Despite it being our closest stellar neighbor, the sun still harbors its mysteries. This plasma fireball is home to a variety of streamers, plumes, and loops. Its outer atmosphere—the corona—can reach temperatures exceeding 1,000,000 C.
At NASA’s Goddard Space Flight Center, scientists use a combination of real time observations and computer simulations to study the sun. Underlying the sun’s activity is a magnetic field, which is responsible for such phenomena as auroras on Earth, and the interplanetary magnetic field and radiation spacefaring missions must traverse. The laws of electromagnetism hold dominion over the sun’s actions, but pinpointing where the invisible magnetic field originates has proven difficult.
“We’re not sure exactly where in the sun the magnetic field is created,” said NASA space scientist Dean Pesnell. “It could be close to the solar surface or deep inside the sun—or over a wide range of depths.”
The plasma comprising the sun is a gas-like state of matter, which has had its electrons and ions separated. The resulting movements from the super-charged particles creates the magnetic fields, which in turn further affect how the particles move.
“Magnetic fields are a little like rubber bands,” according to NASA. “They consist of continuous loops of lines of force that have both tension and pressure. Like rubber bands, magnetic fields can be strengthened by stretching them, twisting them, and folding them back on themselves.”
The system for magnetic field creation is known as solar dynamo. Extreme ultraviolet lithography allows scientists to view the sun’s magnetic fields when they manifest above the sun’s surface as loops in the corona. An instrument called a magnetograph can be used to measure the magnetic loops’ footpoints, where the magnetic loops meets the sun’s surface. The instrument can help scientists measure the strength and direction of the magnetic fields.
Those real time observations are combined with computer simulations, which mimic solar material movement and magnetism. For instance, the Potential Field Source Surface model helps scientists visualize how the sun’s magnetic fields flux around the fiery orb.
For now, what scientists do know is that the sun’s magnetic system goes through an 11-year cycle. Each solar eruption results in a die down of activity. This continues until the sun reaches a point known as the solar minimum. From there, the activity ramps up into a solar maximum, which occur approximately 11 years after the last solar maximum.
Going forward, scientists will attempt to figure out just how the sun’s magnetic field is generated, and what secrets its interior structure holds.