Shear instability: Auroral arc deformation and anomalous momentum transport
Shear instability: Auroral arc deformation and anomalous momentum transport
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剪切不稳定性：极光弧变形和反常动量传输
DOI：
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发表时间：
1978
期刊：
影响因子：
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通讯作者：
Tetsuya Sato
中科院分区：
文献类型：
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作者：
A. Miura;Tetsuya Sato
数值研究了二维静电剪切不稳定性的时间演化，特别是极光弧的旋转形变和磁层边界上的动量输送。结果表明，增长涡旋的空间结构与被称为“旋度”的小尺度极光形变相吻合。由剪切不稳定引起的反常粘度约为0.08aV0，其中a是流速变化V0的特征距离。假设磁层边界处a=2 0 0 km，V0=2 5 0 km/S，则反常粘性变为4×10 1 3cm2 S−1，与埃克斯福德(1964年)根据典型磁暴的能量需求估算的值相当，甚至更大。文中还研究了充分发展的静电湍流的光谱能量。结果表明，观测到的功率谱能量可以很好地用k−4形式的幂定律来表示。
Temporal evolution of a two-dimensional electrostatic shear instability is numerically studied with special attention to rotational deformation of auroral arcs and momentum transport across the magnetospheric boundary. It is found that the spatial structure of the growing vortex is in good agreement with the small-scale auroral deformation called ‘curl.’ An anomalous viscosity arising from the shear instability is found to be given approximately by 0.08 aV0, where a is the characteristic distance over which the flow velocity changes by V0. If we assume that a = 200 km and V0 = 250 km/s at the magnetospheric boundary, the anomalous viscosity becomes 4 × 1013 cm² s−1, which is comparable to, or even larger than, the value estimated by Axford (1964) from energy requirements of a typical magnetic storm. Spectral energies of fully developed electrostatic turbulence are also studied. It is found that the observed power spectral energies can well be represented by a power law of the form k−4.