The dust coma of comet P/Halley: measurements on the Vega-1 and Vega-2 spacecraft
The dust coma of comet P/Halley: measurements on the Vega-1 and Vega-2 spacecraft
复制标题
P/哈雷彗星的尘埃彗发：Vega-1 和 Vega-2 航天器上的测量
DOI：
--
复制
发表时间：
1988
期刊：
影响因子：
--
通讯作者：
R. Sagdeev
中科院分区：
文献类型：
--
作者：
J. Simpson;D. Rabinowitz;A. Tuzzolino;L. Ksanfomality;R. Sagdeev
质量> 10−13 g的彗发尘埃粒子的空间、时间和质量分布，我们用DUCMA仪器测量并在早些时候报道过（Simpson等人，1986年a），已被证实和扩展，以揭示额外的属性的尘埃昏迷。我们已经分析了通量与核距离R的平方反比关系（Δ R −2），并表明在测量的质量范围内有明确的包络边界。在这些边界内高于这些R −2“基线”的通量增强区域被确定为尘埃喷流。特别感兴趣的是巨大的通量增强最近的方法为织女星-1，我们表明，质谱是类似的遭遇前的光谱，并有一个平稳的上升率的强度超过4秒导致的峰值。这是一个通量梯度类似于其他几个小得多的通量增强入境和出境发现。某些喷流的终端速度的质量依赖性与最近的预测是一致的，并且两个航天器观察到的重复喷流-当追溯到核时-与Sekanina和Larson（1986）预测的活动区域相关。我们已经发现了具有广泛质量的粒子以簇或“包”的形式到达（即，尘埃粒子的非泊松分布）在整个包络线边界以外的区域-即尘埃彗发的边缘区域。这些观测结果表明，从核中发射出的是由小粒子组成的大团块，这些团块在向外传播时会轻微地碎裂，从而解释了在包层边界之外观测到的10−13 g粒子。此外，尘埃通量的任务已经确定。最后，我们报告说，无论是DUCMA电子和灰尘传感器保持其校准和性能在整个遭遇和遭遇后的行星际任务。
The spatial, temporal and mass distributions of coma dust particles for masses > 10−13 g, which we measured with the DUCMA instruments and reported earlier (Simpson et al., 1986a), have been confirmed and extended to reveal additional properties of the dust coma. We have analyzed the inverse square dependence (∝ R −2) of flux with distance R from the nucleus and show that there are well-defined envelope boundaries for the measured range of masses. Regions of enhanced fluxes above these R −2 ‘baselines’ inside these boundaries are identified as dust jets. Of special interest is the giant flux enhancement near closest approach for Vega-1, for which we show that the mass spectrum is similar to the pre-encounter spectra and that there is a smooth rate of rise of intensity over more than four seconds leading into the peak. This is a flux gradient similar to that found for several other much smaller flux enhancements inbound and outbound. The mass dependence of terminal velocities for some jets is consistent with recent predictions, and recurring jets observed by both spacecraft—when traced back to the nucleus—correlate with the active regions predicted by Sekanina and Larson (1986). We have discovered particles with a wide range of masses arriving in clusters or ‘packets’ (i.e., a non-Poisson distribution of dust particles) throughout the regions beyond the envelope boundaries — namely, the fringe regions of the dust coma. These observations suggest the emission from the nucleus of large conglomerates of small particles which gently disintegrate as they travel outward to account for the 10−13 g particles observed beyond the envelope boundaries. Also, dust fluences over the missions have been determined. Finally, we report that both the DUCMA electronics and dust sensors maintained their calibrations and performance throughout the encounters and during the post-encounter interplanetary missions.