The Sun triggers an X-class solar flare, sending coronal mass ejections toward Earth. Active sunspot AR3777 in early August 2024 triggered the most powerful of three solar flares in that period, sending another coronal mass ejection toward Earth with a possible geomagnetic storm. CMEs are powerful explosions of magnetic fields and plasma that result from solar flares on the Sun that can lead to powerful geomagnetic storms on Earth.
X-class solar flares are the most powerful class of solar flares, and the X designation is followed by a number from 1 to 9 that indicates their power, with 9 being the strongest. In fact, there is no speed limit for coronal mass ejections. The August 8 eruption exceeded 2.2 million miles per hour (1,000 km/s)!
ESA’s Solar Orbiter spacecraft has provided crucial data to answer a question that has puzzled scientists for decades: where the energy comes from to heat and accelerate the solar wind. Working in tandem with NASA’s Parker Solar Probe, Solar Orbiter shows that the energy needed to power this outflow comes from large-scale variations in the Sun’s magnetic field.
The solar wind is a constant stream of charged particles that escapes from the sun’s atmosphere (called the corona) and flies past Earth. It is the collision of the solar wind with our planet’s atmosphere that causes the colorful aurora borealis in our skies.
The “fast” solar wind moves at over 500 km/s, equivalent to a whopping 1.8 million km/h. Curiously, this wind leaves the Sun’s corona at a slower speed, so something is speeding it up as it moves away. Million-degree winds naturally cool by expanding into a larger volume and becoming less dense, like air on Earth when you climb a mountain. Yet they cool more slowly than you would expect based on this effect alone.
So what provides the energy needed to accelerate and heat the fastest parts of the solar wind? Data from ESA’s Solar Orbiter and NASA’s Parker Solar Probe have provided compelling evidence that the answer lies in large-scale fluctuations in the sun’s magnetic field known as Alfvén waves.
“Before this work, Alfvén waves had been suggested as a potential energy source, but we didn’t have definitive evidence,” says co-author of the first paper Yeimi Rivera of the Center for Astrophysics at Harvard and the Smithsonian Institution in Massachusetts.
In a normal gas, such as the Earth’s atmosphere, the only type of wave that can be transmitted is sound waves. However, when gas is heated to extreme temperatures, such as in the Sun’s atmosphere, it enters an electrified state known as plasma and responds to magnetic fields. This allows waves called Alfvén waves to form in a magnetic field. These waves store energy and can effectively transport it through the plasma.
A normal gas expresses its stored energy in the form of density, temperature, and velocity. However, in a plasma, the magnetic field also stores energy. Both Solar Orbiter and Parker Solar Probe contain the necessary instruments to measure the properties of the plasma, including its magnetic field.
Although the two spacecraft are at different distances from the Sun and in completely different orbits, in February 2022 the spacecraft happened to be aligned with the same solar wind stream.
Parker, operating at 13.3 solar radii (about 9 million km) from the sun at the outermost edges of the solar corona, was the first to cross the stream. Solar Orbiter, operating at 128 solar radii (89 million km), then crossed the stream a day or two later. “This work was only possible because of the special alignment of the two spacecraft, which were sampling the same solar wind stream at different stages of its journey from the sun,” Yeimi says.
Taking full advantage of this rare alignment, the team compared measurements of the same plasma flow at two different locations. They first converted the measurements into four key energy quantities, which included a measure of the stored energy in the magnetic field, called the energy flux wave.
Since energy can neither be created nor destroyed, only converted from one form to another, the team compared Parker’s readings with Solar Orbiter’s. They made this comparison both with and without the magnetic energy term.
“We found that if we didn’t account for the wave energy flux in Parker, we couldn’t exactly match the amount of energy that Solar Orbiter had,” says co-author Samuel Badman of the Center for Astrophysics at Harvard and the Smithsonian Institution in Massachusetts.
Near the Sun, where Parker measured the flux, about 10% of all energy was found in the magnetic field. In Solar Orbiter, that number dropped to just 1%, but the plasma sped up and cooled more slowly than expected.
After comparing the numbers, the team concluded that the lost magnetic energy provided acceleration and slowed the cooling of the plasma, while providing some of its own heating.
