Based on the OMNI2 database for the period from 1976 to 2019, the behavior of the relative abundance of helium ions Nα/Np is investigated inside interplanetary coronal mass ejections (ICMEs). It is shown that the previously discovered anticorrelation between Nα/Np and the parameter β inside ICMEs is due to the dependence on magnetic pressure (or the magnitude of the interplanetary magnetic field), while the dependence of Nα/Np on the magnitude of the thermal pressure weakly falling in a magnetic cloud and increases in EJECTA. The data obtained are consistent with the previously suggested hypothesis that an electric current enriched with helium ions flows inside an ICME [1–3].

This study is concerned with the relative helium abundance variations, as well as other solar wind plasma and interplanetary magnetic field parameters, inside interplanetary coronal mass ejections on medium spatial scales (10 5 –10 6 km). The analysis is based on long-term WIND spacecraft measurements. It is shown that those scales lack an unambiguous anticorrelation between the helium abundance and plasma parameter β that was revealed on spatial scales greater than 10 6 km. Events with significant positive and negative correlations are observed with the same probability. In this case, both types of structures can be observed: structures in which the helium abundance grows simultaneously with an increase in the interplanetary magnetic field that are similar to those observed on large scales, as well as structures in which the helium abundance increases with a decline in the interplanetary magnetic field.

Studying the direction of the solar wind flow is a topical problem of space weather forecasting. As a rule, the quiet and uniform solar wind propagates radially, but significant changes in the solar wind flow direction can be observed, for example, in compression regions before the interplanetary coronal mass ejections (Sheath) and Corotating Interaction Regions (CIR) that precede high-speed streams from coronal holes. In this study, we perform a statistical analysis of the longitude (φ) and latitude (θ) flow direction angles and their variations on different time scales (30 s and 3600 s) in solar wind large-scale streams of different types, using WIND spacecraft data. We also examine the relationships of the value and standard deviations SD of the flow direction angles with various solar wind parameters, regardless of the solar wind type. We have established that maximum values of longitude and latitude angle modulus, as well as their variations, are observed for Sheath, CIR, and Rare, with the probability of large deviations from the radial direction (>5°) increasing. The dependence on the solar wind type is shown to decrease with scale. We have also found that the probability of large values of SD(θ) and SD(φ) increases with increasing proton temperature (Tp) in the range 5–10 eV and with increasing proton velocity (Vp) in the range 400–500 km/s.

We investigated variations on scales of 10 4 –10 5 km and local spatial inhomogeneities in the density of protons N p , doubly ionized helium ions (α-particles) N α , and the relative abundance of helium N α / N p in the solar wind. Measurements taken by two spacecraft, SPEKTR-R and WIND , separated in space by a distance of more than 1 million km, are analyzed, and the correlation coefficient between measurements of the corresponding parameters at different time intervals is determined. For intervals with a generally high level of correlation of plasma parameters, variations in the level of local (over shorter subintervals) correlation were analyzed. We showed that a low level of local correlation of all studied parameters is relatively common. The level of local correlation depends on the type of large-scale solar wind stream, as well as on the bulk velocity of the flow and the degree of flux variability. In addition, a low level of local correlation is often characterized by a negative component B x of the interplanetary magnetic field. The regions of local spatial inhomogeneities in the densities of protons and helium and the relative abundance of helium are identified and their size is estimated.

In the present work, we study the possibility of assessing the inhomogeneities of the ionic composition along the axis of the magnetic cloud using the method that was recently used by Song et al. (2021). Possible violations of the used assumptions do not allow one to draw reliable conclusions.

First, we would like to note that MCs have several generally accepted properties that distinguish them from other large-scale types of solar wind (see, for example, a review by Zurbuchen and Richardson [2006]). These properties include their ionic mass and charge composition. In particular, it has been noted that (1) enhanced α/proton ratio of He2 +/H+ is >8% (Hirshberg et al., 1972; Borrini et al. 1982), (2) the elevated oxygen charge states of O7+/O6+ are >1 (Henke et al., 2001; Zurbuchen et al., 2003), and (3) the unusually high Fe charge states of QFe are >12 (Bame et al., 1979; Lepri et al., 2001; Lepri and Zurbuchen, 2004). Although parameters used to identify MCs were assessed by Huang et al. (2020), these MC criteria were not discussed in important sections of paper including the Introduction, Event Selection Methodology, or Discussion. In contrast with generally accepted structures of scientific publications, the authors only briefly mentioned the criteria in the Results section (in the description of Figs. 3e, 3g and 3f). Results obtained by the authors either completely or partially contradict MC properties listed. For example, for data presented (1) He2+/H+ was <8%, (2) O7+/O6+ > 1 only applied to some fast MCs, and not slow MCs, and (3) QFe > 12 was true for fast MCs, but not slow MCs. The authors do not discuss these differences. This divergence from generally accepted properties of MCs indicates that the analysis performed and its conclusions are incorrect.

In the present work, we study the possibility of assessing the inhomogeneities of the ionic composition along the axis of the magnetic cloud using the method that was recently used by Song et al. (2021). Possible violations of the used assumptions do not allow one to draw reliable conclusions.

Solar wind — a plasma stream flowing out of the solar corona — is interesting both as a carrier of solar activity and as an example of a collisionless plasma. We present the main results of Russian studies in recent years. The original MHD model allows interpreting the bifurcation of the heliospheric current sheet during maximum activity years as occurring due to the quadrupole component of the heliomagnetic field. On a scale of the order of millions of kilometers, the solar wind consists of transient solar formations. On these scales, one of the basic geomagnetic forecast problems has been solved: it was shown that the interplanetary magnetic field can be assumed stable at times of about three hours. At small scales (hundreds to thousands of kilometers), local structures are formed that can be regarded, both individually and statistically, as turbulent cascades .

