At https://spaceweather.com on Thursday the 15th September we learned that during a minor geomagnetic storm on February 4th, dozens of Starlink satellites fell out of their orbit. A weak CME hit the earth and the magnetic field gave way resulting in a minor storm. How did this happen, the author asks. The storm pumped 1200 gigawatts of energy into the upper atmosphere and the extra energy heated the upper atmosphere and sharply increased aerodynamic drag on the satellites.
Space X launched the Starlink satellites on February 3rd. Only a quarter of them survived the geomagnetic storm – 36 out of 49 were brought down.
At https://phys.org/news/2022-09-byzantine-solar-eclipse-illuminate-obscure.html … In a new study in ‘Publications of the Astronomical Society of the Pacific’ Japanese researchers combed through ancient records, including those of the Byzantine Greeks, in order to identify and locate solar eclipses that occurred around the eastern Mediterranean region in the 4th to 7th centuries AD. Until now, solar eclipse records were scarce in this part of the world, which was strange. They are interested in them in order to understand the earth’s rotational variability in the past. The investigators were able to identify the locations of five total solar eclipses – in AD346, 418, 484, 601, and 693. The key variable they were looking for was the difference between time measured according to the earth’s rotation and time independent of the earth’s rotation. These variations represent changes in the actual length of a day on earth – presumably as a result of the orbital path of the earth around the sun.
The new data appears to shed light on the variation in earth’s rotation on a centennial timescale. They are thus able to help reform the study of other global phenomena throughout history, such as sea level changes.
The full paper can be downloaded at https://iopscience.iop.org/article/10.1088/1538-3873/ac6b56 …