Under photochemical equilibrium condition, electron density near peak varies as the square root of total peak ionization rate. Thus by averaging the longitudinal variation of latter, the mean primary and secondary peak electron densities in upper ionosphere of Mars using measured mass densities at LST 16 hrs are estimated to be ~8.56 ¿ 104 cm-3 and ~1.81 ¿ 104 cm-3. On comparison with mean electron densities at LST 3--4 hrs for observational period Dec. 24--31, 1998, at same solar zenith angle, it is found that the estimated primary peak electron density at LST 16 hrs is more by a factor of ~1.06. With this analogy, the estimated secondary peak electron density should be ~3.76 ¿ 104 cm-3 instead of ~1.81 ¿ 104 cm-3. Thus, in order to obtain the estimated secondary peak electron density of ~3.76 ¿ 104 cm-3, soft X-ray flux should be increased by a factor of ~4.31.