Expect a moderate geomagnetic storm and aurora on 5-6 Dec.

A large coronal hole that we wrote about in our post from 7 Nov.  (also see an early post on 14 Sep.) is again crossing the solar central meridian. Image on the left taken by AIA instrument on board NASA's Solar Dynamics Observatory shows the coronal hole early 2 December 2025 (universal time). This coronal hole developed at the end of April, 2025 (8 months ago!) and since then was steadily growing. The coronal hole coincides with a large area of weak unipolar magnetic field of mostly negative polarity (right panel, see white outline  plotted over a magnetogram taken by GONG station at Learmonth, Australia). The magnetic field from this area opens up to the interplanetary space forming a high speed solar wind stream. One should expect that in about 4 days (5-6 Dec), the solar wind from this stream will intersect with Earth's magnetosphere and cause a moderate geomagnetic storm and aurora.