A void left within the wake of a very highly effective gust of photo voltaic wind precipitated the environment of Mars to dramatically balloon outwards.
Because the MAVEN spacecraft in orbit round Mars recorded a sudden, sharp drop in photo voltaic particles when the wind handed on 26 December 2022, it concurrently recorded a weird and startling change within the Martian environment. The planet’s magnetosphere and ionosphere expanded hundreds of kilometers, greater than tripling in dimension.
The final time we noticed this phenomenon was in 1999, when a sudden drop within the photo voltaic wind precipitated Earth’s magnetosphere to swell outwards, increasing its volume 100-fold.
It is a uncommon glimpse how Mars behaves when its circumstances within the Photo voltaic System all of a sudden change, and will give us some insights into how Photo voltaic System-like planets work together with their environments round totally different sorts of stars.
It is also the type of measurement that may solely be made in situ – demonstrating the worth of placing spacecraft in orbit round totally different worlds in our Photo voltaic System, to see how they work together with every little thing else.
“When we first saw the data, and how dramatic the drop in the solar wind was, it was almost unbelievable,” says astronomer Jasper Halekas of the College of Iowa and the lead creator on a brand new examine on the occasion.
“We formed a working group to study the event, and we have found this time period to be rich with incredible findings.”
The photo voltaic wind is kind of fixed within the Photo voltaic System, and the entire planets are embedded in it. It is a stream of particles that blow out from the Solar, in all instructions, on a regular basis, creating ambient strain all through the Photo voltaic System, weakening with distance and ultimately subsiding at a boundary known as the heliopause.
However the energy of that stream can fluctuate with photo voltaic exercise. As an example, areas of weakened solar magnetic fields on the floor of the Solar can launch a extra highly effective photo voltaic wind, bombarding the system with stronger, extra quite a few photo voltaic particles.
The wind that gusted by Mars on 26 December 2022 was totally different once more. It consisted of two photo voltaic winds, a slower one which was swept up and engulfed by a quicker wind coming in from behind earlier than persevering with outward as one tremendous wind.
MAVEN recorded the upper density of particles from this double photo voltaic wind. As soon as the wind handed by the orbiting observatory detected a big drop in particle density – a uncommon void of extraordinarily weak and low density photo voltaic wind, and a drop in photo voltaic wind strain, too. The density dropped by an element of 100. The strain dropped by an element of 10.
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And, as the pressure around it dropped, the Martian atmosphere responded.
The solar wind typically pushes against a planet’s magnetosphere, which on planets like Earth is largely generated by the churning of its molten insides. Now, Mars doesn’t have a global magnetosphere of its own; but it has what is known as an induced magnetic field, created by magnetic fields embedded in the solar wind becoming tangled in Mars’ ionosphere.
This ionosphere and the induced magnetic field therein vastly expanded outwards, like Mars’ atmosphere was taking off a too-tight corset. The induced magnetic field became unmagnetized, and the layer between it and the solar wind – the bow shock – grew much calmer than usual.
This, the researchers say, could yield valuable insights into how atmospheric loss occurs on Mars and planets like it elsewhere in the galaxy. It could be an important piece of the puzzle when identifying what makes a planet habitable.
“We’re actually attending to see how Mars responds when the photo voltaic wind is successfully eliminated,” Halekas says. “It makes for an excellent outlier examine on what Mars can be like if it had been orbiting a much less ‘windy’ star.”
The staff is presenting its findings on the American Geophysical Union Fall Meeting 2023.
