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The Effects of Solar Wind Structure on Nanodust Dynamics in the Inner Heliosphere
Journal of Geophysical Research: Space Physics ( IF 2.8 ) Pub Date : 2020-10-10 , DOI: 10.1029/2020ja028463
A. R. Poppe 1 , C. O. Lee 1
Affiliation  

Several interplanetary spacecraft have inferred the presence of nanometer‐sized dust grains in the inner heliosphere accelerated to near‐solar wind velocities based on observations by radio wave antennas. These “nanodust” grains exhibit unique behavior in interplanetary space as they are strongly affected by both the solar gravitational force and the electromagnetic Lorentz force from the convecting interplanetary magnetic field. Here, we study the dynamics of nanodust grains in the inner heliosphere via a combination of background electromagnetic fields from the coupled Wang‐Sheeley‐Arge/Enlil heliospheric model and a nanodust grain charging and dynamics model. The model results predict strong time variability in the nanodust velocity and flux distributions at 1 au within a single Carrington rotation (CR) driven by a combination of nanodust grain size, heliospheric current sheet tilt, and varying heliospheric plasma parameters. In contrast, the general character of nanodust dynamics does not drastically change from one CR to the next. Despite including observationally driven heliospheric plasma conditions, the modeled nanodust impact rates do not agree with in situ observations by the STEREO A and B WAVES instruments, especially with regard to CR‐to‐CR variability. We interpret this data‐model disagreement as evidence that additional time variability must be present in the production rate of nanodust grains in the inner heliosphere. We discuss possibilities for this time variability, including non‐steady‐state collisional cascades, variability in nanodust trapping regions, and the impulsive disruption of inner solar system comets and/or asteroids.

中文翻译:

太阳风结构对内太阳圈纳米粉尘动力学的影响

根据无线电波天线的观测,一些行星际航天器已经推断出加速到接近太阳风速的内部日球层中存在纳米级尘埃颗粒。这些“纳米尘”粒子在行星际空间中表现出独特的行为,因为它们受到对流行星际磁场对流的太阳引力和电磁洛伦兹力的强烈影响。在这里,我们通过耦合Wang-Sheeley-Arge / Enlil日球模型的背景电磁场以及纳米粉尘的电荷和动力学模型,研究了内部日光层中纳米尘埃颗粒的动力学。该模型结果预测,纳米粉尘粒度,日球层当前薄板倾斜度和日圆等离子体参数变化共同驱动,单个卡灵顿旋转(CR)会在1 au内纳米粉尘的速度和通量分布具有很强的时间变化性。相反,纳米粉尘动力学的一般特征不会从一个CR急剧变化到另一个。尽管包括观测驱动的日圆等离子体条件,但模拟的纳米尘埃撞击率与STEREO A和B WAVES仪器的原位观测结果不一致,特别是在CR到CR的变化方面。我们将此数据模型的差异解释为证据,即内部日光层中纳米尘埃颗粒的生产率中必须存在额外的时间变异性。我们讨论了这种时间可变性的可能性,
更新日期:2020-10-20
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