One-dimensional transient response of the inner magnetosphere at the magnetic equator, 1. Transfer function and poles

M. Itonaga, Akimasa Yoshikawa, K. Yumoto

Research output: Contribution to journalArticle

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Abstract

One-dimensional transient response of the inner magnetosphere at the magnetic equator is investigated using two models of altitude distribution of the Alfvén speed VA. The present paper concentrates on the transfer function of the system under consideration and its poles, which govern the transient response of the system. The poles, which are mathematical counterparts of the cavity resonances, appear owing to the inhomogeneity of VA and their locations depend on the altitude distribution of VA as well as the position of external source (or outer boundary of the inner magnetosphere). Even if there exists no strong Alfvén velocity gradient at the outer boundary, an observable cavity-mode oscillation in the Pi2 range can be excited because of the existence of a strong gradient of the plasmapause within the inner magnetosphere. However, the existence of a strong gradient at the outer boundary brings about a long-lived nature of the cavity-mode oscillation as well as calls some new poles into existence. While the surface of the solid earth forms the inner boundary at which the almost perfect reflection of wave takes place, the ionosphere is of secondary importance as a reflector of wave. The existence of the solid earth plays an essential role in the observability of the compressional oscillation arising from the cavity resonance all over the inner magnetosphere. The real part of each pole has a negative value, meaning that the cavity-mode oscillation decays with a damping factor of absolute value of the real part of the pole. Such a damping is primarily due to the leakage of energy through the outer boundary of the inner magnetosphere.

Original languageEnglish
Pages (from-to)21-48
Number of pages28
JournalEarth, Planets and Space
Volume49
Issue number1
Publication statusPublished - 1997

Fingerprint

magnetic equator
transient response
transfer function
magnetospheres
transfer functions
magnetosphere
cavity
poles
cavities
oscillation
solid Earth
oscillations
gradients
damping
plasmapause
inhomogeneity
ionospheres
reflectors
leakage
ionosphere

All Science Journal Classification (ASJC) codes

  • Earth and Planetary Sciences (miscellaneous)

Cite this

One-dimensional transient response of the inner magnetosphere at the magnetic equator, 1. Transfer function and poles. / Itonaga, M.; Yoshikawa, Akimasa; Yumoto, K.

In: Earth, Planets and Space, Vol. 49, No. 1, 1997, p. 21-48.

Research output: Contribution to journalArticle

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