Explosive Events in the Magnetosphere: Investigating Unusual Substorm in Earth's Magnetotail

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The illustration shows magnetic field lines around the Earth reconnecting in the magnetotail, usually one of the first signs of a substorm. An internally funded Southwest Research Institute project is investigating the nature of substorms, specifically a 2017 event when reconnection appeared to occur without inciting a substorm. Credit: NASA/Goddard Space Flight Center-Conceptual Image Lab

Using NASA's MMS mission data, SwRI explores unusual substorm events in Earth's magnetotail to better understand magnetic reconnection and its effects on the global magnetosphere.

Southwest Research Institute (SwRI) is investigating an unusual event in the Earth's magnetotail, the elongated extension of the planet's magnetosphere trailing away from the Sun. SwRI scientists are examining the nature of substorms, fleeting disturbances in the magnetotail that release energy and often cause aurorae, using data from NASA's Magnetospheric Multiscale (MMS) mission.

Since their launch in 2015, the MMS spacecraft have been surveying the magnetopause, the boundary between the magnetosphere and surrounding plasma, for signs of magnetic reconnection, which occurs when magnetic field lines converge, break apart, and reconnect, explosively converting magnetic energy into heat and kinetic energy. In 2017, MMS observed signs of magnetic reconnection in the magnetotail but not the normal signs of a substorm that accompany reconnection, such as strong electrical currents and perturbations in the magnetic field.

Illustration of the four MMS spacecraft in orbit in Earth's magnetic field. Credit: NASA

Understanding Substorms and Reconnection

"We want to see how the local physics observed by MMS affects the entire global magnetosphere," said SwRI's Dr. Andy Marshall, a postdoctoral researcher. "By comparing that event to more typical substorms, we are striving to improve our understanding of what causes a substorm and the relationship between substorms and reconnection."

During the one-year project, SwRI will compare in situ MMS measurements of reconnection affecting local fields and particles to global magnetosphere reconstructions created by the Community Coordinated Modeling Center at NASA's Goddard Space Flight Center using the University of Michigan's Space Weather Modeling Framework.

Implications for Magnetosphere Research

"It's possible that significant differences exist between the global magnetotail convection patterns for substorms and non-substorm tail reconnection," Marshall said. "We have not looked at the movement of the magnetic field lines on a global scale, so it could be that this unusual substorm was a very localized occurrence that MMS happened to observe. If not, it could reshape our understanding of the relationship between tail-side reconnection and substorms."

MMS is the fourth NASA Solar Terrestrial Probes Program mission. Goddard Space Flight Center built, integrated, and tested the four MMS spacecraft and is responsible for overall mission management and mission operations. The principal investigator for the MMS instrument suite science team is based at SwRI in San Antonio. Science operations planning and instrument commanding are performed at the MMS Science Operations Center at the University of Colorado's Laboratory for Atmospheric and Space Physics in Boulder.