A newly launched NASA Earth science CubeSat mission, Electrojet Zeeman Imaging Explorer (EZIE), aims to investigate the electrojets that are instrumental in forming the northern lights in more detail.
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High-intensity currents known as electrojets travel in the ionosphere, close to the North and South Poles, 100 kilometers above Earth's upper atmosphere1. Every second, they force almost one million amperes of electricity around the poles.
Launched on March 14, 2025, on SpaceX's Transporter-13 mission from Vandenberg Space Force Base in California, EZIE will map and produce images of the electrojets within the aurora.
The three 6U CubeSats that make up EZIE were developed by Johns Hopkins University's Applied Physics Laboratory (APL). The three satellites' main goal is to investigate the production and behavior of auroral electrojets2, in an effort to evaluate how well the scientific models that describe the electrojets match reality and get a better understanding of the physics of the Earth's magnetosphere. It is anticipated that the data gathered by EZIE would allow the scientific community to propose more precise models pertaining to auroras and geomagnetic storms.
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What Are Auroral Electrojets?
The Sun’s energy interacts with Earth’s magnetic field and upper atmosphere to create powerful electrojets.
As the solar wind (a constant stream of charged particles from the Sun) reaches Earth, it flows through our planet’s magnetic field and enters the ionosphere near the Poles. These particles generate intense electric currents as they move through this upper atmospheric layer. In the process, they also excite atmospheric gases, lighting up the sky with the brilliant displays known as the Northern and Southern Lights. However, they are also a threat to space assets like satellites and critical terrestrial infrastructure1.
Earth and space are linked by a vast electric circuit, one that includes electrojets as a key component. These powerful currents can cause sudden disturbances in Earth’s magnetic field, leading to abrupt shifts that are often detected during geomagnetic storms.
Measuring Magnetism from Space: The Zeeman Effect
The physical phenomenon called the Zeeman effect is used to study the properties of electrojets.
Atoms and molecules in their natural unperturbed state are occupied by electrons in the ground state energy level structure. When the atom is exposed to a magnetic field, particular energy levels can split into several sub-levels. This splitting of energy levels due to a magnetic field is called the Zeeman effect3.
When excited electrons relax between the Zeeman levels they emit photons. By measuring these emitted photons, scientists can gather valuable insights into both the molecular structure and the magnetic fields that caused the energy level splitting.
For example, oxygen molecules subjected to a magnetic field emit microwave radiation at 118 GHz, a result of Zeeman splitting2.
Inside the EZIE Mission
EZIE contains detection equipment capable of measuring molecular radiation generated by the Zeeman effect. The three CubeSats are outfitted with the Microwave Electrojet Magnetogram (MEM) sensor to carry out their job. Four integrated 118 GHz heterodyne spectropolarimeters, which are the main parts of the MEM payload, will be utilized to detect the 118 GHz microwave radiation released by oxygen molecules during Zeeman splitting2.
The strength and of the magnetic field influencing the oxygen molecules can be determined by examining the strength of the Zeeman splitting. The current causing the magnetic field is then back calculated using the magnetic field data.
EZIE In Orbit
Each of the three suitcase-sized CubeSats is moving two to ten minutes apart. These CubeSats are positioned about 550 kilometers above the ground and follow one another in a polar orbit.
What makes this spacecraft concept unique is that the satellites glide rather than rely on traditional propulsion. By adjusting the orientation of their solar panels, similar to how a glider controls its wings, the satellites can maneuver and maintain proper spacing relative to one another.
The evolution of the electrojets over time requires at least two spacecraft. Finding out how much the currents' size, shape, and flow patterns have changed in the two to ten minutes between satellites gives valuable insight into the current's direction, intensity, and structural evolution.
Scientific and Technological Significance
The goal of the EZIE mission is to advance the understanding of the auroral electrojets' composition, development, and effects on space weather. This is a pioneering mission conducting such a thorough analysis of the aurora.
The region where electrojets occur is at an altitude that is too high for high-altitude balloons and too low for traditional satellites to operate effectively, which has historically made it challenging to research. EZIE's sensors are precisely focused on the phenomena of interest, and the device itself is positioned at the optimal distance. Prior to this, the technology required to conduct such an investigation was unavailable.
Future Outlook
One important component of space weather prediction that currently lacks data is auroral electrojets, which EZIE is now positioned to solve. Along with other NASA missions like the THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission investigating Earth's magnetosphere4 and HelioSwarm, a heliophysics mission designed to investigate solar wind plasma turbulence5, EZIE bridges another knowledge gap.
Scientists will be better able to lessen the effects of space weather with the capabilities provided by such NASA missions. Furthermore, a thorough grasp of origins and effects of electrojets will benefit future generations engaged in space travel.
References and Further Reading
- EZIE Blog. "EZIE is a mission to explore the Sun and the system that drives space weather near Earth." NASA. Available online at: https://science.nasa.gov/mission/ezie/
- Bouzoukis, Konstantinos-Panagiotis, Georgios Moraitis, Vassilis Kostopoulos, and Vaios Lappas. "An Overview of CubeSat Missions and Applications." Aerospace 12, no. 6 (2025): 550.
- Sivarajah, Ilamaran. "Studies of Sympathetic Cooling of Sodium Ions by Ultracold Neutral Sodium Atoms." Ph. D. Thesis (2012).
- THEMIS-ARTEMIS. "Time History of Events and Macroscale Interactions during Substorms (THEMIS) - Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS)." NASA. Available online at: https://science.nasa.gov/mission/themis-artemis/#:~:text=Launched%20in%202007%2C%20THEMIS%20studies,processes%20closer%20to%20the%20Moon
- HelioSwarm. "HelioSwarm will help improve our understanding of the dynamics of the Sun, the Sun-Earth connection, and the constantly changing space environment." NASA. Available online at: https://science.nasa.gov/mission/helioswarm/#:~:text=HelioSwarm%20consists%20of%20one%20hub,California%2C%20will%20provide%20project%20management.
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