Dayside Merging Topology with Component Reconnection

1
Dayside Merging Topology with Component
Reconnection

• T. E. Moore NASA/GSFC/LEP, Code 692, Greenbelt,
  MD 20771, USA
• M. O. Chandler NASA/MSFC/SSD, Code SD50,
  Huntsville, AL 35812 USA
• Outline
• Evidence for low shear reconnection, supporting
  earlier work
• Cowley 1976 Paschmann et al., 1990, 1993,
  Onsager Fuselier, 1994,...
• Simultaneity with high shear reconnection
• Global distribution of reconnection
• vs Crooker, 1977 Luhman, 1984
• Local dependence on IMF (Pdyn)
• Issues
• Opening/closing of flux tubes?
• Relationship to sash?

Z
Y
Topology based on anti-parallel, or high shear
reconnection Crooker, JGR 1979 Luhman JGR 1984
2
Dayside High Latitude Reconnection

• Evidence for supra-cusp high shear reconnection,
  NBZ, BY
• Russell et al. 1998 GRL
• Fedder et al. Simulation
• Sunward, equatorward flows
• Scudder et al. 1999
• Reconnection microphysics
• Note low latitude sunward convection suggests
• Lower latitude reconnection drawing plasma to
  magnetopause
• Should spread laterally, otherwise, per
  SongRussell 94, tbd and Wolf 97

Approx. Magnetopause
3
Dayside Low Latitude Reconnection

• Evidence for sub-cusp reconnection
• Chandler et al., JGR, Oct. 1999
• Same 29 May 1996 event,
• D-shaped magnetosheath distributions (65 km/s, 50
  eV)
• Cold ionospheric component (2 eV)
• Other cases, e.g. 2000/05/08-0730
• Low latitude reconnection pumping dayside plasma
  and flux into magnetosheath upstream of high lat.
  Site
• Simultaneous, long-lived high low lat
  reconnection.

4
Simultaneous Hi/Lo Lat Reconnection Sites
NBz SBZ
Chandler et al. 10/99 JGR?
Savin et al. 02/00 ISTP?
Pumps lobe plasma
Pumps Lobe Plasma
Rates dep. on IMF, Pdyn
Rates dep. on IMF, Pdyn
Pumps Plasmsphere
Pumps Plasmsphere
5
Component Reconnection Neutral Line Orientation
for Varying Magnetic Shear
Simplified for equal fields More generally, NL
has equal normal components

• Let reconnection occur along a continuous neutral
  line from subsolar pt.
• Local neutral line determined by local field
  magnitudes, directions
• Shear, reconnection rates vary with local
  conditions (GonzalezMozer74?)

6
Dayside Reconnection for Typical ShearQ 90 Bz
0
Z
Y
7
Dayside Reconnection with Atypical Shear Q
90 NBZ Q 90 SBZ
Low shear
High Shear
Opened Flux Tubes
Opened Flux Tubes
Low shear
High Shear
High Shear
Low shear

• Opens lobe tubes into overdraped tubes in flanks
• Opens low rate of closed tubes into overdraped
  tubes in flanks

• Opens closed tubes into lobes
• Realigns low rate of lobe tubes

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Summary component reconnection topology varys
with IMF, but differently...

• Typical Bz 0
• Closed and lobe flux tubes become open flank flux
  tubes
• Moderate, skewed polar cap convection
• Northward Bz
• Lobe flux tubes become open flank flux tubes
• Polar cap convection reduced, reversed
• Southward Bz
• Closed flux tubes become open lobe tubes
• Rapid antisunward polar cap convection
• Conclusions/Inferences
• sash changes sides with IMF rotation!
• Accounts for theta aurora dynamics?

NL Topology based on anti-parallel, or high shear
reconnection
NL Topology based on component reconnection