Global impulse burst of geomagnetic pulsations in the frequency range of 0.2–5 Hz as a precursor of the sudden commencement of St. Patrick’s Day 2015 geomagnetic storm

Magnetospheric response of two types in PSc geomagnetic pulsations to interaction with interplanetary shock waves

“…To assess the possible signal propagation delay between the longitudinally spaced observatories, we have compared filtered signals at two frequencies. Figure 11 indicates that there are no delays at 0.5 and 1.2 Hz (in [Parkhomov et al, 2017], the delay between stations of daytime and nighttime sectors is 4 s).…”

“…The onset of oscillations in the packet (arrow in Figure 6, i) is clearly ahead of the onset of the magnetic impulse. Parkhomov et al [2014Parkhomov et al [ , 2017 considered the packet as a precursor of the sudden impulse, which could be classified as SSC. Note that in our case the magnetic impulse occurs during the development of the magnetic storm main phase.…”

“…Induction magnetometers with high sensitivity and 100 Hz sampling rate installed in observatories allow us to find new features of sudden magnetic impulses. Parkhomov et al [2014Parkhomov et al [ , 2017 have reported on short-term (≤20 s) precursors of SSCimpulsive bursts of geomagnetic pulsations in a frequency range 0.2-7 Hz, which occur before sudden commencements of geo-magnetic storms with a sharp increase in the horizontal component ΔH. The bursts were observed mainly for the northward vertical component of the interplanetary magnetic field (IMF).…”

“…Parkhomov et al [2014] have studied characteristics of pulsation bursts, employing data from ground-based magnetometers and solar wind (SW) parameters. Parkhomov et al [2017] in addition to ground-based data including magnetic field and riometer absorption observations utilized particle precipitation data from POES satellites. It has been shown that the onset of the magnetic storm on March 17, 2015 was preceded by the global generation of a train of oscillations with a duration of ~4 s. On the day side, this train was, in turn, preceded by energetic electron and proton precipitation, which might have been due to the development of cyclotron instability during compression of the magnetosphere.…”

“…A characteristic feature of the bursts of geomagnetic pulsations examined by Parkhomov et al [2014;2017] is a comb-shaped character of energy distribution in the oscillation spectrum. This distribution is usually called the spectral resonance structure (SRS) and is associated with the presence of the ionospheric Alfvén resonator (IAR) in the magnetosphere [Polyakov, Rapoport, 1981;Belyaev et al, 1989] or with interference of lightning discharge signals, which are direct and reflected from the upper ionosphere [Fedorov et al, 2014].…”