Electron trajectories diverge exponentially in a sufficiently small-scale electrostatic field with a static external magnetic field. This electron trajectory instability results in the electron heating in field structure typical for the collisionless shock front ramp. The magnitude of the effect is sufficient to explain the observed heating at the Earth’s bow shock and interplanetary shocks. The heating features are consistent with the observations.

• Received 10 August 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.1259