Open AccessObservations of X‐ray and EUV fluxes during X‐class solar flares and response of upper ionosphere
Author(s) -
Mahajan K. K.,
Lodhi Neelesh K.,
Upadhayaya Arun K.
Publication year - 2010
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010ja015576
Subject(s) - flare , physics , solar flare , astrophysics , ionosphere , extreme ultraviolet lithography , solar cycle 24 , flux (metallurgy) , tec , sunspot , solar minimum , solar cycle , atmospheric sciences , astronomy , plasma , solar wind , optics , magnetic field , materials science , quantum mechanics , metallurgy
Most studies dealing with solar flare effects in the upper ionosphere, where ionization is caused by EUV photons, have been based upon X‐ray fluxes measured by the SOLRAD and GOES series of satellites. To check the validity of such studies, we compare simultaneous observations of GOES X‐ray fluxes and SOHO EUV fluxes for 10 X‐class solar flares which occurred during the maximum phase of sunspot cycle 23. These include the greatest flare of 4 November 2003, the fourth greatest flare of 28 October 2003 and the 14 July 2000 Bastille Day flare. We find that the peak intensities of the X‐ray and EUV fluxes for these flares are poorly correlated, and this poor correlation is again seen when larger data containing 70 X‐class flares, which occurred during the period January 1996 to December 2006, are examined. However, this correlation improves vastly when the central meridian distance (CMD) of the flare location is taken into account. We also study the response of the upper ionosphere to these fluxes by using the midday total electron content (TEC), observed for these flares by Liu et al. (2006). We find that peak enhancement in TEC is highly correlated with peak enhancement in EUV flux. The correlation, though poor with the X‐ray flux, improves greatly when the CMD of flare location is considered.