A modeling study of ionospheric conductivities in the high-latitude electrojet regions
A modeling study of ionospheric conductivities in the high-latitude electrojet regions
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DOI：
10.1029/2003ja010181
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发表时间：
2004-04
影响因子：
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通讯作者：
Beichen Zhang;Y. Kamide;Rui-yuan Liu;H. Shinagawa;K. Iwamasa
中科院分区：
文献类型：
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作者：
Beichen Zhang;Y. Kamide;Rui-yuan Liu;H. Shinagawa;K. Iwamasa
[1]准确确定电离层电导率对于更好地估计高层大气特别是高纬度地区的能量沉积十分重要。通常的做法是假设电导率的增强是由太阳辐射和粒子沉降引起的，这可以被视为外部来源。然而，很少有人注意到电喷射电流本身的存在所造成的影响。我们称这种效应为影响电离层电导率的内因。电喷射电流的存在改变了电导率，并且，反过来，已经改变的电导率修改了电流系统。也就是说，磁层-电离层耦合电流系统中预计会发生反馈过程。我们使用一个一维的高纬度电离层模型，其中的连续性方程，以及动量和能量方程，求解自洽研究电导率在极光区存在的电射流。Farley-Buneman不稳定性，这可能发生在电射流区域的加热效应，被认为是。电射流相关的焦耳加热和摩擦加热也被考虑在内。热过程进行了分析，在响应于电喷射电流。由于热结构的变化，我们证明了由于化学反应速率的变化，从而导致更高的电子密度的电导率的响应。电导率的高度剖面的响应是由离子和电子与中性组分的碰撞频率的变化决定的，而电导的增强主要是由电子密度引起的。结果表明，霍尔和彼得森电导，即，高度积分电导率显著增加。霍尔电导和佩德森电导之间的比率也会发生很大变化。
[1] It is important to accurately determine the ionospheric conductivities for a better estimation of energy deposition in the upper atmosphere, particularly at high latitudes. It is a common practice to assume that enhancements in the conductivities are caused by solar radiation and particle precipitation, which can be regarded as external origins. However, little attention has been paid to effects caused by the presence of electrojet currents themselves. We call this effect an internal origin for influencing the ionospheric conductivities. The presence of electrojet current changes the conductivities, and, in turn, the already changed conductivities modify the current systems. That is, a feedback process is expected to take place in magnetosphere-ionosphere coupling current systems. We use a one-dimensional high-latitude ionospheric model in which the continuity equations, as well as momentum and energy equations, are solved self-consistently to study the conductivities in auroral regions where electrojets exist. The heating effect from the Farley-Buneman instability, which possibly occurs in the electrojet regions, is considered. Electrojet-related joule heating and frictional heating are also taken into account. Thermal processes are analyzed in response to the electrojet current. As a result of changes in the thermal structure, we demonstrate the response of the conductivities due to changes in the chemical reaction rate, which results in a higher electron density. The response of altitude profiles of the conductivities is determined by changes in the collision frequency of ions and electrons with neutral components, while an enhancement in the conductance is mainly caused by the electron density. The results show that both the Hall and Pedersen conductances, i.e., the height-integrated conductivities, increase significantly. The ratio between Hall and Pedersen conductances also changes considerably.