Introduction to Space Weather Magnetosphere: Plasma, Current and Particles Oct. 29, 2009 CSI 662 / PHYS 660 Fall, 2009 Jie Zhang Copyright ©

Roadmap Part 1: The Sun Part 2: The Heliosphere Part 3: The Magnetosphere Part 4: The Ionsophere Part 5: Space Weather Effects Part 3: The Magnetosphere Topology Plasmas and Currents Geomagnetic Activities

The Magnetosphere: Plasma and Currents CSI 662 / PHYS 660 October 22 2009 The Magnetosphere: Plasma and Currents References: Kallenrode: Chap. 8.3 and 8.7 Prolss: Chap. 5

Plasma Physics Charged Particles in Electromagnetic Fields: Reference: Kallenrode, Chap. 2 Particle Gyration motion and Lorentz force Particle Drifts in Electromagnetic Field Adiabatic Invariance

Magnetosphere Fast and Slow Wind

Plasmasphere Plasmasphere is dominated by a dense and cold plasma of ionospheric origin, e.g, O+, N+ L shell: 1.2 – 5 Density: 10000 (inner) particles cm-3 100 (outer) particles cm-3 Low energy particles, ~ 1ev e.g, 0.6 ev: gyro = 0.1 s, bounce = 2 hour, drift = 45 year Corotation with the Earth Density is extremely low, e.g., 0.1 particles cm-3 , in other magnetospheric regions outside the plasmasphere

Magnetotail Plasma Sheet Plasma sheet is a slab-like particle population centered on the mid-plane of the magnetotail It separates the tail into two lobes: north lobe and south lobe There is a magnetic polarity reversal across this sheet Populated by medium energetic particles (5 kev) Reservoir of particles which precipitate and produce aurora Plasma sheet is highlighted in yellow Fast and Slow Wind

Current System

Magnetopause Current: Dayside Also called Chapman-Ferraro current Separating Earth’s magnetic field and plasma from the solar wind Current is induced when charged particles are deflected by the magnetopause magnetic field Stagnation point: at the nose, SW speed becomes zero Location: ~ 10 RE Fast and Slow Wind

Tail Currents and Neutral Sheet Current Cross-tail current in the magnetopause Neutral sheet current on the equatorial plane These two currents form a closed circuit in the magneto-tail Partially closed with ionosphere during storm time Fast and Slow Wind

Ring Current Fast and Slow Wind L shell: 3 – 6 The ring current is caused by azimuthal drift of charged particles Particles are of medium energy e.g., 1 – 200 kev Particles originate from both ionosphere and solar wind Particle density can increase greatly during disturbed solar wind condition, thus increase ring current significantly, causing geomagnetic storms. Fast and Slow Wind

Motion of Charged Particles Charged particles are trapped in the inner magnetosphere, subject to the following three types of motion (Kallenrode CH2) Gyration Bounce motion Drift motion Fast and Slow Wind

Gyration Motion Fast and Slow Wind

Drift Motion (Kallenrode: Table 2.2) Fast and Slow Wind

Drift Motion: E X B Drift Fast and Slow Wind

Drift Motion: Gravitation Fast and Slow Wind

Drift Motion: Magnetic Gradient Fast and Slow Wind

Drift Motion: Magnetic Curvature Fast and Slow Wind

Drift Current Fast and Slow Wind

Adiabatic Invariants Fast and Slow Wind Periodic motion can be characterized by a conserved quantity under adiabatic condition: The general form in terms of p and q, the generalized momentum and coordinate Fast and Slow Wind

First Adiabatic Invariant: The Magnetic Moment Fast and Slow Wind

Bouncing Motion and Magnetic Mirroring Fast and Slow Wind

Second Adiabatic Invariant: Longitudinal Invariant Fast and Slow Wind

Third Adiabatic Invariant: Flux Invariant Fast and Slow Wind

The End