![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2021\/01\/mm_fats_infographic_w_nasa_id-242x350.jpg\")
<\/p>\nIt\u2019s one of the greatest mysteries in solar physics. Dubbed the coronal heating problem, the issue arises from the fact that the solar corona, or Sun\u2019s atmosphere, is millions of degrees hotter than the layers directly below it.<\/p>\n
This goes against modeling that suggests the corona should be far cooler than the layers below it.<\/p>\n<\/p>\n
Numerous theories have been proposed to explain the problem, but a persistent issue in exploring this solar dynamic has been a lack of technological ability to directly observe the underlying processes that could account for the heat.<\/p>\n
The problem of seeing this region of the Sun is dwindling, not just because of new missions such as NASA\u2019s Parker Solar Probe and European Space Agency\u2019s\/NASA\u2019s Solar Orbiter. <\/p>\n
Additionally, advancements in computer technology now allow images and observations from other spacecraft, like NASA\u2019s Solar Dynamics Observatory, to be reprocessed to extract more detailed data.<\/p>\n
One of the theories put forward to explain the coronal heating problem came in 1972 from Dr. Eugene Parker, for whom the Parker Solar Probe is named. He proposed that nanoflares, tiny eruptions on the Sun\u2019s surface that are one-billionth the size of a normal solar flare, cause the corona to heat up to its observed temperatures. <\/p>\n
The issue with nanoflares is that even with advancements in technology, they are incredibly difficult to detect, and just because a bright flash is observed, it is not necessarily a nanoflare. <\/p>\n
<\/p>\n
Credit: NASA<\/p>\n
In order to be classified as a nanoflare, the event has to meet two specific criteria. First, it must be triggered by magnetic reconnection, a phenomenon previously reported on \u2014 as well as their connection to nanoflares \u2014 by NASASpaceflight in August 2020. <\/p>\n
Second, and crucially, it must heat the solar corona, which can lie upwards of thousands of kilometers above where the nanoflares occur.<\/p>\n
\u201cYou have to examine if the energy from a nanoflare can be dissipated in the corona,\u201d said Shah Bahauddin, Research Faculty at the Laboratory of Atmospheric and Space Physics at the University of Colorado, Boulder \u2014 lead author of a new study revealing the first look at what is widely accepted to be a nanoflare\u2019s full life-cycle.<\/p>\n
\u201cIf the energy goes somewhere else, that doesn\u2019t solve the coronal heating problem.\u201d<\/p>\n
The discovery stemmed from an observation by Bahauddin of tiny bright loops approximately 100 kilometers apart in the Transition Zone (the layer below the corona) as seen in observations from NASA\u2019s Interface Region Imaging Spectrograph (IRIS) spacecraft.<\/p>\n
A deeper investigation revealed the bright spots to be millions of degrees hotter than their surroundings and contained smaller amounts of lighter elements and a larger proportion of heavier elements which also showed as brighter and more energetic.<\/p>\n
The elemental discovery was the opposite of expectation; lighter elements should move more quickly than heavier elements. But Bahauddin observed the lighter elements were not moving while the heavy elements were traveling upwards towards the corona at speeds of 100 km\/s.<\/p>\n
For comparison, the International Space Station orbits the Earth at 7.6 km\/s.<\/p>\n
Bahauddin and his team ran simulations to determine what underlying mechanism unseen in the IRIS data could be responsible. The simulations showed that magnetic reconnection was the only known possible cause.<\/p>\n
During these brief, energy-packed magnetic reconnection events, heavier elements are able to keep moving in the electric field created as their momentum is greater than that of their lighter counterparts.<\/p>\n
The heavy elements gain more and more energy in the electric field as they are accelerated upward into the corona\u2026 where they can then transfer that energy in the form of heat.<\/p>\n
With that data in hand, the team realized they could be dealing with a nanoflare and sought subsequent observations of the same region at the same time from other missions.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2021\/01\/screen_shot_2020-12-21_at_10.00.30_am.png\")
<\/p>\n
A loop brightening. Each inset frame zooms in to the selected region in the frame to its left. The frame on the far right is the most zoomed in, showing the potential nanoflare.
(Credit: NASA\/SDO\/IRIS\/Shah Bahauddin)<\/p>\n
That led them to the Solar Dynamics Observatory (SDO), data from which was able to confirm that just 20 seconds after the nanoflare was observed, a sudden-heating of the corona by multi millions of degrees occurred directly above.<\/p>\n
\u201cSDO gave us this important information: Yes, this is indeed increasing the temperature, transferring energy to the corona,\u201d said Bahauddin.<\/p>\n
Based on findings presented in December 2020 in the journal Nature Astronomy<\/i>, researchers, and their peers, generally agree that this is a nanoflare as well as the first full life-cycle observation of such an event.<\/p>\n
The seeming direct connection between the observed nanoflare and the superheating event of the corona provides support for Dr. Parker\u2019s nanoflare theory to solve the coronal heating problem\u2026 but doesn\u2019t prove it.<\/p>\n
While Bahauddin\u2019s team has documented 10 further instances of bright loops and coronal super-heating events directly above them since that first observation, the team cautioned a great deal of work remains in determining if these:<\/p>\n
Meanwhile, solar physicists focusing on other dynamics of the corona have also used NASA\u2019s Solar Dynamics Observatory to more deeply explore the structures that create the ever-present flow of charged particles \u2014 called the solar wind \u2014 outward from the Sun to distances well beyond 100 astronomical units (AU).<\/p>\n