Automated Identification of Current Sheets—A New Tool to Study Turbulence and Intermittency in the Solar Wind

Abstract

We propose a new method of the automated identification of current sheets (CSs) that represents a formalization of the visual inspection approach employed in case studies. CSs are often identified by eye via the analysis of characteristic changes in the interplanetary magnetic field (IMF) and plasma parameters. Known visual and semi‐automated empirical methods of CS identification are exact but do not allow a comprehensive statistical analysis of CS properties. Existing automated methods partially solve this problem. Meanwhile, these methods suggest an analysis of variations of the IMF and its direction only. In our three‐parameter empirical method, we employ both the solar wind plasma and IMF parameters to identify CSs of various types. Derivatives of the IMF strength, the plasma beta and the ratio of the Alfvén speed VA to the solar wind speed V taken with the one‐second cadence are used. We find that the CS daily rate R correlates with the solar wind temperature T rather than with V and is proportional to the sum of the kinetic and thermal energy density ∼V2(N+5N′)+10T(N + N′), where N′ = 2 cm−3 is the background level of the solar wind density N. Maxima of R are associated with stream/corotating interaction regions and interplanetary mass ejection sheaths. A multiyear list of CSs identified at 1 AU can be found at https://csdb.izmiran.ru/.

Importance of accurate consideration of the electron inertia in hybrid-kinetic simulations of collisionless plasma turbulence: 1. The 2D limit

“…On the other hand, this limits their validity to scales much larger than the electron scales. Space observations of collisionless plasma turbulence by multi-spacecraft missions (Cluster and MMS) in the Earth's magnetosphere and the solar wind, however, revealed electron-and ion-scale breaks in the power spectra as well as the formation of current sheet (CS) structures from ion to electron scales [20][21][22] . On the other hand, even hybrid-kinetic simulations with inertia-less electrons have already shown that in evolving turbulent CSs, the electrons become the main current carriers 15 and that these CSs thin down to the grid scale 23 .…”

Electron-to-ion Bulk Speed Ratio as a Parameter Reflecting the Occurrence of Strong Electron-dominated Current Sheets in the Solar Wind

“…Spacecraft routinely observe electric-current-carrying thin plasma layers, or current sheets (CSs), in collisionless space plasmas (e.g., Nakamura et al 2006;Sundkvist et al 2007;Greco et al 2009;Podesta 2017a;Azizabadi et al 2021;Jain et al 2021;Khabarova et al 2021b). In the solar wind, CSs are formed at discontinuities that separate regions with differently directed magnetic fields (Syrovatskiǐ 1971).…”

“…These are secondary signatures identifying ion-dominated CSs. An overview of both visual and automated methods of CS identification in the heliosphere can be found in Khabarova et al (2021b).…”

“…Below, we will show an example of crossing of such a CS with MMS in the solar wind. If one knows specific features characterizing the occurrence of strong electron-dominated CSs in the solar wind, then it is possible to apply commonly accepted techniques for CS identification to recognition of electrondominated CSs from the in situ data, using an ordinary spacecraft resolution of 1−3 s (Khabarova et al 2021b). It also would be interesting and useful to find secondary or indirect signatures of strong electron-carried currents.…”

“…It is aimed at a preliminary estimation of the ability of the u e /u i parameter to recognize plasma structures associated with electron-dominated CSs. Then, we utilize the Wind spacecraft observations, identifying such magnetoplasma structures and comparing their found locations with those of ion-dominated CSs, using the method described by Khabarova et al (2021b). Finding an approximate location of electron-dominated CSs may be very useful for future statistical studies of solar wind CSs in which electrons are the main current carriers.…”