Solar Spicules Launched by Magnetic Reconnection on Sun’s Surface

Vivid orange streamers of super-hot, electrically charged gas (plasma) arc from the surface of the Sun reveal the structure of the solar magnetic field rising vertically from a sunspot. Credit: Hinode, JAXA/NASA

New observations of solar spicules, ubiquitous jet-like plasma features that punctuate the Sun’s atmosphere, suggest they are generated by the energy released as the two disparate magnetic fields snap back into alignment near the solar surface. Shortly after, the spicules channel hot solar plasma into the overlying corona, according to the study.

At any given moment, about a million geyser-like spicules are erupting from the Sun’s surface, launching columns of plasma into the Sun’s upper atmosphere, known as the corona. Although this highly dynamic solar phenomenon has been observed from Earth for more than a century, studying it is difficult as each spicule — from formation to collapse — lasts only a few minutes.

It has been speculated that spicules may be involved with the transfer of energy and solar plasma from the Sun’s surface to feed the much hotter corona and the solar wind. However, the origin of spicules and their role in heating the solar corona remain poorly understood, and the multiple theoretical explanations that have been proposed to explain their origins are debated.

From the Goode Solar Telescope at the Big Bear Solar Observatory in California, Tanmoy Samanta and colleagues observed emerging spicules and the nearby magnetic fields at high temporal resolution. The authors discovered that many spicules occurred within a few minutes of the appearance of a patch of reverse-polarity magnetic field, within the surrounding dominant-polarity field.

Samanta et al. suggest that energy released as the two disparate magnetic fields snap back into alignments (also known as magnetic reconnection) triggered enhanced spicular activity. Simultaneous observations of the overlying corona demonstrated local heating of the Sun’s upper atmosphere.

Reference: “Generation of solar spicules and subsequent atmospheric heating” by Tanmoy Samanta, Hui Tian, Vasyl Yurchyshyn, Hardi Peter, Wenda Cao, Alphonse Sterling, Robertus Erdélyi, Kwangsu Ahn, Song Feng, Dominik Utz, Dipankar Banerjee and Yajie Chen, 15 November 2019, Science.
DOI: 10.1126/science.aaw2796