Kinetic magnetic holes in the high-speed streams during solar cycle 23

Potapov, A.S.

Автор: Potapov Alexander S.
Журнал: Planetary and Space Science
Том: 192
Год издания: 2020
Издательство: Elsevier BV
Местоположение издательства: Netherlands
Номер статьи: 105066
DOI: 10.1016/j.pss.2020.105066
Аннотация: One of the important elements of solar wind turbulence is the so-called “magnetic holes” (MHs), sharp temporary drops in the intensity of the interplanetary magnetic field. Using solar wind data from the ACE and Wind spacecraft, distribution and evolution of kinetic-type MHs are investigated. In particular, in the first part of this study, we examine fifteen high-speed Alfvenic streams with a high helicity value, which are mainly CIR streams. The period from 1997 to 2011 is covered, with one stream per year selected. A total of 207 kinetic MHs with duration of 3–129 s were detected in 15 high-speed streams with a total duration of 1004 h. The occurrence rate of holes is about 5 events per day (0.2 per hour), which far exceeds the average frequency of MH observation in the slow wind. The median value of the MH depth is 1.52 nT, the maximum is 22.5 nT. The occurrence rate of holes monotonically increases with decreasing their duration. During the solar cycle, the probability of MH observation increases at minimum and during the early growth phase (1997–1998 and 2008–2010), reaching 0.32 events per hour. In the second part, the dynamics of MHs during their convective transfer by the solar wind was tracked. We used 1-s ACE and Wind magnetometer data during the movement of the Wind SC from the magnetosphere to the libration point L1 against the background of the passage of five high-speed streams. We studied the evolution of MHs observed consistently first on the ACE SC, and then, as a result of their transfer by the wind stream, to the Wind SC. Fifteen MHs were selected whose transfer time between satellites deviated from the calculated one by no more than 15%. Of these, 9 MHs are of the linear type, 5 MHs are of rotational type, and one more was observed against the background of the chaotic behavior of the magnetic field components. The evolution of the MHs during their convective transfer was diverse: from the full shape retention to its significantchange both towards the deepening of the hole and the steepening of its front, and towards its significant spreading. The possible modulation effect of MHs on wave phenomena in the magnetosphere is discussed.
Добавил в систему: Потапов Александр Сергеевич

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Kinetic magnetic holes in the high-speed streams during solar cycle 23статья