Space Plasma Characteristics
Space plasma pioneers Hannes Alfvén and Carl-Gunne Fälthammar divided the plasmas in the solar system into three different categories:
| Classification of Magnetic Cosmic Plasmas |
| Characteristic |
Space plasma density categories
(Note that density does not refer to only particle density) |
Ideal comparison |
| High density |
Medium Density |
Low Density |
| Criterion |
λ << ρ |
λ << ρ << lc |
lc << λ |
lc << λD |
| Examples |
Stellar interior
Solar photosphere |
Solar chromosphere/corona
Interstellar/intergalactic space
Ionosphere above 70 km |
Magnetosphere during
magnetic disturbance.
Interplanetary space |
Single charges
in a high vacuum |
| Diffusion |
Isotropic |
Anisotropic |
Anisotropic and small |
No diffusion |
| Conductivity |
Isotropic |
Anisotropic |
Not defined |
Not defined |
Electric field parallel to B
in completely ionized gas |
Small |
Small |
Any value |
Any value |
Particle motion in plane
perpendicular to B |
Almost straight path
between collisions |
Circle
between collisions |
Circle |
Circle |
Path of guiding centre
parallel to B |
Straight path
between collisions |
Straight path
between collisions |
Oscillations
(e.g. between mirror points) |
Oscillations
(e.g. between mirror points) |
| Debye Distance λD |
λD << lc |
λD << lc |
λD << lc |
λD >> lc |
Magnetohydrodynamics
suitability |
Yes |
Approximately |
No |
No |
|
| λ=Mean free path. ρ= Larmor radius (gyroradius) of electron. λD=Debye length. lc=Characteristic length |
|