11.1 Magnetic Dipole Field

11.1 Magnetic Dipole Field (2) B 

11.1 Magnetic Dipole Field (3) B BB BrBr dr rd  r  r

11.2 Geomagnetic Field

11.2 Geomagnetic Field (2)

11.3 Geomagnetic variations

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

11.3 Geomagnetic variations (2) Disturbance field D=B-B Sq -B L –D=D st -D s D st is the storm-time variation caused by the ring current disturbances D s 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 –0 0, 0 +, 1 -, 1 0, 1 +, 2 -, … 9 -, 9 0, 9 + –Planetary Kp index: average of the 12 stations

11.4 Ionospheric Layers

11.4 Ionospheric Layers (2)

11.4 Ionospheric Layers (3)

11.4 Ionospheric Layers (4)

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: F a ~g, dT/dz, dn/dz F a|| =F a sinI u az =u a|| sinI See Fig.11.7 for effects of neutral wind and E. I FaFa u az F a || B u a|| I

11.4 Ionospheric Layers (5)