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On the transition from collisionless to collisional magnetohydrodynamics
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| Zeitschriftentitel: | Journal of Geophysical Research: Space Physics |
|---|---|
| Personen und Körperschaften: | , |
| In: | Journal of Geophysical Research: Space Physics, 106, 2001, A2, S. 1955-1960 |
| Format: | E-Article |
| Sprache: | Englisch |
| veröffentlicht: |
American Geophysical Union (AGU)
|
| Schlagwörter: |
| author_facet |
Strangeway, R. J. Raeder, J. Strangeway, R. J. Raeder, J. |
|---|---|
| author |
Strangeway, R. J. Raeder, J. |
| spellingShingle |
Strangeway, R. J. Raeder, J. Journal of Geophysical Research: Space Physics On the transition from collisionless to collisional magnetohydrodynamics Paleontology Space and Planetary Science Earth and Planetary Sciences (miscellaneous) Atmospheric Science Earth-Surface Processes Geochemistry and Petrology Soil Science Water Science and Technology Ecology Aquatic Science Forestry Oceanography Geophysics |
| author_sort |
strangeway, r. j. |
| spelling |
Strangeway, R. J. Raeder, J. 0148-0227 American Geophysical Union (AGU) Paleontology Space and Planetary Science Earth and Planetary Sciences (miscellaneous) Atmospheric Science Earth-Surface Processes Geochemistry and Petrology Soil Science Water Science and Technology Ecology Aquatic Science Forestry Oceanography Geophysics http://dx.doi.org/10.1029/2000ja900116 <jats:p>Magnetosphere‐ionosphere coupling entails the interaction of two quite different plasmas. The magnetosphere is to a large extent a collisionless magnetohydrodynamic (MHD) fluid, while the ionosphere is strongly collisional. As such the relationship between the electric currents and electric field appear to be fundamentally different in the two regimes. For the magnetosphere the currents are determined by the forces within the plasma, while in the ionosphere the current and electric field are related through an anisotropic Ohm's law. Here we explore the transition between these two regimes and show that there is a clear ordering of the governing equations, with a single “collisional Ohm's law” that contains both the collision‐frequency‐dependent Pedersen and Hall conductivities and collisionless MHD terms, without making any prior assumptions concerning the ordering of the collision frequencies. The generalized Ohm's law of MHD is also present, but this equation reduces to the statement that within the ionosphere the magnetic field is “frozen” to the electron fluid, unless electron collision frequencies become comparable to the electron gyrofrequency. It is the freezing‐in of the electron fluid that leads to the direct equivalence of mechanical and electromagnetic loads. This equivalence of loads also indicates that Poynting flux traveling upward out of the ionosphere can only occur if there is a convergence of horizontal Poynting flux in excess of the ionospheric Joule dissipation.</jats:p> On the transition from collisionless to collisional magnetohydrodynamics Journal of Geophysical Research: Space Physics |
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10.1029/2000ja900116 |
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Geologie und Paläontologie Geographie Chemie und Pharmazie Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft Biologie Allgemeine Naturwissenschaft Physik Technik |
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American Geophysical Union (AGU), 2001 |
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| title |
On the transition from collisionless to collisional magnetohydrodynamics |
| title_unstemmed |
On the transition from collisionless to collisional magnetohydrodynamics |
| title_full |
On the transition from collisionless to collisional magnetohydrodynamics |
| title_fullStr |
On the transition from collisionless to collisional magnetohydrodynamics |
| title_full_unstemmed |
On the transition from collisionless to collisional magnetohydrodynamics |
| title_short |
On the transition from collisionless to collisional magnetohydrodynamics |
| title_sort |
on the transition from collisionless to collisional magnetohydrodynamics |
| topic |
Paleontology Space and Planetary Science Earth and Planetary Sciences (miscellaneous) Atmospheric Science Earth-Surface Processes Geochemistry and Petrology Soil Science Water Science and Technology Ecology Aquatic Science Forestry Oceanography Geophysics |
| url |
http://dx.doi.org/10.1029/2000ja900116 |
| publishDate |
2001 |
| physical |
1955-1960 |
| description |
<jats:p>Magnetosphere‐ionosphere coupling entails the interaction of two quite different plasmas. The magnetosphere is to a large extent a collisionless magnetohydrodynamic (MHD) fluid, while the ionosphere is strongly collisional. As such the relationship between the electric currents and electric field appear to be fundamentally different in the two regimes. For the magnetosphere the currents are determined by the forces within the plasma, while in the ionosphere the current and electric field are related through an anisotropic Ohm's law. Here we explore the transition between these two regimes and show that there is a clear ordering of the governing equations, with a single “collisional Ohm's law” that contains both the collision‐frequency‐dependent Pedersen and Hall conductivities and collisionless MHD terms, without making any prior assumptions concerning the ordering of the collision frequencies. The generalized Ohm's law of MHD is also present, but this equation reduces to the statement that within the ionosphere the magnetic field is “frozen” to the electron fluid, unless electron collision frequencies become comparable to the electron gyrofrequency. It is the freezing‐in of the electron fluid that leads to the direct equivalence of mechanical and electromagnetic loads. This equivalence of loads also indicates that Poynting flux traveling upward out of the ionosphere can only occur if there is a convergence of horizontal Poynting flux in excess of the ionospheric Joule dissipation.</jats:p> |
