Authors: Ivan Vasko (UC Berkeley), Ajay Lotekar (IRF, Sweden), Tai Phan (UC Berkeley), Kaz Alimov (UC Berkeley), Stuart Bale (UC Berkeley), Forrest Mozer (UC Berkeley), Anton Artemyev (UCLA)

We present analysis of 18,785 kinetic-scale current sheets collected over 124 days of Wind spacecraft measurements in the solar wind at 11 Samples/s magnetic field resolution and also 11,200 kinetic-scale current sheets collected over 10 days of Parker Solar Probes measurements during the first encounter. Although the current sheet properties at 0.2 and 1 au are different in physical units, these properties as well as epoch magnetic field profiles are essentially identical after appropriate normalization by background plasma parameters. We demonstrate that the current sheets are statistically asymmetric, although statistically the magnetic field magnitude varies across the current sheets by only a few percent. The current density is dominated by the parallel (magnetic field-aligned) component, although the perpendicular current density tends to be larger at larger plasma betas. Based on these observations we demonstrate that the current sheets have to be elongated along background magnetic field and their geometry depends on local plasma beta. The current density does not statistically exceed local Alfven current density J_A corresponding to the drift between ions and electrons of local Alfvén speed.

The collected current sheets are proton kinetic-scale structures with thickness in the range from 0.1 to 10 proton inertial lengths. At both 0.2 and 1 au, the current sheets with smaller thickness tend to have larger current density and the observed trend is well described by the following scaling relation, J₀/J_A=0.17·(h/d_p)^a with a≈-(0.3-0.5), where h is the current sheet thickness and d_p is the proton inertial length. The magnetic shear angle ang across the current sheets is also scale-dependent with the observed trends well described as follows, ang=19^°·(h/d_p)^a with a≈0.5-0.7. We argue that these scale-dependencies are strong indications that kinetic-scale current sheets at both 0.2 and 1 au are produced by turbulence cascade.

We show that the current sheets at both 0.2 and 1 au are in the parameter range where reconnection is not suppressed by diamagnetic drift of the X-line. We argue this necessary condition for magnetic reconnection is automatically satisfied due to the geometry of current sheets dictated by their source, which is the turbulence cascade. We conclude that reconnection in the solar wind is not likely to be suppressed or controlled by the diamagnetic suppression condition.