2020 February 25
Explanation: How similar is Jupiter’s magnetic field to Earth’s? NASA’s robotic Juno spacecraft has found that Jupiter’s magnetic field is surprisingly complex, so that the Jovian world does not have single magnetic poles like our Earth. A snapshot of Jupiter’s magnetic field at one moment in time, as animated from Juno data, appears in the featured video. Red and blue colors depict cloud-top regions of strong positive (south) and negative (north) magnetic fields, respectively. Surrounding the planet are imagined lines of constant magnetic field strength. The first sequence of the animated video starts off by showing what appears to be a relatively normal dipole field, but soon a magnetic region now known as the Great Blue Spot rotates into view, which is not directly aligned with Jupiter’s rotation poles. Further, in the second sequence, the illustrative animation takes us over one of Jupiter’s spin poles where red magnetic hotspots are revealed to be extended and sometimes even annular. A better understanding of Jupiter’s magnetic field may give clues toward a better understanding of Earth’s enigmatic planetary magnetism.
Tomorrow’s picture: planet lost
说明：木星的磁场与地球有多少相似之处？NASA的朱诺号自动探测器已经发现木星的磁场异乎寻常的复杂，所以木星世界不像我们地球那样有个单一的磁极。这段视频是将朱诺号获取的各个时刻的木星磁场数据做成了动画。红色和蓝色分别描绘了强正（南）磁场和负（北）磁场的云顶区域。行星周围是想象的磁力线（注：原文为lines of constant magnetic field strength）。视频最开始显示出一个相对正常的偶极场，但接着一个如今被称为“大蓝斑”的磁力区转入画面之中，这个区域与木星自转的极区并不重合。在视频的第二段，模拟动画转到了木星自转极的视角，可以看到红色的磁力区占据了较大的范围，有些地方呈现为环状。对木星磁场的进一步了解有助于提高我们对于地球上神秘的行星磁场的认识。