Solar radiation storms are caused by strong magnetic eruptions that accelerate charged particles in the solar atmosphere, especially protons, to high speeds. These protons can reach speeds close to the speed of light and travel from the Sun to Earth in a matter of minutes. Once they reach Earth, these protons penetrate our magnetosphere, especially near the poles.
Coronal mass ejections and associated solar flares often accompany magnetic eruptions.
NOAA ranks these storms on a scale of S1–S5 based on proton measurements from the GOES satellite. A storm begins when fluxes of protons with energies ≥ 10 MeV reach or exceed a certain threshold and ends when they fall below this level. These storms can last from a few hours to several days.
Solar radiation storms can damage satellites, electronics, and the biological DNA of living organisms due to the energetic protons. In extreme cases, aircraft crews flying at high latitudes may experience radiation exposure. These protons can also ionize the atmosphere, affecting the ionosphere and disrupting radio communications.
The SWPC (Space Weather Prediction Center) forecasts the likelihood of minor radiation storms in its three-day forecast. They issue warnings about expected events and warnings about certain radiation levels.
Coronal mass ejections
Coronal mass ejections (CMEs) are ejections of plasma and magnetic fields from the solar corona. They can eject billions of tons of material and move away from the Sun at speeds up to 3000 km/s. Fast CMEs can reach Earth in 15-18 hours, while slow ones take several days.
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These emissions often begin due to magnetic reconnection in the twisted structures of the Sun’s magnetic field. This could be accompanied by a solar flare and cause a CME. They usually occur in active regions or near filaments and prominences. A CME moving faster than the solar wind can cause a shock wave, accelerating charged particles and intensifying the radiation storm.
The key characteristics of a CME are size, speed, and direction, which are analyzed using coronagraphic images. The main instrument for this is the LASCO coronagraph on the orbiting SOHO observatory, which can observe the solar corona at different distances from the Sun. Other tools, such as the coronagraph, are on board the STEREO-A spacecraft.
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The DSCOVR satellite at L1 is the first warning probe to observe incoming CMEs. Abrupt changes in density, interplanetary magnetic field, and solar wind speed indicate the arrival of a CME. This data can provide a warning of a shock wave’s arrival at Earth, allowing analysts to forecast potential geomagnetic storms or other spatial weather events.
Solar flares and radio blackouts
Credit: NASA/GSFC/SDO
Solar flares are powerful bursts of electromagnetic radiation from the Sun that affect the Earth’s ionosphere. Their radiation travels at the speed of light and reaches the Earth in minutes. These flares can increase the ionization of a denser ionosphere layer, the so-called D-layer, which disrupts high-frequency radio communications, especially in the 3-30 MHz range.
Solar flares often occur in active regions of the Sun, where strong magnetic fields predominate. Such areas are often associated with sunspot clusters. When these magnetic fields become unstable, they release energy that manifests as solar flares.
The intensity of solar flares is classified by peak emission in the spectral range of 0.1–0.8 nm (soft X-rays).
X-ray flux levels start at level “A” (beginning at 10-8 W/m 2 ).
The next level, ten times higher, is level “B” (≥ 10 -7 W/m 2);
they are followed by “C” class flashes (10 -6 W/m 2),
“M” class flashes (10 -5 W/m 2) and, finally,
“X” class flashes (10 -4 W/m 2 ).
The last “X” class flare was on August 7, 2023. On this day there were 3 M class flares and 6 lower C class flares.
In total, 11 flares of the highest class X were registered in 2023. The most powerful of them occurred on February 17, 2023.
In October 2023, solar activity is expected to be low to moderate, with an M-class flare.
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