Features of the impact of the solar wind diamagnetic structure on Earth’s magnetosphere

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The results presented in this review reflect the fundamentals of the modern understanding of the nature of the structure of the slow solar wind (SW) along the entire length from the Sun to the Earth's orbit. It is known that the source of the slow quasi-stationary SW on the Sun is the belt and the chains of coronal streamers The streamer belt encircles the entire Sun as a wave-like surface (skirt), representing a sequence of pairs of rays with increased brightness (plasma density) or two lines of rays located close to each other. Neutral line of the radial component of the solar global magnetic field goes along the belt between the rays of each of these pairs. The streamer belt extends in the heliosphere is as the heliospheric plasma sheet (HPS). Detailed analysis of data from Wind and IMP-8 satellites showed that HPS sections on the Earth orbit are registered as a sequence of diamagnetic tubes with high density plasma and low interplanetary magnetic field. They represent an extension of rays with increased brightness of the streamer belt near the Sun. Their angular size remains the same over the entire way from the Sun to the Earth's orbit. Each HPS diamagnetic tube has a fine internal structure on several scales, or fractality. In other words, diamagnetic tube is a set of nested diamagnetic tubes, whose angular size can vary by almost two orders of magnitude. These sequences of diamagnetic tubes that form the base of slow SW on the Earth's orbit has a more general name — diamagnetic structures (DS). In the final part of this article, a comparative analysis of several events was made, based on the results of this review. He made it possible to find out the morphology and nature of the origin of the new term “diamagnetic plasmoids” SW (local amplifications of plasma density), which appeared in several articles published during 2012–2018. The analysis carried out at the end of this article, for the first time, showed that the diamagnetic plasmoids SW are the small-scale component of the fractal diamagnetic structures of the slow SW, considered in this review.

Diamagnetic structures as a basis of quasi-stationary slow solar wind

Еселевич¹

2019

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Magnetospheric response to the interaction with the sporadic solar wind diamagnetic structure

Parkhomov

Еселевич

et al. 2021

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We report the results of a study on the movement of the solar wind diamagnetic structure (DS), which is a sequence of smaller-scale microDS being part of the May 18, 2013 coronal mass ejection, from a source on the Sun to Earth’s surface. DS determined from the high negative correlation coefficient (r=–0.9) between the IMF modulus (B) and the SW density (N) on the ACE and Wind satellites at the L1 point, on the THB and THC satellites (r=–0.9) in near-Earth orbit, and on the THA satellite inside the magnetosphere is carried by the solar wind from the Sun to Earth’s orbit, while maintaining its fine internal structure. Having a large size in the radial direction (≈763 Rᴇ, where Rᴇ is the Earth radius), DS flows around the magnetosphere. At the same time, microDS of size ≤13 Rᴇ passes through the bow shock and magnetopause as a magnetized plasmoid in which the ion concentration increases from 10 cm⁻³ to 90 cm⁻³, and the velocity decreases as it moves toward the magnetotail. When a microDS passes through the magnetopause, a pulsed electric field of ~400 mV/m is generated with subsequent oscillations with a period of T~200 s and an amplitude of ~50 mV/m. The electric field accelerates charged particles of the radiation belt and produces modulated fluxes of protons in an energy range 95–575 keV on the day side and electrons in 40–475 keV and protons in 95–575 keV on the night side. In the duskside magnetosphere (19–23 MLT), the substorm activation is observed in geomagnetic pulsations and auroras, but without a magnetic negative bay. In the post-midnight sector (01–05 MLT), a sawtooth substorm occurs without the growth phase and breakup with deep modulation of the ionospheric current and auroral absorption. The duration of all phenomena in the magnetosphere and on Earth is determined by the period of interaction between DS and the magnetosphere (~4 hrs). To interpret the regularities of the magnetospheric response to the interaction with DS, we consider alternative models of the impulsive passage of DS from SW to the magnetosphere and the classical model of reconnection of IMF and the geomagnetic field.

Solar activity cycle 25: the first three years

Yazev,

Isaeva,

Hos-Erdene

2023

We analyze features of current solar activity cycle 25 for the first three years of its development (2020–2022). Compared to cycle 24, the current cycle is shown to exceed the previous one in the number of sunspot groups (1.5 times), the number of flares (1.8 times), and the total flare index (1.5 times). We have found that distributions of sunspot groups during cycles 24 and 25 differ in maximum area. Solar cycle 25, unlike cycle 24, exhibits the most significant increase in the number of sunspot groups with areas up to 30 pmh and in the interval from 570 to 1000 pmh. In contrast to cycle 24, the degree of north-south asymmetry in cycle 25 is significantly reduced. This allows us to predict an increased height of cycle 25, as compared to cycle 24 (by 20–50 %), in accordance with the Gnevyshev—Ol rule, as well as the possible unimodal nature of the cycle.