How the Earth’s magnetic field changes the solar wind to a gentle breeze



Wrapping our planet and protecting us from the damaging solar wind is an invisible magnetic field. The solar wind is a stream of plasma or charged particles like protons and electrons released from the outer layers of the sun. Without a magnetic field, the solar wind could destroy the atmosphere of our planet and make it habitable.

But how exactly does the process work? For the first time, researchers explain how the Earth's magnetic field pushes aside the powerful solar wind without any damage. As the Earth moves around the sun, it creates an arc-shaped wave or a bow shock in front of itself, much like what happens in front of a moving speedboat. When the electrons in the solar wind meet the impact of the arc, their speed accelerates momentarily to such an extent that the electron current becomes unstable and decomposes. This interaction slows down electrons and converts energy into heat.

"If you stand on top of a mountain, you could be knocked down by a fast wind," explained lead author Li-Jen Chen of the University of Maryland. "Fortunately, when the solar wind crashes into Earth's magnetic field, the impact of the arc protects us by slowing down this wind and turning it into a nice warm breeze, now we have a better idea of ​​how this happens."

The finding is based on data collected by NASA's Magnetospheric Multiscale (MMS) mission. The MMS mission consists of four identical satellites that study the Earth's magnetic field by interacting with the solar wind and taking three-dimensional measurements every 30 milliseconds. The data helps researchers better understand the role of the magnetic field around the Earth.

"These extremely fast MMS measurements allowed us to finally see the process of electron heating in the thin shock layer," said co-author Thomas Moore of Goddard Space at NASA. Flight center "This is innovative because now we have the ability to identify the mechanism in operation, instead of simply observing its consequences."

During the mission, the researchers observed the solar wind electron before, during, and after the encounter with a shock arc and found that it took only 90 milliseconds for the arc shock to destabilize and decompose electrons.

"New observations of electron acceleration in arc collision rewrite the current understanding of electron warming.For example, researchers did not expect arc discharge to accelerate the electron stream of the solar wind at speeds that we observe, "Chen said." The study of electron warming is important not only to understand how the Earth protects the arc, but potentially for satellites, space travel and perhaps to explore other planets in the future. "

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