a. For daily and 81 day averaged values of F10.7, S10.7 and M10.7 the values given in Table A-1 shall be used.
NOTE 1 Ap is only weakly correlated with the solar activity indices. It has a seasonal variation and is higher at the equinoxes.
NOTE 2 81 days corresponds to 3 solar rotations and 81 day averaged values are used as input for atmosphere models.
b. For fixed index values, the numbers given in Table 6‑3 for low, moderate and high solar and geomagnetic activities shall be used:
1. The longterm values are averaged values for periods longer than 27 days.
2. The long-term values apply as well for periods of 1 week or longer.
3. The short-term values are daily values.
c. The temporal evolution in ap shown in Table 6‑4 shall be used to describe the worst case fluctuations during successive three-hour intervals for a total duration of 24 hours.
d. The ap values of Table 6‑4 shall be used together with the relevant (low, moderate or high) long term averaged values of F10.7, S10.7 and M10.7 given in Table 6‑3.