The data also show how important magnetic configurations known as backswings are to wind acceleration. Backswings are large deviations in the sun’s magnetic field lines and are examples of Alfvén waves. They have been observed since the first solar probes in the 1970s, but their detection rate has increased dramatically since Parker Solar Probe became the first spacecraft to fly through the sun’s corona in 2021 and found that backswings cluster together into patches.
The new work confirms that these kinks contain enough energy to account for the missing portion of the acceleration and heating of the fast solar wind.
“This new work cleverly brings together some major pieces of the solar puzzle. More and more data collected by Solar Orbiter, Parker Solar Probe and other missions show us that different solar phenomena actually work together to create this unusual magnetic environment,” says Daniel Müller, ESA Solar Orbiter Project Scientist.
And it’s not just information about our solar system. “Our sun is the only star in the universe whose winds we can measure directly. So what we’ve learned about our sun is potentially applicable to at least other solar-type stars and perhaps other types of stars that have winds,” Samuel says.
The team is now working to extend their analysis to apply to slower forms of solar wind to see if the energy from the Sun’s magnetic field plays a role in accelerating and heating them.
The huge sunspot responsible for the spectacular auroras in May has triggered a major X-class solar flare. The hyperactive sunspot region shows no sign of slowing down in the coming months.
The emerging sunspot region AR3697 made its presence known by producing another powerful X-class solar flare that emerged from behind the southeastern edge of the Sun. The solar flare peaked at 10:35 a.m. ET (14:35 GMT) on May 29, 2024, causing a shortwave radio blackout across Western Europe and the eastern United States.
AR3697 is a returning version of sunspot AR3664, which was responsible for the massive G5 geomagnetic storm that occurred in mid-May of that year – the most powerful solar storm since 2003, which produced spectacular auroras around the world.
Immediately after the May 20 flare, Solar Orbiter’s Energetic Particle Detector (EPD) detected a burst of ions moving at tens of thousands of kilometers per second and electrons moving close to the speed of light.
Coinciding with this event, computers on BepiColombo and Mars Express (two ESA planetary missions) saw a big jump in memory errors, likely caused by energetic particles from the sun hitting physical memory cells inside the spacecraft. Mars Express project scientist Olivier Vitasse notes: “These technical data are designed to monitor the health of the spacecraft, but this shows that they can also be used to detect space weather events, which were not really foreseen!”
Soon after, Solar Orbiter’s Metis coronagraph saw the Sun hurl a so-called “coronal mass ejection,” and the MAG magnetometer recorded its arrival at the spacecraft about a day later. The huge bubble of plasma, made up of charged particles moving at an average speed of about 1,400 km/s, caused large fluctuations in the magnetic field measured by the spacecraft. The Sun hurled so much material that it was even seen from Earth by the ESA/NASA SOHO mission.
These different data sets allow us to track the movement of particles and electromagnetic fields from this massive ejecta throughout the solar system. This, in turn, helps improve the accuracy of solar activity modeling.
The strongest flare of the highest class X occurred on the Sun on May 27, the Institute of Applied Geophysics (IPG) reported to TASS.
“At 10:08 Moscow time, a 36-minute X2.9 flare was registered in the X-ray range,” the IPG reported. The flare has already disrupted shortwave radio communications.
After a series of powerful flares on the star, a powerful magnetic storm began on Earth in early May. On the night of May 11, it reached an extreme level of power, which was recorded for the first time since August 2005.
Eight strong flares, one of which was of the highest class X, occurred on the Sun on May 29, the Institute of Applied Geophysics (IPG) told TASS.
“High solar activity on Wednesday resulted in a series of M-class flares and one X1.4/2B flare lasting 87 minutes. This flare was accompanied by a coronal mass ejection, bursts of radio emission, and disruption of shortwave radio communications,” the IPG reported.
Seven strong M-class flares were recorded in different sunspot groups. The first M 1.3 flare lasting 15 minutes occurred at 04:06 Moscow time, the last one, also M1.3, lasting 28 minutes, occurred at 22:10 Moscow time. The strongest M5.7 flare was recorded at 21:41 Moscow time. The previous X2.9 flare was recorded on May 27.
