A coronal mass ejection (CME) is a large cloud of electrically charged particles from the upper atmosphere or corona of the sun that heats up to enormous temperatures and takes off at high speed by the energy released in a solar flare. These hot spots of plasma can have spectacular effects on the planets in their path, and while CMEs do not pose a direct threat to life on Earth, they can potentially damage the technologies on which human society is based. .
“CMEs can cause geomagnetic storms when they arrive in the near-Earth environment,” said Stephanie Yardley, a space meteorologist at University College London, UK. “These produce ground-induced currents that degrade electrical networks and can also affect the accuracy of GPS and GNSS satellite navigation systems.”
What causes CMEs?
CMEs originate from the same process they create solar flares – are formed when a large loop of the sun’s magnetic field, which is propelled through the visible surface or photosphere, joins near its base and suddenly reconnects to a lower level. This process releases a large amount of excess energy in the form of high energy electromagnetic radiation, and also heats the gases around the reconnection site, sometimes to temperatures of 36 million degrees Fahrenheit (20 million degrees Celsius) or more. This gives the particles around the site, including those in the now isolated loop of the upper magnetic field, a massive increase in speed and energy, producing a huge bubble of expanding hot gas escaping the gravitational pull of the sun and escapes through space. CMEs can travel at speeds of hundreds of miles per second; the fastest and most energetic can take less than a day to reach Earth’s orbit, but on average it takes about 84 hours, according to the National Oceanic and Atmospheric Administration. Space weather prediction center.
Coronal mass ejections 2022
Here is a list of the CMEs launched by the sun in 2022, based on data collected by software that detects images of the so-called LASCO instrument (a spectrometric coronograph) aboard the ship SOHO (Solar and Heliosphere Observatory).
Largest CMEs of the Year (Source: SpaceWeatherLive.com) CMDuration (hours) Top Speed20 May 31 3,732 miles / sec (1,179 km / s) 19 May 30 284 mph (136 km / s) 18 226 km / s May 18 226 miles / s (365 km / s) 17 May 30 2291 mi / s (469 km / s) 16 May 30 1462 m / s (744 km / s) 15 May 30 3778 mi / s (1,252 km / s) 14 May 29 2380 mi / s (612) km / s) May 13 29 0287 mi / s (462 km / s) May 12 2190 mi / s (306 km / s ) 11 May 29 1282 mi / s (455 km / s) 10 May 29 1168 mi / s (271 km / s) s) 9 May 306 km / s 8 28 May 11,021 mi / s (1,644 km / s) s) 7 May 2809 mi / s (1,302 km / s) 6 May 0340 mi / s (548 km / s) 5 28 May 2467 mi / s (753 km / s) 4 28 May 4346 mi / s (558 km / s) 3 May 28 2289 mi / s (466 km / s) 2 May 27 2280 mi / s (452 km / s) 1 May 27 1313 mi / s (504 km / s)
Geomagnetic storms
When the Earth is in the firing line of a CME, the results can be spectacular. The material contained in a CME is electrically charged and carries tangled remnants of the cut magnetic loop, so it can strongly distort the Earth’s magnetic field, known as the magnetosphere.
This field usually deflects the constant stream of particles known as the solar wind as it rises from the sun. This compresses the sun-oriented side magnetosphere, but creates a long tail (called a magnetotail) that extends far beyond. the moonnight side orbit. Most of the solar wind is completely deflected around the magnetosphere, but particles charged with certain energies can be trapped in donut-shaped regions thousands of miles above the Earth’s surface known as the Van Allen radiation belts. , while others are channeled into the atmosphere above the poles. . Here, charged particles collide with gas particles in the Earth’s upper atmosphere, energizing these molecules to create the beautiful glow of auroras, such as the northern lights.
The arrival of a CME can upset this delicate balance. The increase in the number of particles passing through the Earth causes many more of them to be channeled into the atmosphere above the poles, creating intense auroras that extend to much lower latitudes. Meanwhile, increasing pressure in the magnetosphere and interactions with magnetic fields entangled within the CME temporarily deform the magnetosphere, bringing it much closer to Earth.
Also, the effect is not just magnetic. A so-called physical phenomenon electromagnetic induction means that a changing magnetic field usually causes electric currents to flow through nearby materials. In the case of a CME hitting our planet, all the conductors on Earth, including Earth itself, are exposed.
