Kinetic-scale current sheets in the solar wind at 1 AU: Scale-dependent properties and critical current density

Abstract

We present analysis of 17,043 proton kinetic-scale current sheets collected over 124 days of Wind spacecraft measurements in the solar wind at 11 Samples/s magnetic field resolution. The current sheets have thickness $\lambda$ from a few tens to one thousand kilometers with typical value around 100 km or from about 0.1 to 10${\lambda }_p$ in terms of local proton inertial length ${\lambda }_p$. We found that the current density is larger for smaller scale current sheets, $J_0\approx 6nA/{\mathrm{m}}^2\cdot (\lambda /100\mathrm{km}{)}^{-0.56}$ , but does not statistically exceed critical value $J_A$ corresponding to the drift between ions and electrons of local Alvén speed. The observed trend holds in normalized units, $J_0/J_A\approx 0.17\cdot (\lambda /{\lambda }_p{)}^{-0.51}$. The current sheets are statistically force-free with magnetic shear angle correlated with current sheet spatial scale, $\Delta \theta \approx 19^{\circ }\cdot (\lambda /{\lambda }_p{)}^{0.5}$. The observed correlations are consistent with local turbulence being the source of proton kinetic-scale current sheets in the solar wind, while mechanisms limiting the current density remain to be understood.

7 pages + list of references, 5 figures

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Cited by in corpus (1)

• Kinetic-scale current sheets in near-Sun solar wind: properties, scale-dependent features and reconnection onset