The Space Weather Prediction Center (SWPC) , a unit of the U.S. Department of Commerce under NOAA,which sits alongside its terrestrial National Weather Service, has issued a Geomagnetic Storm Watch for all of Earth for Sunday, September 26 for the possibility of G1 or G2 storm conditions.
On Thursday, a sunspot, known as AR2871, experienced two explosive eruptions, each producing a significant M-class solar flare. Solar flares are classified according to their strength, on a B-C-M-X scale. B flares are the smallest while X are the largest. Similar to the Richter scale used to help quantify earthquakes, each letter represents a ten-fold increase in energy output. Within each letter class, there is also a finer scale that usually extends from 1-9. Within the powerful X class of flares, the number could exceed 9 to reflect a massive flare event.
While there are fears that a future blast from the sun will disrupt electricity, communication, and internet lines for weeks, this event does not seem to have that type of potential with it. However, some impacts, including an electrified display of the Northern Lights at northern latitudes, are expected.
AR2871 initially produced a M1.8 flare and a subsequent coronal mass ejection (CME). According to the SWPC, initial analysis and model run indicate an overtaking of the slightly slower CME that was also produced by region 2871 earlier on the 23rd with an arrival anticipated for the first half of September 27.
A coronal hole high speed stream, known as CH HSS for short, is due to hit the Earth by midday on the 26th. The National Weather Service’s Space Weather Prediction Center (SWPC) says, “Isolated G1 (Minor) geomagnetic storming is likely 26 September as a positive polarity CH HSS extension from the Northern crown becomes geoeffective.” A previous Space Weather Forecast Discussion released by the SWPC also says G2 conditions are also a possibility.
Right now, the SWPC says there is a 30% chance of only active geomagnetic activity on the 26th, a 40% chance of a “minor storm”, a 25% chance of a “moderate storm”, and a 1% chance of a “strong-extreme storm.”
The Sun is the primary cause of space weather. At times, the Sun can be thought of as going through a “stormy” period where its surface is more active than normal. When this happens, the Sun can send streams of energized particles out in all directions. When these energized particles interact with the outer reaches of our atmosphere, the aurora borealis (the Northern Lights) and the aurora australis (the Southern Lights) can result.
Dark regions on the Sun known as coronal holes are one of the main drivers of space weather now. According to the Space Weather Prediction Center, coronal holes appear as dark regions on the Sun because they are cooler than the surrounding plasma and are open magnetic field lines. The Sun’s outermost part of its atmosphere, which is known as the corona, is where these dark regions appear. The solar corona was also one of the main features of the Sun scientists were most excited to study during the past solar eclipse. You are able to notice these features in extreme ultraviolet (EUV) and soft x-ray solar images.
Solar wind is always flowing from the Sun and towards Earth but coronal holes are known for releasing enhanced solar wind. Coronal holes can develop anywhere on the sun and are more common during solar minimum. One solar rotation of the Sun occurs every 27 days and coronal holes are sometimes able to last several of these. It is common to see persistent coronal holes at the north and south pole of the Sun but sometimes they can expand towards the equator of the Sun resulting in a larger region. Normally, coronal holes located near the Sun’s equator, result in faster solar wind arriving at Earth. It is common to see coronal holes produce G1-G2 geomagnetic storming levels and sometimes on rare occasions, upwards to G3 levels have been met.
Geomagnetic storms are rated on a 1-5 scale, with 1 being the weakest and 5 having the most potential for damage. Even a G1 geomagnetic storm could create issues: there could be weak power grid fluctuations and minor impacts on satellite operations. Aurora, also known as the “Northern Lights”, could be visible at high latitudes from northern Michigan and Maine to points north. Impacts and aurora change as the geomagnetic storm scale increase.
NOAA forecasters analyze these features and have to take them into account during each forecast. If Earth is experiencing the effects of a coronal hole and a coronal mass ejection is forecasted to impact Earth, the combined effects could result in a more significant impact and more intense geomagnetic storming. Analyzing data from the DSCOVER and ACE satellite is one way forecasters can tell when the enhanced solar wind from a coronal hole is about to arrive at Earth. A few things they look for in the data to determine when the enhanced solar wind is arriving at Earth:
• Solar wind speed increases
• Temperature increases
• Particle density decreases
• Interplanetary magnetic field (IMF) strength increases
While these solar events can help illuminate the sky with stunning aurora, they can also do considerable harm to electronics, electrical grids, and satellite and radio communications. That isn’t expected this week, but such an event could happen in the future.
On September 1-2 in 1859, a powerful geomagnetic storm struck Earth during Solar Cycle 10. A CME hit the Earth and induced the largest geomagnetic storm on record. The storm was so intense it created extremely bright, vivid aurora throughout the planet: people in California thought the sun rose early, people in the northeastern U.S. could read a newspaper at night from the aurora’s bright light, and people as far south as Hawaii and south-central Mexico could see the aurora in the sky.
The event severely damaged the limited electrical and communication lines that existed at that time; telegraph systems around the world failed, with some telegraph operators reporting they received electric shocks.
A June 2013 study by Lloyd’s of London and Atmospheric and Environmental Research (AER) in the U.S. showed that if the Carrington event happened in modern times, damages in the U.S. could exceed $2.6 trillion, roughly 15% of the nation’s annual GDP.
While typically known for their weather forecasts, the National Oceanic and Atmospheric Administration (NOAA) and its National Weather Service (NWS) is also responsible for “space weather.” While there are private companies and other agencies that monitor and forecast space weather, the official source for alerts and warnings of the space environment is the Space Weather Prediction Center (SWPC). The SWPC is located in Boulder, Colorado and is a service center of the NWS, which is part of NOAA. The Space Weather Prediction Center is also one of nine National Centers for Environmental Prediction (NCEP) as they monitor current space weather activity 24/7, 365 days a year.
