2011 SuperDARN Workshop       

Upstream Pc3 ULF wave signatures observed near the Earth's cusp

T.K. Yeoman (1), M.J. Engebretson (2), M.R. Lessard (3), and H. Kim (3)
(1) Department of Physics and Astronomy, University of Leicester, Leicester, UK
(2) Augsburg College, Minneapolis, MN, USA
(3) University of New Hampshire, Durham, NH, USA

abstract. Pc 3-4 pulsations (f ~ 10-100 mHz) which originate in the ion foreshock upstream of the Earth?s bow shock due to the interaction between reflected ions and the solar wind are frequently observed in ground-based pulsation magnetometer data. Previous studies have noted increased Pc 3-4 wave power in the vicinity of the dayside cusp and inferred that the upstream waves gained entry via the cusp, although more recent studies have revealed a more complex picture. Here, we examine Pc3-4 wave power near local noon observed by search coil magnetometers at three closely-spaced stations on Svalbard, during times when an extended interval of HF radar backscatter indicative of the cusp is detected by the Hankasalmi SuperDARN radar. The location of the equatorward edge of the HF radar cusp may then be directly compared with the Pc3-4 wave power measured at three latitudes as the cusp migrates across the stations on a statistical basis. These observations are not consistent with wave entry into the magnetosphere via the cusp proper, but rather along closed field lines equatorward of the cusp, which map to the low-latitude boundary layer or outer magnetosphere.

Sakaguchi KaoriNICT Japan