论文标题

统计分析太阳风转回的方向,形状和大小

Statistical analysis of orientation, shape, and size of solar wind switchbacks

论文作者

Laker, Ronan, Horbury, Timothy S., Bale, Stuart D., Matteini, Lorenzo, Woolley, Thomas, Woodham, Lloyd D., Badman, Samuel T., Pulupa, Marc, Kasper, Justin C., Stevens, Michael, Case, Anthony W., Korreck, Kelly E.

论文摘要

帕克太阳能探头(PSP)的前两个轨道中的主要发现之一是磁换回,其偏转主导了磁场测量值。确定其形状和大小可以提供其起源的证据,这仍然不清楚。单个太阳风流的先前工作表明,尽管无法确定其主要轴的方向,但它们是较长的薄结构。我们研究了这种较长的性质是否延伸到其他太阳风流,同时确定沿流中的折返方向对齐的方向。我们试图了解折返的大小和方向以及流速和航天器轨迹如何结合起来,以产生过去和将来的轨道的观察到的结构持续时间。我们搜索了对齐方向,该方向产生了与长而薄的结构最一致的航天器切割方向和折返持续时间的组合。最佳对齐方向的结果拟合了长而薄的结构的预期形式,该结果确定了该流的折返的宽度和纵横比。折返的平均宽度为$ 50,000 \,\ rm {km} $,其宽高比为$ 10 $。我们发现,折回来不沿着背景流动方向对齐,而是沿当地帕克螺旋形成对准,也许表明它们沿着磁场传播。由于观察到的折返持续时间取决于航天器如何通过结构切割,因此不能仅使用持续时间来确定单个事件的大小或影响。对于将来的PSP轨道,较大的航天器横向组件与更径向比对的折返相结合将导致持续时间较长的折返变得不那么普遍。

One of the main discoveries from the first two orbits of Parker Solar Probe (PSP) was the presence of magnetic switchbacks, whose deflections dominated the magnetic field measurements. Determining their shape and size could provide evidence of their origin, which is still unclear. Previous work with a single solar wind stream has indicated that these are long, thin structures although the direction of their major axis could not be determined. We investigate if this long, thin nature extends to other solar wind streams, while determining the direction along which the switchbacks within a stream were aligned. We try to understand how the size and orientation of the switchbacks, along with the flow velocity and spacecraft trajectory, combine to produce the observed structure durations for past and future orbits. We searched for the alignment direction that produced a combination of a spacecraft cutting direction and switchback duration that was most consistent with long, thin structures. The expected form of a long, thin structure was fitted to the results of the best alignment direction, which determined the width and aspect ratio of the switchbacks for that stream. The switchbacks had a mean width of $50,000 \, \rm{km}$, with an aspect ratio of the order of $10$. We find that switchbacks are not aligned along the background flow direction, but instead aligned along the local Parker spiral, perhaps suggesting that they propagate along the magnetic field. Since the observed switchback duration depends on how the spacecraft cuts through the structure, the duration alone cannot be used to determine the size or influence of an individual event. For future PSP orbits, a larger spacecraft transverse component combined with more radially aligned switchbacks will lead to long duration switchbacks becoming less common.

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