Student Thermal Energetic Activity Module (STEAM) X-ray Spectrometer On The PUNCH Small Explorer

The Student Thermal Energetic Activity Module (STEAM) will explore how solar coronal plasmas are heated in flares and active regions by measuring the abundances of elements with low first ionization potential (FIP) using soft (0.5-10 keV) and hard (5-30 keV) X-rays to distinguish signatures of reconnection-based coronal heating mechanisms.

Typically, coronal abundances of low-FIP elements (e.g. Mg, Si, Fe, Ca) are enhanced by a factor of 4 above chromospheric values. Measuring the abundances of low FIP elements for various ions of these elements at different temperatures provides insight into the coronal or chromospheric origins of the heated plasma. X-ray emissions, including spectral lines and continuum, provide the most direct signatures of hot coronal plasma.

STEAM uses miniaturized commercial soft and hard X-ray spectrometers to measure individual incident photons and their energies. Combined, the detectors will capture a broad range of X-ray emissions from 0.5 to 30 keV, with spectral resolutions better than 0.2 and 1 keV FWHM in soft and hard X-rays, respectively, providing a comprehensive look at thermal plasma evolution. STEAM will generate spectra with a cadence of 10 seconds and will be optimized to observe flares of GOES class C1-X1 and active regions above GOES class A1. STEAM will utilize forward modeling with bremsstrahlung and atomic emission databases to fit physical parameters such as temperature and elemental abundance to observed spectral data.

STEAM is a student payload hosted on one of the PUNCH Small Explorer spacecraft with an expected launch in late 2023 and 2-year prime mission. STEAM’s spectral observations of solar flares and active regions in soft and hard X-rays during the rising phase and maximum of solar cycle 25 will measure a wide range of activity to help constrain potential coronal heating mechanisms. STEAM is in the preliminary design phase and completing critical trade studies. We will present the STEAM science motivation, design, current progress, and future outlook.