The outer atmosphere of the sun is said to be way hotter than its surface, and scientists have collected some evidence—considered the strongest to date—that justify what makes it so. The evidence points to nanoflares.
Nanoflares, according to NASA, are continuous showering of impulsive heat bursts. Interestingly, all these heat bursts are undetectable individually. One thing’s for sure, however, it provides the strange extra heat to the outer atmosphere of the sun.
What the scientists have found even more shocking is how recent observations have come from merely six minutes of data gathering from an Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS), a mission that rolled out April 23 last year. The spectrographs collect data on the amount of material present in a given temperature by way of recording various light wavelengths.
Such instrument can properly work only in space, atop the atmosphere that surrounds the Earth, which is why EUNIS went up almost 200 miles above the ground onboard a rocket that flies for merely 15 minutes or so. It gathers new data image every 1.3 seconds, tracking the material’s properties over a broad scope of temperatures in the complicated solar atmosphere.
NASA says the photosphere, which is the visible surface of the sun, is around 6,000 Kelvins, but the corona reaches on regular basis temperatures that are as hot as 300 times.
For space scientist Jeff Brosius of the Catholic University and of the Goddard Space Flight Center of NASA, the finding is quite puzzling since things typically become cooler further away from the source of heat.
“When you're roasting a marshmallow you move it closer to the fire to cook it, not farther away,” says Brosius in a statement.
The method, by which magnetic energy running across the corona is transformed into the heat raising temperature, has been given several theories by the scientists. Yet very few observations have “high enough resolution over a large enough area” to differentiate these predictions.
Moreover, these scientists have assumed that a heap of nanoflares can possibly heat up the solar material in the atmosphere to as high as 10 million Kelvins. The solar material cools down very quickly, creating plenty of solar material at one to three million degrees seen often in the corona. The very hot material’s feeble presence should stay, however, according to them.
"This weak line observed over such a large fraction of an active region really gives us the strongest evidence yet for the presence of nanoflares,” Brosius says.
The scientists will further explore such ideas and theories by collecting more observations as instruments and tools for such research improve as well.
The complete results of the study are published in the August 2014 issue of The Astrophysical Journal.