Effect of electrojet irregularities on DC current flow
Effect of electrojet irregularities on DC current flow
复制标题
电喷射不规则性对直流电流的影响
DOI：
10.1029/2004ja010788
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
J. F. Mckenzie
中科院分区：
文献类型：
--
作者：
S. Buchert;T. Hagfors;J. F. Mckenzie
[1]本文研究了极光和赤道电急流中等离子体密度不规则性对产生这些不规则性的直流电流的影响。结果表明，理论预测的额外耗散和偏离的方向上的平均电流流动的E0 × B 0/B2，在一般的协议与观测。输入到湍流等离子体的平均功率等于外部施加的电场和平均电流的乘积，可以等同于导致等离子体没有不规则性但具有增加的碰撞频率的功率输入。类似地，可以计算由于不规则性而导致的电流方向的偏差，并将其与在没有不规则性但具有增加的碰撞频率的等离子体中引起的偏差进行比较，并从该比较中指定由不规则性引起的等离子体中的异常耗散。我们的研究应用基本原理，并处理由外场驱动的平均电流，包括在微扰量的二阶项的平均值的影响。我们不讨论引起等离子体不规则性的基本过程，只讨论它们对平均电流的影响。异常耗散或增加的视碰撞频率，直接关系到等离子体密度起伏的角功率谱。结果表明，在这些异常碰撞中的直流电流耗散的功率是完全相同的，通过正常的碰撞由波模式组成的功率谱导致的异常直流电流耗散的功率耗散。该研究还表明，饱和的不稳定性，引起的电射流湍流，可能是由电流的异常电阻率的控制，而不是由本地的非线性效应。
[1] A study is presented of the effect of plasma density irregularities in the auroral and equatorial electrojets on the DC currents giving rise to these irregularities. It is shown that the theory predicts extra dissipation and deviation in the direction of the mean current flow from that of E0 × B0/B2, in general agreement with observations. The average power input to the turbulent plasma, equal to the product of the externally applied electric field and the mean current, can be equated to the power input with that resulting in a plasma devoid of irregularities but with an increased collision frequency. Similarly one can compute the deviation in direction of the current flow due to the irregularities and compare this with the deviation caused in a plasma without irregularities, but with an increased collision frequency, and from this comparison assign an anomalous dissipation in the plasma caused by the irregularities. Our study applies elementary principles and deals with the mean current driven by an external field, including effects of the mean values of second order terms in the perturbed quantities. We do not discuss the elementary processes giving rise to the irregularities in the plasma; only their effect on the mean current flow. The anomalous dissipation or the increased apparent collision frequency, is related directly to the angular power spectrum of plasma density fluctuations. It is shown that the power dissipated by the DC current in these anomalous collisions is exactly the same as the power dissipated through normal collisions by the wave modes making up the power spectrum leading to the anomalous DC current dissipation. The study also suggests that the saturation of the instabilities, giving rise to the electrojet turbulence, is likely to be caused by the control of the current by the anomalous resistivity rather than by local nonlinear effects.