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| author | Strangeway, R. J., Raeder, J. |
| author_facet | Strangeway, R. J., Raeder, J., Strangeway, R. J., Raeder, J. |
| author_sort | strangeway, r. j. |
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| container_start_page | 1955 |
| container_title | Journal of Geophysical Research: Space Physics |
| container_volume | 106 |
| description | <jats:p>Magnetosphere‐ionosphere coupling entails the interaction of two quite different plasmas. The magnetosphere is to a large extent a collisionless magnetohydrodynamic (MHD) fluid, while the ionosphere is strongly collisional. As such the relationship between the electric currents and electric field appear to be fundamentally different in the two regimes. For the magnetosphere the currents are determined by the forces within the plasma, while in the ionosphere the current and electric field are related through an anisotropic Ohm's law. Here we explore the transition between these two regimes and show that there is a clear ordering of the governing equations, with a single “collisional Ohm's law” that contains both the collision‐frequency‐dependent Pedersen and Hall conductivities and collisionless MHD terms, without making any prior assumptions concerning the ordering of the collision frequencies. The generalized Ohm's law of MHD is also present, but this equation reduces to the statement that within the ionosphere the magnetic field is “frozen” to the electron fluid, unless electron collision frequencies become comparable to the electron gyrofrequency. It is the freezing‐in of the electron fluid that leads to the direct equivalence of mechanical and electromagnetic loads. This equivalence of loads also indicates that Poynting flux traveling upward out of the ionosphere can only occur if there is a convergence of horizontal Poynting flux in excess of the ionospheric Joule dissipation.</jats:p> |
| doi_str_mv | 10.1029/2000ja900116 |
| facet_avail | Online, Free |
| finc_class_facet | Geologie und Paläontologie, Geographie, Chemie und Pharmazie, Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft, Biologie, Allgemeine Naturwissenschaft, Physik, Technik |
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| imprint | American Geophysical Union (AGU), 2001 |
| imprint_str_mv | American Geophysical Union (AGU), 2001 |
| institution | DE-Gla1, DE-Zi4, DE-15, DE-Rs1, DE-Pl11, DE-105, DE-14, DE-Ch1, DE-L229, DE-D275, DE-Bn3, DE-Brt1, DE-Zwi2, DE-D161 |
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| physical | 1955-1960 |
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| series | Journal of Geophysical Research: Space Physics |
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| spelling | Strangeway, R. J. Raeder, J. 0148-0227 American Geophysical Union (AGU) Paleontology Space and Planetary Science Earth and Planetary Sciences (miscellaneous) Atmospheric Science Earth-Surface Processes Geochemistry and Petrology Soil Science Water Science and Technology Ecology Aquatic Science Forestry Oceanography Geophysics http://dx.doi.org/10.1029/2000ja900116 <jats:p>Magnetosphere‐ionosphere coupling entails the interaction of two quite different plasmas. The magnetosphere is to a large extent a collisionless magnetohydrodynamic (MHD) fluid, while the ionosphere is strongly collisional. As such the relationship between the electric currents and electric field appear to be fundamentally different in the two regimes. For the magnetosphere the currents are determined by the forces within the plasma, while in the ionosphere the current and electric field are related through an anisotropic Ohm's law. Here we explore the transition between these two regimes and show that there is a clear ordering of the governing equations, with a single “collisional Ohm's law” that contains both the collision‐frequency‐dependent Pedersen and Hall conductivities and collisionless MHD terms, without making any prior assumptions concerning the ordering of the collision frequencies. The generalized Ohm's law of MHD is also present, but this equation reduces to the statement that within the ionosphere the magnetic field is “frozen” to the electron fluid, unless electron collision frequencies become comparable to the electron gyrofrequency. It is the freezing‐in of the electron fluid that leads to the direct equivalence of mechanical and electromagnetic loads. This equivalence of loads also indicates that Poynting flux traveling upward out of the ionosphere can only occur if there is a convergence of horizontal Poynting flux in excess of the ionospheric Joule dissipation.</jats:p> On the transition from collisionless to collisional magnetohydrodynamics Journal of Geophysical Research: Space Physics |
| spellingShingle | Strangeway, R. J., Raeder, J., Journal of Geophysical Research: Space Physics, On the transition from collisionless to collisional magnetohydrodynamics, Paleontology, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Atmospheric Science, Earth-Surface Processes, Geochemistry and Petrology, Soil Science, Water Science and Technology, Ecology, Aquatic Science, Forestry, Oceanography, Geophysics |
| title | On the transition from collisionless to collisional magnetohydrodynamics |
| title_full | On the transition from collisionless to collisional magnetohydrodynamics |
| title_fullStr | On the transition from collisionless to collisional magnetohydrodynamics |
| title_full_unstemmed | On the transition from collisionless to collisional magnetohydrodynamics |
| title_short | On the transition from collisionless to collisional magnetohydrodynamics |
| title_sort | on the transition from collisionless to collisional magnetohydrodynamics |
| title_unstemmed | On the transition from collisionless to collisional magnetohydrodynamics |
| topic | Paleontology, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Atmospheric Science, Earth-Surface Processes, Geochemistry and Petrology, Soil Science, Water Science and Technology, Ecology, Aquatic Science, Forestry, Oceanography, Geophysics |
| url | http://dx.doi.org/10.1029/2000ja900116 |