Ionospheric Joule heating and Poynting flux in quasi-static approximation
Ionospheric Joule heating and Poynting flux in quasi-static approximation
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准静态近似中的电离层焦耳热和坡印廷通量
DOI：
10.1029/2012ja017841
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
and R. Fujii
中科院分区：
文献类型：
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作者：
Vanhamäki;H.;A. Yoshikawa;O. Amm;and R. Fujii
能量流是磁层-电离层耦合的一个重要方面。电磁能量以坡印廷通量的形式从磁层传输到电离层，在电离层以焦耳加热的形式消散。最近，Richmond导出了一个“等势边界波印亭通量（EBPF）定理”，即边界为等势曲线的磁通管内的波印亭通量在磁通管的电离层脚点内耗散。在本文中，我们通过分别考虑电离层电流系统的无旋度和无散度部分以及Hall和Pedersen部分，更深入地研究了Richmond的EBPF定理。我们的主要发现是i)无散度电流平均无耗散，ii)无旋度Pedersen电流负责整个电离层焦耳加热，iii)垂直坡印亭通量和电离层焦耳加热之间的点向匹配被霍尔和Pedersen电导的梯度打破。当在整个电离层或以等势曲线为界的任何区域上积分时，结果i)和ii)成立。目前的研究仅限于准静态现象。更一般的主题，电动力学焦耳加热和波印亭通量，包括感应效应，将在未来的研究中解决。
Energy flow is an important aspect of magnetosphere‐ionosphere coupling. Electromagnetic energy is transported as Poynting flux from the magnetosphere to the ionosphere, where it is dissipated as Joule heating. Recently Richmond derived an “Equipotential Boundary Poynting Flux (EBPF) theorem”, that the Poynting flux within a flux tube whose boundary is an equipotential curve is dissipated inside the ionospheric foot point of the flux tube. In this article we study Richmond's EBPF theorem more closely by considering the curl‐free and divergence‐free parts as well as the Hall and Pedersen parts of the ionospheric current system separately. Our main findings are that i) divergence‐free currents are on average dissipationless, ii) the curl‐free Pedersen current is responsible for the whole ionospheric Joule heating and iii) pointwise match between vertical Poynting flux and ionospheric Joule heating is broken by gradients of Hall and Pedersen conductances. Results i) and ii) hold when integrated over the whole ionosphere or any area bounded by an equipotential curve. The present study is limited to quasi‐static phenomena. The more general topic of electrodynamic Joule heating and Poynting flux, including inductive effects, will be addressed in a future study.