Role of cascade transitions in an excitation of initial level of red coronal line

The rate of excitation of the 3psup(52)Psub(1/2) level of FeX ion as a result of the excitation of high-lying levels of the 3s3p6 and 3s23p43d configurations and radiative de-excitation is calculated. It is found that cascade processes are equivalent to the rate of excitation of the 2Psub(1/2) level g approximately 4x5x10-9cm3sec-1, which is more than 5 times the rate of direct excitation from the ground state. The interpretation of red coronal line observations has led to T <= 1x3x106 deg K and Hsub(e) approximately 10 8 cm -3 near the poles; from the relation of red and green line intensities for calm equatorial areas it is found that T approximately 1x6x106 deg K. Attention is given to the possible role of the gas radial flow in increasing the red line width near the poles