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Understanding the Magnetosphere: Forces and Particle Motion

Explore the magnetic field, plasmas, currents, and force balance in the Earth's magnetosphere. Learn about radiation belts, plasma parameters, particle energization, and guiding center drift velocity in the plasmasphere.

hubertrichards
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Understanding the Magnetosphere: Forces and Particle Motion

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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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