A rapid, global and prolonged electron radiation belt dropout observed with the Global Positioning System constellation

[1] A rapid loss of energetic (>230 keV) electrons from the outer radiation belt was observed with the GPS constellation between 1430 and 1730 UTC on 7 May 2007. The rapid loss occurred from 4 < L* < 6 over all measured energies above 230 keV. Currently accepted rapid loss mechanisms include magnetopause shadowing and/or outward diffusion, and precipitation to the atmosphere due to wave-particle interactions. Here the loss timescale is ∼2 hr, and the magnetopause is near L = 8, which requires unrealistically high outward diffusion rates. Current estimates of the loss timescales associated with EMIC waves, plasmaspheric hiss and whistler-mode chorus are too long, even in combination, to explain the observed losses inside L* ≃ 6.