NOAA Is Rewriting the Book on How to Rank Solar Storms: The Capabilities, the Science, and Our Understanding of the Science — A lot has changed in space weather in the last 25 years. Technology has improved, and scientists have learned more about extreme space weather events from historic geomagnetic storms like the Halloween solar storm of October 2003 and the Gannon Event of May 2024. Looking to the future, scientists at the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center (SWPC) are now looking for ways to better inform the public about space weather events that can impact Earth. That’s why NOAA is asking the public for input on how to rewrite its space weather scales.
NOAA, in collaboration with the National Weather Service (NWS), has issued a solicitation asking organizations and the public to share information on what changes could help update the space weather scales (the submission period has now closed). The goal is to make it easier to understand the space weather conditions that may occur and how they may impact people in space and on Earth, as well as the various systems that have been affected in the past.
An illustration of a coronal mass ejection impacting Earth’s atmosphere. Mark Garlick/Science Photo Library
The NOAA Space Weather Scales were created in 1999, when space weather began to gain popularity with the advent of new technologies for studying weather in outer space. Spacecraft were equipped with various instruments to study the solar wind and monitor solar activity. They were modeled after existing scales used to classify meteorological events on Earth. The scales describe three types of environmental impacts, based on the three main groups of impacts that result from solar flares. In addition, each scale includes information about how likely each type of event is to occur on average and the type of intensity associated with each level.
For geomagnetic storms, magnitude categories focus on the impact on spacecraft, power grids, and other ground infrastructure.
In solar radiation categories, effects include biological effects on astronauts and aircraft passengers, as well as possible effects on satellites and other systems.
The third scale, radio outages, focuses on the impact of space weather on high frequency (HF) radio communications as well as navigation systems.
Emergency response organizations like the Federal Emergency Management Agency (FEMA) have begun asking more questions of the SWPC about whether and how radio blackouts might affect satellite and cellphone communications, based on the wording of the radio blackout scale. Other examples have included concerns about varying levels of “radiation” from a solar storm. Spacecraft operators are also interested in new scales of space weather as more commercial companies rely on satellites to provide services.
NOAA is expected to complete its findings on the new space weather conditions by the end of the year, and the information will then be shared with various government agencies, including the White House, the Department of Energy, the Department of Transportation, and the Federal Aviation Administration (FAA). The results will guide teams at NOAA and NWS in deciding what changes need to be made in the short and long term.
The index of energy stored by the Sun has reached record values for the 21st century. The solar cycle index, which shows the energy stored in a star, has, contrary to all forecasts, reached practically record values for the 21st century, exceeding the levels of the two previous solar cycles, Sergei Bogachev, head of the Solar Astronomy Laboratory at the Space Research Institute of the Russian Academy of Sciences, told RIA Novosti.
“Data on the solar cycle index for August 2024 have been received and entered into world catalogs, and they look extremely interesting. According to them, the average value of the index in August was 215.5, which became an absolute record not only for the current 25th, but also for the previous 24th solar cycle, the maximum of which occurred in 2012-2014,” Bogachev said.
According to him, higher levels of solar activity in the 21st century were observed only in 2000-2001, at the peak of the then developing 23rd activity cycle. Moreover, even then the height of the cycle was lower than now, and amounted to 213. A higher value, which is an absolute record for the current century – 244, was registered in July 2000.
The level of the cycle is measured by the number of sunspots and their groups visible per month on the side of the Sun facing the Earth. It reflects the reserves of magnetic and flare energy stored by the Sun. Such calculations have been conducted since 1749 (the solar cycle that was developing at that time received the number zero).
Bogachev emphasized that the current situation on the Sun does not correspond to previously made forecasts. It was expected that the maximum would be almost two times lower and would definitely be inferior to the peaks of the two previous cycles. Moreover, according to him, a significant number of scientists believe that even such high values are only intermediate, and maximum activity will be reached in 2025.
“The solar cycle reaching near-record values has not yet led to a synchronous increase in flare activity. Currently, the frequency of flares and magnetic storms has increased significantly, but the events of May this year still remain record-breaking in strength. Nevertheless, the risks of major events in September are very high,” the scientist added.
The Russian Academy of Sciences has warned of a solar plasma cloud hitting the Earth on September 13. The solar plasma cloud will hit the Earth on Thursday evening with a probability of 99.9 percent, the Solar Astronomy Laboratory of the Space Research Institute and the Institute of Solar Terrestrial Physics of the Russian Academy of Sciences reported.
“The results of modeling of the third plasma emission that has occurred in recent days have been received, which, with a probability of 99.9 percent, will hit the planet this time. <…> At the moment, calculations show the arrival of solar matter tomorrow at about 10 p.m. Moscow time,” says the message published on the evening of September 11.
As scientists emphasized, the models used this time had almost no probability of error. The Russian Academy of Sciences assessed the strength of the expected magnetic storm as moderate.
The laboratory models also indicate a high probability of northern lights in mid-latitudes.
The most active aurora season” could be just a few weeks away. September could be the best time to see the brightest auroras, thanks to the Earth’s tilt that causes more intense geomagnetic activity around the equinox.
In May, the most powerful geomagnetic storm in two decades hit Earth, causing intense displays of the northern lights as far south as Florida and Mexico. There are no guarantees, but there is reason to believe that there could be more intense geomagnetic storms than usual in the weeks either side of this month’s autumnal equinox (September 22). That could mean a shortened auroral season.
