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11.1 Magnetic Dipole Field

11.1 Magnetic Dipole Field

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11.1 Magnetic Dipole Field

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  1. 11.1 Magnetic Dipole Field

  2. 11.1 Magnetic Dipole Field (2) I B

  3. 11.1 Magnetic Dipole Field (3) r Br B dr r rdq Bq q

  4. 11.2 Geomagnetic Field

  5. 11.2 Geomagnetic Field (2)

  6. 11.3 Geomagnetic variations

  7. 11.3 Geomagnetic variations (1) The geomagnetic field shows significant variability during quiet times and magnetically disturbed periods. Quiet time variability results from tidal waves caused by solar heating and lunar gravitational forces. Tidal motion moves ions across field lines generating dynamo electric fields. Solar-quiet current system – Sq currents Lunar current system – L currents

  8. 11.3 Geomagnetic variations (2) Disturbance field D=B-BSq-BL D=Dst-Ds Dst is the storm-time variation caused by the ring current disturbances Ds is the disturbance caused by auroral particle precipitation Kp index Local K index: 12 stations (in the northern mid-latitudes) measure the average magnetic variation for every 3 hours with log scale 00, 0+, 1-, 10, 1+, 2-, … 9-, 90, 9+ Planetary Kp index: average of the 12 stations

  9. 11.4 Ionospheric Layers

  10. 11.4 Ionospheric Layers (2)

  11. 11.4 Ionospheric Layers (3)

  12. 11.4 Ionospheric Layers (4)

  13. 11.4 Dominant Processes in the Ionosphere • E and F1 region: photochemistry is dominant • F2 region: photochemistry and diffusion • Topside F2 region: diffusion is dominant • Plasma motion along B • Ambipolar diffusive forces are vertical: Fa~g, dT/dz, dn/dz Fa||=FasinI uaz=ua||sinI See Fig.11.7 for effects of neutral wind and E. I Fa|| Fa I ua|| uaz B

  14. 11.4 Ionospheric Layers (5)