New Delhi: On 15 Sep, the National Oceanic and Atmospheric Administration (NOAA) declared a G3 (Strong) Geomagnetic Storm in Earth’s atmosphere. The geomagnetic storm was caused by a high speed stream (HSS) from a coronal hole (CH) aimed straight at the Earth that crossed the central meridian on 10 Sep. Geomagnetic storms occur when unsteady solar winds interact with Earth’s magnetosphere; the region in Earth’s atmosphere that contains all the geomagnetic fields. When magnetized plasma ejected from the Sun collides with these magnetic fields, it triggers disturbances known as geomagnetic storms. For the event lasting from 15-16 Sep, there were surges of plasma observed emerging from the Sun’s outer corona. There were also observations made around the large coronal hole in the Sun, showing strong storms and solar flares.
The estimated K-index. (Image Credit: SWPC).
To monitor the magnitude of these geomagnetic solar storms, NOAA uses the K-index. “Kp is an excellent indicator of disturbances in the Earth’s magnetic field and is used by SWPC to decide whether geomagnetic alerts and warnings need to be issued for users who are affected by these disturbances”, says NOAA. The geomagnetic storming commenced late on Sunday evening and continued till Monday afternoon, before the disturbances subsided to below the storming threshold. The yellow and orange bars indicate geomagnetic storming, with the disturbances reaching storming levels again this afternoon. The system uses a number scale to indicate the magnitudes; with kp = 5 being declared as a G1 magnitude storm, and kp = 9, as G5, which is the most extreme storm event.
Space Weather Forecast
According to the Space Weather Prediction Centre (SWPC) operated by the NOAA, “Unsettled to G1 (Minor) storming, with a chance for G2 (Moderate), is expected on 16 Sep as HSS effects persist. Unsettled to active levels are expected on 17 Sep followed by quiet to unsettled conditions on 18 Sep as HSS conditions gradually diminish.” According to the forecast by the Solar Influences Data Analysis Centre (SIDC) operated by the Royal Observatory of Belgium, “The solar wind conditions are expected to continue to be elevated under the HSS influence over the next days.”
By Jiya Mishra