Yuri I. Yermolaev

Large-scale disturbances in the interplanetary medium are the main cause of the global perturbations inside Earth’s magnetosphere. Transition region called magnetosheath is known to be located in front of the magnetosphere in which plasma and magnetic field properties, as well as their variations differ significantly from those in the solar wind. Particularly, plasma passage through the magnetosheath has been demonstrated to modify substantially features of the cascade of turbulent fluctuations of the solar wind, with the pattern of the modification being different for quiet and disturbed conditions in the interplanetary medium. In this study, we examine features of turbulent cascade formation in the magnetosheath during interplanetary manifestation of coronal mass ejection (ICME), by analyzing several cases of ICME interactions with the magnetosphere. The analysis is conducted by comparing magnetic field variations measured simultaneously in the solar wind and in the dayside magnetosheath by Wind, Cluster, THEMIS, and MMS spacecraft in 2016–2017. Interaction of ICME with the magnetosphere is shown to cause the least change in the fluctuation power if there is a compression region in front of it; on the opposite, when there is no compression region, the fluctuation power increases considerably. ICMEs that caused significant changes in the Dst index were determined to be accompanied by the least changes in the turbulent cascade in the magnetosheath, whereas the most significant modification of the turbulence features were observed during ICMEs which did not trigger substantial geomagnetic disturbances

Large-scale disturbances in the interplanetary medium are the main cause of the global perturbations inside Earth’s magnetosphere. Transition region called magnetosheath is known to be located in front of the magnetosphere in which plasma and magnetic field properties, as well as their variations differ significantly from those in the solar wind. Particularly, plasma passage through the magnetosheath has been demonstrated to modify substantially features of the cascade of turbulent fluctuations of the solar wind, with the pattern of the modification being different for quiet and disturbed conditions in the interplanetary medium. In this study, we examine features of turbulent cascade formation in the magnetosheath during interplanetary manifestation of coronal mass ejection (ICME), by analyzing several cases of ICME interactions with the magnetosphere. The analysis is conducted by comparing magnetic field variations measured simultaneously in the solar wind and in the dayside magnetosheath by Wind, Cluster, THEMIS, and MMS spacecraft in 2016–2017. Interaction of ICME with the magnetosphere is shown to cause the least change in the fluctuation power if there is a compression region in front of it; on the opposite, when there is no compression region, the fluctuation power increases considerably. ICMEs that caused significant changes in the Dst index were determined to be accompanied by the least changes in the turbulent cascade in the magnetosheath, whereas the most significant modification of the turbulence features were observed during ICMEs which did not trigger substantial geomagnetic disturbances

The magnetosphere response to interplanetary drivers depends on their type. The reliability of their identification affects сonclusions made on the basis of an analysis of the relationships between the solar wind and the magnetosphere. In this paper, we analyze the list of moderate and strong geomagnetic storms and their interplanetary sources for the period of 2009–2019 presented by Qiu et al. It is shown that some of the events in this list were defined incorrectly, and their interpretation differs in ∼20% of cases from our catalog by Yermolaev et al. (http://www.iki.rssi.ru/omni/) for the solar wind types Sheath, ICME, and CIR, and in ∼28% of cases from the catalog of Richardson and Cane for ICME. Using the uncorrected list of Qiu et al. can lead to incorrect identification of interplanetary drivers of magnetic storms and false conclusions. It is recommended to use the classification of interplanetary drivers from catalogs of events accepted by the scientific community as reference ones.

The study estimates the contribution of middle-scale solar wind structures (variations recorded by a spacecraft during ~10 min intervals) in turbulence development in the transition region behind the bow shock. The analysis is based on simultaneous measurements of plasma and/or magnetic field parameters in the solar wind, in the dayside magnetosheath, and on the flanks. The study adopts measurements by Wind, THEMIS, and Spektr-R spacecraft. The properties of the magnetic field and ion flux fluctuation spectra are analyzed in the 0.01–4 Hz frequency range, which corresponds to the transition from MHD to kinetic scales. The dynamics of turbulence properties in the magnetosheath is governed by large-scale disturbances, while structures with smaller scales have an effect in the absence of large-scale structures.

