Corotating solar wind streams and recurrent geomagnetic activity: A review

Abstract

[1] Solar wind fast streams emanating from solar coronal holes cause recurrent, moderate intensity geomagnetic activity at Earth. Intense magnetic field regions called Corotating Interaction Regions or CIRs are created by the interaction of fast streams with upstream slow streams. Because of the highly oscillatory nature of the GSM magnetic field z component within CIRs, the resultant magnetic storms are typically only weak to moderate in intensity. CIR-generated magnetic storm main phases of intensity Dst < À100 nT (major storms) are rare. The elongated storm ''recovery'' phases which are characterized by continuous AE activity that can last for up to 27 days (a solar rotation) are caused by nonlinear Alfven waves within the high streams proper. Magnetic reconnection associated with the southward (GSM) components of the Alfvén waves is the solar wind energy transfer mechanism. The acceleration of relativistic electrons occurs during these magnetic storm ''recovery'' phases. The magnetic reconnection associated with the Alfvén waves cause continuous, shallow injections of plasma sheet plasma into the magnetosphere. The asymmetric plasma is unstable to wave (chorus and other modes) growth, a feature central to many theories of electron acceleration. It is noted that the continuous AE activity is not a series of substorm expansion phases. Arguments are also presented why these AE activity intervals are not convection bays. The auroras during these continuous AE activity intervals are less intense than substorm auroras and are global (both dayside and nightside) in nature. Owing to the continuous nature of this activity, it is possible that there is greater average energy input into the magnetosphere/ ionosphere system during far declining phases of the solar cycle compared with those during solar maximum. The discontinuities and magnetic decreases (MDs) associated with interplanetary Alfven waves may be important for geomagnetic activity. In conclusion, it will be shown that geomagnetic storms associated with high-speed streams/CIRs will have the same initial, main, and ''recovery'' phases as those associated with ICME-related magnetic storms but that the interplanetary causes are considerably different.

Relativistic electron response to the combined magnetospheric impact of a coronal mass ejection overlapping with a high‐speed stream: Van Allen Probes observations

“…The electron response immediately following the HSS impact on 9 November shows the classic signatures noted by earlier observers [Kanekal, 2006;Tsurutani et al, 2006]. For example, examination of electron response from both MagEIS and REPT instruments show an expected energy-dependent differences in flux levels.…”

“…HSS, which are often associated with CIRs (corotating interaction regions) and CMEs both cause geomagnetic storms. The latter usually resulting in stronger storms (typically Dst < −100 nT) with a shorter recovery phase as compared to CIRs [Tsurutani et al, 2006]. While the electron response to IP drivers is a balance between energization and loss processes operating within the magnetosphere [Reeves et al, 2003], when there are increased fluxes associated with CIR-driven storms, they tend to occur at higher L shells, i.e., radial distances.…”

Dynamics of large‐scale solar wind streams obtained by the double superposed epoch analysis

“…We made our own data archive including OMNI data and calculated (using OMNI data) additional parameters. In order to classify different SW types, we use method similar to ones which are based on comparison of relations of kinetic, thermal, and magnetic field energies in the studied SW streams and the corresponding relations in average solar wind and described in many papers (see reviews by Zurbuchen and Richardson [2006], Wimmer-Schweingruber et al [2006], Tsurutani et al [2006], and references therein). For this purpose we determine the following parameters: velocity V, density N, proton temperature T, module and components of IMF, proton thermal pressure NkT, proton plasma parameters (ratio of thermal and magnetic field pressures), ratio of measured temperature, and temperature estimated on the basis of average velocity-temperature relation T∕T exp , derivatives of them and compare them with standard threshold criteria which are present in Table 1 of paper by Yermolaev et al [2009].…”

Long term evolution of geomagnetic activity under the influence of 11 year cyclic variations in solar activity during solar cycle 23 and 24

“…It has been found that the geomagnetic and solar activity correlation has decreased since the end of the 19th century, and the lag between them has increased. The variations of Rz and aa were in phase in the early period (solar cycles [11][12][13][14], and became out of phase in later periods (with a lag of 2 years in solar cycle 22) [4].…”

“…The geomagnetic activity has been found to be well correlated with the solar wind speed (v), the southward component (Bz) of the interplanetary magnetic field (IMF) and the product BzV 2 [5,9,10,11]. The solar sources of geomagnetic activity are generally thought to be of two categories [12,13]. One source, Coronal Mass Ejections (CMEs), has a frequency of occurrence that is in phase with the sunspot cycle while the second source, high-speed solar wind streams, is out of phase with the sunspot cycle.…”