A method of calculating 0–20 Å solar X-ray flux and its spectral distribution using 9.1 cm spectroheliograms

Abstract

1–8 A, 2–12 A and 8–20 A non-flare X-ray flux data and 9.1 cm spectroheliograms for 1237 days during the period July 1966 to June 1970 have been studied to derive physical models of λ < 20 A X-ray emitting regions on the Sun under quiescent (non-flare) conditions. The preferred regions of emission below 20 A which coincide with the coronal active regions characterised by enhanced 9.1 cm microwave emission are found to have temperature lying between 1.8 and 3 × 106 K, emission measure 1049–1050 and electron density 109-1010 per cc. The average area of an active region is 1020 cm2. A slow gradient of temperature and electron density is seen to exist around a region of peak activity, both temperature and electron density decreasing outwards. Based on the derived physical model of the emitting regions a new method is presented for calculating X-ray flux and spectral energy distribution in this wave length region using daily 9.1 cm solar spectroheliograms. The calculated values are in good agreement with the observed values.