A new method to calculate the time delay of the Pi2 pulsations

Propagation of irregular magnetic pulsation using cross wavelet and maximum time energy methods

“…The 48 Pi2 events reported by Ghamry and Fathy (2016) have been studied again in the current work. Data obtained from Carson City (CCNV), Mcgrath (MCGR), The Pas (TPAS) and Kuujjuarapik (KUUJ) stations which belong to the ground magnetometer network of the Time History of Events and Macroscale Interactions during Substorms (THEMIS).…”

“…The wavelet transform of a time series is fully explained in Ghamry and Fathy (2016). The wavelet is a powerful analytical method for decomposing the time series because it contains wide types of filters which have different scales (frequency width) and shapes.…”

“…where T is the common Pi 2 period around which the calculation is being performed. The XWT criterion in the current study is similar to that set by Ghamry and Fathy (2016). First, visually we inspect the Pi 2 event at both stations, second the raw data filtered in the Pi 2 range [40-150 s].…”

“…In addition to this problem, timing the Pi2 onset shows another difficulty as the higher latitudinal stations have ±1 min identification of the substorm onset-time of the magnetospheric substorm or intensification (Rostoker et al, 1980). Ghamry and Fathy (2016) released a new method to determine the Pi2 time delay using the cross wavelet technique. According to their statistical analysis of 48 events, the cross wavelet gave more reliable results than the ordinary cross correlation.…”

A comprehensive analysis of the geomagnetic storms occurred during 18 February and 2 March 2014

“…Pi2 pulsations at low latitude are good indicators to substorm onset because they are not only observed in the nightside but also in the dayside (Yanagihara and Shimizu, 1966). Pi2 pulsation is considered as a result of hydromagnetic disturbances driven by sudden change in magnetospheric convection or reconfiguration in the magnetotail during the substorm expansive phase, so it is considered a better proxy of substorm onset than its counterpart at middle and high latitude (Yumoto 1986;Ghamry et al, 2011Ghamry et al, , 2012Hamada et al, 2015;Ghamry and Fathy 2016). Plasmaspheric cavity resonance (PCR), plasmaspheric virtual resonance (PVR), and plasmapause surface mode are considered major source mechanisms of Pi2 pulsations (Allan et al, 1986;Zhu and Kivelson, 1989;Lee, 1996;Lee and Kim, 1999;Lee and Lysak, 1999;Takahashi et al, 2003;Lee and Takahashi, 2006;Kwon et al, 2013;Ghamry et al, 2015;Ghamry, 2015).…”