The differences in the dynamics of the asymmetrical part of the geomagnetic disturbance at middle and low latitudes during magnetic storms initiated by different interplanetary sources are analyzed. The analysis is performed with the SYM-H, ASY-H, and Dst indices from the OMNI database during the periods of 58 intense magnetic storms with –270 ≤ Dstmin ≤ –90 nT that were recorded in 1995–2017 and initiated by one of the solar wind structures: compressed corotating interaction regions (CIRs); interplanetary coronal mass ejections (ICMEs) including magnetic clouds (MCs) and Ejecta “pistons”; and compressed Sheath regions in front of ICMEs. The interplanetary sources were identified on the basis of the catalog of large-scale solar-wind phenomena (ftp://ftp.iki.rssi.ru/pub/omni/). A double superposed epoch analysis with reference points at the onset of the storm and during Dstmin was used. It is shown that the ASY-H values during Sheath-driven storms are, on average, 40% higher than for storms of other groups and that the ASY-H maximum occurs ~3 h earlier than Dstmin during Sheath-driven storms and 1–2 h earlier during MC-driven storms, which may indicate a more intense and uneven energy inflow during these periods. It is assumed that this energy inflow may be provided by the proton flux with energies of >10 MeV observed by the GOES geostationary satellites, which increases by more than two orders of magnitude in the intervals of Sheath-driven storms as compared to storms of other groups.

This work is devoted to the study of properties of spectra of turbulent solar wind fluctuations in plasma compression regions, such as CIR (the plasma compression regions in front of high-speed streams from coronal holes) and SHEATH (the compression regions in front of interplanetary manifestations of coronal mass ejections EJECTA and magnetic clouds MC). The spectra of ion flux fluctuations, on both magnetohydrodynamic and ion-kinetic scales, are considered on the basis of data from the BMSW spectrometer on the SPEKTR-R spacecraft with a high (up to 31 ms) time resolution. The comparison of turbulent characteristics in the plasma compression regions and in the undisturbed solar wind is carried out both on a separate example and using extensive statistical material. It is shown in the paper that the turbulent cascade characteristics on the kinetic interval can significantly change in the plasma compression regions, and the signatures of a change in the main processes that determine the energy dissipation are revealed in them, which may cause increased heating in the regions under consideration.

This work is a continuation of our previous articles (Yermolaev et al., 2015, ; 2017, ; 2018, ), which describe the average temporal profiles of interplanetary plasma and field parameters in large-scale solar-wind (SW) streams: corotating interaction regions (CIRs), interplanetary coronal mass ejections (ICMEs including both magnetic clouds (MCs), and ejecta), and sheaths as well as interplanetary shocks (ISs). In this work, we analyze the average profile of helium abundance,N-alpha/N-p, for 1976-2016. Our results confirm the main results that were obtained in earlier studies:N-alpha/N(p)is higher in quasi-stationary fast streams than in slow ones; it slowly changes in compression regions CIRs and sheaths from values in undisturbed SW to values in the corresponding fast stream type pushing like a piston, in high-speed stream (HSS) flow for CIRs, or in ICME for sheaths; in ejecta, it is close to the abundance observed in undisturbed streams, and it is maximal in MCs. For the first time, the results show thatN(alpha)/N(p)correlates with the proton beta-parameter in compression regions CIRs and sheath and anticorrelates in ICMEs. TheN(alpha)/N(p)versus beta dependence is stronger in MCs than in ejecta and may be used as an indicator of conditions at the place on the Sun where CMEs are formed.

A recent paper by Owens (2018) presents a statistical analysis of the properties of interplanetary coronal mass ejections (ICMEs) and variations in their compositions and ion charge-state signatures using data from the Advanced Composition Explorer (ACE) spacecraft. However, the article contains several serious flaws, which we will discuss here.

The magnetosheath is an integral element of solar–terrestrial relations. The paper analyzes the influence of the solar wind parameters and their variability, as well as the topology of the bow shock on the characteristics of plasma turbulence in the magnetosheath on scales corresponding to the transition from the inertial region of a turbulent cascade to the dissipative one. The analysis is based on extensive statistics of measurements of the BMSW instrument with high time resolution on board the Spektr-R satellite in the magnetosheath in 2011–2018. It is shown that the variability of the solar wind plasma density and the interplanetary magnetic field magnitude, as well as the angle between the normal to the bow shock and the interplanetary magnetic field has the greatest influence on the form of the turbulent cascade directly behind the bow shock.

This paper discusses the errors in analyzing solar-terrestrial relationships, which result from either disregarding the types of interplanetary drivers in studying the magnetosphere response on their effect or from the incorrect identification of the type of these drivers. In particular, it has been shown that the absence of selection between the Sheath and ICME (the study of so-called CME-induced storms, i.e., magnetic storms generated by CME) leads to errors in the studies of interplanetary conditions of magnetic storm generation, because the statistical analysis has shown that, in the Sheath + ICME sequences, the largest number of storm onsets fell on the Sheath, and the largest number of storms maxima fell at the end of the Sheath and the beginning of the ICME. That is, the situation is observed most frequently when at least the larger part of the main phase of storm generation falls on the Sheath and, in reality, Sheath-induced storms are observed. In addition, we consider several cases in which magnetic storms were generated by corotating interaction regions, whereas the authors attribute them to CME.