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
Read more about this topic: Astrophysical Plasma
Famous quotes containing the word space:
“Sir Walter Raleigh might well be studied, if only for the excellence of his style, for he is remarkable in the midst of so many masters. There is a natural emphasis in his style, like a man’s tread, and a breathing space between the sentences, which the best of modern writing does not furnish. His chapters are like English parks, or say rather like a Western forest, where the larger growth keeps down the underwood, and one may ride on horseback through the openings.”
—Henry David Thoreau (1817–1862)