The influence of magnetospheric substorms on SuperDARN radar backscatter

J A Wild,A Grocott

doi:10.1029/2007ja012910

Abstract

The SuperDARN ionospheric radar network is a leading tool for investigating the near‐Earth space environment. However, reductions in ionospheric backscatter have been reported during magnetospheric substorms. We have therefore investigated the impact of substorms upon SuperDARN backscatter during 3005 substorms and find that the global level of scatter maximizes just prior to substorm onset. In the nightside ionosphere, backscatter poleward of ∼70° magnetic latitude is reduced, with radar echoes shifting to lower latitudes. An examination into the frequency‐dependence of nightside backscatter evolution during substorms reveals that although most backscatter data is based upon operations in the 08–14 MHz range, higher operating frequencies may offer improved performance in the period just prior to and immediately following expansion phase onset. We suggest that the SuperDARN array of high‐frequency coherent‐scatter radars, and in particular those radars with the ability to simultaneously operate at dual frequencies, will play a key role in future space‐ and ground‐based studies of substorms.

Highlights

[1] The SuperDARN ionospheric radar network is a leading tool for investigating the near-Earth space environment
An equatorward migration of radar backscatter has previously been reported during the substorm growth phase [Lewis et al, 1997] while a loss of backscatter is sometimes reported in the nightside ionosphere during substorm onset, an effect attributed to absorption of HF radio waves by the enhanced electron densities in the substorm precipitation region [Milan et al, 1999] and rapid changes in HF propagation conditions [Gauld et al, 2002]
SuperDARN data was used to examine the northern hemisphere ionospheric convection pattern during 67 substorms identified by the far ultra violet (FUV) auroral imager on board the IMAGE satellite

Summary

Introduction

[2] Since the concept was first proposed by Akasofu [1964], the substorm has proven to be one of the greatest challenges in solar-terrestrial physics. [6] Given the increasing use of SuperDARN measurements for both global and localized investigations of ionospheric flow during substorms and the upcoming focus of international research effort on the substorm process prompted by NASA’s Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, a comprehensive investigation into the influence of magnetospheric substorms upon the level of ionospheric backscatter recorded by the SuperDARN network is desirable.

Methodology

Results

Conclusions