Solar wind is the main source of atmospheric sodium on Mercury

(ORDO NEWS) — No object in the solar system is more powerfully affected by the solar wind than Mercury. The planet’s magnetic field deflects the solar stream of electrically charged particles at a distance of only 1,000 kilometers from the surface of Mercury, at a point called the magnetopause.

The lines of the Sun’s magnetic field are carried by the solar wind and bend when they collide with the lines of Mercury. Under favorable conditions, these curved lines break and meet the lines of Mercury in a phenomenon called magnetic reconnection.

During reconnection, solar wind particles can enter Mercury’s magnetic field. Such particle transfers are called flux transfer events (FTEs), and a burst of FTEs in rapid succession is known as an FTE shower (FTE shower).

Scientists are investigating the impact of these showers on the planet’s surface using data collected by NASA’s MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) spacecraft, which orbited Mercury between 2011 and 2015.

As the spacecraft passed through Mercury’s magnetopause and approached the surface, the FIPS (Fast Imaging Plasma Spectrometer) onboard ion mass spectrometer recorded the local content of sodium group ions, including sodium, magnesium, aluminum and silicon ions.

Simultaneously, the onboard magnetometer measured the local magnetic environment. During the MESSENGER orbital mission, this scenario was repeated 3748 times, and half of them included the observation of an FTE shower.

The researchers conducted a statistical analysis of the abundance of sodium group ions in Mercury’s atmosphere.

They found that during approaches coinciding with an FTE shower, the abundance of sodium group ions in the atmosphere is about 50% higher than during periods without an FTE shower.

After examining several potential mechanisms for such an increase, the scientists concluded that the most likely cause is the dispersion of the solar wind.

According to the authors, these MESSENGER observations are an important indicator of the dynamics of Mercury’s thin atmosphere. In addition, more information is likely to be received in early 2026, when the joint European-Japanese mission BepiColombo arrives at Mercury.

The mission consists of two spacecraft, one aimed at Mercury and the other aimed at its magnetosphere. They should provide unprecedented details about solar wind sputtering caused by FTE.


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