Soft X‐ray irradiances during solar flares observed by TIMED‐SEE

Abstract

Observations from the Thermosphere Ionosphere Mesosphere Energetics Dynamics–Solar Extreme Ultraviolet Experiment (TIMED‐SEE) are analyzed to determine the solar soft X‐ray energy emission during a solar flare. The TIMED‐SEE X‐ray ultraviolet Photometer System (XPS) detectors utilize broadband photodiodes that observe from 0.1 to 27 nm. The XPS observed 29 flares of various strengths over a 6‐month period in 2002. We describe an emission measure technique to interpret the broadband observations and determine a best fit flare spectrum. This technique is applied to the 29 flares observed by the XPS. Our results show that most of the enhancement in the solar spectrum during a flare comes from the 0–2 nm wavelength range. We also show that the XPS calculated 0.1–0.8 nm irradiance for brighter M‐class and X‐class flares is in good agreement with the Geostationary Operational Environmental Satellites (GOES) observed 0.1–0.8 nm irradiance. Also, the XPS 0–7 nm flare irradiance is well correlated with the 0.1–0.8 nm irradiance observed by GOES. We show that the total 0–7 nm irradiance of smaller X‐class flares (X1–X5) calculated at the time of the XPS observation provides 2–3 times the energy of the quiet Sun 0–7 nm irradiance.