《自然》（20240829出版）一周论文导读

 
《自然》（20240829出版）一周论文导读  
 

 

编译|李言

Nature, 29 August 2024, Volume 632 Issue 8027

《自然》2024年8月29日，第632卷，8027期

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地球科学Earth Science

Earth’s ambipolar electrostatic field and its role in ion escape to space

地球的双极静电场及其在离子逃逸到太空中扮演的角色

▲ 作者：Glyn A. Collinson, Alex Glocer et al.

▲ 链接：https://www.nature.com/articles/s41586-024-07480-3

▲摘要：

在此，我们报告在250千米至768千米范围内，仅由电离层电子向外压力产生的行星静电场（E∥⊕=1.09±0.17μVm?1）存在+0.55±0.09V的电位降。我们的实验表明，地球的双极静电场控制着极地电离层的结构，将范围高度提升至271%。

我们认为这将使冷O+离子向磁层的供应增加了3800%以上，其中波粒相互作用等其他机制可以加热并进一步加速它们达到逃逸速度。地球的静电场足够强大到驱动极地风，并且可能是主导大部分磁层的冷氢离子群的起源。

▲ Abstract：

Here we report the existence of a +0.55?±?0.09?V electric potential drop between 250?km and 768?km from a planetary electrostatic field (E∥⊕?=?1.09?±?0.17?μV?m?1) generated exclusively by the outward pressure of ionospheric electrons. We experimentally demonstrate that the ambipolar field of Earth controls the structure of the polar ionosphere, boosting the scale height by 271%. We infer that this increases the supply of cold O+ ions to the magnetosphere by more than 3,800%, in which other mechanisms such as wave–particle interactions can heat and further accelerate them to escape velocity. The electrostatic field of Earth is strong enough by itself to drive the polar wind and is probably the origin of the cold H+ ion population1 that dominates much of the magnetosphere.

天文学Astronomy

A nebular origin for the persistent radio emission of fast radio bursts

快速射电暴持续射电发射的星云起源

▲ 作者：Gabriele Bruni, Luigi Piro et al.

▲ 链接：https://www.nature.com/articles/s41586-024-07782-6

▲ 摘要：

在此，我们报告在距离413Mpc的重复快速射电暴源FRB20201124A相关的第三个亮度较低的持续射电源的检测，这大大扩展了预测关系到低亮度—低法拉第旋转测量范围（<1000?rad?m?2）。

在较低的法拉第旋转测量值下，预期的射电光度低于当今射电望远镜的探测极限。这些发现支持了这样一种观点，即到目前为止观测到的持续射电源是由快速射电暴环境中的星云产生的，并且由于较弱的磁离子介质，具有低法拉第旋转测量的快速射电暴可能不会显示出持续射电源。

这与将年轻的磁星作为快速射电暴中心引擎的模型基本一致。在该模型中，周围的电离星云或双星系统中的相互作用激波为持续的射电源提供动力。

▲ Abstract：

Here we report the detection of a third, less luminous persistent radio source associated with the repeating FRB source FRB?20201124A at a distance of 413?Mpc, substantially expanding the predicted relation into the low luminosity–low Faraday rotation measure regime (<1,000?rad?m?2). At lower values of the Faraday rotation measure, the expected radio luminosity falls below the limit-of-detection threshold for present-day radio telescopes. These findings support the idea that the persistent radio sources observed so far are generated by a nebula in the FRB environment and that FRBs with low Faraday rotation measure may not show a persistent radio source because of a weaker magneto-ionic medium. This is generally consistent with models invoking a young magnetar as the central engine of the FRB, in which the surrounding ionized nebula—or the interacting shock in a binary system—powers the persistent radio source.

工程学Engineering

Passive wing deployment and retraction in beetles and flapping microrobots

甲虫和扑翼微型机器人翅膀的被动展开和收拢

▲ 作者：Hoang-Vu Phan, Hoon Cheol Park & Dario Floreano

▲ 链接：https://www.nature.com/articles/s41586-024-07755-9

▲摘要：

在此，我们展示了犀金龟可以毫不费力地展开它们的后翅，而不需要肌肉活动。我们展示了打开鞘翅会将像弹簧一样的后翅部分从身体上释放出来，从而为随后的拍打动作提供所需的空间，从而使后翅进入飞行位置。