Why Observe X-rays? 

  • X-ray emissions are the most direct signatures of hot plasmas, without contributions from cooler chromospheric material.
  • Soft X-rays (SXRs) are highly sensitive diagnostic of high temperature material and are easy to measure. 
  • Hard X-rays (HXRs) in conjunction with soft X-rays, give a more complete look at plasma evolution by extending our range of sensitivity to higher temperatures.


Above shows intensities of spectral line emission from various elements based on temperature (in Kelvin) and wavelength. Circled are the signatures STEAM will be focusing on based on our spectrometer capabilities.

How are we going to measure X-rays?

  • Use two different detectors, a Soft X-ray and Hard X-ray spectrometer
  • Spectrometers accumulate individual photons and assign them into spectral histogram bins based on their energy levels. Spectrometers will observe the sun at a 10-second cadence. Individual 10-second spectra (“histograms”) can then be summed together to improve our statistics for analysis.


Snapshot of simulated spectrum accumulation. The lower red line represents a single histogram from a single measurement. The white line represents the total  spectrum: multiple red histograms added together.

Field of View & Cosmic Background X-ray Radiation

STEAM has taken into account estimated values for expected cosmic background radiations within our instrument sensitives and compared against sample Active Regions and Flare activity data. It was clear upon our analysis that the background X-ray radiation would not interfere with our scope to within a 10-degree field of view. This has allowed for more flexibility in design collaboration with NFI.