The source of the major solar energetic particle events from super active region 11944

TL;DR

This study identifies the plasma at the footpoints of active region 11944 as the source of major gradual solar energetic particle events, linking spectroscopic signatures to near-Earth measurements and localizing the process to the chromosphere.

Contribution

It provides direct observational evidence connecting plasma at active region footpoints to SEP events, clarifying the source and elemental fractionation process.

Findings

Plasma at active region footpoints explains SEP composition signatures.

Elemental fractionation occurs at the top of the chromosphere.

SEP material is continually released and accelerated during flares.

Abstract

Shock waves associated with fast coronal mass ejections (CMEs) accelerate solar energetic particles (SEPs) in the long duration, gradual events that pose hazards to crewed spaceflight and near-Earth technological assets, but the source of the CME shock-accelerated plasma is still debated. Here, we use multi-messenger observations from the Heliophysics System Observatory to identify plasma confined at the footpoints of the hot, core loops of active region 11944 as the source of major gradual SEP events in January 2014. We show that the elemental composition signature detected spectroscopically at the footpoints explains the measurements made by particle counting techniques near Earth. Our results localize the elemental fractionation process to the top of the chromosphere. The plasma confined closest to that region, where the coronal magnetic field strength is high (a few hundred Gauss), develops the SEP composition signature. This source material is continually released from magnetic confinement and accelerated as SEPs following M-, C-, and X-class flares.