Generation of magnetic and particle Pc5 pulsations during the recovery phase of strong magnetic storms

Abstract

The dynamics of intense ultra-low-frequency (ULF) activity during three successive strong magnetic storms during 29-31 October 2003 are considered in detail. The spatial structure of Pc5 waves during the recovery phases of these storms is considered not only from the perspective of possible physical mechanisms, but as an important parameter of the ULF driver of relativistic electrons. The global structure of these disturbances is studied using data from a worldwide array of magnetometers and riometers augmented with data from particle detectors and magnetometers on board magnetospheric satellites (GOES, LANL). The local spatial structure is examined using the IMAGE magnetometers and Finnish riometer array. Though a general similarity between the quasi-periodic magnetic and riometer variations is observed, their local propagation patterns turn out to be different. To interpret the observations, we suggest a hypothesis of coupling between two oscillatory systemsa magnetospheric magnetohydrodynamic (MHD) waveguide/resonator and a system consisting of turbulence + electrons. We propose that the observed Pc5 oscillations are the result of MHD waveguide excitation along the dawn and dusk flanks of the magnetosphere. The magnetospheric waveguide turns out to be in a meta-stable state under high solar wind velocities, and quasi-periodic fluctuations of the solar wind plasma density stimulate the waveguide excitation.

Global Pc5 pulsations during strong magnetic storms: excitation mechanisms and equatorward expansion

“…The consideration of Pc5 events under study raises some important questions about the physical nature and generation mechanisms of these pulsations. The global spatiotemporal dynamics of Pc5 pulsations during magnetic storms 28-31 October 2003 was considered by Kozyreva (2005, 2009) and Pilipenko et al (2010). Those observations and current study have noticed several uncommon, and still not well-understood, features of global Pc5 wave activity during this storm:…”

“…Though the basic Pc5 wave features during these storms have been described (e.g., Kleimenova and Kozyreva, 2005;Pilipenko et al, 2010), in contrast with previous papers we pay more attention to the mid-and lowlatitude features of these waves. These observations raise, in our opinion, many important questions about the possible excitation mechanisms of Pc5 magnetic pulsations during magnetic storms.…”

Spatial distribution of spectral parameters of high latitude geomagnetic disturbances in the Pc5/Pi3 frequency range

“…The negligible contribution of stormtime intervals to the general pattern is due to a small number of storms during the analyzed period. However, storm-time ULF spatial and MLT distributions may differ dramatically from those during quiet times and from one storm to another ( Kleimenova and Kozyreva, 2005;Lee et al, 2007;Pilipenko et al, 2010).…”

ULF wave activity during the 2003 Halloween superstorm: multipoint observations from CHAMP, Cluster and Geotail missions

“…Apart from Wang et al (2008), Pc5 waves on 31 October 2003 identified in the geosynchronous GOES satellites' measurements, Pilipenko et al (2010) have found that during periods of ground Pc5 activity enhancement on 29 and 31 October 2003 (05:00-24:00 and 00:00-19:00 UT, respectively), the GOES 10 satellite located in the morning sector of the magnetosphere detected Pc5 pulsations, most evident in the toroidal component. Rae et al (2005) presented an interval of extremely longlasting narrowband Pc5 pulsations during the recovery phase of a large geomagnetic storm on 25 November 2001.…”