Peculiarities of the Heliospheric State and the Solar-Wind/Magnetosphere Coupling in the Era of Weakened Solar Activity

Yermolaev, Yu. I.; Лодкина, И. Г.; Khokhlachev, Alexander A.; Yermolaev, M. Yu.

doi:10.3390/universe8100495

Cited by 16 publications

(4 citation statements)

References 16 publications

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“…However, because the CIR driven storms are small in number, we consider only the 196 ICME driven storms for the epoch analysis in this paper. The number of storms, especially CIR‐driven storms, are small compared to previous studies (e.g., Yermolaev et al., 2022) because only the clear storms satisfying four selection criteria are identified. The ICME driven storms could be generated by both magnetic clouds and area of compression in front of them, the sheath (Yermolaev et al., 2014).…”

Section: Discussionmentioning

confidence: 86%

Double Superposed Epoch Analysis of Geomagnetic Storms and Corresponding Solar Wind and IMF in Solar Cycles 23 and 24

et al. 2023

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The large (fluctuating) electric currents flowing at different regions in the magnetosphere and ionosphere during space weather events produce large fluctuations in the geomagnetic field lasting from several hours to several days in all latitudes (e.g., Akasofu, 1981;Gonzalez et al., 1994;Svalgaard, 1977). The field fluctuations at low latitudes are produced mainly by the enhanced low latitude magnetospheric ring current; they undergo 3-phase variations and are referred as geomagnetic storms. At high latitudes, the field fluctuations are produced mainly by the enhanced high latitude ionospheric auroral electrojet current; they undergo irregular variations and are referred as storm-time substorms or activities. At mid latitudes, the field fluctuations are the combined effect of the poleward extension of the low latitude fluctuations and equatorward extension of the high latitude fluctuations; they undergo 2-phase variations and are referred also as geomagnetic storms (e.g.

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Section: Discussionmentioning

confidence: 86%

Double Superposed Epoch Analysis of Geomagnetic Storms and Corresponding Solar Wind and IMF in Solar Cycles 23 and 24

et al. 2023

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“…In one of our recent papers [19], we also showed that the time profiles of all SW parameters in all types of large-scale phenomena in SCs 23-24 have a similar shape with the same profiles in SCs 21-22, but located at lower values. In addition, there is a sharp drop in the number of ICMEs in the last two cycles [25,27]. These results indicate a weakening of the solar wind during the Sun's transition from the epoch of high activity in SCs 21-22 to the epoch of low activity in SCs 23-24.…”

Section: Introductionmentioning

confidence: 79%

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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“…Indeed, having previously smoothed the accumulated hourly data the Dst index and the β parameter from [Kurazhkovskaya et al, 2021] by a running average, we plot Dst(β) for the interval of 168 hrs from storm commencements. This time interval covers the average duration of the storm main phase, which, according to [Yermolaev et al, 2007], is 74 hrs, and the storm recovery phase, which on average lasts for 5-7 days. Figure 4 It can be seen that the trajectory of variation in the Dst index depending on the β parameter in the storm main phase is seen to differ from its trajectory in the recovery phase.…”

Section: Discussionmentioning

confidence: 99%

Hysteresis effect between geomagnetic activity indices (Ap, Dst) and interplanetary medium parameters in solar activity cycles 21–24

Kurazhkovskaya,

Kurazhkovskii

2023

Solar-Terrestrial Physics

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We have studied the relationship of geomagnetic activity indices (Ap, Dst) on time intervals, equal to solar cycles (∼11 years), with solar activity indicators and heliospheric parameters. It is shown that the plots of the Ap and Dst indices versus solar activity indicators, as well as versus heliospheric parameters, i.e. solar wind and IMF parameters in the ascending and descending phases of solar activity cycles 21–24 do not coincide, which is indicative of the hysteresis phenomenon. The Ap and Dst indices form hysteresis loops with all parameters we analyze during cycles 21–24. The shape and area of the hysteresis loops, as well as the direction of rotation, clockwise or counterclockwise, depend significantly on indicators of solar activity, heliospheric parameters and change from cycle to cycle. We have found a tendency for the extension and area of the hysteresis loops to decrease from cycle 21 to cycle 24. Analysis of the variability in the shape and size of the hysteresis loops formed by the Ap and Dst indices with solar indicators and heliospheric parameters gives reason to believe that the obtained loops reflect the long-term evolution of the solar wind energy flux, which determines global geomagnetic activity and the magnetospheric ring current intensity in the ascending and descending phases of solar activity cycles 21‒24.

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Peculiarities of the Heliospheric State and the Solar-Wind/Magnetosphere Coupling in the Era of Weakened Solar Activity

Cited by 16 publications

References 16 publications

Double Superposed Epoch Analysis of Geomagnetic Storms and Corresponding Solar Wind and IMF in Solar Cycles 23 and 24

Double Superposed Epoch Analysis of Geomagnetic Storms and Corresponding Solar Wind and IMF in Solar Cycles 23 and 24

Helium Abundance Decrease in ICMEs in 23–24 Solar Cycles

Hysteresis effect between geomagnetic activity indices (Ap, Dst) and interplanetary medium parameters in solar activity cycles 21–24

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