The rotation of the Sun has long been a thorn in the flesh of solar physicists: an active region becomes interesting and is out of sight as the Sun rotates. At the eye of the earth, any tempest-fostering bit of magnetism can generally be observed no more than two weeks, until it disappears in the solar limb. NOAA 13664 an unusually severe area, which contributed to the creation of spectacular aurora and broad technical interference in 2024 was made an exception.
This was not by chance but by geometry. The Solar Orbiter of ESA, which was launched in 2020, does not remain attached to the Earth-Sun line, but instead circulates around the Sun on an orbit roughly six months long and is in a position to see things that are obscured by the Earth. Even better, according to solar physicist Ioannis Kontogiannis of ETH Zurich and IRSOL in Locarno, “Fortunately, the Solar Orbiter mission, launched by the European Space Agency (ESA) in 2020, has broadened our perspective.”
The researchers were able to create an almost continuous portrait of one active region with three solar rotations by knitting the Solar Orbiter views on the far side with near-side images of Solar Dynamics Observatory. This left the outcome of 94 days of tracking with few gaps between them beginning at the beginning of the region on 16 April 2024 and continuing until its decline after 18 July 2024. According to Kontogiannis, “This is the longest continuous series of images ever created for a single active region: it’s a milestone in solar physics.”
The continuity of active regions is important since active regions are not simply aggregations of sunspots, but are dynamic magnetic machines. When magnetized plasma starts to rise up through the surface of the sun, lines of magnetic fields bend, interweave and occasionally entangle themselves to form patterns that are effective in the storage of energy. Complexity was seen to accumulate in episodes with NOAA 13664 with an increasingly intertwined field as time progressed. The group noted that a particularly complex structure led to the largest geomagnetic storms since 2003 and attributed long-term magnetic evolution to the type of bursts that are significant on Earth.
The stakes are practical. The solar storms may disrupt radio communications and navigation and increase the radiation exposure of the flight crews and destroy satellites. One of the most commonly cited is the 38 out of 49 satellite loss of February 2022 due to enhanced atmospheric drag during a geomagnetic disturbance a more detailed study of the Starlink satellite loss is found in a Space Weather study. The activity of NOAA 13664 in 2024 was also overlapping daily operations but at lower altitude. “Even signals on railway lines can be affected and switch from red to green or vice versa,” says Louise Harra, professor at ETH Zurich and director of the Davos Physical Meteorological Observatory. “That’s really scary.” She added that “Modern digital agriculture was particularly affected,” with disrupted satellite, drone, and sensor signals costing farmers time and, in some cases, harvest quality.
The record of 94 days can provide the clearer, longer-run perspective on prediction of logic: when the magnetic field of a given area gets very complicated, one can expect the release of stored energy, but the time and magnitude are hard to predict. “We’re not there yet. But we’re currently developing a new space probe at ESA called Vigil which will be dedicated exclusively to improving our understanding of space weather,” Harra says.
Vigil will monitor the Sun in the Lagrange point number 5 which is a vantage that should give up to four to five days of further notice on some of these effects before they spin into view of the Earth. The NOAA 13664 lesson is that warning time is not a symbolic convenience, it is engineering margin.
