Ion and electron pulses observed in the magnetotail and rapid annihilation of magnetic field lines

Hydrogen, helium, and CNO ion and electron pulses were detected in the magnetotail, and in the upstream region from the Earth's bow shock. It was found that, in the magnetotail, ions appeared more frequently in the dusk than in the dawn quarter whereas the electron population had a reversed asymmetry. This spatial distribution: a polarization in the same direction as the electric field in the neutral sheet: suggests that these particles are accelerated by the electric field induced by a rapid annihilation of magnetic field lines. From the observed particle energies, the annihilation speed was estimated and found to be as high as 0.2 u/sub A/, where u/sub A/ is the Alfven speed