Local Time Dependence of Pi2 Pulsations Observed along the 210 Magnetic Meridian

Local time dependence of Pi2 pulsations is studied statistically using the 210 magnetic meridian (MM) data at various latitudes. In totaly, 249 Pi2 events are recognized in one month of data from February, 1995. 68% of the Pi2 events are observed at night time within this month at the low latitude station Moshiri (MSR; L= 1.59). For both occurrence and wave amplitude, there are three maxima at premidnight, slightly post midnight, and prenoon with two minima in the late afternoon and just after sunrise. The amplitudes of three maxima decrease with decreasing magnetic latitude, where the decreasing rates are significantly different. The wave frequency shows different spectral content and different local time dependence at auroral latitude, and middle to low latitudes. The mid- to low-latitude Pi2s have an additional higher frequency component compared with the auroral-latitude Pi2s. The local time dependence of the "equatorial enhancement" is also obtained, which agrees with previous studies at most local times except for the large ratio seen in the few hours after sunrise that has not been previously reported.