Unraveling the Mysteries of the Sun: NASA’s Parker Solar Probe
The sun, our closest star, is the most extensively studied celestial object in the universe. Its light illuminates our days, and for ages, researchers have meticulously observed the dark spots adorning its luminous surface. In recent years, telescopes on Earth and in space have analyzed sunbeams across the electromagnetic spectrum, while experiments have probed the sun’s atmosphere and captured samples of the solar wind.
The Coronal Heating Problem
One of the most perplexing questions in solar physics has been the extreme temperature of the sun’s corona, which reaches millions of degrees Celsius, far surpassing the surface temperature of around 5,500°C. This phenomenon, known as the coronal heating problem, has puzzled scientists for decades.
The Role of Magnetic Fields
At the sun’s surface, magnetic fields concentrate at the edges of swirling convective cells called supergranules. These magnetic fields give rise to the stunning coronal loops visible during solar eclipses. In some regions, these loops are ruptured, releasing charged particles that form the supersonic solar wind and shape the heliosphere, a vast bubble encompassing the solar system.
Parker Solar Probe: A Mission to Touch the Sun
To unravel the mysteries of coronal heating, NASA launched the Parker Solar Probe in 2018, named after astrophysicist Eugene Parker, who predicted the existence of the solar wind in the 1950s. The spacecraft utilized Venus flybys to gradually approach the sun, and on April 28, 2021, it entered the corona for the first time, becoming the closest spacecraft to our star and the fastest human-made object ever launched.
Groundbreaking Observations and Discoveries
The Parker Solar Probe’s near-sun observations have revolutionized our understanding of coronal heating. By decoding magnetic signatures in the solar wind, the spacecraft revealed that the plasma flows outward in streamlets that often match the sizes of the convective supergranules on the sun’s surface. These streamlets contain S-shaped structures called “switchbacks,” formed by brief reversals in the local magnetic field. Switchbacks are believed to originate from the collision and reconnection of closed and open magnetic loops, a process known as interchange reconnection. These reconnection events release energy and plasma, heating the corona and accelerating solar wind particles.
The Future of Solar Exploration
While some scientists are not entirely convinced that the coronal heating problem is fully resolved, the field is converging on the idea that small-scale magnetic fields play a crucial role. The concentration of magnetic fields at the edges of convective granules triggers a series of events that ultimately lead to the supersonic solar wind and the extreme temperatures observed in the corona. Later this year, the Parker Solar Probe will make even closer approaches to the sun, breaking its own records and seeking answers to remaining solar mysteries.
Original story reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.
3 Comments
Brace yourselves, NASA’s about to turn up the heat like never before!
NASA’s playing with fire, and honestly, we’re here for it.
NASA’s really stepping into the sun’s spotlight this time, aren’t they?