Meteor head echo altitude distributions and the height cutoff effect studied with the EISCAT HPLA UHF and VHF radars
Meteor head echo altitude distributions and the height cutoff effect studied with the EISCAT HPLA UHF and VHF radars
复制标题
使用 EISCAT HPLA UHF 和 VHF 雷达研究流星头回波高度分布和高度截止效应
DOI：
10.5194/angeo-22-1575-2004
复制
发表时间：
2004
影响因子：
1.9
通讯作者：
A. Pellinen‐Wannberg
中科院分区：
文献类型：
--
作者：
A. Westman;G. Wannberg;A. Pellinen‐Wannberg
抽象。流星头部回波高度分布是由EISCAT VHF（224 MHz）和UHF（930 MHz）高功率大孔径（HPLA）雷达收集的数据导出的。在高海拔的一端，分布突然切断的方式让人想起的轨迹回波高度天花板效应与经典的流星雷达观察。目标的尺寸被证明是远小于VHF和UHF探测波长，但两个系统的截止高度仍然明显不同，VHF截止位于几公里以上的UHF之一。一个单次碰撞的流星-大气相互作用模型被用来证明，质量范围在（1.3-7.2）微克的流星将电离，使得在VHF截止高度或其附近首先达到224 MHz的临界电子密度，并在UHF截止高度达到930 MHz的临界密度。所观察到的季节性变化的截止高度被证明是随海拔高度的大气密度的季节性变化的函数。假设探测所需的电子密度在临界密度的量级，那么高度突然截止可以解释为微流星体联合尺寸-速度分布在大质量、高速端下降得如此之快，以至于在一定高度以上，可探测事件的数量变得微乎其微。相反，在低质量分布端的流星将逐渐被延迟，使得它们产生的电离永远不会达到临界密度。这些粒子将保持不可观测。关键词。无线电科学（仪器和技术）.星际物理学（星际尘埃）.一般或杂项（新领域）
Abstract. Meteor head echo altitude distributions have been derived from data collected with the EISCAT VHF (224MHz) and UHF (930MHz) high-power, large-aperture (HPLA) radars. At the high-altitude end, the distributions cut off abruptly in a manner reminiscent of the trail echo height ceiling effect observed with classical meteor radars. The target dimensions are shown to be much smaller than both the VHF and the UHF probing wavelengths, but the cutoff heights for the two systems are still clearly different, the VHF cutoff being located several km above the UHF one. A single-collision meteor-atmosphere interaction model is used to demonstrate that meteors in the (1.3–7.2)µg mass range will ionise such that critical electron density at 224MHz is first reached at or around the VHF cutoff altitude and critical density at 930MHz will be reached at the UHF cutoff altitude. The observed seasonal variation in the cutoff altitudes is shown to be a function of the seasonal variation of atmospheric density with altitude. Assuming that the electron density required for detection is in the order of the critical density, the abrupt altitude cutoffs can be explained as a consequence of the micrometeoroid joint size-speed distribution dropping off so fast at the large-mass, high-velocity end that above a certain altitude the number of detectable events becomes vanishingly small. Conversely, meteors at the low-mass end of the distribution will be gradually retarded such that the ionisation they generate never reaches critical density. These particles will remain unobservable. Key words. Radio science (instruments and techniques) – Interplatery physics (interplanetary dust) – General or miscellaneous (new fields)