Dynamics of Large‐Scale Solar‐Wind Streams Obtained by the Double Superposed Epoch Analysis: 4. Helium Abundance

Yermolaev, Yu. I.; Лодкина, И. Г.; Yermolaev, M. Yu.; Рязанцева, М. О.; Rakhmanova, L. S.; Бородкова, Н. Л.; Shugay, Yu. S.; Slemzin, V. A.; Veselovsky, I. S.; Rodkin, Denis

doi:10.1029/2020ja027878

Cited by 11 publications

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References 39 publications

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“…MC differs from ejecta mainly in its higher and more regular magnetic field. These and other differences are described in more detail in [30,40,51]. As already shown earlier (see, for example, [30]), the difference in the properties of SH MC and SH EJ is small (i.e., their properties depend little on the type of ICME piston-MC or ejecta), but their properties depend on the presence of shock ISs (i.e., they depend on the speed of propagation of ICMEs relative to the preceding quiet solar wind).…”

Section: Methodsmentioning

confidence: 99%

What Solar–Terrestrial Link Researchers Should Know about Interplanetary Drivers

et al. 2021

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One of the most promising methods of research in solar–terrestrial physics is the comparison of the responses of the magnetosphere–ionosphere–atmosphere system to various types of interplanetary disturbances (so-called “interplanetary drivers”). Numerous studies have shown that different types of drivers result in different reactions of the system for identical variations in the interplanetary magnetic field. In particular, the sheaths—compression regions before fast interplanetary CMEs (ICMEs)—have higher efficiency in terms of the generation of magnetic storms than ICMEs. The growing popularity of this method of research is accompanied by the growth of incorrect methodological approaches in such studies. These errors can be divided into four main classes: (i) using incorrect data with the identification of driver types published in other studies; (ii) using incorrect methods to identify the types of drivers and, as a result, misclassify the causes of magnetospheric-ionospheric disturbances; (iii) ignoring a frequent case with a complex, composite, nature of the driver (the presence of a sequence of several simple drivers) and matching the system response with only one of the drivers; for example, a magnetic storm is often generated by a sheath in front of ICME, although the authors consider these events to be a so-called “CME-induced” storm, rather than a “sheath-induced” storm; (iv) ignoring the compression regions before the fast CME in the case when there is no interplanetary shock (IS) in front of the compression region (“sheath without IS” or the so-called “lost driver”), although this type of driver generates about 10% of moderate and large magnetic storms. Possible ways of solving this problem are discussed.

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Section: Methodsmentioning

confidence: 99%

What Solar–Terrestrial Link Researchers Should Know about Interplanetary Drivers

et al. 2021

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“…The results of the analysis showed that the helium abundance in an ICME correlates with the IMF magnitude and, as a consequence, the helium abundance increases with a decrease in the proton parameter β, which is the ratio of the thermal proton pressure to the magnetic one. Such a relationship between the helium abundance and the parameter β in an ICME was previously revealed when comparing the time profiles of parameters calculated for different SW streams by the double superposed epoch method [22,29]. This fact was considered as an indication that a helium-enriched electric current exists inside ICMEs.…”

Section: Introductionmentioning

confidence: 71%

“…Their spatial scale along the Sun-Earth axis at an average speed of ~400 km/s is about 10 7 km. Compared with slow undisturbed SW streams, these phenomena are characterized by an increased relative helium abundance [5,20,21]; however, a high helium abundance itself is not an unambiguous criterion of ICMEs [22]. ICMEs include two types of streams: magnetic clouds (MCs) and Ejecta.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, the dependences of the helium abundance on parameters inside ICMEs are considered in two periods: in the epoch of high solar activity from 1976 to 1996 (SCs [21][22], and in the epoch of low activity from 1997 to 2019 (SCs [23][24]. The main goal of the research is to find out how dependences in MCs and Ejecta have changed after the change of solar activity epoch at the end of the 20th century.…”

Section: Introductionmentioning

confidence: 99%

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Helium Abundance Decrease in ICMEs in 23–24 Solar Cycles

et al. 2022

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Based on the OMNI database, the influence of the solar activity decrease in solar cycles (SCs) 23–24 on the behavior of the relative helium ions abundance Nα/Np inside interplanetary coronal mass ejections (ICMEs) is investigated. The dependences of the helium abundance on the plasma and interplanetary magnetic field parameters in the epoch of high solar activity (SCs 21–22) and the epoch of low activity (SCs 23–24) are compared. It is shown that Nα/Np significantly decreased in SCs 23–24 compared to SCs 21–22. The general trends of the dependences have not changed with the change of epoch, but the helium abundance dependences on some parameters (for example, the magnitude of the interplanetary magnetic field) have become weaker in the epoch of low activity than they were in the epoch of high activity. In addition, the dependence of the helium abundance on the distance from spacecraft to the ICME axis was revealed; the clearest dependence is observed in magnetic clouds. The Nα/Np maximum is measured at the minimum distance, which confirms the hypothesis of the existence of a helium-enriched electric current inside an ICME.

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“…Variations in the proton and He ++ ion parameters and the Nα/Np at large distances of >10 6 km are directly related to the properties of the upper corona of the Sun and the mechanisms of solar wind formation in this region. It is therefore important to determine the relative density of helium relative to the variations in the main (proton) component due to local physical processes at small distances of ~10 3 km [6][7][8][9][10][11] and references therein.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of He++ Ions at Interplanetary and Earth’s Bow Shocks

et al. 2022

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Experimental investigations of the fine plasma structure of interplanetary shocks are extremely difficult to conduct due to their small thickness and high speed relative to the spacecraft. We studied the variations in the parameters of twice-ionized helium ions (4He++ ions or α-particles) in the solar wind plasma during the passage of interplanetary shocks and Earth’s bow shock. We used data with high time resolution gathered by the BMSW (Bright Monitor of Solar Wind) instrument installed on the SPEKTR-R satellite, which operated between August 2011 and 2019. The MHD parameters of He++ ions (the bulk velocity Vα, temperature Tα, absolute density Nα, and helium abundance Nα/Np) are analyzed for 20 interplanetary shocks and compared with similar parameters for 25 Earth bow shock crossings. Measurements from the WIND, Cluster, and THEMIS satellites were also analyzed. The correlations in the changes in helium abundance Nα/Np with the parameters βi, θBn, and MMS were investigated. The following correlation between Nα/Np and the angle θBn was found: the lower the value of θBn, the greater the drop in helium abundance (Nα/Np) falls behind the IP shock front. For Earth’s bow shock crossings, we found a significant increase in the helium abundance (Nα/Np) in quasi-perpendicular events.

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Dynamics of Large‐Scale Solar‐Wind Streams Obtained by the Double Superposed Epoch Analysis: 4. Helium Abundance

Cited by 11 publications

References 39 publications

What Solar–Terrestrial Link Researchers Should Know about Interplanetary Drivers

What Solar–Terrestrial Link Researchers Should Know about Interplanetary Drivers

Helium Abundance Decrease in ICMEs in 23–24 Solar Cycles

Dynamics of He++ Ions at Interplanetary and Earth’s Bow Shocks

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