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the latest 48 hours of photon flux data


from the CELIAS/SEM sensor

on the SoHO Spacecraft

In the first plot, below, the top panel shows the 1st-order flux from SEM, which measures the absolute solar EUV flux in a passband of ±40 Angstroms about the 304 Angstrom HEII line. Two-minute averages are plotted for the latest 48 hours.

The second panel shows the zero-order EUV flux, which is the absolute solar EUV flux in a passband of 1-500 Angstroms, two-minute averages.

The third panel shows the quantity alpha, which is a measure of solar X-ray flux. It has the same time resolution as the first two panels, but it is dimensionless.

The second plot again shows the alpha index, here plotted on a log scale.

selected SEM figures during some interesting time periods

Combined plot of data ending at 0140 GMT on Oct 23, 2018

Plot of Alpha index ending at 0140 GMT on Oct 23, 2018

The SEM home page has a description of the SEM instrument. SEM is part of the CELIAS instrument package on the SOHO spacecraft. The SEM was designed and constructed by USC (Darrell Judge, Don McMullin, Howard Ogawa and colleagues), and is integrated into the CELIAS/STOF sensor (M. Hilchenbach, Lead Co-I). D. Hovestadt and E. Moebius were instrumental in getting the SEM added to the SOHO instrument payload. The data processing and presentation on this web page are courtesy the CELIAS/MTOF crew at U of Md.

the Proton Monitor home page