Probes Confirm Earth Acts Like a Giant Particle Accelerator

From Ars Technica:

The twin probes were designed to fly right through the areas of the most intense radiation. NASA The narrative of the first few things put in orbit generally focuses on the space race between the US and Soviet Union. So it's often forgotten that some of the first objects put into space actually discovered something new: the Van Allen belts. These areas of high-energy particles are held in place by the Earth's magnetic fields, and they pose a radiation hazard to any people and equipment that orbit within them. Initially, the Van Allen belts were thought to be largely static, which meant explaining how the particles they contained ended up at such high energies wasn't much of an issue. After all, if the particles are there for a while, there's plenty of time to get them up to speed. But, over time, observations revealed that the radiation environment around the planet was very dynamic. This meant that something must be giving the particles their energy relatively quickly. Debate quickly split between two models: one where the particles entered the belts carrying a lot of energy, and one where they were accelerated once they entered the core of the radiation zone. The debate was left unsolved until NASA put the Van Allen Probes into space. These satellites followed a highly elliptical orbit that took them right through the heart of the Van Allen belt, allowing them to generate a cross-section of the radiation environment that revealed the location and energy of the charged particles. During a particular mass injection from the Sun, they were able to capture the dynamics as lots of new particles entered the belts.

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