Ubiquitous Occurrences of Multi-scale Layers of Magnetic Reconnection across a Solar Wind Stream Interaction Region at 1 AU

We present a first record of significantly enhanced occurrences of magnetic reconnection exhausts as measured by the Wind satellite across a stream interaction region (SIR) at 1 AU from 10:11:20 UT on 4 Jan 2019 to 09:58:00 UT on 5 Jan 2019. The activity is clustered in a slow wind compression regime ahead of the SIR interface with a deflected, compressed fast wind. The 43 exhausts of this 1-day SIR dominate a distribution of 71 exhausts as obtained by a multi-window sliding technique application to the 8-day period on 1-9 Jan 2019. Active current sheets inside the SIR are associated with normal directions mostly near the ecliptic plane and a more azimuthal-than-Parker magnetic field direction at 1 AU. We find that exhausts wider than 500 ion inertial lengths are typically present just upstream and inside this SIR rather than within unperturbed slow and fast winds beyond a shocked solar wind. The observations suggest that plasma and field compressions may be crucial elements in driving a break-up of large-scale current sheets embedded in SIRs into smaller, multi-layered current sheet segments through magnetic reconnection.