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Geomagnetic storms are influenced by Earth's atmosphere

A recent study highlights the crucial role played by Earth’s upper atmosphere in shaping large geomagnetic storms. The study underscores the profound influence these storms can have on satellite communications, with potential disruptions to power grids, radio signals, and GPS.

The international collaborative study was led by Nagoya University in Japan and the University of New Hampshire in the United States. The research offers intriguing new insights into the development of geomagnetic storms. 

Solar wind

Historically, the Sun has been perceived as the primary driver of geomagnetic storms. The Sun’s outer layer, composed of hot charged particles, emits a solar wind which interacts with Earth’s magnetosphere. 

These interactions with the magnetic field around our planet are known to influence space weather, affecting both Earth and our technological assets in space.

Central to the magnetosphere is the magnetotail, which extends in the direction of the solar wind. Within it lies the plasma sheet region, dense with charged particles or plasma. This region acts as a reservoir for particles that infiltrate the inner magnetosphere, triggering the currents behind geomagnetic storms.

Focus of the study 

The goal of the study was to determine the proportion of plasma in the magnetosphere originating from Earth, especially during geomagnetic storm events. 

The team focused on a significant geomagnetic storm that occurred between September 7-8, 2017, caused by a huge coronal mass ejection from the Sun. This storm disrupted the magnetosphere, leading to interference with crucial communication systems.

Ion transport dynamics 

To understand the ion transport dynamics during the storm, the team leveraged data from various space missions, like the NASA/Magnetospheric Multiscale (MMS) mission, the Japanese Arase mission, the ESA/Cluster mission, and the NASA/Wind mission. 

By distinguishing ions from the solar wind and the ionosphere, the experts identified significant changes in the near-earth plasma sheet’s composition and characteristics, which directly influence the progression of a geomagnetic storm. 

Study implications 

“The most important discovery was that at the beginning of the geomagnetic storm, the plasma changed from mostly solar to mostly ionospheric,” explained study lead author Lynn Kistler. “This shows that the geomagnetic storm drives more outflow from the Earth’s ionosphere, and that the ionospheric plasma can move quickly throughout the magnetosphere.”  

“Overall, our research contributes to understanding the development of geomagnetic storms by showing the importance of Earth’s ionospheric plasma.”

“We found compelling evidence that plasmas from not only the Sun but also the Earth drive a geomagnetic storm. In short, the properties of the plasma sheet (the density, the particle energy distribution, the composition) will affect geomagnetic storms, and these properties are different for different sources.” 

The study is published in the journal Nature Communications.

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