Applied Mathematics and Mechanics (English Edition) ›› 2016, Vol. 37 ›› Issue (2): 181-192.doi: https://doi.org/10.1007/s10483-016-2022-8

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Sufficient conditions of Rayleigh-Taylor stability and instability in equatorial ionosphere

Sicheng WANG1, Sixun HUANG1,2   

  1. 1. Institute of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China;
    2. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
  • 收稿日期:2015-04-17 修回日期:2015-07-21 出版日期:2016-02-01 发布日期:2016-02-01
  • 通讯作者: Sixun HUANG E-mail:huangsxp@163.com
  • 基金资助:

    Project supportedbythe National Natural Science Foundation of China (Nos. 41575026 and 41175025)

Sufficient conditions of Rayleigh-Taylor stability and instability in equatorial ionosphere

Sicheng WANG1, Sixun HUANG1,2   

  1. 1. Institute of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China;
    2. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
  • Received:2015-04-17 Revised:2015-07-21 Online:2016-02-01 Published:2016-02-01
  • Contact: Sixun HUANG E-mail:huangsxp@163.com
  • Supported by:

    Project supportedbythe National Natural Science Foundation of China (Nos. 41575026 and 41175025)

摘要:

Rayleigh-Taylor (R-T) instability is known as the fundamental mechanism of equatorial plasma bubbles (EPBs). However, the sufficient conditions of R-T instability and stability have not yet been derived. In the present paper, the sufficient conditions of R-T stability and instability are preliminarily derived. Linear equations for small perturbation are first obtained from the electron/ion continuity equations, momentum equations, and the current continuity equation in the equatorial ionosphere. The linear equations can be casted as an eigenvalue equation using a normal mode method. The eigenvalue equation is a variable coefficient linear equation that can be solved using a variational approach. With this approach, the sufficient conditions can be obtained as follows:if the minimum systematic eigenvalue is greater than one, the ionosphere is R-T unstable; while if the maximum systematic eigenvalue is less than one, the ionosphere is R-T stable. An approximate numerical method for obtaining the systematic eigenvalues is introduced, and the R-T stable/unstable areas are calculated. Numerical experiments are designed to validate the sufficient conditions. The results agree with the derived suf-ficient conditions.

关键词: variational approach, Rayleigh-Taylor (R-T) instability, sufficient condition, equatorial iono-sphere

Abstract:

Rayleigh-Taylor (R-T) instability is known as the fundamental mechanism of equatorial plasma bubbles (EPBs). However, the sufficient conditions of R-T instability and stability have not yet been derived. In the present paper, the sufficient conditions of R-T stability and instability are preliminarily derived. Linear equations for small perturbation are first obtained from the electron/ion continuity equations, momentum equations, and the current continuity equation in the equatorial ionosphere. The linear equations can be casted as an eigenvalue equation using a normal mode method. The eigenvalue equation is a variable coefficient linear equation that can be solved using a variational approach. With this approach, the sufficient conditions can be obtained as follows:if the minimum systematic eigenvalue is greater than one, the ionosphere is R-T unstable; while if the maximum systematic eigenvalue is less than one, the ionosphere is R-T stable. An approximate numerical method for obtaining the systematic eigenvalues is introduced, and the R-T stable/unstable areas are calculated. Numerical experiments are designed to validate the sufficient conditions. The results agree with the derived suf-ficient conditions.

Key words: equatorial iono-sphere, Rayleigh-Taylor (R-T) instability, sufficient condition, variational approach

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