After a series of powerful flares on the star, a powerful magnetic storm began on Earth in early May. On the night of May 11, it reached an extreme level of power, for the first time since August 2005. The flares affected the planet’s information transmission systems, for example, some Starlink satellites were “knocked out” of their orbital positions.
Solar flares are divided into five classes depending on the power of X-ray radiation: A, B, C, M and X. The minimum class A0.0 corresponds to a radiation power of 10 nW per 1 sq. m in the Earth’s orbit. When moving to the next letter, the power increases by 10 times. Flares are usually accompanied by emissions of solar plasma, clouds of which, reaching the Earth, can provoke magnetic storms.
On June 11, Solar Orbiter witnessed another X-class solar flare, occurring on the far side of the Sun at AR3664. Understanding the behaviour of active regions like AR3664 throughout their lifetime will ultimately help predict how solar flares will affect Earth. ESA missions provide eyes and ears across the Solar System, using space science for the benefit of Earth.
Solar Orbiter’s observations of the far side of the Sun provide a glimpse of what ESA’s Vigil space weather forecasting mission will do. By observing the left side of the Sun (as seen from Earth), the spacecraft has provided a constant stream of near-real-time data on potentially dangerous solar activity before it is visible from Earth.
“Adding Vigil data to our space weather services can give us forecasts 4-5 days earlier for certain space weather effects and provide more detail than ever before. Such early warnings give astronauts time to take shelter and operators of satellites, power grids and telecommunications systems time to take protective measures,” says Giuseppe Mandorlo, Vigil project manager at ESA.
Scientists registered five powerful solar flares on July 14, one of which was of the highest class X, the Institute of Applied Geophysics (Federal State Budgetary Institution “IPG”) told TASS.
“On July 14 at 05:34 Moscow time, an X1.3 flare lasting 29 minutes was recorded in the X-ray range in the sunspot group 3738 (S12W39), the IPG reports.
In addition, on Sunday night there were M5.0, M2.7, M1.7 flares, and in the morning there was an M3.0 flare.
After the flares, the level of influence of solar X-ray bursts on the Earth’s ionosphere, according to space weather data, was at the R3 (strong) level on a scale of five indicators, where the highest is R5 (extreme).
Scientists registered eight powerful M-class solar flares on July 28, the Institute of Applied Geophysics (Federal State Budgetary Institution “IPG”) told TASS.
The first flare (M7.9) occurred at 04:51 Moscow time, and the last (M1.7) at 17:22 Moscow time. The flares were registered in different groups of sunspots.
The most powerful flare, close to class X, was recorded by scientists at 04:57 Moscow time. “In the X-ray range, in the spot group 3766 (S07E10), a flare M9.9 lasting 8 minutes was recorded,” the IPG reports.
In addition, after a series of flares, the level of influence of solar X-ray bursts on the Earth’s ionosphere rose to R2 (moderate) on a scale of five indicators, where the highest level is R5 (extreme). According to space weather monitoring, four flares (M1.6, M9.9, M7.9, M7.8) were accompanied by disruption of HF radio communications.
Scientists registered the third highest class X solar flare in July on July 29, the Institute of Applied Geophysics (FGBU IPG) reported to TASS.
“On July 29 at 05:37 Moscow time, an X1.5 flare lasting 10 minutes was recorded in the X-ray range in the sunspot group 3764 (S05W04),” the report says.
Previously, outbreaks of X1.2 (July 14) and X1.9 (July 16) were reported.
Solar flares are divided into five classes depending on the power of X-ray radiation: A, B, C, M and X. The minimum class A0.0 corresponds to a radiation power of 10 nanowatts per 1 square meter in the Earth’s orbit. When moving to the next letter, the power increases by 10 times. Flares are usually accompanied by emissions of solar plasma, clouds of which, reaching the Earth, can provoke magnetic storms.
Scientists registered five powerful solar flares on August 14, one of them was of the highest class X, the Institute of Applied Geophysics (FGBU “IPG”) told TASS. It is noted that the flare was accompanied by a disruption of HF radio communications.
