A few months ago, scientists determined that the Sun’s current sunspot/solar storm cycle had hit its peak and was likely to remain that way for up to a year. At the same time, NASA’s Sun-studying heliophysics program was ramping up to its own maximum, with its Parker Solar Probe making the closest approach ever to the Sun in December (passing within 6.1m km of its surface), and the launch of not one or two, but six new Sun-studying missions in 2025.
The timing isn’t coincidental. Not only is there more to be learned by studying the Sun at its most active, but there is an underlying urgency to learn how to warn for what is often called a Carrington-level event—a gigantic solar storm with potentially catastrophic repercussions.
The Carrington Event was the first-ever-seen solar flare, observed by British astronomer Richard Carrington in 1859. It might also have produced the strongest geomagnetic storm in recorded history. When the resulting disturbance hit Earth, northern and southern lights were reported in Cuba and Queensland. A magnetometer jumped off the scale in India, and telegraph lines experienced current surges that set fires in the U.S.
Today, Joe Westlake, director of NASA’s Heliophysics Division (which studies the effects of the Sun throughout the Solar System), tells Cosmos that such an event would have done a lot more than set fires. “It would have meant blackouts to power grids. It would have meant issues with GPS, issues with communications, all sorts of things,” he says. Bottom line: understanding how the Sun behaves is important.
The first of this year’s Sun-studying missions is PUNCH, which will put four suitcase-sized satellites in low-Earth orbit, from which they will monitor the solar corona, the solar wind, and the impact of the solar wind on Earth.
Next up is EZIE, which consists of three smaller (shoebox-sized) satellites, designed to do the opposite of what PUNCH will do. Instead of looking outward at the solar wind coming toward us, it will look at what happens, lower down, when the solar wind hits the Earth, focusing on electrojets, the electromagnetic currents that connect incoming space weather to the northern and southern lights we love to watch. “EZIE is to look at the 3D structure of that entire system,” Westlake says.
Another mission, currently scheduled for launch on 13 April, is TRACERS, which will have two small spacecraft, also in low-Earth orbit, designed to track the magnetic connection between the solar wind and the Earth, not at night, when the aurora are visible, but on its daylight side.
After that there will be a pause until September, when NASA plans to send up two more heliophysics missions in a single launch: IMAP and the Carruthers Geocorona Observatory. These will go to a destination called L1, a point about 1.5m km between the Earth and the Sun, where a delicate balance of gravitational forces allow a spacecraft to stay on station indefinitely, with minimal expenditure of manoeuvring fuel.
Read more about the impact of our benign Sun
IMAP is designed to study the furthest reaches of the heliosphere, all the way out to where the solar wind hits interstellar space. At that boundary—already probed by the two Voyager spacecraft as they exited the Solar System—Westlake says, solar-wind particles collide with the interstellar medium and can be sent in any direction, including all the way back to L1. By measuring the time it takes for changes in the outbound solar wind to create such reflections, Westlake says, it’s possible to measure the distance to the heliosphere boundary and map it in a process much like that by which sonar uses reflected sound pulses to map underwater terrain.
The Carruthers Geocorona Observatory, on the other hand, is simply a space telescope designed to look back at the Earth and use faint ultraviolet light emissions to monitor how the furthest-out portions of our atmosphere react to incoming solar events.
NASA says on the Carruther’s website: “To date, only four images exist of the exosphere. The first image was from Carruthers’ telescope when it was placed on the Moon during the Apollo 16 mission in 1972. The telescope was sensitive to ultraviolet light that was absorbed and re-emitted by neutral particles of hydrogen in the exosphere. Scientists call this ultraviolet emission the geocorona, which is Latin for “Earth’s Crown.”
The final scheduled mission is ESCAPADE, designed to place two spacecraft in Mars orbit to study how the solar wind affects its atmosphere—useful not just for understanding the Martian atmosphere, but for helping future Mars missions prepare for what they might have to deal with.
“So,” Westlake says, it’s five launches, six missions, and if we count the spacecraft, thirteen… It’s a really exciting year for us in heliophysics.”
