra Coronagraph images Interplanetary particle spectra and abundances Photospheric magnetograms
	TRACE UV and XUV high resolution images
	GOES Images from the Soft X-Ray Imager
	ACE Interplanetary particle spectra and abundances
	Ground-Based Observatories Radio and optical images and spectra Photospheric magnetograms

Technical Facts