Friday, October 20, 2017

Polar Geomagnetic Storms Could Hit Earth This Weekend

Artist illustration of events on the sun changing the conditions in Near-Earth space. Image Credit: NASA

Polar geomagnetic storms could hit Earth when a new solar stream wind will arrive at our planet this weekend, according to the National Oceanic and Atmospheric Administration (NOAA). In result, weak power grid fluctuations can occur and auroras may be visible at high latitudes such as Canada and Alaska.

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 (GICs) in the power grid and pipelines. When the storms are observable only in the auroral zones, they are called polar magnetic storms.

NOAA estimates that there is a 45 percent chance of polar geomagnetic storms on October 21-22. The area of possible impact is described as poleward of 65 degrees geomagnetic latitude. The agency also expects G1 (minor) geomagnetic storms on October 24-25 and November 7-11, as well as possible G2 (moderate) geomagnetic storms on October 25 and November 10, caused by 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.

NOAA informs that the solar activity is expected to be generally at very low levels till November 11. However, there is a chance for C-flares (relatively weak) with the return of old active regions (ARs) on the Sun, designated 2682 and 2683.

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