Abstract
The strong inhomogeneities in plasma parameters in the ionosphere and adjacent regions can trap waves in the upper end of the ULF range (Pc1/Pi1). The topside ionosphere is characterized by a rapidly increasing Alfvén speed with a scale height on the order of 1000 km. Shear-mode Alfvén waves in this region can be partially trapped at frequencies in the 0.1-1.0 Hz range. The same structure can trap fast-mode compressional waves in this frequency band. Since these waves can propagate across magnetic field lines, this structure constitutes a waveguide in which energy can propagate at speeds comparable to the Alfvén speed, typically on the order of 1000 km/s. Hall effects in the ionosphere couple these two wave modes, so that the introduction of a field-aligned current by means of a shearmode Alfvén wave can excite compressional waves that can propagate in the waveguide. In the limit of infinite ionospheric conductivity, these waves are isolated from the atmospheric fields; however, for finite conductivity, ionospheric and atmospheric waves are coupled. Transverse magnetic modes in the atmosphere can propagate at ULF frequencies and form global Schumann resonances with the fundamental at 8 Hz. It has been suggested that signals that propagate at the speed of light through this atmospheric waveguide can rapidly transmit signals from the polar region to lower latitudes during sudden storm commencements.
| Original language | English |
|---|---|
| Title of host publication | Magnetospheric ULF Waves |
| Subtitle of host publication | Synthesis and New Directions, 2006 |
| Publisher | Blackwell Publishing Ltd. |
| Pages | 289-306 |
| Number of pages | 18 |
| ISBN (Electronic) | 9781118666319 |
| ISBN (Print) | 9780875904344 |
| DOIs | |
| Publication status | Published - Jan 1 2006 |
Publication series
| Name | Geophysical Monograph Series |
|---|---|
| Volume | 169 |
| ISSN (Print) | 0065-8448 |
| ISSN (Electronic) | 2328-8779 |
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All Science Journal Classification (ASJC) codes
- Geophysics
Cite this
Resonant cavities and waveguides in the ionosphere and atmosphere. / Lysak, R. L.; Yoshikawa, Akimasa.
Magnetospheric ULF Waves: Synthesis and New Directions, 2006. Blackwell Publishing Ltd., 2006. p. 289-306 (Geophysical Monograph Series; Vol. 169).Research output: Chapter in Book/Report/Conference proceeding › Chapter
}
TY - CHAP
T1 - Resonant cavities and waveguides in the ionosphere and atmosphere
AU - Lysak, R. L.
AU - Yoshikawa, Akimasa
PY - 2006/1/1
Y1 - 2006/1/1
N2 - The strong inhomogeneities in plasma parameters in the ionosphere and adjacent regions can trap waves in the upper end of the ULF range (Pc1/Pi1). The topside ionosphere is characterized by a rapidly increasing Alfvén speed with a scale height on the order of 1000 km. Shear-mode Alfvén waves in this region can be partially trapped at frequencies in the 0.1-1.0 Hz range. The same structure can trap fast-mode compressional waves in this frequency band. Since these waves can propagate across magnetic field lines, this structure constitutes a waveguide in which energy can propagate at speeds comparable to the Alfvén speed, typically on the order of 1000 km/s. Hall effects in the ionosphere couple these two wave modes, so that the introduction of a field-aligned current by means of a shearmode Alfvén wave can excite compressional waves that can propagate in the waveguide. In the limit of infinite ionospheric conductivity, these waves are isolated from the atmospheric fields; however, for finite conductivity, ionospheric and atmospheric waves are coupled. Transverse magnetic modes in the atmosphere can propagate at ULF frequencies and form global Schumann resonances with the fundamental at 8 Hz. It has been suggested that signals that propagate at the speed of light through this atmospheric waveguide can rapidly transmit signals from the polar region to lower latitudes during sudden storm commencements.
AB - The strong inhomogeneities in plasma parameters in the ionosphere and adjacent regions can trap waves in the upper end of the ULF range (Pc1/Pi1). The topside ionosphere is characterized by a rapidly increasing Alfvén speed with a scale height on the order of 1000 km. Shear-mode Alfvén waves in this region can be partially trapped at frequencies in the 0.1-1.0 Hz range. The same structure can trap fast-mode compressional waves in this frequency band. Since these waves can propagate across magnetic field lines, this structure constitutes a waveguide in which energy can propagate at speeds comparable to the Alfvén speed, typically on the order of 1000 km/s. Hall effects in the ionosphere couple these two wave modes, so that the introduction of a field-aligned current by means of a shearmode Alfvén wave can excite compressional waves that can propagate in the waveguide. In the limit of infinite ionospheric conductivity, these waves are isolated from the atmospheric fields; however, for finite conductivity, ionospheric and atmospheric waves are coupled. Transverse magnetic modes in the atmosphere can propagate at ULF frequencies and form global Schumann resonances with the fundamental at 8 Hz. It has been suggested that signals that propagate at the speed of light through this atmospheric waveguide can rapidly transmit signals from the polar region to lower latitudes during sudden storm commencements.
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UR - http://www.scopus.com/inward/citedby.url?scp=84969268834&partnerID=8YFLogxK
U2 - 10.1029/169GM19
DO - 10.1029/169GM19
M3 - Chapter
SN - 9780875904344
T3 - Geophysical Monograph Series
SP - 289
EP - 306
BT - Magnetospheric ULF Waves
PB - Blackwell Publishing Ltd.
ER -