The nature of reflection and mode conversion of MHD waves in the inductive ionosphere: Multistep mode conversion between divergent and rotational electric fields

Akimasa Yoshikawa, M. Itonaga

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42 Citations (Scopus)

Abstract

The nature of reflection and mode conversion of MHD waves at the high-latitudinal inductive ionosphere is analyzed, based on the current conservation law of wave modes. The term "inductive ionosphere" refers to the nonzero rotational electric field or nonzero compressional magnetic field in the reflection process of shear Alfvén waves on the ionosphere. The finite rotational electric field causes mutual induction between the divergent and rotational current systems at the ionosphere. The one-step Hall effect for the divergent electric field of the shear Alfvén wave produces a rotational Hall current and excites the ionospheric surface compressional wave. The Hall effect for the rotational electric field of an ionospheric surface compressional wave produces a divergent Hall current (two-step Hall effect), which feeds back the compressional magnetic energy to the reflected field-aligned current. We find that the renormalization of the ionospheric rotational electric field to the reflection process of the shear Alfvén wave causes some peculiarities in the distribution of ionospheric currents and mode-converted wave magnetic fields. Such peculiarities become particularly obvious in the high-conducting ionosphere. For example, in the ionospheric current distributions, a considerable component of the ionospheric divergent current is accounted for by the divergent Hall current. The rotational Hall and Pedersen currents cancel each other out and lead to zero total ionospheric rotational current. The amplitude of the poloidal magnetic field transmitted from the toroidal magnetic field of the incident shear Alfvén wave shows a nonlinear dependence on ΣHP. It also shows a new type of effective ionospheric shielding effect in the ΣPA parameter space for a fixed ΣHP condition. We assert that the inductive response of the ionosphere should become an indispensable concept for reflection, mode conversion, transmission, and generation of various phenomena relating to the field-aligned current system.

Original languageEnglish
Article number1999JA000159
Pages (from-to)10565-10584
Number of pages20
JournalJournal of Geophysical Research: Space Physics
Volume105
Issue numberA5
Publication statusPublished - May 1 2000

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Ionosphere
electric field
Magnetohydrodynamics
ionospherics
ionospheres
Hall currents
ionosphere
magnetic fields
Shear waves
Electric fields
shears
S waves
electric fields
S-wave
Hall effect
Magnetic fields
ionospheric currents
magnetic field
field aligned currents
Surface waves

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

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title = "The nature of reflection and mode conversion of MHD waves in the inductive ionosphere: Multistep mode conversion between divergent and rotational electric fields",
abstract = "The nature of reflection and mode conversion of MHD waves at the high-latitudinal inductive ionosphere is analyzed, based on the current conservation law of wave modes. The term {"}inductive ionosphere{"} refers to the nonzero rotational electric field or nonzero compressional magnetic field in the reflection process of shear Alfv{\'e}n waves on the ionosphere. The finite rotational electric field causes mutual induction between the divergent and rotational current systems at the ionosphere. The one-step Hall effect for the divergent electric field of the shear Alfv{\'e}n wave produces a rotational Hall current and excites the ionospheric surface compressional wave. The Hall effect for the rotational electric field of an ionospheric surface compressional wave produces a divergent Hall current (two-step Hall effect), which feeds back the compressional magnetic energy to the reflected field-aligned current. We find that the renormalization of the ionospheric rotational electric field to the reflection process of the shear Alfv{\'e}n wave causes some peculiarities in the distribution of ionospheric currents and mode-converted wave magnetic fields. Such peculiarities become particularly obvious in the high-conducting ionosphere. For example, in the ionospheric current distributions, a considerable component of the ionospheric divergent current is accounted for by the divergent Hall current. The rotational Hall and Pedersen currents cancel each other out and lead to zero total ionospheric rotational current. The amplitude of the poloidal magnetic field transmitted from the toroidal magnetic field of the incident shear Alfv{\'e}n wave shows a nonlinear dependence on ΣH/ΣP. It also shows a new type of effective ionospheric shielding effect in the ΣP/ΣA parameter space for a fixed ΣH/ΣP condition. We assert that the inductive response of the ionosphere should become an indispensable concept for reflection, mode conversion, transmission, and generation of various phenomena relating to the field-aligned current system.",
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N2 - The nature of reflection and mode conversion of MHD waves at the high-latitudinal inductive ionosphere is analyzed, based on the current conservation law of wave modes. The term "inductive ionosphere" refers to the nonzero rotational electric field or nonzero compressional magnetic field in the reflection process of shear Alfvén waves on the ionosphere. The finite rotational electric field causes mutual induction between the divergent and rotational current systems at the ionosphere. The one-step Hall effect for the divergent electric field of the shear Alfvén wave produces a rotational Hall current and excites the ionospheric surface compressional wave. The Hall effect for the rotational electric field of an ionospheric surface compressional wave produces a divergent Hall current (two-step Hall effect), which feeds back the compressional magnetic energy to the reflected field-aligned current. We find that the renormalization of the ionospheric rotational electric field to the reflection process of the shear Alfvén wave causes some peculiarities in the distribution of ionospheric currents and mode-converted wave magnetic fields. Such peculiarities become particularly obvious in the high-conducting ionosphere. For example, in the ionospheric current distributions, a considerable component of the ionospheric divergent current is accounted for by the divergent Hall current. The rotational Hall and Pedersen currents cancel each other out and lead to zero total ionospheric rotational current. The amplitude of the poloidal magnetic field transmitted from the toroidal magnetic field of the incident shear Alfvén wave shows a nonlinear dependence on ΣH/ΣP. It also shows a new type of effective ionospheric shielding effect in the ΣP/ΣA parameter space for a fixed ΣH/ΣP condition. We assert that the inductive response of the ionosphere should become an indispensable concept for reflection, mode conversion, transmission, and generation of various phenomena relating to the field-aligned current system.

AB - The nature of reflection and mode conversion of MHD waves at the high-latitudinal inductive ionosphere is analyzed, based on the current conservation law of wave modes. The term "inductive ionosphere" refers to the nonzero rotational electric field or nonzero compressional magnetic field in the reflection process of shear Alfvén waves on the ionosphere. The finite rotational electric field causes mutual induction between the divergent and rotational current systems at the ionosphere. The one-step Hall effect for the divergent electric field of the shear Alfvén wave produces a rotational Hall current and excites the ionospheric surface compressional wave. The Hall effect for the rotational electric field of an ionospheric surface compressional wave produces a divergent Hall current (two-step Hall effect), which feeds back the compressional magnetic energy to the reflected field-aligned current. We find that the renormalization of the ionospheric rotational electric field to the reflection process of the shear Alfvén wave causes some peculiarities in the distribution of ionospheric currents and mode-converted wave magnetic fields. Such peculiarities become particularly obvious in the high-conducting ionosphere. For example, in the ionospheric current distributions, a considerable component of the ionospheric divergent current is accounted for by the divergent Hall current. The rotational Hall and Pedersen currents cancel each other out and lead to zero total ionospheric rotational current. The amplitude of the poloidal magnetic field transmitted from the toroidal magnetic field of the incident shear Alfvén wave shows a nonlinear dependence on ΣH/ΣP. It also shows a new type of effective ionospheric shielding effect in the ΣP/ΣA parameter space for a fixed ΣH/ΣP condition. We assert that the inductive response of the ionosphere should become an indispensable concept for reflection, mode conversion, transmission, and generation of various phenomena relating to the field-aligned current system.

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