Plasma Precipitation in the Sun’s Atmosphere Falls in Unexpected Places

Findings of plasma precipitation in the solar atmosphere show that rain appears in unexpected places. The findings could mean that rain could come in the form of fine fog and heavy rain, new evidence shows. Finally, tracking the movement of this plasma could help solve the mystery of why the solar atmosphere, or corona, is so hot.

The Sun receives precipitation similar to the Earth, but with plasma instead of water. As hot plasma moves to the colder part of the corona, it condenses and falls back toward the surface of the Sun, much as hot air condenses into clouds that form water droplets that rain on the Earth.

“Physics is literally the same,” said solar physicist Emily Mason of American Catholic University in Washington, DC, who presented new observations of coronal precipitation at the three-year Earth-Sun Summit on May 22nd.

Scientists have seen coronal precipitation before, mostly in the form of rain in solar regions associated with flares. But it can happen anywhere in the corona where temperatures fluctuate from warmer to cooler, Mason said.

Theoretical studies by others, including his colleague Spiro Antiochos at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have shown that the high band, which can extend 6 solar radii above the Sun’s surface, can be hotter at the base than at its ends. so it should be raining heavily (SN Online: 8/17/17).

“My job is to find him,” Mason said. So he looked for bright plasma blobs that fell into high tape in video recorded in extreme ultraviolet light by NASA’s Solar Dynamics Observatory, but found nothing.

However, he found a shower in a shorter loop, called a zero point topology, that only extends up to about 0.1 solar radius above the surface. “This thing is pouring in like crazy,” he said. Corona rain falls in one of these smaller loops for 30 hours.

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This is surprising because the shorter loop is supposed to have a smaller bottom -up temperature difference than the high tape, making such deposition difficult. Moreover, Mason believes that shorter loops actually do not produce more rain than tape, but plasma droplets in such loops can be larger and more visible.

In high tape, due to smoother temperature changes, the droplets will eventually become smaller – perhaps as small as grains of sand. “It’s there, but you can’t see it,” he replied.

Mason later discovered dimmer rain in medium -sized pseudo streams, supporting this idea. Modern telescopes cannot see small droplets, but the Daniel K. Inouye Solar Telescope under construction in Hawaii may be able to see them.

One solar mystery that has long existed is that the corona is millions of degrees warmer than the surface of the Sun (SN Online: 8/20/17). Scientists believe that the additional heat may come from an unknown constant source – as if the corona were on a hot plate – or from many small short energy bursts (SN: 05/30/15, p. 7).

“The new rainfall results support the idea of using slabs because it will create the necessary temperature differences in short loops,” said NASA physicist Goddard Nicolin Viall, who was not involved in the findings.

“The fact that it rains limits the likelihood of coronal warming occurring,” Wiall said. “The fact that he found it is very important.”