# Presentation: 407703

## 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’?

- Topology based on anti-parallel,
- or high shear reconnection
- Crooker, JGR 1979
- Luhman JGR 1984

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- Y

## 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 Song&Russell ‘94, tbd and Wolf ‘97

- 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 Song&Russell ‘94, tbd and Wolf ‘97

**Dayside High Latitude Reconnection**

- Approx.
- Magnetopause

## 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. 2000/05/08-07:30
- Low latitude reconnection pumping dayside plasma and flux into magnetosheath upstream of high lat. Site
- Simultaneous, long-lived high & low lat reconnection.

## Simultaneous Hi/Lo Lat Reconnection Sites: 			NBz				SBZ

**Chandler et al. 10/99 JGR?**

- Pumps lobe plasma

- Pumps Plasmsphere

- Rates
- dep. on
- IMF, Pdyn

**Savin et al. 02/00 ISTP?**

- Pumps Plasmsphere

- Pumps Lobe Plasma

- Rates
- dep. on
- IMF, Pdyn

## Component Reconnection: Neutral Line Orientation for Varying Magnetic Shear

- 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 (Gonzalez&Mozer’74?)

- Simplified for equal fields;
- More generally, NL has equal normal components

## Dayside Reconnection for Typical Shear= 90; Bz = 0 

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## Dayside Reconnection with Atypical Shear: 	  ≤ 90; NBZ			  ≥ 90; SBZ 

- Low shear

- High Shear

- Low shear

- High Shear

- High Shear

- Low shear

- Opened
- Flux
- Tubes

- Opened
- Flux Tubes

**Dayside Reconnection with Atypical Shear: ****	**** ******** ≤ 90; NBZ****	****	****	**** ******** ≥ 90; SBZ **

- 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

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

**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 component reconnection

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