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The Magnetosphere

The Magnetosphere. Feifei Jiang, UCLA. fjiang@igpp.ucla.edu. Outline. Magnetic field Plasmas Currents Force Balance. The Earth’s Main Field. Dipole in spherical coordinates. L. L0. Dipole field lines. The Stretched Tail. Magnetic Reconnection. Viscous Interaction.

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The Magnetosphere

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  1. The Magnetosphere Feifei Jiang, UCLA fjiang@igpp.ucla.edu

  2. Outline • Magnetic field • Plasmas • Currents • Force Balance

  3. The Earth’s Main Field Dipole in spherical coordinates L L0 Dipole field lines

  4. The Stretched Tail Magnetic Reconnection Viscous Interaction

  5. The Tail Plasma Sheet Plasma parameters in the central plasma sheet E B N = 0.1~0.5 cm-3 Ti = 2~10 keV Ti/Te = 6 EXB Mantle particles will ExB drift towards the center of the tail To move from the center of mantle to the center of plasma sheet

  6. The Radiation Belts • One proton belt: • 0.1~ 100 MeV, peak near L~1.8 • Two electron belts with a slot region: • For E> 1 MeV peak near L=1.6 and 4.0 Re Source: ~keV particles in the plasma sheet How are these particles energized? 1. Acceleration by chorus waves 2. Radial diffusion 3. Substorm injection

  7. The Plasmasphere Guiding center drift velocity • Cold, dense plasmas: • ~103 cm-3, ~1 eV • Plasmapause, 3~5 Re depending on geomagnetic activity • 2 sources: Polar wind and convection Stagnation Point

  8. Currents in the Magnetosphere

  9. Magnetopause Current The current crossing y=y0 per unit length in z

  10. Tail Current

  11. Field-aligned current Region 1 current: Flow shear/parallel flow vorticity Region 2 current: surfaces of constant pressure are not aligned with magnetic shells

  12. Ring Current Magnetic field of a current loop Dessler-Parker-Sckopke relationship

  13. Force Balance At the magnetopause nose K=0.89, a ~ 2.4 At the magnetopause on the tail side At the tail plasma sheet

  14. Thank you

  15. Particle Motion in the Magnetosphere

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