Labels:book | bulletin board | earth | poster | reckoner | sky | trade name OCR: and t(T-TDAWN) AT Evaluating equation 7 at sunset (T-TDAWN T), we find cos Xeff SUNSET CoS 1+3 XNOON {+exp -T (10) which completes the specification of f.F2 at night via equations 1 and 7 Finally to avoid unphysical disconi itinuities in cos Xeff just after sunrise, we do not allow cos Xeff DAY to fall below its value just prior to sunrise as computed from equation Thus we impose the condition cos Xeff DAY MAX cos Xeff SUNSET .exp [T-24)/TN cos Xeff DAY (eq 7) (11) The basic foF2 model is there fore given in equations 1. and 10 for nighttime (ie, , TsUNSET T<TDAWN) and equations 1,7 and 11 for daytime (TDAWN <T<TSUNSET). EQUATION OF TIME In this section, we present simple analytical approximations for the times of local noon sunrise and sunset, and for the noon value of the solar zenith an ...
