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Transfer function analysis of thermospheric perturbationsApplying perturbation theory, a spectral model in terms of vectors spherical harmonics (Legendre polynomials) is used to describe the short term thermospheric perturbations originating in the auroral regions. The source may be Joule heating, particle precipitation or ExB ion drift-momentum coupling. A multiconstituent atmosphere is considered, allowing for the collisional momentum exchange between species including Ar, O2, N2, O, He and H. The coupled equations of energy, mass and momentum conservation are solved simultaneously for the major species N2 and O. Applying homogeneous boundary conditions, the integration is carred out from the Earth's surface up to 700 km. In the analysis, the spherical harmonics are treated as eigenfunctions, assuming that the Earth's rotation (and prevailing circulation) do not significantly affect perturbations with periods which are typically much less than one day. Under these simplifying assumptions, and given a particular source distribution in the vertical, a two dimensional transfer function is constructed to describe the three dimensional response of the atmosphere. In the order of increasing horizontal wave numbers (order of polynomials), this transfer function reveals five components. To compile the transfer function, the numerical computations are very time consuming (about 100 hours on a VAX for one particular vertical source distribution). However, given the transfer function, the atmospheric response in space and time (using Fourier integral representation) can be constructed with a few seconds of a central processing unit. This model is applied in a case study of wind and temperature measurements on the Dynamics Explorer B, which show features characteristic of a ringlike excitation source in the auroral oval. The data can be interpreted as gravity waves which are focused (and amplified) in the polar region and then are reflected to propagate toward lower latitudes.
Document ID
19860019847
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Mayr, H. G. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Harris, I. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Varosi, F. (Science Applications Research Riverdale, Md., United States)
Herrero, F. A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Spencer, N. W. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 12, 2013
Publication Date
June 1, 1986
Publication Information
Publication: Thermosphere Dynamics Workshop, Volume 2
Subject Category
Geophysics
Accession Number
86N29319
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle19860019829Collected WorksThermosphere Dynamics Workshop, volume 2
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