The ionospheric signature of transient dayside reconnection and the associated pulsed convection return flow

• Main Authors: S. E. Milan, M. Lester, R. A. Greenwald, G. Sofko
• Format: Article
• Language: English
• Published: Copernicus Publications 1999-09-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/17/1166/1999/angeo-17-1166-1999.pdf

Three SuperDARN coherent HF radars are employed to investigate the excitation of convection in the dayside high-latitude ionosphere in response to transient reconnection occurring in the cusp region. This study demonstrates the existence of transient antisunward-propagating backscatter features at the expected location of the ionospheric footprint of the cusp region, which have a repetition rate near 10 min. These are interpreted as the ionospheric signature of flux transfer events. Moreover, transient sunward-propagating regions of backscatter are observed in the convection return flow regions of both the pre- and post-noon sectors. These patches are observed to propagate towards the noon sector from at least as far around the auroral zone as 07 MLT in the pre-noon sector and 17 MLT in the post-noon sector, travelling with a velocity of approximately 1.5 to 2 km s^-1. These return flow patches have a repetition rate similar to that of the transient features observed at local noon. While providing supporting evidence for the impulsive nature of convection flow, the observation of sunward-propagating features in the return flow region is not consistent with current conceptual models of the excitation of convection.<br><br><b>Key words. </b>Ionosphere (plasma convection) · Magnetospheric physics (magnetopause · cusp · and boundary layers; magnetosphere-ionosphere interactions)