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An extreme distortion of the Van Allen belt arising from the ‘Hallowe'en’ solar storm in 2003


The Earth's radiation belts—also known as the Van Allen belts1—contain high-energy electrons trapped on magnetic field lines2,3. The centre of the outer belt is usually 20,000–25,000 km from Earth. The region between the belts is normally devoid of particles2,3,4, and is accordingly favoured as a location for spacecraft operation because of the benign environment5. Here we report that the outer Van Allen belt was compressed dramatically by a solar storm known as the ‘Hallowe'en storm’ of 2003. From 1 to 10 November, the outer belt had its centre only 10,000 km from Earth's equatorial surface, and the plasmasphere was similarly displaced inwards. The region between the belts became the location of high particle radiation intensity. This remarkable deformation of the entire magnetosphere implies surprisingly powerful acceleration and loss processes deep within the magnetosphere.

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Figure 1: Energetic electron data from a low-altitude Earth-orbiting spacecraft showing both a long historical record of the Van Allen radiation belts and the specific effects of the 2003 Hallowe'en storm.
Figure 2: Extreme ultraviolet (EUV) images of the Earth's plasmasphere during late October and early November 2003.
Figure 3: Diagrams of the three-dimensional view of the Earth's outer radiation belt and its relationship to the plasmasphere.

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This work was supported by NASA. We thank members of the SAMPEX and IMAGE science teams for data and discussions.

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Correspondence to D. N. Baker.

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Baker, D., Kanekal, S., Li, X. et al. An extreme distortion of the Van Allen belt arising from the ‘Hallowe'en’ solar storm in 2003. Nature 432, 878–881 (2004).

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