Evidence of the Solar EUV hot channel as a magnetic flux rope from remote-sensing and in-situ observations

TL;DR

This study provides observational evidence linking hot channels in the solar corona to magnetic flux ropes, using remote sensing and in-situ measurements to confirm their identity during a CME event.

Contribution

It demonstrates that hot channels observed in the corona are the same structures as magnetic flux ropes detected in the solar wind, confirming their role in CMEs.

Findings

Hot channels are visible in high-temperature images but not in low-temperature images.

The magnetic cloud near Earth matches the erupting hot channel in the corona.

The magnetic cloud shows a low-ionization core and high-ionization shell, consistent with the hot channel.

Abstract

Hot channels (HCs), high temperature erupting structures in the lower corona of the Sun, have been proposed as a proxy of magnetic flux ropes (MFRs) since their initial discovery. However, it is difficult to make definitive proof given the fact that there is no direct measurement of magnetic field in the corona. An alternative way is to use the magnetic field measurement in the solar wind from in-situ instruments. On 2012 July 12, an HC was observed prior to and during a coronal mass ejection (CME) by the AIA high-temperature images. The HC is invisible in the EUVI low-temperature images, which only show the cooler leading front (LF). However, both the LF and an ejecta can be observed in the coronagraphic images. These are consistent with the high temperature and high density of the HC and support that the ejecta is the erupted HC. In the meanwhile, the associated CME shock was identified ahead of the ejecta and the sheath through the COR2 images, and the corresponding ICME was detected by \textit{ACE}, showing the shock, sheath and magnetic cloud (MC) sequentially, which agrees with the coronagraphic observations. Further, the MC contained a low-ionization-state center and a high-ionization-state shell, consistent with the pre-existing HC observation and its growth through magnetic reconnection. All of these observations support that the MC detected near the Earth is the counterpart of the erupted HC in the corona for this event. Therefore, our study provides strong observational evidence of the HC as an MFR.