Other
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmsa43b..01t&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #SA43B-01
Other
7519 Flares, 7538 Solar Irradiance, 2479 Solar Radiation And Cosmic Ray Effects
Scientific paper
Solar spectral irradiances shortward of 31 nm, i.e., XUV (0.1 - 10 nm) and some EUV (10 - 31 nm) irradiances, are the dominant source of 180-450 km altitude thermospheric heating and F1 and F2 ionospheric layer photoionization. These spectral irradiances are mostly absorbed by atomic oxygen which is the dominant species in this altitude region at most levels of solar activity. Wavelengths in this spectral range are highly variable during solar flares and, at the shortest wavelengths, can increase by up to two orders of magnitude in a few minutes from flare start to flare peak. There currently is not a consistent method for operational solar XUV and EUV flare spectral, magnitude, and duration estimation although the geoeffectiveness of these characteristics on short time scales is significant. We report on three new integrated irradiance indices, Xb10, Xhf, and X10.7, that provide space weather users the knowledge of flare spectral characteristics, magnitude, and duration once a flare has started. The solar X-ray flux reported by NOAA/SEC, specifically the GOES one-minute 0.1-0.8 nm band XUV 0.1-0.8, are irradiance measurements that combine flaring and non-flaring sources. We separate the flare and background components to create X-ray indices that are geoeffectively-relevant. In order to provide flare magnitude and duration once it has started, we demonstrate a flare model using the correlation between dXhf/dt, flare magnitude, and duration. The time rate of change of Xhf, i.e., dXhf/dt, is obtained after separating the Xb10 background so that the actual flare start time, rise phase, and decay shape can be determined. Additionally, the daily Xb10 can be more useful than the daily mean value for comparing solar X-ray variability to other daily solar indices. Results for the October-November 2003 storm period are presented.
Bouwer S.
Tobiska W.
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