How Solar Wind Flows From the Sun Like Water From a Shower Head

A new report reveals that the sun generates a solar wind by spewing out high-speed particles like water from a shower head. The Parker Space Probe, a NASA spacecraft launched in 2018, collects data of the corona, the sun’s outer atmosphere, to provide insight into this phenomenon. One of the key mysteries in solar research has been the fact that the corona, which has temperatures of millions of degrees, is much hotter than the surface of the relatively cool 10,000 degrees Fahrenheit sun. The Parker probe was named after Eugene N. Parker, an astrophysicist from the University of Chicago, who predicted the existence of the solar wind in 1958.

The sun has an atmosphere consisting of tenuous gases that is pushed up by fusion reactions within it while being dragged downward by gravity. The forces are balanced so that the sun neither collapses nor blows apart. However, the forces do not cancel everywhere, resulting in a ‘leaky balloon’ effect. Stuart Bale, a physicist at the University of California, Berkeley, who heads an instrument on the Parker Solar Probe that analyses electric and magnetic fields in the solar wind, along with his colleagues found that solar wind streams match patterns of hot gases rising and cooler gases falling within the sun. Charged particle convection generates magnetic fields, which snap and reconnect, releasing energy that contributes to the heating of the corona. This reconnection appears to accelerate the solar wind particles.

Observations of the sun revealed that the solar wind comes out of coronal holes, which are regions where the magnetic field continues far outward into space instead of wrapping around and coming back down in another area of the sun. The Parker spacecraft’s instruments showed that the solar wind was not uniform over these coronal holes, but instead the particles emerged in microstreams, like jets from a shower head. The microstreams’ periodic pattern matched that of the supergranulation, and this suggests that magnetic reconnection near the sun’s surface plays a vital role in the acceleration of the particles. The report concludes that this is a substantial step towards solving the puzzle of why the solar corona is millions of degrees hotter than the relatively colder surface of the sun.