Fig. 3

Maximum a fmin and d dfmin values within ± 1 h of solar flare as a function of solar flare peak flux, b fmin and e dfmin values as a function of solar flare peak flux and cos χ, where χ is the solar zenith angle, and c fmin and f dfmin normalized by (cos χ)^0.5 as a function of solar flare peak flux. The total number of events for this analysis is shown by a histogram with blue lines using the right y-axis scale in Fig. a, d. fmin and dfmin values respectively in b, e are distinguished by the same color from the color bar on the right side, and blue, light blue, and green lines show Eq. (1) for fmin = 2.5, 3.5, and 5 MHz, respectively. Vertical solid lines in a, c, d, and f show the standard deviation, ± 1σ. In a, the red curve shows Eq. (1) at the subsolar point (χ = 0°) and the dashed red line shows Eq. (1) at χ = 88°. Solid red curves in c and f show the normalized Eq. (1), and the blue curve in f shows best-fitted function represented by Eq. (3)