New Delhi: A coronal hole (CH) high speed stream (HSS) has induced a strong geomagnetic storm on the Earth. The coronal hole crossed the central meridian on 10 September, following which it was aimed straight at the Earth. The magnetic field lines on the coronal hole are aligned, and instead of trapping the plasma or hot gas that makes up the Sun, the material is propelled outwards into space, resulting in a steady stream of energetic particles. This high speed stream is not as violent or chaotic as a coronal mass ejection (CME), that are charged clouds of energetic particles launched outwards through interplanetary space by the Sun.
The G3 storm alert. (Image Credit: SWPC).
According to the Solar Influences Data Analysis Centre (SIDC) operated by the Royal Observatory of Belgium, “Enhanced solar wind parameters are expected in the next 24 hours with the arrival of high speed streams from the SIDC Coronal Hole 116 (negative polarity), which started to cross the central meridian on Sep 10.” The Space Weather Prediction Centre (SWPC) operated by the US National Atmospheric and Oceanic Administration (NOAA) issued an alert, and in its forecast says, “The solar wind environment is expected to be enhanced over 15-17 Sep due to negative polarity CH HSS influences. Further enhancements are possible on 15 Sep as the CME from 11 Sep passes in close proximity to Earth.”
Space Weather Forecast
Minor geomagnetic storming commenced late on Sunday, and peaked early on Monday morning, before returning to minor storm levels. According to the forecast by the UK Met Office, “A fast wind from a large coronal hole to the west of the disc will affect Earth throughout the forecast, peaking during Day 1(15 Sep). Geomagnetic conditions are expected to be unsettled to active (Kp3-4) for much of Day 1 (15 Sep), with likely G1 Minor storm (Kp5) intervals and a very slight chance of an isolated G2 Moderate storm (Kp6). From Day 2 (16 Sep) conditions are expected to return to mostly Quiet to unsettled (Kp1-3) with a reducing chance of active or G1 intervals through the period.”