The Plasmaspheric Shoulder

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The Plasmaspheric Shoulder
Daniel Ober Dennis Gallagher
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Shoulder
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Studies From the 60s and 70s

• Previous studies have observed a pattern of
  localized westward followed by eastward
  convection electric fields following storm onset.
• This is found through whistler measurements of
  nightside radially inward, then outward,
  convection of the plasmapause.

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Wiemer Electric Field Model
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Electric Potential Pattern in the Equatorial
Magnetosphere
0300 UT May 24
Kp 8
Westward electric field
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Equipotential Contours
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Plasmasphere Model Setup
Electric field Used modified Sojka et al JGR,
1986 two-cell convection pattern with additional
substorm related electric field. Electric field
strength parameterized by Kp. Substorm electric
field on for 1 hour (0300-0400 UT). Magnetic
field Tsyganenko T96 magnetic field
model. Model is driven by actual Kp index.
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Electric Potential Patterns in the Equatorial
Magnetosphere
0300 UT May 24
1200 UT May 24
1200 UT May 23
Kp 2
Kp 8
Kp 5
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Plasmasphere Model Results
1200 UT
0400 UT
0800 UT
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Observed Plasmasphere
Modeled Plasmasphere
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So Where Do We Go?

• How can shoulder formation mechanism be
  confirmed?
• Voids formation? And filling?
• Fingers voids?
• Small-scale structures?
• Reduced density channel formation?
• H/He ratio? PP?

• Reduce numerical diffusion
• PS Ring current interaction
• PS Superthermal electron population interaction
• Meso-scale ionospheric sources and losses
• Electric fields

Domination of What
Domination of How