Characteristics of Pi 2 magnetic pulsations observed at the CPMN stations: A review of the STEP results

From analyses of magnetic data from the Circum-pan Pacific Magnetometer Network (CPMN) stations, we can find the following wave characteristics of Pi 2 magnetic pulsations. (1) Pi 2 pulsations observed on the ground are an ensemble of various hydromagnetic modes excited at high, middle, low, and equatorial latitudes. Each mode exhibits its own propagation (timing) and spatial illumination. (2) There are apparent longitudinal propagation and latitudinal time delays of the maximum Pi 2 magnetic energy among the CPMN stations within 100 sec. (3) When a single low-latitude station is located in the sectors of 00–24 hr LT, 20–03 hr local time (LT), and 23-01 hr LT, respectively, 62%, 79%, and 100% of auroral breakups identified by the Polar satellite have associated Pi 2s. 66% of the low-latitude Pi 2s occur within 1 min of the auroral breakups, and 85% within 2 min. Pi 2s are still a good indicator of substorm onsets, but they should be used with care.

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