Science2 publishers2 min readPublished
Radiation belt simulations matched the May 2024 dropout only when compression and outflow coincided
Xingzhi Lyu and colleagues have reconstructed how the outer Van Allen belt lost its most energetic electrons during the strongest geomagnetic storm since 2003, and the reconstruction worked only under a tight timing assumption.
The Scientist · Science desk
What happened
- The May 2024 superstorm filled night skies in many parts of the world with aurorae and disrupted infrastructure, including the GPS signals agricultural equipment relies on.
- Satellite observations showed the outer Van Allen belt suddenly and dramatically losing its highly energetic electrons while the storm was under way.
- Xingzhi Lyu's team quantified the depletion using data from JAXA's Arase satellite, then re-ran the event in the VERB model, which is built to reproduce radiation belt dynamics.
- The simulation reproduced the observed loss only when the sudden outward transport of electrons began nearly at the same moment as a strong compression of Earth's magnetosphere.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint The electron transport models commonly used in space weather forecasting do not capture that coupled timing, so what they emit for a storm of this size is not tied to the sequence that produced the 2024 loss.
- decision Anyone maintaining an orbital risk model has to decide whether to encode a timing coupling calibrated on one storm, or wait for a second extreme case before changing anything.
- capability Because the two loss routes dominated in different regions of Earth's magnetic field, a model that reproduces the split could say which parts of the belt drained by which route.
Magnetopause shadowing and local wave scattering both empty the outer belt, in opposite directions. Shadowing moved electrons outward and released them into space; scattering by local waves moved them inward, into Earth's upper atmosphere [11]. Both processes had been studied before this storm [11]. The belts are donut-shaped rings of energetic electrons and protons, mostly from the solar wind, held by Earth's magnetosphere [6].
Lyu and colleagues report the first comprehensive analysis of how the rapid transport happened [4]. A simulation matched to one recorded event shows which processes are sufficient to produce it. It does not show that the same model, run forward on the solar wind data available at the time, would have called the dropout before it happened.
Rapid electron transport during extreme storms had stayed unclear despite decades of research on the hazard, and May 2024 was a rare opportunity to look [8]. The gap back to the previous storm of that class, the Halloween storms of 2003, was about twenty and a half years [1][17]. One event supports the finding that near-simultaneity was needed here, and the next superstorm will be the test of whether it is needed in general.
The link to hardware stays general in this account. Storm-driven changes in the outer belt may be hazardous to satellites [7]. Sarah Stanley's Eos research spotlight puts no number on the electron loss in flux terms and names no affected spacecraft [16].
The paper, "Extreme Radiation Belt Dropout During the May 2024 Superstorm", is published in AGU Advances [5].
What to watch
- Whether the same timing requirement holds when the VERB model is applied to the Halloween 2003 storms or the next extreme event.
- Whether operational forecast centres encode coupled compression-and-transport timing into the electron models they run.
- Whether the full AGU Advances paper reports flux magnitudes and any satellite anomalies the Eos summary leaves out.