Coordinated observations of a high-altitude auroral electrojet by UHF/VHF receivers, magnetometers and meridian scanning photometer

摘要

UHF/VHF beacon receivers deployed in Alaska measure the latitude profile of relative total electron content over Alaska and frequently across the auroral oval. On March 9, 2008, these receivers observed a plasma density enhancement at 147 km. These observations are supported by collocated scanning photometer measurements. A simple model current consistent with magnetic field perturbations observed by a chain of magnetometers across Alaska corresponds spatially to the enhanced density observed by the receivers. Hence, these measurements suggest that the auroral electrojet is flowing at 147 km, which is unusually high. Indeed, the ratio of the 630.0 nm and 427.8 nm emissions and the strength of the magnetic perturbation suggest the electrojet is flowing at a lower altitude. We attribute this difference to thermospheric compositional changes associated with particle and Joule heating that could result in a lower ratio of the 630.0 nm and 427.8 nm emissions and higher conductivity corresponding to observed density enhancement.