Multi-instrument probing of the polar ionosphere under steady northward IMF

Abstract

Abstract. Observations are presented of the polar ionosphere under steady, northward IMF. The measurements, made by six complementary experimental techniques, including radio tomography, all-sky and meridian scanning photometer optical imaging, incoherent and coherent scatter radars and satellite particle detection, reveal plasma parameters consistent with ionospheric signatures of lobe reconnection. The optical green-line footprint of the reconnection site is seen to lie in the sunward plasma convection of the lobe cells. Downstream in the region of softer precipitation the reverse energy dispersion of the incoming ions can be identi®ed. A steep latitudinal density gradient at the equatorward edge of the precipitation identi®es the general location of an adiaroic boundary, separating the open ®eld lines of polar lobe cells from the closed ®eld of viscous-driven cells. Enhancements in plasma density to the south of the gradient are interpreted as ionisation being recon®gured as it is thrust against the boundary by the antisunward¯ow of the viscous cells near noon. Each of the instruments individually provides valuable information on certain aspects of the ionosphere, but the paper demonstrates that taken together the dierent experiments complement each other to give a consistent and comprehensive picture of the dayside polar ionosphere.

Multi-instrument study of footprints of magnetopause reconnection in the summer ionosphere

“…The structure was bounded on its equatorward edge by a footprint of the adiaroic wall across which no plasma¯ows. In a subsequent multiinstrument study, it was found that the EISCAT Svalbard radar showed evidence of increased electron temperatures within the region of ion dispersion (Pryse et al, 2000).…”

Ionospheric signatures of the low-latitude boundary layer under conditions of northward IMF and small clock angle

“…An abrupt boundary in ion flows measured by the ESR radar was presented in Pryse et al (2000b). Comparisons of the boundary location with optical emissions and plasma drift measured by the CUTLASS radar, showed it to be located at the equatorward edge of the polar cap where the sunward flow of the reverse polar cells, in this instance lobe cells, gave way to the viscous cells at lower latitudes.…”

“…If the reverse cells are entirely on open magnetic field lines they are referred to as lobe cells (Reiff and Burch, 1985). DMSP particle data have revealed reverse ion energy dispersion characteristic of the reconnection with energy decreasing with decreasing latitude (Øieroset et al, 1997), radio tomography has identified spatial structures in the electron density distribution (Pryse et al, 2000b) and recently Oksavik et al (2006) have documented that electron density structures may form inside lobe cells due to soft electron precipitation. In its simplest form, an adiaroic boundary separates the polar regime on open magnetic field lines from the lower-latitude viscous regime on closed field lines, across which plasma cannot enter or leave the polar cap.…”

“…In its simplest form, an adiaroic boundary separates the polar regime on open magnetic field lines from the lower-latitude viscous regime on closed field lines, across which plasma cannot enter or leave the polar cap. The boundary between the two regimes has been identified at small IMF clock angles in ion flow measurements by the EISCAT Svalbard radar (ESR) by comparison with the equatorward boundary of redline cusp emission (Pryse et al, 2000b), and it was also a feature of the ESR flow observations of Pitout et al (2001) under B z positive but with variable clock angle. Milan et al (2003) used low level UV aurora in the polar cap, co-located with magnetosheath precipitation, to locate the open/closed magnetic field line boundary under northward IMF, identifying the boundary with the equatorward edge of the emission.…”

EISCAT Svalbard radar observations of ionospheric signatures of magnetopause reconnection during a changing IMF Bz polarity

“…The location of the EISCAT Svalbard Radar (ESR) at 78.2 • N is more favourable for observations in the vicinity of the cusp. Signatures of equatorial reconnection have been seen by this radar when observing along the magnetic field (Pryse et al, 2000a) and spatial structures of increased electron temperatures within the reverse ion-dispersion of lobe reconnection have been identified in a multi-instrument investigation of the ionosphere under steady northward IMF (Pryse et al, 2000b). The current paper develops the use of the ESR to investigate the spatial signatures of reconnection processes in the ionospheric plasma.…”