Researchers have revealed that it rains on the Sun, the immense thermonuclear entity that radiates heat through fusion. This phenomenon, known as coronal rain, consists of superheated plasma formed by shifting flows of elements like iron, silicon, and magnesium.
Scientists from the Institute for Astronomy at the University of Hawai”i have shed light on this unusual occurrence, drawing parallels between solar rain and the rainfall patterns observed in their volcanic island environment.
So, does it truly rain on the Sun? The answer is both yes and no. While there are parallels to Earth”s rain, the Sun”s version consists of cool, dense blobs of plasma falling from its corona, the outermost layer of its atmosphere. Unlike Earth, where rain is composed of water droplets, solar rain is comprised of electrically charged gas that can reach temperatures of millions of degrees.
As this coronal rain descends toward the Sun”s surface, it unveils a hidden aspect of the star: its magnetic fields. The charged plasma follows these magnetic loops, creating dramatic arcs that can tower to heights equivalent to five Earths stacked on top of one another.
The exact process of how this solar rain forms remains elusive. It is frequently observed following intense solar flares, with downpours associated with rapid heating that creates coronal loops. Despite extensive research, modeling and predicting coronal rain has been challenging.
New insights suggest that the formation of coronal rain may depend on the uneven distribution of elements in the Sun”s corona. This finding contradicts previous assumptions that the elemental composition was static. According to Luke Benavitz, an astronomy graduate student at IfA and a co-author of the study, “Current models assume that the distribution of various elements in the corona is constant throughout space and time, which clearly isn”t the case.”
In their simulations, Benavitz and his team found that when variations in elemental distribution were taken into account, coronal rain began to condense in just 35 minutes. Earlier models, in contrast, suggested that hours or even days of heating were necessary for such rain to occur. “It”s exhilarating to see that when we allow elements like iron to change over time, the models align with actual solar observations,” Benavitz noted.
While other mechanisms may be at play, the researchers believe that these fluctuations in elemental abundance directly influence the cooling of plasma in the Sun”s atmosphere, leading to coronal rain. They concluded, “This discovery is significant as it enhances our understanding of the Sun”s operations.” Jeffrey Reep, another IfA astronomer and study co-author, emphasized the broader implications, stating that this research may prompt a reevaluation of existing theories regarding coronal heating.
The findings of this study have been published in The Astrophysical Journal.
