Rain is a typical phenomenon on Earth. There’s a comparable phenomenon on the Solar, referred to as coronal rain. It’s associated to the coronal heating and magnetic subject, and performs a basic position within the mass cycle between the new, tenuous corona and the cool, dense chromosphere.
Coronal rain often takes place in post-flare loops and the non-flaring energetic area coronal loops. It’s typically categorised into two classes: flare-driven and quiescent coronal rain, relying on its relation to the flare. Each sorts of coronal rain kind alongside buildings which are magnetically closed.
Lately, a analysis staff led by Dr. Li Leping from the Nationwide Astronomical Observatories of the Chinese language Academy of Sciences (NAOC) discovered a new kind of coronal rain forming alongside open magnetic buildings, away from the magnetically closed area.
A sequence of research has been issued since 2018, amongst which the newest paper was revealed in The Astrophysical Journal on April 1.
The researchers proposed a new formation mechanism for coronal rain alongside open magnetic buildings facilitated by interchange magnetic reconnection between open and closed magnetic buildings.
On this formation mechanism, the higher-lying open buildings reconnect with the lower-lying closed loops, forming a magnetic dip within the former. The plasma, surrounding the dip, converges into the dip, ensuing within the enhancement of plasma density within the dip. The density enhancement triggers thermal instability. Cooling and condensation of scorching coronal plasma within the dip thus happens. The cool condensation falls towards the solar floor as coronal rain.
No flare was detected throughout the reconnection and condensation course of. The new kind of coronal rain thus belongs to the class of quiescent coronal rain.
“The quiescent coronal rain forming alongside the open buildings is kind of completely different from the flare-driven coronal rain in post-flare loops and the quiescent coronal rain in non-flaring energetic area loops that happen within the closed loops,” stated Dr. Li Leping, the primary creator of the sequence of research.
All of the reconnection and condensation occasions investigated earlier than occurred above the limb.
“Whether or not the condensation facilitated by reconnection can nonetheless be noticed on the disk, and the way it performs, are open questions,” stated Prof. Hardi Peter from the Max Planck Institute for Solar System Analysis (MPS), a co-author of the sequence of research.
The researchers discovered that the reconnection condensation occasions from September 2010-September 2011, noticed above the jap (western) limb of the Solar Terrestrial Relations Observatory (STEREO A (B)), occurred on the disk of the Solar Dynamics Observatory (SDO).
“The occasion introduced is necessary for understanding the worldwide image of condensation formation within the solar ambiance and the mixed observations deliver a really fascinating means to research such a coronal condensation occasions,” the reviewer of the paper commented.
Above the limb, the intense condensations and the next coronal rain, facilitated by reconnection between open and closed buildings, have been clearly detected. Nonetheless, on the disk, the reconnection buildings have been troublesome to watch. Furthermore, darkish condensations appeared and moved to the floor as on-disk coronal rain.
“If solely the on-disk observations can be found, the relation between the condensations and reconnection, proven clearly by the off-limb observations, couldn’t be recognized,” stated Dr. Li. “We propose that some on-disk condensation occasions seen within the transition area and chromospheric strains may very well be facilitated by interchange reconnection.”
Supply:Leping Li et al, On-disk Solar Coronal Condensations Facilitated by Magnetic Reconnection between Open and Closed Magnetic Constructions, The Astrophysical Journal (2021). DOI: 10.3847/1538-4357/abe537
https://iopscience.iop.org/journal/0004-637X
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