Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF B y and conductivity gradients

Using DMSP F13 data in conjunction with IMF data we investigate the newly discovered channels of enhanced (1.5–3 km/s) antisunward convection occurring at the dawn (06:00–09:00 MLT) or dusk (15:00–18:00 MLT) flanks of the polar cap for different combinations of IMF B y polarity, hemisphere (NH/SH) and the dawn/dusk MLTs. Dawn-side cases where this flow channel appears occur for the following combinations: NH-dawn/ B y >0 and SH-dawn/ B y B y B y >0. The flow channels are placed in the context of particle precipitation regimes/boundaries and ionospheric conductivity gradients. They are found to be threaded by "old open field lines" ("time since reconnection" >10 min) characterized by polar rain precipitation. In the dawn-side cases (NH-dawn/ B y >0 and SH-dawn/ B y B y component. The HBL/LLBL-ionosphere coupling via Birkeland currents C1/C2 is a source of dawn-dusk convection asymmetry and Svalgaard-Mansurov effect which must be added to the effect of magnetic tension acting on "newly open field lines".

[1]  T. Karlsson,et al.  Plasma transport along discrete auroral arcs and its contribution to the ionospheric plasma convection , 2008 .

[2]  S. Wing,et al.  Polar rain gradients and field-aligned polar cap potentials , 2008 .

[3]  H. Carlson,et al.  On the relationship between thin Birkeland current arcs and reversed flow channels in the winter cusp/cleft ionosphere , 2008 .

[4]  C. Farrugia,et al.  Momentum transfer at the high-latitude magnetopause and boundary layers , 2008 .

[5]  H. Carlson,et al.  Reversed flow events in the winter cusp ionosphere observed by the European Incoherent Scatter (EISCAT) Svalbard radar , 2007 .

[6]  Charles J. Farrugia,et al.  Poleward moving auroral forms (PMAFs) revisited: responses of aurorae, plasma convection and Birkeland currents in the pre- and postnoon sectors under positive and negative IMF B y conditions , 2007 .

[7]  Charles J. Farrugia,et al.  Role of poleward moving auroral forms in the dawn-dusk auroral precipitation asymmetries induced by IMF By , 2007 .

[8]  Charles J. Farrugia,et al.  Dayside aurorae and polar arcs under south-east IMF orientation , 2006 .

[9]  Raymond A. Greenwald,et al.  Dependencies of high-latitude plasma convection: Consideration of interplanetary magnetic field, seasonal, and universal time factors in statistical patterns , 2005 .

[10]  C. Farrugia,et al.  Detailed dayside auroral morphology as a function of local time for southeast IMF orientation: implications for solar wind-magnetosphere coupling , 2004 .

[11]  M. Dunlop,et al.  Pulsed flows at the high-altitude cusp poleward boundary, and associated ionospheric convection and particle signatures, during a Cluster - FAST - SuperDARN- Søndrestrøm conjunction under a southwest IMF , 2004 .

[12]  H. Carlson,et al.  High‐resolution observations of the small‐scale flow pattern associated with a poleward moving auroral form in the cusp , 2004 .

[13]  Charles J. Farrugia,et al.  Temporal and spatial aspects of the cusp inferred from local and global ground- and space-based observations in a case study , 2004 .

[14]  C. Farrugia,et al.  Temporal variations in a four‐sheet field‐aligned current system and associated aurorae as observed during a Polar‐ground magnetic conjunction in the midmorning sector , 2003 .

[15]  J. Foster,et al.  Average characteristics and activity dependence of the subauroral polarization stream , 2002 .

[16]  T. Tanaka,et al.  Interplanetary magnetic field B y and auroral conductance effects on high‐latitude ionospheric convection patterns , 2001 .

[17]  G. Siscoe,et al.  Deflected magnetosheath flow at the high‐latitude magnetopause , 2000 .

[18]  M. Freeman,et al.  Geoeffectiveness of three Wind magnetic clouds: A comparative study , 1998 .

[19]  M. Watanabe,et al.  Synthesis models of dayside field‐aligned currents for strong interplanetary magnetic field By , 1996 .

[20]  T. Karlsson,et al.  A statistical study of intense low‐altitude electric fields observed by Freja , 1996 .

[21]  D. Weimer,et al.  Models of high‐latitude electric potentials derived with a least error fit of spherical harmonic coefficients , 1995 .

[22]  J. M. Ruohoniemi,et al.  Interhemispheric asymmetry of the high-latitude ionospheric convection pattern , 1994 .

[23]  W. J. Burke,et al.  Auroral ionospheric signatures of the plasma sheet boundary layer in the evening sector , 1994 .

[24]  N. Crooker,et al.  Lobe cell convection as a summer phenomenon , 1993 .

[25]  W. F. Denig,et al.  Ionospheric signatures of pulsed reconnection at the Earth's magnetopause , 1993, Nature.

[26]  J. Slavin,et al.  Characterization of the IMF By ‐dependent field‐aligned currents in the cleft region based on DE 2 observations , 1993 .

[27]  P. Newell,et al.  Ground and satellite observations of an auroral event at the cusp/cleft equatorward boundary , 1992 .

[28]  G. Siscoe,et al.  A high‐latitude, low‐latitude boundary layer model of the convection current system , 1991 .

[29]  C. Russell,et al.  Plasma flow reversals at the dayside magnetopause and the origin of asymmetric polar cap convection , 1990 .

[30]  Mike Lockwood,et al.  The excitation of plasma convection in the high‐latitude ionosphere , 1990 .

[31]  Mike Lockwood,et al.  Midday auroral breakup events and related energy and momentum transfer from the magnetosheath , 1990 .

[32]  David J. Southwood,et al.  The ionospheric signature of flux transfer events , 1987 .

[33]  J. Scudder,et al.  Polar rain - Solar coronal electrons in the earth's magnetosphere , 1985 .

[34]  Göran Marklund,et al.  Auroral arc classification scheme based on the observed arc-associated electric field pattern , 1983 .

[35]  F. Mariani,et al.  Magnetic loop behind an interplanetary shock: Voyager, Helios and IMP-8 observations , 1981 .

[36]  W. J. Burke,et al.  Effects of high‐latitude conductivity on observed convection electric fields and Birkeland currents , 1980 .

[37]  C. T. Russell,et al.  Initial ISEE magnetometer results: magnetopause observations , 1978 .

[38]  R. Heelis,et al.  Dayside auroral arcs and convection , 1978 .

[39]  C. Meng,et al.  Dawn‐dusk gradient of the precipitation of low‐energy electrons over the polar cap and its relation to the interplanetary magnetic field , 1977 .

[40]  Eigil Friis-Christensen,et al.  Interplanetary magnetic-field direction and high-latitude ionospheric currents , 1972 .

[41]  L. Blomberg,et al.  High-Latitude Ionospheric Convection Patterns Dependent on the IMF Orientation , 2007 .

[42]  M. Smith.  Transient dayside reconnection and its effects on the ionosphere , 1994 .

[43]  M. Gussenhoven.  POLAR RAIN AND THE QUESTION OF DIRECT PARTICLE ACCESS , 1989 .

[44]  F. Mozer,et al.  High-latitude electric fields and the three-dimensional interaction between the interplanetary and terrestrial magnetic fields , 1974 .