Modelling the solar EUV flux: on the variability of the EUV emission as measured by the SUMER instrument
As far as Solar-Terrestrial relationships are concerned, and so in the space weather context, the solar EUV flux plays a major role since it is the principal source for the diurnal ionosphere. It is unfortunately badly known, although several models exist, very few measurements were available on its variability before the SOHO spacecraft (an ESA/NASA mission). Our study aims to build a new solar EUV flux model. We estimate the line intensities from solar regions with various types of activity. We then correlate ground-based solar images with the different fractions of the sun covered by these regions. This allows to synthesize the solar EUV irradiance from ground-based observations. We processed more than 750 data files of the SUMER instrument onboard SOHO, and computed the spectral radiance for 174 EUV lines ranging from 70 nm to 110 nm and covering a temperature range from 20000K to 106K. Data were split into different characteristic areas (quiet sun, coronal hole, and active region) using the simultaneous measurements of the EIT telescope. We define the typical radiances for these regions and compute synthetic spectra using the differential emission measures.
Solspa 2001, Proceedings of the Second Solar Cycle and Space Weather Euroconference
- Pub Date:
- March 2002
- Solar Extreme UV