Observations of He-like and H-like Ar ( Ar xvii and Ar xviii ) lines at 3.949 Å and 3.733 Å respectively with the RESIK X-ray spectrometer on the CORONAS F spacecraft , together with temperatures and emission measures from the two channels of GOES , have been analyzed to obtain the abundance of Ar in flare plasmas in the solar corona .
The line fluxes per unit emission measure show a temperature dependence like that predicted from theory , and lead to spectroscopically determined values for the absolute Ar abundance , A ( { Ar } ) = 6.44 \pm 0.07 ( Ar xvii ) and 6.49 \pm 0.16 ( Ar xviii ) which are in agreement to within uncertainties .
The weighted mean is 6.45 \pm 0.06 , which is between two recent compilations of the solar Ar abundance and suggest that the photospheric and coronal abundances of Ar are very similar .