Occurrence distributions of the auroral kilometric radiation ordinary and extraordinary wave modes
Occurrence distributions of the auroral kilometric radiation ordinary and extraordinary wave modes
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DOI：
10.1029/2002ja009579
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发表时间：
2003-11
影响因子：
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通讯作者：
J. Hanasz;M. Panchenko;H. Feraudy;R. Schreiber;M. Mogilevsky
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文献类型：
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作者：
J. Hanasz;M. Panchenko;H. Feraudy;R. Schreiber;M. Mogilevsky
[1]利用Interball-2（Auroral）卫星的偏振观测资料，确定了极光千米辐射（AKR）及其右非常波（R-X）和左寻常波（L-O）模的发生率分布。AKR在昼侧（20%的观测时间）比在夜侧（70%）少得多。它的大部分发生范围从MLT下午的不变纬度80延伸到夜间的60。与夜侧AKR一样，昼侧AKR也是通过电子回旋脉塞不稳定性产生的。这是从R-X模式在昼侧与夜侧类似的支配下得出的结论。在白天，AKR的L-O模式的频率（AKR时间的30%）大约是夜晚（10%）的三倍。在下午的时候，L-O更频繁地出现在较低的不变纬度。这可以用L-O模从远超出R-X模“视界”的夜面源传播来解释。我们发现两类圆偏振光谱：“规则的”，与占主导地位的R-X模式中观察到的AKR频谱的上部和较低的L-O模式在其下部，和补丁的“不规则的”，与不同的极化随机交织在整个频率范围内的AKR。对于“规则”光谱，L-O/R-X功率比在0.2和0.002之间。对于“不规则”的，它们在1和0.01之间。首次报道的“不规则”光谱被解释为由于R-X射线对夜面源附近等离子体密度波动的不规则折射。我们还显示了另一个组成部分的AKR观察到的向阳面，这可能来自向阳面源的方向可能与尖点或低纬度边界层的证据。
[1] Occurrence distributions of the auroral kilometric radiation (AKR) and its right-hand extraordinary (R-X) and left-hand ordinary (L-O) wave modes are determined from polarization measurements on Interball-2 (Auroral). The AKR is much less frequent on the dayside (20% of the observing time) than on the nightside (70%). A bulk of its occurrence extends from invariant latitude of 80 at afternoon hours of MLT to 60 at night hours. Like the nightside AKR, the dayside one is generated through the electron-cyclotron maser instability. This is concluded from domination of the R-X mode on the dayside similarly to the nightside. On the dayside the L-O mode of AKR is roughly three times more frequent (30% of the AKR time) than that on the nightside (10%). At afternoon hours the L-O occurs more frequently at lower invariant latitudes. This is explained by propagation of the L-O mode from nightside sources far beyond the “horizon” of the R-X mode. We find two classes of the circular polarization spectra: “regular,” with the dominating R-X mode observed in the upper part of the AKR frequency spectrum and the weak L-O mode in its lower part, and patchy “irregular,” with different polarizations interwoven randomly over the whole frequency range of AKR. For “regular” spectra the L-O/R-X power ratios are between 0.2 and 0.002. For the “irregular” ones they are between 1 and 0.01. The “irregular” spectra, reported for the first time, are interpreted as due to irregular refraction of the R-X rays on the plasma density fluctuations near the nightside sources. We show also evidence of another component of the AKR observed on the dayside, which arrives from directions of possible dayside sources likely related to the cusp or the low-latitude boundary layers.