Magnetosphere Ionosphere Coupling IonosphericPerspective.pdf

Rod Heelis, U.T. Dallas, GEM/CEDAR, 2005 M/I Coupling Slide 1 Magnetosphere Ionosphere Coupling: Ionospheric Perspective Outline ? Current Systems Connecting the Ionosphere and Magnetosphere ? Electromagnetic Energy Inputs Joule Heating, Momentum Coupling, Poynting Vector ? Particle Energy Inputs Electrical Coupling, Particle Acceleration ? Ionospheric Plasma Outflow ? Alfven Waves Rod Heelis, U.T. Dallas, GEM/CEDAR, 2005 M/I Coupling Slide 2 Magnetosphere Ionosphere Coupling Magnetospheric Currents Perpendicular to B produced plasma pressure gradients and magnetic field stresses. Ionospheric Currents Perpendicular to B produced by electric fields and neutral winds. Gradients in these currents require field aligned currents that must be consistent. Electric fields produced in the magnetosphere and ionosphere will modify the horizontal currents ( directly in the ionosphere ; indirectly in the magnetosphere) to make the field-aligned currents consistent. In the ionosphere ExB drift motion of the plasma is coupled to the neutral gas through collisions. The changing ionosphere and thermosphere change the conductivity. Precipitating particles carrying field-aligned currents change the ionospheric conductivity. Thus the E+UxB current is modified. The ionosphere-thermosphere is an active element in the circuit. It is both a source and a sink in the circuit. Rod Heelis, U.T. Dallas, GEM/CEDAR, 2005 M/I Coupling Slide 3 Jtail Jneutral sheet Jring Jpartial ring Magnetosphere Ionosphere Coupling A divergence in the horizontal current must be accompanied by a change in the field- aligned currents. If this condition cannot be satisfied by the original driver then a polarization electric field is established to modify the current. In the magnetosphere the requirement for closed loop flows demands that field-a