Friday, April 20, 2018

Moderate Geomagnetic Storm Hits Earth

Credit: NOAA

A G2-class (moderate) geomagnetic storm hit the Earth today due to the arrival of an isolated, positive polarity coronal hole high-speed stream (CH HSS) or potential glancing blow effects from a minor unrecognized coronal mass ejection (CME).

"G2 (Moderate) geomagnetic storm levels were observed at 08:25 UTC (04:25 ET) and 10:44 UTC (06:44 ET) on April 20,” National Oceanic and Atmospheric Administration (NOAA) informs on its website. 

G2-class storm can cause voltage alarms and transformer damage in high-latitude power systems. When it comes to possible impact on spacecraft operations, in result of such storm, corrective actions to orientation may be required by ground control. Moderately strong geomagnetic storm can also spark auroras and cause fading of HF radio propagation at higher latitudes. 

In general, 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. 

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. 

CMEs are huge explosions of magnetic field and plasma from the sun's corona. When CMEs impact the Earth’s magnetosphere, they are responsible for geomagnetic storms and enhanced aurora. 

NOAA reveals solar activity is expected to be generally at very low levels until May 12. However, another minor storming may occur on May 6-10, due to effects from a recurrent positive polarity CH HSS.

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