Characteristics of the Heliospheric Current Sheets at the Sector Boundaries: Wind Observations from 1995–2020

Abstract

We report results of a statistical study of 1197 heliospheric current sheet (HCS) events associated with the sector boundaries observed by the Wind spacecraft between 1995 and 2020. The average property of the HCS events can be characterized as follows: (1) The width of the current sheets ranges between ∼600 km and 1.1 × 10 6 km, with an average width of 1.06 ± 2.37 × 10 5 km; (2) The longitude (in Geocentric Solar-Ecliptic coordinate) of the HCS normal shows a large peak at ∼210° (0° sunward pointing) and a longer tail at smaller angles; (3) The latitudinal angle (inclination) of the HCS normal shows a near symmetric distribution (peak and average ∼0°); (4) The yearly occurrence rate is relatively constant (∼46 or 3.4 events per solar rotation), without showing a clear solar cycle dependence; (5) There are solar cycle variations in the properties of the plasma and field within the current sheets and these variations follow closely with the background solar wind plasma and field; (6) A mild (∼10%) proton temperature increase within the HCS, suggesting that heating of the solar wind proton can occur within the current sheet; and (7) A sudden decrease in the proton temperature anisotropy ( T ∥ / T ⊥ ) toward unity within ∼3 hr of the HCS was identified. These results suggest that on the large scale the HCS at 1 au is a relatively stable and persistent solar wind structure throughout the solar cycle. On the small scale the HCS property is probably controlled by the dynamics of the current system, which is still poorly known.