This means that currents flow and clutter electrical networks and can disrupt satellite-based navigation systems.
The Carrington event
Richard Carrington created this sunspot drawing at the top of the Carrington event in 1859. (Image credit: Richard Carrington) (opens in a new tab)
These electrical effects were how the first geomagnetic storm, and the most powerful known, was detected in 1859. That year, British astronomers Richard Carrington and Richard Hodgson detected an explosion in the solar atmosphere (the first and most bright solar flare never observed) and soon after a CME arrived and caused magnetic damage around the world. The changing magnetism around the wires of the newly built electric telegraph network created strong electric currents that sparked pylons, struck telegraph operators, and even allowed messages to be sent without external power. At the same time, the spectacular auroras extend to the tropics, illuminating the night sky bright enough to read the newspapers. Reported by cable (opens in a new tab).
“The Carrington event produced the most powerful geomagnetic storm on record. It was also the fastest CME observed and only took 17.5 hours to reach Earth,” Yardley said. “Theoretically, CMEs can have a speed limit of about 3,000 km / s. [6.7 million mph]which is consistent with the available energy of the regions of strong magnetic fields that produce them. “
How do CMEs affect Earth and astronauts?
The Earth’s magnetosphere protects the planet from the wrath of the sun. (Image credit: NASA) (opens in a new tab)
Fortunately for life on Earth, the magnetosphere and atmosphere combine to form an effective barrier that deflects and blocks CME particles from reaching the surface of our planet, according to NASA (opens in a new tab). Despite moving at incredibly fast speeds by daily standards, the energies of CME particles are too low to penetrate the magnetosphere. Above the poles, where some of the particles are channeled downwards, they collide and give energy to atoms and dispersed gas molecules, usually at altitudes between 80 and 145 kilometers, to produce auroras, according to a 1946 classic. the magazine Terrestrial magnetism and atmospheric electricity (opens in a new tab).
Astronauts in low Earth orbit (for example aboard the International Space Station) remain well within the magnetosphere and also benefit from their shielding effect; in fact, the passage of a CME offers a surprising benefit, as its flooding of low-energy material briefly. provides an additional layer of protection against high-energy cosmic ray particles emitted by violent events elsewhere in our galaxy and beyond, according to NASA.
However, for astronauts outside the magnetosphere, for example, on a future mission to Mars, higher-energy particles within a CME can pose a significant health risk. NASA scientists and engineers are busy researching different options (opens in a new tab) to provide shielding.
Risks to technology
While CMEs may not pose a major direct threat to life, the huge technological advances since the Carrington event make human society much more vulnerable to the indirect effects of CMEs. In 2003, for example, a geomagnetic storm triggered by the largest solar flare of the modern era affected the electricity supply to Sweden and South Africa, while planes were diverted to avoid high-altitude flights. on the poles. Some 47 satellites experienced failure, either due to radiation damage or static electricity accumulating on their surfaces, while astronauts aboard the ISS were forced to retreat to the parts. most heavily armored station, according to one Report of the Royal Academy of Engineering on solar time (opens in a new tab).
Solar flares can also shorten the life of satellites in another way: a major eruption or the energizing particles of a CME can heat up the Earth’s upper atmosphere and cause it to expand substantially, increasing drag. of satellites in orbits close to Earth and spiraling them inward. to re-enter the atmosphere and burn. In February 2022, SpaceX lost a fleet of more than 40 Starlink mini-satellites (opens in a new tab) this way after its launch coincides with a solar storm, the MIT Technology Review reported.
Can CMEs be predicted?
A 2008 Report of the National Academy of Sciences (opens in new tab) estimated that a severe geomagnetic storm could have an impact of up to $ 2 trillion in both immediate damage and side effects, and it will take the world up to a decade to recover. But while there is no way to prevent a major CME from heading for Earth, precautions can reduce the impact. Satellites can be placed in safe mode where they are less likely to suffer lasting damage, and power grids can also be protected.
“For example, the [U.K.] National Grid can reduce the impact on its power systems by turning on as many power lines and high-voltage equipment as possible to reduce the overcurrent load flowing through its system so they don’t get overwhelmed, “Yardley said.
For these and other reasons, it is vital to keep track of CMEs so that various precautions can be taken prior to their arrival. “Once the CMEs are observed, their propagation is modeled to predict their time of arrival on Earth,” Yardley said. “Our arrival …