Characteristics of Multi-Scale Current Sheets in the Solar Wind at 1 AU Associated with Magnetic Reconnection and the Case for a Heliospheric Current Sheet Avalanche

Wind spacecraft measurements are analyzed to obtain a current sheet (CS) normal width d_cs distribution of 3374 confirmed magnetic reconnection exhausts in the ecliptic plane of the solar wind at 1 au. The d_cs distribution displays a nearly exponential decay from a peak at d_cs = 25 d_i to a median at d_cs = 85 d_i and a 95th percentile at d_cs = 905 d_i with a maximum exhaust width at d_cs = 8077 d_i. A magnetic field θ-rotation angle distribution increases linearly from a relatively few high-shear events toward a broad peak at 35° < θ < 65°. The azimuthal ϕ angles of the CS normal directions of 430 thick d_cs ≥ 500 d_i exhausts are consistent with a dominant Parker-spiral magnetic field and a CS normal along the ortho-Parker direction. The CS normal orientations of 370 kinetic-scale d_cs < 25 d_i exhausts are isotropic in contrast, and likely associated with Alfvénic solar wind turbulence. We propose that the alignment of exhaust normal directions from narrow d_cs ∼ 15–25 d_i widths to well beyond d_cs ∼ 500 d_i with an ortho-Parker azimuthal direction of a large-scale heliospheric current sheet (HCS) is a consequence of CS bifurcation and turbulence within the HCS exhaust that may trigger reconnection of the adjacent pair of bifurcated CSs. The proposed HCS-avalanche scenario suggests that the underlying large-scale parent HCS closer to the Sun evolves with heliocentric distance to fracture into many, more or less aligned, secondary CSs due to reconnection. A few wide exhaust-associated HCS-like CSs could represent a population of HCSs that failed to reconnect as frequently between the Sun and 1 au as other HCSs.