Duskside Sub‐Auroral Polarization Streams (SAPS) and Dawnside Subauroral Flows During the Magnetically Quiet 24 November and Moderately Active 25–27 November 2008

Abstract

AbstractThis study investigates the coupled solar wind‐magnetosphere‐ionosphere (SW‐M‐I) system during the magnetically quiet (Kp < 3) 24 November and moderately active (Kp ≤ 4‐) 25–27 November 2008. Its main characteristics specified include the (a) antisunward propagating solar‐wind Alfven waves, (b) oscillating Interplanetary Magnetic Field (IMF) leading to undershielding at southward IMF and to overshielding and a three‐cell (dusk, dawn, reverse) polar convection pattern at northward IMF, (c) Kelvin‐Helmholtz (K‐H) waves on the magnetopause, and (d) subauroral plasma flows on the duskside and dawnside. These include the westward Sub‐Auroral Polarization Streams (SAPS) streaming sunward along the dusk cell and the eastward subauroral flows streaming sunward along the dawn cell and antisunward along the dawnside reverse cell. These subauroral flows were driven by the combination of their underlying polarization electric (E) field and unshielded penetration E field (PEF) or shielding E field. While the subauroral flows became mostly enhanced by the combined polarization and PEFs, the duskside SAPS flows were suppressed by the shielding E field and structured by the K‐H waves. From these findings we conclude that (i) the above‐describe conditions (a–d) promoted the development of duskside and dawnside subauroral polarization E fields, (ii) the resultant duskside SAPS and dawnside subauroral flows followed the convection streams evidencing a close association with the polar convection pattern, and (iii) the SAPS flows became structured by the K‐H waves.