substorm-wedge current system

atmospheric science

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July 14, 2026

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The substorm-wedge current system is a phenomenon observed during magnetospheric substorms, which are distinct events from magnetic storms. This system involves the diversion of tail current into the ionosphere, creating westward and eastward electrojets. These currents enhance auroral activity and cause sudden changes in Earth's magnetic field, inducing strong electric fields. These fields energize particles, leading to auroras and increased atmospheric conductivity. On the ground, these effects can disrupt electrical transmission lines and pipelines.1

Magnetospheric substorms are characterized by an "expansion phase" where magnetic field lines reconnect, releasing energy and causing auroral displays. The "substorm-wedge current system" is crucial in this process, as it helps localize the reconnection region and divert current to the ionosphere. This system is a key component in understanding the dynamics of Earth's magnetosphere during these events.123

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geomagnetic field
Expansion phase
The substorm-wedge current system causes sudden changes in the magnetic field at Earth’s surface during substorms. These changes induce very strong localized electric fields. These transient electric fields energize particles to high energy and propel them earthward. Loss of these particles to the atmosphere causes the…
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The substorm-wedge current system causes sudden changes in the magnetic field at Earth’s surface during substorms. These changes induce very strong localized electric fields. These transient electric fields energize particles to high energy and propel them earthward. Loss of these particles to the atmosphere causes the…
Read More

THEMIS
…disturbances in Earth’s magnetosphere, called substorms, that cause spectacular auroral displays. The mission also involved an array of ground stations. THEMIS found that substorms occur about 120,000 km (75,000 miles) from the surface of Earth when magnetic field lines break and release energy after they reconnect.
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…disturbances in Earth’s magnetosphere, called substorms, that cause spectacular auroral displays. The mission also involved an array of ground stations. THEMIS found that substorms occur about 120,000 km (75,000 miles) from the surface of Earth when magnetic field lines break and release energy after they reconnect.
Read More