This is due to the so-called Russell-McPherron effect, which explains why the periods around the Earth’s two equinoxes, in March and September, often tend to have the most colourful auroras.
The solar wind is a stream of charged particles from the Sun that is suddenly amplified by solar flares and coronal mass ejections (CMEs) – powerful blasts of radiation and solar material. Magnetic activity on the Sun has an 11-year cycle. It should be peaking right now. But that’s not why auroral season may be imminent. Auroras occur when charged particles from the solar wind enter the Earth’s magnetic field and collide with oxygen and nitrogen molecules in the atmosphere; this excites the molecules, causing them to emit brightly coloured light.
While the Earth’s magnetic field and the solar wind’s field are usually out of alignment, due to the Russell-McPherron effect, the Earth’s magnetic poles are tilted during the equinoxes to more easily receive charged particles. Because the south-facing magnetic fields within the solar wind cancel out the Earth’s north-facing magnetic field, cracks open in the Earth’s magnetosphere, causing the solar wind to flow more easily along the magnetic field lines. This geometry works well for the Northern Hemisphere, as the September equinoxes feature 12 hours of darkness followed by 12 hours of daylight.
In recent days, several plasma emissions have been registered on the Sun, but all of them were directed past the Earth. Some of the plasma clouds were ejected from the opposite side of the Sun and in this position, in principle, were not considered dangerous. But on September 7, a large emission occurred on the visible side of our star, which could touch our planet with its edge. This became the reason for the forecast for the evening of Tuesday, September 10, of magnetic storms of weak and medium level of class G1 – G2.
On September 9, the Sun ejected a new large mass of plasma, and this time almost exactly in the direction of Earth. The probability of a head-on impact of the new cloud on our planet is more than 90%.
As reported on the website of the Laboratory of Solar Astronomy of the Space Research Institute of the Russian Academy of Sciences and the Institute of Solar Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences, space images show a cloud of solar matter, approximately 30 million kilometers in size, moving at a speed of approximately 800 km/s.
Although the number of sunspots on the Sun reached another 20-year high in August 2024, recent solar flares have yet to surpass the two solar flares of September 2017. One of those flares, which occurred seven years ago, on September 10, 2017, still holds the record.
In September 2017, the decline phase of the previous solar cycle (Solar Cycle 24), which peaked in 2014, began. After a period of low solar activity, the active region AR 12673 quickly came to the scene. AR 12673 produced a number of X-class solar flares, the most notable of which were on September 6 and 10, 2017.
These flares were initially recorded as X8.2 and X9.3, but were later reclassified as X13.3 and X11.8 following NOAA’s flare recalibration in 2020. These flare classes have not yet reached their final peaks in the current Solar Cycle 25, despite much higher levels of solar activity overall.
Although the September 10, 2017 flare, which occurred 7 years ago, was slightly smaller of the two outbursts, it set a number of records, including: the fastest magnetic output, the fastest CME acceleration, the most powerful long-duration gamma-ray source.
Sunspots are areas of strong magnetic field on the surface of the Sun that are cooler (6,330 degrees Fahrenheit or 3,500˚C) than the surrounding surface of the Sun (9,930˚F or 5,500˚C), giving them a darker appearance. Sunspot magnetic fields have been measured continuously for decades, and there is a well-known correlation between the strength/complexity of a sunspot’s magnetic field and its ability to produce large solar flares.
A sunspot’s magnetic field can grow or weaken over time, evolving continuously over the typical sunspot lifetime of several weeks. In the days leading up to the solar flares of September 6 and 10, 2017, AR 12673 produced one of the fastest magnetic field displays ever observed in a solar active region. Without this rapid magnetic field display, the largest flares of the solar cycle would likely not have been possible.
Solar flares are the conversion of energy from magnetic energy in the Sun’s atmosphere into particle acceleration, heating of solar plasma, and emission of light across the spectrum. About 50% of solar flares are associated with a coronal mass ejection (CME), an eruption of solar plasma from the Sun’s atmosphere.
Solar flares and coronal mass ejections are often confused, but they can be distinguished more easily using the following analogy: imagine a cannon being fired. The explosion of gunpowder, the sound of the explosion, and the flash from the muzzle can be thought of as a solar flare, while a coronal mass ejection is the ejected cannonball.
The September 10, 2017 flare produced a large coronal mass ejection (CME) over the western limb of the Sun, not aimed directly at Earth. This large flare-induced CME was synchronized with the fastest coronal mass acceleration ever observed and one of the fastest initial coronal mass velocities (4,300 km/s).
Solar flares emit light across most of the spectrum, from radio waves to X-rays. Gamma rays, the highest-energy wavelengths of light, are produced only in the most powerful solar flares. The flare on September 10, 2017, not only produced a clear gamma-ray signal, but it continued to emit gamma rays for more than 12 hours. Observed by NASA’s Fermi Gamma-ray Space Telescope, this solar flare’s gamma-ray emission set a record as the strongest gamma-ray source ever observed in the sky for more than 12 hours.
Along with the gamma ray emission, the event also produced one of the largest solar energetic particle storms observed from the Earth’s surface, which also lasted for several hours. A typical solar flare lasts tens of minutes, with the largest X-class flares typically lasting about an hour. However, some solar flares, aptly called “long-duration events,” can last much longer than an hour. The September 10, 2017 flare is an extreme example of this, and there is strong evidence that the flare lasted more than 24 hours, much longer than the observed gamma ray source.