Gourt > Science > Physics > Plasma > Space Plasmas
An astrophysical plasma is a plasma (an ionized gas) found in astronomy whose physical properties are studied in the science of astrophysics. The vast majority of the baryonic matter of the universe is thought to consist of plasma, a state of matter in which atoms and molecules are so hot, that they have ionized by breaking up into their constituent parts, negatively charged electrons and positively charged ions. Although influenced by gravity, because the particles are charged, they are also strongly influenced by electromagnetic forces, that is, by magnetic and electric fields.
All known astrophysical plasmas are magnetic. They also contain equal numbers of electrons and ions so that they are electrically neutral overall. And because plasmas are highly conductive, any charge imbalances are readily neutralised. However, because plasma phenonenon are very complex, charge imbalances can occur, resulting in a characteristic known as quasineutrality. An example is the influence of our Sun's magnetic field on the electrons and ions in the interplanetary medium (or Solar wind) resulting in the heliospheric current sheet, the largest structure in the Solar system.
Characteristics
Space plasma pioneers Hannes Alfvén and Carl-Gunne Fälthammar divided cosmic plasmas into three different categories (note that other characteristics of low-particle-density interstellar and intergalactic plasmas, means that they are characterised as medium density):
| 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 Ionopshere above 70km | 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 (eg. between mirror points) | Oscillations (eg. between mirror points) |
| Debye Distance λD | λD << lc | λD << lc | λD << lc | λD >> lc |
| Magnetohydrodynamics suitability | Yes | Approximately | No | No |
Adapted From Cosmical Electrodynamics (2nd Ed. 1952) Alfvén and Fälthammar
Interstellar Medium :: Astronomy
Solar System :: Astronomy
Astrophysics :: Physics
Magnetoconvection in sheared magnetic fields
N. H. Bian and O. E. Garcia The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resis ... [Phys. Plasmas 15, 102901 (2008)] published Wed Oct 1, 2008.
Modulational instability of electromagnetic electron-cyclotron wave packets in the magnetosphere with non-Maxwellian electron distribution
H. Abbasi and H. Hakimi Pajouh The satellite observations of the magnetosphere in the low-frequency ion dynamics revealed several facts: (1) localized structures for electric field signal parallel to the magnetic field; (2) anisotropy for the electron velocity distribution such that T<
V. S. Mikhailenko, V. V. Mikhailenko, and K. N. Stepanov The effect of transverse velocity shear of plasma flow parallel to the embedded magnetic field on the generation of electrostatic ion cyclotron waves is studied analytically by using kinetic formalism. It is found that electron-neutral collisions are destabilizing, as it is in shearless plasma flows ... [Phys. Plasmas 15, 092901 (2008)] published Mon Sep 15, 2008.
CLUSTER satellite - Magnetospheric physics with the 4 CLUSTER satellites
Darthmouth University Space Plasma Theory - Physics of the inner magnetosphere
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Imperial College Space Physics Department - Homepage of Imperial College's Space Physics group
ISCAT - The company provides modelling and numerical simulations for space plasmas related issues.
Lockheed Martin Space Plasmas Group - The Space Physics Laboratory (LMSPL) is a Department within Lockheed Martin Missiles and Space Company's Advanced Technology Center.
Microgravity Combustion Science - A NASA-Glenn Research Center site devoted to microgravity and combustion science experiments.
Modeling of the Atmosphere Magnetosphere Ionosphere System (MAMI) - This investigation is part of the International Solar Terrestrial Project (ISTP). The program combines satellite and ground based observations with theory and modeling to better understand the energetics and dynamics of the near Earth environment.
NASA Cosmic and Heliospheric Learning Center - Tutorial on solar wind, calendar of solar wind meetings and activities, links to solar wind news articles.
Meta Description: [ Cosmicopia at NASA/GSFC -- Sun -- Solar Wind ]
NGDC/STP - On-Line Glossary of Solar-Terrestrial Terms - Extensive glossary of space plasma and heliospheric lingo.
Meta Description: [ NOAA National Geophysical Data Center Solar-Terrestrial Physics Division and collocated World Data Center for Solar-Terrestrial Physics, Boulder. ]
Our Star, The Sun - A short tutorial (in English and Spanish) about the Sun and solar effects on Earth prepared at the Space Environment Laboratory of the National Oceanic and Atmospheric Administration.
Plasmas - the 4th State of Matter - Tutorial on many types of plasmas by Contemporary Physics Education Project.
Rutherford Appleton Laboratory - Space Science and Technology Department, Rutherford Appleton Laboratory
Solar Physics Tutorial by Marshall Space Flight Center - The site offers an extensive introduction to the sun and space weather, including news stories and related projects.
Space and Plasma Physics at Univ Maryland - SPP Group conducts research in many areas of space and plasma physics
Space Plasma Group, University of London - Simulations of space plasmas and experimental spacecraft data analysis.
Space Plasma Physics - Science projects: Investigations of the auroral phenomenon, magnetic fields and electrodynamics of dense interstellar plasma clouds. Based at the Alfvén Laboratory, Royal Institute of Technology in Stockholm, Sweden.
Meta Description: [ Space and Plasma Physics, Alfvén Laboratory, School of Electrical Engineering, Royal Institute of Technology (KTH), Stockholm. ]
Space Plasma Physics at RAL - Space Plasma Physics at RAL. Plasma, Research fields, People, Space missions with which the Rutherford Appleton Laboratory is or has been involved.
Meta Description: [ Solar System Science at the Rutherford Appleton Laboratory ]
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Space Plasma Simulations Group at UCLA - Global magnetosphere simulations.
Meta Description: [ San Diego Super Computer Center ]
Space Wander - Fly through the Universe. Explore space plasma and deep-space mysteries. Real space pictures from NASA. In English, French, Italian, Spanish and Russian.
Meta Description: [ Fly to Mars and Jupiter! Travel through deep space! SpaceWander's award-winning multimedia space trip features real NASA images! Check out our space store for space book, space videos, telescopes, and NASA hats. You can even buy a REAL SPACE TRAVEL! SpaceWander's trip through the Universe fea... ]
U. Iowa Space Plasma Wave Research - Site of the University of Iowa research group describes various undertaken space plasma wave projects including those involving Earth-orbiting and planetary spacecraft.
Meta Description: [ Web home of the radio and plasma wave research group led by Professor Donald Gurnett at the University of Iowa ]
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UCSD Solar and Heliospheric Physics Group - The site describes a number of UCSD projects on solar and heliospheric physics including the solar mass ejection imager and space weather forecasting.
Meta Description: [ UCSD's Center for Astrophysics & Space Sciences Solar and Heliospheric Phsyics Group-
UCSD's research unit in solar and heliospheric physics ]
University of New Hampshire Experimental Space Plasma Group - Satellite and sounding rocket experiments
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