An international team of researchers has used data from NASA’s Solar Dynamic Observatory to discover a brand-new type of explosion in the solar corona, the atmosphere of the Sun. The dramatic event is called a forced magnetic reconnection and could help explain why the corona is hundreds of times hotter than the surface of the Sun.
As reported in The Astrophysical Journal, observations in May 2012 showed erupted material from the surface of the Sun, a so-called prominence, slamming into magnetic lines. The interactions caused a dramatic realignment of the tangled magnetic field lines, releasing energy very quickly and causing an explosion.
The realignment of field lines is a studied featured of the Sun and it is known as magnetic reconnection. But before this study, researchers had no evidence suggesting that it could be forced by a solar eruption.
“This was the first observation of an external driver of magnetic reconnection,” lead author Abhishek Srivastava, a solar scientist at the Indian Institute of Technology (BHU) said in a statement. “This could be very useful for understanding other systems. For example, Earth’s and planetary magnetospheres, other magnetized plasma sources, including experiments at laboratory scales where plasma is highly diffusive and very hard to control.”
The spontaneous magnetic reconnection requires very specific conditions, but the forced one appears to be less strict so they can happen more often, given that there is something to supply the material. In this case, a solar eruption to release the material in the first place, but the team suspects that other solar eruptions such as flares and coronal mass ejections could be equally effective in forcing magnetic reconnection.
“Our thought is that forced reconnection is everywhere,” Srivastava added. “But we have to continue to observe it, to quantify it, if we want to prove that.”
Forced magnetic reconnections heat up material to high temperatures more efficiently than the spontaneous counterpart. For this reason, the solar scientists suspect it might have something to do with the mystery of the corona temperature. The surface of the Sun has a temperature of around 5,499°C (9,930°F) but the corona is over 1 million °C (1.8 million °F).
NASA’s Parker Solar Probe and the upcoming European Solar Orbiter will provide even more data to answer the mystery of how the corona gets heated.