Monte Carlo calculations of the O K \alpha line fluoresced by coronal X-rays and emitted just above the temperature minimum region of the solar atmosphere have been employed to investigate the use of this feature as an abundance diagnostic .
While quite weak , we estimate line equivalent widths in the range 0.02-0.2 Å , depending on the X-ray plasma temperature .
The line remains essentially uncontaminated by blends for coronal temperatures T \leq 3 \times 10 ^ { 6 } K and should be quite observable , with a flux \gtrsim 2 ph s ^ { -1 } arcmin ^ { -2 } .
Model calculations for solar chemical mixtures with an O abundance adjusted up and down by a factor of 2 indicate 35-60 % changes in O K \alpha line equivalent width , providing a potentially useful O abundance diagnostic .
Sensitivity of equivalent width to differences between recently recommended chemical compositions with “ high ” and “ low ” complements of the CNO trio important for interpreting helioseismological observations is less accute , amounting to 20-26 % at coronal temperatures T \leq 2 \times 10 ^ { 6 } K. While still feasible for discriminating between these two mixtures , uncertainties in measured line equivalent widths and in the models used for interpretation would need to be significantly less than 20 % .
Provided a sensitive X-ray spectrometer with resolving power \geq 1000 and suitably well-behaved instrumental profile can be built , X-ray fluorescence presents a viable means for resolving the solar “ oxygen crisis ” .