A Brief Introduction to Space Plasma Physics.pdf - Institute of ...

• Any force capable of accelerating and decelerating
charged particles can cause
r r
them to drift.
r F × B
u F
=
2
qB
– If the force is charge independent the drift motion will
depend on the sign of the charge and can form
perpendicular currents.
• Changing magnetic fields cause a drift velocity.
– If B r changes over a gyro-orbit the radius of curvature will
change.
mv⊥
– ρc
= gets smaller when the particle goes into a region of
qB
stronger B. Thus the drift is opposite to that of E
r B
r
r r × motion.
r
−1
2 ∇B
× B
1 2 B × ∇B
u g
=
2
mv⊥
=
3 2
mv⊥
3
qB
qB
– u g depends on the charge so it can yield perpendicular
currents.