“On August 14 at 09:40 Moscow time, an X1.1 flare lasting 58 minutes was recorded in the X-ray range in the sunspot group 3784 (N13E04),” the report says. In addition, scientists recorded flares of M1.3, M1.2, M4.2 and M4.4. The first occurred on August 14 at 01:45 Moscow time.
Following the series of flares, the level of influence of solar X-ray bursts on the Earth’s ionosphere, according to space weather data, reached R3 (strong) on a scale of five, where the highest is R5 (extreme).
May 2024 has already proven to be a particularly turbulent month for the Sun. During the first full week of May, a flurry of large solar flares and coronal mass ejections (CMEs) launched clouds of charged particles and magnetic fields toward Earth, creating the most powerful solar storm to reach Earth in two decades — and possibly one of the most powerful auroral displays recorded in the past 500 years.
“We’ll be studying this event for years,” said Teresa Nieves-Chinchilla, acting director of NASA’s Moon to Mars (M2M) Space Weather Analysis Directorate. “It will help us test the limits of our models and understanding of solar storms.”
The first signs of the solar storm began late on May 7 with two powerful solar flares. From May 7 to 11, several powerful solar flares and at least seven coronal mass ejections (CMEs) hurtled toward Earth. Eight of the flares during this period were of the most powerful type, known as X-class, with the strongest peak rated at X5.8. (The same solar region has since produced many more large flares, including an X8.7 flare — the most powerful flare seen this solar cycle — on May 14.)
Traveling at speeds of up to 3 million miles per hour, the coronal mass ejections came together in waves that reached Earth beginning on May 10, creating a long-lasting geomagnetic storm that reached a G5 rating, the highest level on the geomagnetic storm scale not seen since 2003.
“All of the coronal mass ejections happened at about the same time, and the conditions were just right for a truly historic storm to occur,” said Elizabeth McDonald, lead scientist for NASA’s Heliophysics Citizen Science Group and a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
When the storm reached Earth, it created bright auroras that could be seen around the world. Auroras were visible even at unusually low latitudes, including in the southern United States and northern India. The strongest auroras were observed on the night of May 10, and they continued to light up the night sky throughout the weekend. Thousands of reports sent to the NASA-funded citizen science site Aurorasaurus are helping scientists study the event to learn more about auroras.
“Cameras — even standard cellphone cameras — are much more sensitive to the colors of the aurora than they used to be,” McDonald said. “By collecting images from around the world, we have a huge opportunity to learn more about the aurora through citizen science.”
According to one measure of geomagnetic storm strength called the Storm Disturbance Timing Index, which dates back to 1957, this storm was similar to historical storms in 1958 and 2003. And with reports of auroras visible as low as 26 degrees magnetic latitude, this recent storm could rival some of the lowest-latitude auroral sightings recorded in the past five centuries, though scientists are still evaluating that ranking.
“It’s a little harder to evaluate storms over time because our technology is constantly changing,” says Delores Knipp, a research professor in the Smead Aerospace Engineering Science Department and a senior scientist at the NCAR High Altitude Observatory in Boulder, Colorado. “Aurora visibility isn’t a perfect metric, but it allows us to compare over centuries.”
McDonald encourages people to continue to submit auroral reports to Aurorasaurus.org, noting that even those that are not observed are valuable in helping scientists understand the scale of the event.
Ahead of the storm, the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center, which is responsible for forecasting the impacts of solar storms, sent out alerts to power grid operators and commercial satellites to help them mitigate potential impacts.
The warnings helped many NASA missions prepare for the storm, and some spacecraft shut down certain instruments or systems in advance to avoid problems. NASA’s ICESat-2, which studies the polar ice sheets, went into safe mode, likely because of increased drag from the storm.
Better data on how solar events affect Earth’s upper atmosphere is critical to understanding the impact of space weather on satellites, human missions, and ground and space infrastructure. To date, only a few limited direct measurements exist in this region. But more are coming. Future missions like NASA’s Geospace Dynamics Constellation (GDC) and Dynamical Neutral Atmosphere-Ionosphere Coupling (DYNAMIC) will be able to see and measure exactly how Earth’s atmosphere responds to the energy influxes that occur during solar storms like this one. Such measurements will also be valuable as NASA sends astronauts to the moon on the Artemis missions and then to Mars.