Have you ever seen the aurora?
Powerful streams of charged particles stream from the Sun and hit Earth's upper atmosphere, exciting particles and generating the beautiful colours we see as the Northern and Southern Lights.
For the first time, a trio of satellites called EZIE is studying how these ‘electrojets’ work.
More aurora science
NASA's EZIE (Electrojet Zeeman Imaging Explorer) will image and map electrical currents inside the aurora, called electrojets.
Electrojets are high-intensity currents that flow 100km (60 miles) above Earth’s upper atmosphere, in the ionosphere, near the North and South Poles.
They push about a million amps of electric current around the poles every second.
EZIE launched from Vandenberg Space Force Base in California on 14 March 2025.
Nelli Mosavi-Hoyer is the programme manager of the EZIE mission at Johns Hopkins University Applied Physics Lab.
We spoke to her to find out more about the mission and what it might discover.
What creates electrojets in the aurora?
They’re formed by interactions between the Sun’s energy, and Earth’s magnetic field and upper atmosphere.
The Sun constantly sends out charged particles in a stream called the solar wind.
When these reach our planet, our magnetic field guides them towards the Poles where they enter the ionosphere.
As these particles move through the ionosphere, they create powerful electric currents. Electrojets and aurorae are closely connected.
When these solar wind particles hit Earth’s atmosphere, they also create the beautiful Northern and Southern Lights by exciting gases in the sky.
We are sending the EZIE satellites at the peak of the solar cycle, the approximately 11-year pattern of rising and falling activity on the Sun.
Electrojets are more active during the peak of the solar cycle, which means more opportunities to study their behaviour.
How will EZIE image those currents?
We’re using a very new technique, called the Zeeman effect, to study the magnetic field.
There’s a very well-known phenomenon where oxygen molecules create microwave emissions at 118GHz.
If there is a magnetic field close to these oxygen molecules, it will split that emission into multiple wavelengths.
By studying the amount of splitting, we can calculate the strength and direction of the magnetic field that is affecting the oxygen molecules.
If you have information about the magnetic field, you can work backwards and find the current responsible for it.
What does the EZIE mission look like?
We have three CubeSats the size of a suitcase, moving 2–10 minutes apart from each other.
These are following each other in polar orbit at an altitude of approximately 550km (350 miles).
The unique thing about this spacecraft is we don’t have propulsion. We glide them.
You can think of the solar panels as a glider’s wing; we command the solar panels to move and that helps us control the separation between the spacecraft.
We need at least two spacecraft to understand how the electrojets evolve over time.
We want to know in the 2–10 minutes [between them] how much the size, shape and flow patterns of those current have changed.
By understanding the changes, we can tell which direction the current is going, its intensity and its structural evolution.
Our goal is to operate for 18 months after launch, though we think by the first five or six months we will answer all our key questions.
What are you trying to find out?
We’d like to understand the structure and evolution of the auroral electrojets, and their impact on space weather.
This is the first mission to look at the aurora in this depth.
Electrojets flow in a region that is hard to study because it’s too high for balloons and too low for satellites to operate.
EZIE is the perfect distance, and the sensors are exactly focused on what we’re interested in. Up to this time, we didn’t have the technology to do this.
What impact do the currents have here on Earth?
Electrojets are part of a huge electric circuit that connects Earth to space. These electrojet currents can cause sudden changes in Earth’s magnetic field.
That can create large magnetic disturbances on the ground if there’s an interruption in the current, sometimes leading to power grid disruptions and satellite issues.
Auroral electrojets are one of the key elements that we don’t have information about when it comes to predicting space weather, and by studying them in detail, scientists will be able to reduce its impact.
Space weather can also harm astronauts, so understanding these currents will help the next generation wanting to go into space.
This interview appeared in the May 2025 issue of BBC Sky at Night Magazine
