In-situ measurements of topside ionosphere electron density enhancements during an HF-modification experiment

Abstract

[1] A Defense Meteorological Satellite Program (DMSP) satellite measured an electron density enhancement of approximately 30% at 840 km altitude on 25 February 2008 during an overpass of the High frequency Active Auroral Research Program (HAARP) research station in Alaska where ionosphere modification experiments were being conducted. An upward ion velocity enhancement of 200 m/s was also observed. Simulation results from a one-dimensional self-consistent ionosphere model indicate that topside electron density enhancements similar in magnitude to the observed enhancements at HAARP follow from electron temperature enhanced ambipolar diffusion, lifting atomic oxygen ions from the peak density layer along the geomagnetic field line up to the DMSP satellite orbit altitude. Assuming the HF pump heats the ionosphere electrons uniformly over a 10 km layer, the effective volume heating rate inferred from the model calculations is approximately 1 nW/m3.