ULF wave activity in high‐speed streams of the solar wind: Impact on the magnetosphere

Abstract

[1] In recent years, the study of solar-magnetospheric interaction has increasingly been focusing on wave phenomena and the role of turbulence in the processes of energy and momentum transfer from the Sun to the Earth's magnetosphere. Here we consider one aspect of the problem -the impact of wave patterns associated with high-speed solar wind streams (HSSs) on the variable geomagnetic field and the trapped radiation. The superposed epoch method was chosen as our research technique. We use observations of the solar wind plasma and the interplanetary magnetic field at libration point L1, as well as measurements of electron fluxes at geostationary orbit and of geomagnetic pulsations on ground. Data from 31 corotating interaction regions (CIR), their sources being coronal holes on the Sun, and 13 streams from coronal mass ejections (CME) were processed. The focus is on the regime of ultra-low frequency (ULF) waves in high-speed flows and ULF fluctuations in the magnetosphere. A significant difference has been revealed between the wave activity characteristics of the two HSS types in the solar wind and on the earth. Irregular pulses are typical for coronal mass ejections and wave-like conditions are common for CIRs. For the latter, the temporal profile of the normalized ULF amplitude in the solar wind is similar to the pulsation amplitude profile on the ground. We also found that a high level of ULF activity in the magnetosphere during CIR intervals is favorable to 2 MeV electron flux enhancement, but does not affect the flux of less energetic electrons.

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

“…Beside KHI, another shear flow instability -similar to the hydrodynamic Miles-Phillips instability -may develop at the magnetopause, and even under lower SW velocity than the KHI. The Miles-Phillips instability is caused by nonlinear ponderomotive wave generation, and its development is determined by the flow velocity profile and flow turbulence (Kurazhkovskaya and Klain, 2012;Potapov, 2013). These notions are based on the well-established statistical fact of strong growth of Pc5 intensity with the increase of the SW velocity (Engebretson et al, 1998;Mathie and Mann, 2001;Pahud et al, 2009).…”

Influence of the interplanetary driver type on the durations of the main and recovery phases of magnetic storms

“…In other works, the selection was either performed only for a limited type of solar wind or for a complex of types. For instance, the authors of several investigations (see, e.g., papers by Turner et al [2009], Richardson and Cane [2012], Keesee et al [2013], Potapov [2013], Yuan and Zong [2013], and Cramer et al [2013]) compared CIR-and CME-driven impacts on the magnetosphere, but they did not take into account that a CME on the Sun results in two different geoeffective types of solar wind streams at 1 AU: an interplanetary CME (ICME-magnetic cloud MC or Ejecta) and a compressed region Sheath before it and did not make a selection between Sheath-and ICME-driven storms. As in this paper, we plan to compare our investigations with results of recent paper by Hutchinson et al [2011], we indicate a definition of "CME" type in the caption of Figure 2 of this paper: "A typical coronal mass ejection (CME) trace seen in ACE OMNI data, with simultaneous increases in all components: interplanetary magnetic field (IMF) magnitude, solar wind (SW) speed, pressure, density, and temperature. "…”

Relativistic electrons of the outer radiation belt and methods of their forecast (review)

“…Figure 2 shows the typical behavior of energetic electron fluxes J ell during a magnetospheric storm, which was obtained by the epoch superposition method for 31 magnetic storms. All these storms were generated by magnetospheric effects of corotating interaction regions (CIR) of fast and slow solar wind [Potapov, 2013]. For the 0-epoch we take the moment of contact between the front of CIR solar wind stream and the magnetopause.…”