DYNAMICAL MODEL FOR THE ZODIACAL CLOUD AND SPORADIC METEORS
DYNAMICAL MODEL FOR THE ZODIACAL CLOUD AND SPORADIC METEORS
复制标题
黄道云和偶发流星的动态模型
DOI：
10.1088/0004-637x/743/2/129
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
P. Jenniskens
中科院分区：
文献类型：
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作者：
D. Nesvorný;D. Janches;D. Vokrouhlický;P. Pokorný;W. Bottke;P. Jenniskens
太阳系尘土飞扬，随着小行星的碰撞和彗星的解体，随着时间的推移，太阳系将变得更加尘土飞扬，只是行星际空间中的小碎片颗粒不会持续很长时间。它们可以被木星从太阳系抛出，在太阳附近被热摧毁，或者被碰撞物理破坏。此外，有些被地球(和其他行星)扫过，产生流星。在这里，我们建立了一个太阳系流星体的动力学模型，并用它来解释流星雷达观测。我们发现，木星家族彗星(JFC)是从氦和反日子方向到达地球的大量流星的主要来源。为了与加拿大流星轨道雷达(CMOR)和先进流星轨道雷达(AMOR)测量的辐射和轨道分布相匹配，我们的模型意味着彗星，特别是JFCs，在到达近日点距离较低的轨道时必须经常解体。此外，毫米粒子的碰撞寿命(1AU时的≳105年)可能比标准碰撞模型中的假设(1AU时的∼104年)更长，这可能是因为这些球粒大小的流星体比之前认为的更强。利用红外天文卫星的观测数据对模型进行了定标，得到太阳系内小流星体的总截面为(1.7~3.5)×10 11km2，质量为∼4×10 19g，与前人的研究结果一致。保持黄道云稳定所需的质量输入估计为∼104-105公斤S−1。这一输入比之前发现的∼大10倍，主要是因为释放出的粒子离太阳更近，碰撞寿命更短，需要以更快的速度提供。地球在直径D=5 μm和1 cm之间的粒子中吸积的总质量被发现是∼15,000吨yr−1(两个不确定系数)，这在长期持续时间设施测量的吸积通量中占有很大份额。大部分健力士粒子以S−1的15公里速度坠入高层大气，应能挺过大气层，并能产生微陨石坠落。这可以解释从南极冰层和平流层采集的样品与星尘航天器从怀尔德2号彗星带来的样品在成分上的相似性。CMOR和AMOR等流星雷达只能看到一小部分吸积通量(分别为∼1%-10%和∼10%-50%)，因为较小的粒子以低速撞击产生的电离水平低于这些雷达的探测能力。
The solar system is dusty, and would become dustier over time as asteroids collide and comets disintegrate, except that small debris particles in interplanetary space do not last long. They can be ejected from the solar system by Jupiter, thermally destroyed near the Sun, or physically disrupted by collisions. Also, some are swept by the Earth (and other planets), producing meteors. Here we develop a dynamical model for the solar system meteoroids and use it to explain meteor radar observations. We find that the Jupiter Family Comets (JFCs) are the main source of the prominent concentrations of meteors arriving at the Earth from the helion and antihelion directions. To match the radiant and orbit distributions, as measured by the Canadian Meteor Orbit Radar (CMOR) and Advanced Meteor Orbit Radar (AMOR), our model implies that comets, and JFCs in particular, must frequently disintegrate when reaching orbits with low perihelion distance. Also, the collisional lifetimes of millimeter particles may be longer (≳ 105 yr at 1 AU) than postulated in the standard collisional models (∼104 yr at 1 AU), perhaps because these chondrule-sized meteoroids are stronger than thought before. Using observations of the Infrared Astronomical Satellite to calibrate the model, we find that the total cross section and mass of small meteoroids in the inner solar system are (1.7–3.5) × 1011 km2 and ∼4 × 1019 g, respectively, in a good agreement with previous studies. The mass input required to keep the zodiacal cloud in a steady state is estimated to be ∼104–105 kg s−1. The input is up to ∼10 times larger than found previously, mainly because particles released closer to the Sun have shorter collisional lifetimes and need to be supplied at a faster rate. The total mass accreted by the Earth in particles between diameters D = 5 μm and 1 cm is found to be ∼15,000 tons yr−1 (factor of two uncertainty), which is a large share of the accretion flux measured by the Long Term Duration Facility. The majority of JFC particles plunge into the upper atmosphere at <15 km s−1 speeds, should survive the atmospheric entry, and can produce micrometeorite falls. This could explain the compositional similarity of samples collected in the Antarctic ice and stratosphere, and those brought from comet Wild 2 by the Stardust spacecraft. Meteor radars such as CMOR and AMOR see only a fraction of the accretion flux (∼1%–10% and ∼10%–50%, respectively), because small particles impacting at low speeds produce ionization levels that are below these radars' detection capabilities.