Characteristics of westward travelling surges during magnetospheric substorms

Data from arrays of magnetometers along lines of constant magnetic latitude and longitude supplemented by all-sky camera and riometer data are used to infer the characteristics of the temporal development and the typical scale size of westward travelling surges which occur during magnetospheric substorms. It is found that the motion of the head of the surge can be quite irregular, and that in extreme cases the surge form may grow and decay in a confined longitudinal sector without suffering any significant westward displacement. The positive D-component perturbation, known to be the characteristic signature of a surge, is generally confined within a longitude range of ~6-10° at ~70° N and is thought to be generated by a filamentary southward ionospheric current flowing at the head of the surge. A comprehensive model three-dimensional current system involving this equatorward current and northwestward current flow in the region to the east of the head of the surge is presented through a detailed comparison of model and observed latitude and longitude profiles of the magnetic disturbance. It is found that best agreement is obtained when the entire electrojet system flows from southeast to northwest relative to the lines of constant magnetic latitude.           ARK: https://n2t.net/ark:/88439/y029714 Permalink: https://geophysicsjournal.com/article/128 &nbsp