Reconnection everywhere!

Published: Wednesday, 09 May 2018


Magnetic fields cross each other and clash all across the Sun in a process called reconnection, which happens to be behind most of the Sun's activity. Dr. Ada Ortiz (ITA, University of Oslo) explains this phenomenon in the first post of #TheScienceOfEST series. 

Huge X3.4-class flare in active region 10930 observed by Hinode on 2006 December 13. Credit: NASA Goddard Space Flight Center.

 

Who said that magnetic field lines never cross each other? The Sun is the perfect scenario to observe magnetic field lines crossing each other in a physical process called reconnection. During this process, magnetic field lines in the solar atmosphere can meet at different directions and angles. Once they clash, their magnetic energy is converted into enormous heating and kinetic energy of the surrounding plasma, which is then ejected in different directions at huge velocities. Big amounts of energy are released during reconnection, producing “fireworks” and the amazing activity we can observe on the Sun. After reconnection, the magnetic field lines reconfigure into a more relaxed energy state.

Reconnection can happen anywhere in the solar atmosphere, from the lowest layers (the photosphere) to the highest layers (transition region and corona) and can produce very energetic flares or coronal mass ejections, where tons of mass are ejected into the interplanetary space. Reconnection usually happens when new magnetic flux emerges into the Sun’s surface. The new magnetic loops rise through the solar atmosphere and interact (reconnect) with the pre-existing loops or with themselves.

The movie accompanying this post shows two adjacent sunspots observed by the Japanese satellite Hinode in 2006. The lower sunspot seems to rotate counter clockwise with respect to the upper sunspot. A lot of shear occurs in the interface between the two sunspots, electric currents are created and magnetic tension is accumulated as the lower sunspot twists. Eventually that magnetic energy is released in the form of a huge flare that ejects plasma and energy in all directions.

The European Solar Telescope (EST), a new 4 meter class solar telescope to be built in the Canary Islands (Spain), will help solar researchers to discern the ultimate details of reconnection at the finest spatial scales thanks to its superb spatial resolution. EST will observe the lower layers of the solar atmosphere, namely the photosphere and the chromosphere, simultaneously to study the magnetic coupling between these two systems.

 

 

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