NASA’s Parker Photo voltaic Probe is on its approach to one other shut encounter with the solar, the place investigators hope the spacecraft will resolve a long-standing photo voltaic thriller: Why is the solar’s outer ambiance hundreds of thousands of levels scorching (Fahrenheit or Celsius), whereas the floor is just about 6,000 levels Fahrenheit (three,300 levels Celsius)?
One idea says that this spectacular heating comes from small magnetic waves shifting forwards and backwards between the solar’s floor and higher ambiance. New analysis based mostly on a earlier NASA mission means that the important thing lies in a area of the solar referred to as the zone of preferential heating.
“Regardless of the physics is behind this superheating, it is a puzzle that has been staring us within the eye for 500 years,” Justin Kasper, lead creator on the brand new analysis, a College of Michigan professor of local weather and house sciences, and principal investigator for the Photo voltaic Wind Electrons Alphas and Protons (SWEAP) instrument onboard the probe, stated in a press release. “In simply two extra years, Parker Photo voltaic Probe will lastly reveal the reply.”
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From what scientists know thus far about this superheating, it is a unusual course of. Some particular person chemical components heat as much as totally different temperatures, and a few heavy ions (or charged particles) get even hotter than the solar’s core.
All this heating makes the photo voltaic ambiance, often known as the corona, balloon above the solar’s floor. That ambiance is seen throughout complete photo voltaic eclipses, when the moon passes in entrance of the solar. For a couple of moments throughout these occasions, the corona shines brightly within the sky.
Additionally embedded within the zone of superheating is a phenomenon generally known as Alfvén waves, that are small magnetic waves in an electrically conducting fluid (comparable to plasma) inside a magnetic area. On the fringe of this superheating zone, the photo voltaic wind (a continuing stream of charged particles emanating from the solar) strikes quick sufficient to flee the waves. However beneath that, the photo voltaic wind particles pingpong and speed up resulting from waves pummeling the particles from each route.
What scientists actually wish to know is simply how far above the solar’s floor this heating extends. Whereas Parker is not shut sufficient to the solar to have reached that time but, the researchers seemed for it utilizing many years of photo voltaic wind observations from NASA’s Wind spacecraft, which launched in 1994 and continues to be working. Particularly, the scientists targeted on observations of helium, a standard aspect within the solar.
The scientists tracked the temperature of helium at totally different altitudes above the solar. The speed of temperature rise in that aspect diminishes as ions within the photo voltaic wind collide with one another. Scientists discovered that the superheating zone ends someplace between 10 and 50 photo voltaic radii above the floor of the solar.
Additional evaluation, nonetheless, recommended that the periphery could be related with the Alfvén level, the gap above the floor at which particles within the photo voltaic wind escape the solar. Earlier analysis has proven that the Alfvén level can rise and fall because the solar will get roughly lively.
So, Kasper and his co-author examined Wind’s knowledge yr by yr. What they discovered stunned them: The outer boundary for the superheating zone and the Alfvén level “moved in lockstep in a completely predictable trend, regardless of being fully impartial calculations,” Kasper stated.
Each these strains will proceed to maneuver as Parker Photo voltaic Probe sneaks nearer and nearer to the solar, so the researchers additionally calculated when the spacecraft would intersect with these boundaries. That second, when the probe can ship again knowledge from these essential areas, ought to occur in 2021 — giving scientists an entire new take a look at our solar.
A paper based mostly on the analysis was printed Tuesday (June four) in The Astrophysical Journal Letters.
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