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What’s happening?
Very early Sunday morning, an immense cloud of solar plasma swept by our planet. While most coronal mass ejections take a few days to reach us once they erupt from the Sun’s surface, this CME was blasted into space early on Saturday.
Crossing the 150 million kilometres of space to reach us in just one day, this CME arrived faster than originally expected. It’s rapid speed contributed to some of the most intense auroras we’ve seen so far in 2025.
The Space Weather Overview, showing the impacts of solar flares (Solar X-ray Flux), solar radiation storms (Solar Proton Flux), and geomagnetic storms. Under geomagnetic activity, the red bar indicates a G4 (severe) storm, orange represents G3 (strong) conditions, light orange is G2 (moderate) levels, yellow marks G1 (minor) levels, and green is substorm conditions. The space weather forecast, with Kp and Geomagnetic Storm rankings expected on June 2, 3, and 4 (UTC time), is shown on the right. The strongest levels in the forecast are during the day on Monday, with up to G2 (moderate) levels late on Monday (03-06UT = 11pm-2am EDT). (NOAA SWPC)
One factor that possibly contributed to this CME’s early arrival was the region of the solar wind the cloud of solar particles was passing through on its way here.
The solar wind is a fairly constant and sedate flow of charged particles from the Sun. When a CME erupts and travels through this flow of the solar wind, it sweeps up the slower-moving particles in its path. This slows the solar storm down, and steals away some of its overall energy.
When this particular CME erupted, though, it did so directly into the fast flow of particles streaming out of a coronal hole that was aimed towards Earth.
The coronal hole imaged by NASA’s Solar Dynamics Observatory (left), and a computer simulation showing the weekend solar storm having moved through the fast stream of the solar wind produced from that coronal hole (right). In the simulation, the plot at the top is the solar wind density, showing that it is very empty in the region of space the CME is passing through, with the plot at the bottom showing the speed of the solar wind, which is extremely fast in that same region of space. (NASA/NOAA/Scott Sutherland)
That fast flow, shown in the computer simulation plots on the right side of the above image, allowed the CME’s speed to ramp up, rather than slow down. As indicated by the swath of white through grey colour of the CME’s speed, it was travelling at speeds of up to 1,500 kilometres per second when it reached Earth (around 5-6 million km/h).
