Solar energetic particle transport via the heliospheric current sheet: Evidence of a ground-level response on All Saints Day, 2014

Abstract

We investigate the physical mechanisms responsible for the solar energetic particle (SEP) event observed on 1 November 2014, during which several ground-based detectors in both hemispheres, specifically those located on the sunlit western side of Earth, recorded simultaneous enhancements in counting rates. The event is attributed to Active Region (AR) 2192, one of the most active sunspot groups of Solar Cycle 24, which at the time was situated near the western limb of the solar disk, approaching the far side of the Sun. A plausible scenario involves a combination of solar eruptive activity, particle acceleration by a shock wave driven by a coronal mass ejection (CME), and the presence of a heliospheric current sheet (HCS) sector crossing, which may have enhanced magnetic connectivity between the Sun and Earth. We emphasize data from the New-Tupi muon detector, operating in scaler mode and located near the central region of the South Atlantic Anomaly (SAA). The particle excess detected on 1 November 2014 by ground-based instruments spanning different rigidity regimes, in conjunction with satellite observations, indicates that the signal was not a localized phenomenon. Assuming a power-law energy spectrum for the SEP population, we find that its high-energy tail in the GeV range is consistent with proton flux measurements reported by GOES-13. We present and discuss the details of these observations.