NASA gets first clear images of Sun's volatile edge

Scientists have long known that the Sun and its atmosphere, or corona, are made of plasma — charged particles separating at extremely high temperatures and traveling along lines delineated by magnetic fields. To define the constant flow of energetic particles extending outward from the Sun and spreading throughout the Solar System astrophysicists created the term "solar wind."

NASA scientists have studied the origin of these positively and negatively charged particles pouring from the Sun's corona since the discovery of solar wind, observing that solar storms are dangerous and have damaged satellites and power transmission lines.

New research recently published in The Astrophysical Journal has for the first time described how plasma undergoes a transition as it moves beyond the surface of the Sun.

Near the Sun, solar wind is structured in distinct rays, but when solar material reaches about 20 million miles out, its form becomes less clear, and its movement more turbulent.

"Eventually, the material starts to act more like a gas, and less like magnetically structured plasma," said Craig DeForest, lead author of the study and a solar physicist at the Southwest Research Institute in Colorado.

The diffusion happen as our star's magnetic field begins to weaken relative to distance, losing control of the flow, forming the boundary that defines the edge of our Sun.