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

2. 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

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

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

5. Magnetosphere
Fast and Slow Wind

6. 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

7. 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

8. Current System

9. 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

10. 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

11. 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

12. 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

13. Gyration Motion
Fast and Slow Wind

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

15. Drift Motion: E X B Drift
Fast and Slow Wind

16. Drift Motion: Gravitation
Fast and Slow Wind

17. Drift Motion: Magnetic Gradient
Fast and Slow Wind

18. Drift Motion: Magnetic Curvature
Fast and Slow Wind

19. Drift Current
Fast and Slow Wind

20. 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

21. First Adiabatic Invariant:
The Magnetic Moment
Fast and Slow Wind

22. Bouncing Motion and
Magnetic Mirroring
Fast and Slow Wind

23. Second Adiabatic Invariant: Longitudinal Invariant
Fast and Slow Wind

24. Third Adiabatic Invariant:
Flux Invariant
Fast and Slow Wind

25. The End