Quasi‐stationary auroral patches observed at the South Pole Station
Quasi‐stationary auroral patches observed at the South Pole Station
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DOI：
10.1029/2006ja012087
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发表时间：
2007
影响因子：
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通讯作者：
Y. Ebihara;Yoshimasa Tanaka;S. Takasaki;A. Weatherwax;M. Taguchi
中科院分区：
文献类型：
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作者：
Y. Ebihara;Yoshimasa Tanaka;S. Takasaki;A. Weatherwax;M. Taguchi
[1]我们介绍了南极站(−74.3°CGLAT)在∼0900和∼1400MLT之间的白天用全天成像仪观测到的准静止极光斑块(QSAP)。QSAP出现在I(557.7 nm)≫I(630.0 nm)的封闭场线区域，每个斑块往往保持其形状、光度和位置长达数小时。由于南极位于地球自转的轴线上，因此不能用自转电场的传统作用来解释QSAP的准静态性质。最有可能的情况是，控制对流势的旋转电势导致磁层冷等离子体的捕获区。在等离子体层形成的类比中，捕获区将捕获来自电离层的冷等离子体，并导致局部增强的等离子体密度(微型等离子体层)，这可能通过回旋波-粒子相互作用导致电子散射。这种情况可能发生在南极位于一条闭合的场线上，并且局部电势由自旋势主导时。QSAP还伴随着Pc5范围内的周期性波动，这与地面磁波动密切相关。假设脉动与场线共振有关，我们可以估计热等离子体的赤道质量密度，它从0.13逐渐增加到0.44amu cm−3。热等离子体密度的增加将支持小等离子体层存在的假设，尽管需要进一步的研究来证实这一假设。
[1] We present quasi-stationary auroral patches (QSAPs) observed by an all-sky imager at the South Pole Station (−74.3° CGLAT) on the dayside between ∼0900 and ∼1400 MLT. QSAPs appeared in a closed field line region where I(557.7 nm) ≫ I(630.0 nm) and each patch tends to preserve its form, luminosity, and location for up to several hours. The quasi-stationary nature of the QSAPs cannot be explained by the traditional role of the corotation electric field because the South Pole is located on the axis of Earth's rotation. The most plausible scenario is that a corotation electric potential, which dominates the convection potential, results in a trapping region of the magnetospheric cold plasmas. On the analogy of the formation of the plasmasphere, the trapping region would capture cold plasmas originated from the ionosphere and result in a locally enhanced plasma density (miniplasmasphere) that may lead to electron scattering through cyclotron wave-particle interactions. This circumstance may occur when the South Pole is located on a closed field line and the local electric potential is dominated by the corotation potential. QSAPs were also accompanied with periodic fluctuations in the Pc 5 range, which coincide closely with ground magnetic fluctuations. Assuming that the pulsation is associated with field line resonances, we could estimate the equatorial mass density of thermal plasmas, which gradually increased from 0.13 to 0.44 amu cm−3. The increase in the thermal plasma density would support the hypothesis that a miniplasmasphere exists, though further investigation is necessary to confirm it.