The Earth as a radio source: Terrestrial kilometric radiation
The Earth as a radio source: Terrestrial kilometric radiation
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DOI：
10.1029/ja079i028p04227
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发表时间：
1974-10
影响因子：
--
通讯作者：
D. Gurnett
中科院分区：
文献类型：
--
作者：
D. Gurnett
在Imp 6和8号卫星上进行的无线电波实验表明，地球在大约50-500 kHz的频率范围内发出非常强烈的电磁辐射。在峰值强度下，在该频率范围内发射的总功率约为109 W。因此，地球是一个非常强烈的行星射电源，其总功率输出相当于木星的十米波射电辐射。我们把这种来自地球的无线电辐射称为地面千米辐射。地面千米辐射似乎起源于极光区的低海拔（小于3.0 RE）。噪声的强度与当地时间和观测点的磁纬度都有明显的依赖关系。在大的径向距离上，辐射主要是在两个圆锥形表面的向极一侧观察到的，这两个圆锥形表面以地球为中心，相对于北方和南方极光带对称地定位。锥形边界的磁纬度从当地早晨的大于50°到当地晚上的磁赤道附近。在这些边界的两极，噪音以零星的“风暴”形式出现，持续半小时至数小时。与从低空极地轨道Dapp卫星获得的极光照片进行比较表明，地面千米辐射与离散极光弧的出现密切相关，这些极光弧发生在极光区的当地傍晚区域。这种关联表明，千米辐射可能是由强烈的“倒V”电子沉淀带产生的，它导致了离散的极光弧。讨论了地面千米辐射产生和传播的可能机制。
Radio wave experiments on the Imp 6 and 8 satellites have shown that the earth emits very intense electromagnetic radiation in the frequency range of about 50–500 kHz. At peak intensity the total power emitted in this frequency range is about 109 W. The earth is therefore a very intense planetary radio source, with a total power output comparable to the decametric radio emission from Jupiter. We refer to this radio emission from the earth as terrestrial kilometric radiation. Terrestrial kilometric radiation appears to originate from low altitudes (less than 3.0 RE) in the auroral region. The intensity of the noise has a pronounced dependence on both the local time and the magnetic latitude of the observing point. At large radial distances the radiation is primarily observed on the poleward side of two cone-shaped surfaces that are centered on the earth and symmetrically located with respect to the northern and southern auroral zones. The magnetic latitude of the cone-shaped boundaries varies from greater than 50° in the local morning to near the magnetic equator in the local evening. Poleward of these boundaries the noise occurs in sporadic ‘storms’ lasting from ½ hour to several hours. Comparisons with auroral photographs obtained from the low-altitude polar-orbiting Dapp satellite show that the terrestrial kilometric radiation is closely correlated with the occurrence of discrete auroral arcs, which occur in the local evening region of the auroral zone. This association indicates that the kilometric radiation is probably generated by intense ‘inverted V’ electron precipitation bands, which cause the discrete auroral arcs. Possible mechanisms that can explain the generation and propagation of the terrestrial kilometric radiation are discussed.