Using satellite data, scientists from the Swedish Institute of Space Physics and Umeå University have discovered that the lunar space environment is far more active than previously believed, as the moon’s surface reflects solar winds—or the continuous flow of plasma from the sun.

The discovery comes in a dissertation by Charles Lue, a member of the Faculty of Science and Technology in the Swedish university’s physics department. Lue’s research focuses on a pair of different interactions: those involving solar wind protons and lunar crustal magnetic anomalies, and those taking place between those same protons and the lunar regolith.

In his dissertation, Lue explains than he and his colleagues used particle sensors carried onboard the Chandrayaan-1 lunar orbiter to study solar wind protons reflecting from the moon, including those that capture an electron from the lunar regolith and are reflected as energetic neutral atoms of hydrogen. They also used computer models and a hybrid plasma solver in their work.

They discovered that the reflection of solar wind protons from magnetic anomalies is a common phenomenon on the moon, and that the phenomenon has an impact on other features, such as the lunar water levels. These interactions had long gone undetected, Lue said, due to the thin nature of the lunar atmosphere and the moon’s lack of a global magnetic field.

Both the lunar dayside and nightside are affected

Because of the thin atmosphere and absence of a global magnetic field, scientists long assumed that the moon passively absorbed solar wind, and that the plasma flow had little to no affect on its surroundings. In his new study, however, Lue found that the moon’s surface and the localized magnetic fields actually reflects some of those protons after all.

Both the lunar dayside and nightside are affected by this phenomenon, the researchers explained. Reflected solar wind particles move in spiraling tracks that carry them from the dayside—where it first strikes the moon’s surface—to the nightside. In regions with strong local magnetism, the flow is restricted on the surface at the same time when nearby regions experience increased flow.

These effects “can even be seen in the form of visible light – like bright swirls imprinted on the surface of the moon,” Lue said. “The observations help us map and understand the variations in the lunar space environment. They also give us clues about the physical processes involved and the long-term effects they have on the lunar surface.”

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Feature Image: Joel Tonyan/Flickr

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