NASA’s MAVEN observes the disappearing solar wind

In December 2022, NASA’s MAVEN (Mars Ambiance and Risky EvolutioN) mission noticed the dramatic and surprising “disappearance” of a stream of charged particles consistently emanating off the sun, often known as the solar wind. This was brought on by a particular sort of solar occasion that was so highly effective, it created a void in its wake because it traveled via the solar system.

As a consequence of this occasion, MAVEN’s measurements at Mars confirmed that the variety of particles making up the solar wind dropped considerably. With out the stress of the solar wind, the Martian environment and magnetosphere expanded by hundreds of kilometers. MAVEN is the one asset at present at Mars in a position to concurrently observe each the sun’s exercise and the response of the Martian environment to those solar influences.

“Once we first noticed the information, and the way dramatic the drop within the solar wind was, it was virtually unbelievable,” mentioned Jasper Halekas, professor on the College of Iowa and the lead creator on a brand new examine on the occasion. “We shaped a working group to check the occasion, and now we have discovered this time interval to be wealthy with unimaginable findings.”

Mars, like all of the planets in our solar system, is consistently immersed within the solar wind. The solar wind exerts stress on the Martian magnetosphere and ionosphere, and drives a lot of the escape of the environment. The solar occasion in December 2022 was brought on by faster-moving solar wind that overtook slower transferring solar wind, which acted like a brush, sweeping and compressing the 2 areas collectively.

This interplay, known as a stream interplay area, left behind a uncommon void of extraordinarily low-density solar wind in its wake, which was noticed by MAVEN. This “disappearance” of the solar wind led to some unimaginable interactions inside Mars’ magnetosphere and ionosphere.

Because the density of the solar wind dropped by an element of 100, it induced the stress to lower and the magnetosphere and ionosphere of the planet have been in a position to develop by hundreds of kilometers—greater than tripled the standard measurement—and dramatically modified in character. The sun’s magnetic area that usually is embedded throughout the Martian ionosphere was pushed outwards, which remodeled the ionosphere from a magnetized to unmagnetized state.

On the similar time, the layer between the solar wind and the magnetosphere turned unusually electromagnetically quiet. MAVEN’s observations of this dramatic occasion and subsequent transformation and enlargement of the entire system is necessary to higher perceive the physics that drive atmospheric and water loss at Mars.

“We’re actually attending to see how Mars responds when the solar wind is successfully eliminated,” Halekas added. “It makes for an important outlier examine on what Mars can be like if it have been orbiting a much less ‘windy’ star.”

Disappearing solar wind occasions on this scale are extraordinarily uncommon and are produced at a time of accelerating solar activity, so this was the primary time the MAVEN mission had the chance to watch such a phenomenon. Whereas different spacecraft at Mars and Earth additionally noticed facets of this occasion, solely MAVEN was in a position to concurrently take measurements from each the sun and the Martian environment’s response to it.

“Observing extreme conditions is all the time scientifically invaluable,” mentioned Shannon Curry, principal investigator for MAVEN on the College of California, Berkeley. “MAVEN was designed to watch a majority of these interactions between the sun and the Martian environment, and the spacecraft supplied distinctive information throughout this actually anomalous solar occasion.”

Because the sun strikes towards solar most, the height of its 11-year exercise cycle, the MAVEN mission might have a good greater impression on our understanding of maximum solar occasions.

“This actually exhibits the cross-divisional position that MAVEN performs at Mars,” mentioned Gina DiBraccio, MAVEN deputy principal investigator and deputy director of the Heliophysics Science Division at NASA’s Goddard House Flight Middle in Greenbelt, Maryland. “MAVEN shouldn’t be solely observing the dynamics of the Martian environment, it is usually monitoring solar inputs to boost our understanding of the sun.”

The examine is being introduced on the American Geophysical Union Fall Meeting in San Francisco.