Now a NASA mission also named for Van Allen has found something new about his belts. By looping through them repeatedly, the twin Van Allen Probes discovered a third band of radiation.
Or at least there were three. The two spacecraft uncovered the previously unknown structure in September. It consisted of fast-moving electrons, situated between the two previously known Van Allen Belts. The discovery was reported in the journal Science. [Daniel N. Baker et al., A Long-Lived Relativistic Electron Storage Ring Embedded in Earth's Outer Van Allen Belt]
But the new structure is no longer. Four weeks after the probes found it, the third ring was wiped out by a strong shock wave emanating from the sun. Still, the unexpected finding shows that the Van Allen Belts are more complex and variable than had been assumed. And that seemingly well-established knowledge about space still may have the capacity to surprise.
—John Matson
