论文标题

帕克太阳能探针观察到的太阳风角动量通量

The Solar Wind Angular Momentum Flux as Observed by Parker Solar Probe

论文作者

Finley, Adam J., Matt, Sean P., Réville, Victor, Pinto, Rui F., Owens, Mathew, Kasper, Justin C., Korreck, Kelly E., Case, A. W., Stevens, Michael L., Whittlesey, Phyllis, Larson, Davin, Livi, Roberto

论文摘要

无法直接观察到太阳旋转周期的长期演变,而是根据其他类似太阳恒星的旋转周期中的趋势来推断。假设太阳旋转为年龄,随着旋转率$ \ propto $ \ age $^{ - 1/2} $,要求当前的太阳能动量 - 速率约为$ 6 \ times 10^{30} $ erg。磁性水力动力学模型以及先前对太阳风(来自Helios和Wind航天器的)的观察结果,通常可以预测一个接近$ 1 \ times 10^{30} $ erg或$ 3 \ times 10^{30} $ erg的值。最近,Parker太阳能探针(PSP)观察到内部地球层局部区域中的切向太阳风速高达$ \ sim50 $ km/s。如果此类旋转流在整个电晕中都普遍存在,则意味着太阳风角动量损失速率是比所有先前所有估计的数量级。在这封信中,我们使用PSP的前两个轨道的数据评估了太阳风中的角动量通量。观察到太阳风既包含较大的阳性(如在近日期内看到)和负角动量通量。我们分析了两个太阳风流,这些太阳风反复通过PSP穿越。第一个是慢风流,其平均角动量磁通在正到负之间波动,第二个是一个中间速度流,其中包含正角动量通量(与恒定的角动量流动更加一致)。当通过整体评估PSP的数据时,平均赤道角动量通量意味着全球角动量损失率约为$ 2.6-4.2 \ times 10^{30} $ ERG(这与先前的飞机的观察结果更一致)。

The long-term evolution of the Sun's rotation period cannot be directly observed, and is instead inferred from trends in the measured rotation periods of other Sun-like stars. Assuming the Sun spins-down as it ages, following rotation rate $\propto$ age$^{-1/2}$, requires the current solar angular momentum-loss rate to be around $6\times 10^{30}$erg. Magnetohydrodynamic models, and previous observations of the solar wind (from the Helios and Wind spacecraft), generally predict a values closer to $1\times 10^{30}$erg or $3\times 10^{30}$erg, respectively. Recently, the Parker Solar Probe (PSP) observed tangential solar wind speeds as high as $\sim50$km/s in a localized region of the inner heliosphere. If such rotational flows were prevalent throughout the corona, it would imply that the solar wind angular momentum-loss rate is an order of magnitude larger than all of those previous estimations. In this letter, we evaluate the angular momentum flux in the solar wind, using data from the first two orbits of PSP. The solar wind is observed to contain both large positive (as seen during perihelion), and negative angular momentum fluxes. We analyse two solar wind streams that were repeatedly traversed by PSP; the first is a slow wind stream whose average angular momentum flux fluctuates between positive to negative, and the second is an intermediate speed stream containing a positive angular momentum flux (more consistent with a constant flow of angular momentum). When the data from PSP is evaluated holistically, the average equatorial angular momentum flux implies a global angular momentum-loss rate of around $2.6-4.2\times 10^{30}$ erg (which is more consistent with observations from previous spacecraft).

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