Thursday, October 12, 2017

Minor Geomagnetic Storms Hit Earth

Credit: NOAA

G1 (minor) geomagnetic storms are currently in progress as Earth moves through a stream of fast-moving solar wind. In result, visible auroras are concentrated around Earth's poles and weak power grid fluctuations could occur. The latest storms could also have minor impact on satellite operations.

Geomagnetic storms can increase the density and distribution of density in the upper atmosphere, causing extra drag on satellites in low-earth orbit. The local heating also creates strong horizontal variations in the in the ionospheric density that can modify the path of radio signals and create errors in the positioning information provided by GPS. While the storms create beautiful aurora, they also can disrupt navigation systems such as the Global Navigation Satellite System (GNSS) and create harmful geomagnetic induced currents in the power grid and pipelines.

National Oceanic and Atmospheric Administration (NOAA) revealed that the ongoing storms could intensify to G2-class (moderate) on Friday, October 13, inducing auroras at lower latitudes as low as New York and Idaho. Such moderate storms could cause voltage alarms in high-latitude power systems and satellite orientation problems.

Although solar activity is forecasted to be at very low levels throughout October, NOAA expects one more moderate geomagnetic storm on October 24-25 and one minor on October 14. The agency underlined that the increase in geomagnetic activity is anticipated in response to multiple, recurrent coronal hole high speed streams (CH HSSs). 

Fast CH HSSs can impact Earth’s magnetosphere enough to cause periods of geomagnetic storming to the G1-G2 levels; although rarer cases of stronger storming may also occur. The larger and more expansive coronal holes can often be a source for high solar wind speeds that buffet Earth for many days.