NOAA Issues ‘Moderate’ Geomagnetic Storm Watch for the Weekend

Residents in thirteen States could get the chance to see the Northern Lights, or the aurora borealis, over the weekend due to a coronal mass ejection (CME) from the sun, according to weather officials from The National Oceanic and Atmospheric Administration (NOAA):

A G2 (Moderate) geomagnetic storm watch is in effect for the 23 March, 2019 UTC-day due to anticipated CME arrival. An asymmetric halo CME was observed in SOHO/LASCO coronagraph imagery and analysis of the CME in both LASCO and STEREO-A coronagraph imagery shows an Earth-directed component is likely. The CME was associated with a C4 flare on 20 March, 2019 at 1118 UTC (0718 EDT). A G1 (Minor) geomagnetic storm watch is in effect for the 24 March, 2019 UTC-day due to persistent CME influence.

According to the map below, the most likely area of an aurora event is between the green line and the yellow line, which appears to encompass parts of New York, northern Illinois, Wisconsin, North and South Dakota, Montana, Idaho, Washington state, Iowa, Michigan, Maine, Vermont, New Hampshire, and Massachusetts.

Map showing the potential for sightings of the Aurora Borealis over the weekend in the United States (NOAA)

NOAA explains the event this way:  Earth’s magnetic field guides the electrons such that the aurora forms two ovals approximately centered at the magnetic poles. During major geomagnetic storms, these ovals expand away from the poles such that aurora can be seen over most of the United States.  Aurora comes in several different shapes. Often the auroral forms are made of many tall rays that look much like a curtain made of folds of cloth. During the evening, these rays can form arcs that stretch from horizon to horizon. Late in the evening, near midnight, the arcs often begin to twist and sway, just as if a wind were blowing on the curtains of light. At some point, the arcs may expand to fill the whole sky, moving rapidly and becoming very bright. This is the peak of what is called an auroral substorm.

During storms, the currents in the ionosphere, as well as the energetic particles that precipitate into the ionosphere add energy in the form of heat that 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 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 pipeline.