The response of the magnetosphere to interplanetary drivers depends on their type. The reliability of their identification affects the conclusions of the analysis of connections between the solar wind and the magnetosphere. In this work, we analyze the list of moderate and strong geomagnetic storms and their interplanetary sources for the period 2009 - 2019, presented in the work of Qiu et al. It is shown that some of the events in this list were identified incorrectly, and their interpretation differs in ~20% of cases from our catalog by Yermolaev et al. (http://www.iki.rssi.ru/pub/omni/) for types of solar wind Sheath, ICME and CIR, and in ~28% of cases from the Richardson and Cane catalog for ICME. Using the unadjusted list of Qiu et al. may lead to incorrect identification of interplanetary drivers of magnetic storms and erroneous conclusions. It is recommended to use the classification of interplanetary events from catalogs of events accepted by the scientific community as reference ones.

The study aims to understand the role of solar wind current sheets (CSs) in shaping the spectrum of turbulent fluctuations and driving dissipation processes in space plasma. Local non-adiabatic heating and acceleration of charged particles in the solar wind is one of the most intriguing challenges in space physics. Leading theories attribute these effects to turbulent heating, often associated with magnetic reconnection at small-scale coherent structures in the solar wind, such as CSs and flux ropes. We identify CSs observed at 1 AU in different types of the solar wind around and within an interplanetary coronal mass ejection (ICME) and analyze the corresponding characteristics of the turbulent cascade. It is found that the spectra of fluctuations of the interplanetary magnetic field may be reshaped due to the CS impact potentially leading to local disruptions in energy transfer along the cascade of turbulent fluctuations. Case studies of the spectra behavior at the peak of the CS number show their steepening at MHD scales, flattening at kinetic scales, and merging of the spectra into a single form, with the break almost disappearing. In the broader vicinity of the CS number peak, the behavior of spectral parameters changes sharply, but not always following the same pattern. The statistical analysis shows a clear correlation between the break frequency and the CS number. These results are consistent with the picture of turbulent reconnection at CSs. The CS occurrence is found to be statistically linked with the increased temperature. In the ICME sheath, there are two CS populations observed in the hottest and coldest plasma.

Magnetosheath is a transition layer between the solar wind and the magnetosphere and may contribute to the geoeffectiveness of various large-scale interplanetary phenomena. In this paper, we examine the dynamics of the turbulent fluctuation spectra behind the bow shock during undisturbed solar wind and when interplanetary coronal mass ejections and corotation interaction regions interact with the magnetosphere. The study is based on statistical analysis of the turbulence features inside the magnetosheath at different distances from the bow shock. We demonstrate that the turbulence features change when plasma crosses the bow shock for the solar wind of all types and they usually recover when plasma moves away from the bow shock. However, peculiarities in the turbulence development occur during interplanetary coronal mass ejections. Moreover, during disturbed solar wind there are relations between the turbulence features at the sub-ion scales and background plasma parameters such as plasma parameter β, the angle θBN between the interplanetary magnetic field and the local bow shock normal, solar wind bulk velocity, and the distance to the magnetosheath boundaries.

Magnetosheath is a transition layer between the solar wind and the magnetosphere and may contribute to the geoeffectiveness of various large-scale interplanetary phenomena. In this paper, we examine the dynamics of the turbulent fluctuation spectra behind the bow shock during undisturbed solar wind and when interplanetary coronal mass ejections and corotation interaction regions interact with the magnetosphere. The study is based on statistical analysis of the turbulence features inside the magnetosheath at different distances from the bow shock. We demonstrate that the turbulence features change when plasma crosses the bow shock for the solar wind of all types and they usually recover when plasma moves away from the bow shock. However, peculiarities in the turbulence development occur during interplanetary coronal mass ejections. Moreover, during disturbed solar wind there are relations between the turbulence features at the sub-ion scales and background plasma parameters such as plasma parameter β, the angle θBN between the interplanetary magnetic field and the local bow shock normal, solar wind bulk velocity, and the distance to the magnetosheath boundaries.

Solar wind is known to have different properties depending on its origin at the Sun. In addition to the differences in plasma and magnetic field parameters, these streams differ due to the properties of turbulent fluctuations involved in the flow. The present study addresses the changes in the turbulence properties in the magnetosheath—the transition region in front of the magnetosphere. This study is based on statistics from the simultaneous measurements of magnetic field fluctuations in the solar wind and in the magnetosheath. Both the dayside and flank magnetosheath regions are focused on to detect the evolution of the turbulent fluctuations during their flow around the magnetosphere. Turbulent cascade is shown to save its properties for fast solar wind streams. Conditions favorable for the preservation of the turbulence properties at the bow shock may correspond to the increased geoefficiency of large-scale solar wind structures.