& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Hemispheric Comparison of Signatures of Flux Transfer Events Kathryn McWilliams and Matt Wessel University of Saskatchewan

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan From Scholer, 1995 FTE Models

FTEs at the Magnetopause (Russell & Elphic, 1979) bipolar field variation

Fall AGU MeetingPhysics & Engineering Physics, University of Saskatchewan Magnetopause (Equator-S) Ionosphere (SuperDARN) (Neudegg et al., 2001) Flux Transfer Events at the Magnetopause bipolar boundary-normal FTE signatures poleward moving radar auroral forms (PMRAFs)

Fall AGU MeetingPhysics & Engineering Physics, University of Saskatchewan Poleward Moving Radar Patches (STARE) poleward moving patches during Aug 28, 1978, storm patches emanate from polar cap boundary (Sofko et al., 1979; 1985)

Fall AGU MeetingPhysics & Engineering Physics, University of Saskatchewan STARE Patches & GEOS-2 M’pause Crossings (Sofko et al., 1979; 1985) GEOS-2 footprint in patch upwelling ions GEOS-2 footprint poleward of patch 10X fewer upwelling ions

Fall AGU MeetingPhysics & Engineering Physics, University of Saskatchewan Pulsed Ionospheric Flows (PIFs) vs. PMRAFs oscillating flow magnitude (with continuous data) discrete poleward moving patches (with data gaps) PMRAFs PIFs

MHD Simulation – No Dipole Tilt Raeder, Annales Geophysicae, 2006 “Stagnation line” – separates northward and southward flow Relatively smooth flow away from subsolar point (Earth-Sun line) No evident plasmoids Reconnection relatively smooth Space & Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

MHD Simulation – Large Dipole Tilt Raeder, Annales Geophysicae, 2006 “Stagnation line” located off Earth-Sun line, towards winter hemisphere Reconnection X-line forms winter-ward of Sun-Earth line Plasmoid forms in region of flow towards winter cusp Field lines draped around plasmoid from summer cusp form second X-line Plasmoid moves towards winter cusp No plasmoid observed in summer hemisphere Space & Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

3D Simulations – Development Along Magnetopause Raeder, Annales Geophysicae, 2006 Space & Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

Fall AGU MeetingPhysics & Engineering Physics, University of Saskatchewan 2-D Electric Field in Footprint of Reconnection Patch of SuperDARN backscatter: –footprint of reconnected field lines –measured by two overlapping SuperDARN radars (CUTLASS) Compared patch motion to ExB drift (McWilliams et al., 2001)

Fall AGU MeetingPhysics & Engineering Physics, University of Saskatchewan patch expands and moves azimuthally convection speed differs from patch motion at first 2-D Electric Field in Footprint of Reconnection

Fall AGU MeetingPhysics & Engineering Physics, University of Saskatchewan Two phases of motion: (1) reconnection (2) convection FTEs are not necessarily “small” 2-D Electric Field in Footprint of Reconnection 1 2

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Recent Observations Korotova & Sibeck, GRL, 2008 Considered m’pause crossings Interball-1 on dayside only during northern summer months; north=summer, south=winter Included only FTEs during neg. IMF Bz –Bz < -1 nT Interball-1 FTEs observed exclusively in WINTER hemisphere

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Signatures of FTEs 4 hours UT Geotail FTEs SuperDARN poleward moving forms 18 Jan 1999 (NH winter) McWilliams et al., AG, 2004

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Survey of Poleward Moving Radar Auroral Forms only examined poleward moving forms (PMRAFs) no modulated continuous drifts (PIFs) Radar Frequency is important! Before 2002 used single day and single night transmitter frequency Con: You have to be lucky to get good propagation Pro: Motion of patches is geophysical frequency change

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Survey of SuperDARN PMRAFs Noted days when PMRAFs evident (visual inspection) viewing angle important

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Comparing N&S Hem. The “one hope” frequency makes things difficult Not guaranteed that radio wave will refract enough to scatter back from cusp/mantle patches Kerguelen = SH Hankasalmi = NH Ker Han

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Question Answered! …sort of Simultaneous poleward moving form in winter and summer hemisphere This is RARE

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Seasonal Dependence? Hankasalmi data only –Does not run “sounding” mode, so patch motion is geophysical Visual inspection of PMRAFs over nearly a full solar cycle 1997 – 2006 FTE: 1893 days No FTE: 3468 days (~35% FTE)

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan Probably Not… Our day-frequency is not optimized for season So we take what we can get The number of days with FTEs strongly resembles the amount of ionospheric backscatter overall throughout the year No seasonal trend in SuperDARN PMRAFs

Summary and Future Work Study motivated by simulations and observations of FTEs in winter hemisphere –Modelled plasmoids form in on winter side of Sun-Earth line –Modelled plasmoids carried through winter cusp –FTEs detected in winter hemisphere by Interball-1 Reconnection footprint should map to both hemispheres, so particles are expected to precipitate into both hemispheres, regardless of where plasmoid forms SuperDARN does not see seasonal dependence on occurrence of PMRAFs –Simultaneous observations by Hankasalmi and Kerguelen More sophisticated analysis of statistics is required –More detail on duration of PMRAFs, beams involved, etc. –Relationship to upstream IMF orientation Space & Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

Fall AGU MeetingPhysics & Engineering Physics, University of Saskatchewan FTEs observed at Geotail only under certain IMF conditions (+B y and +B z ). SuperDARN transients suggest FTEs occurred at all times, regardless of IMF orientation. FTEs SuperDARN PMRAFs IMF By (McWilliams et al., 2004) IMF Bz Geotail

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan

& Atmospheric StudiesPhysics & Engineering Physics, University of Saskatchewan