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Context

• The Sun sent out a powerful “X-class” solar flare that peaked at 8.03 AM on March 29.
• The flare was classified as an X1.2 flare. The X-class denotes the most intense flares.

SOLAR FLARES: https://www.iasgyan.in/daily-current-affairs/solar-flares

Types of Solar Flares

• There are five classes of solar flares, according to National Oceanic and Atmospheric Administration.
• Their designation depends on the intensity of X-rays emitted.
• Each class letter represents a 10-fold increase in energy output, similar to the Richter scale that measures the strength of earthquakes.
• Solar flares are classified as A, B, C, M or X according to the peak flux (in watts per square metre, W/m²) of 1 to 8 Ångströms X-rays near Earth, as measured by XRS instrument onboard the GOES-15 satellite which is in a geostationary orbit over the Pacific Ocean. The table below shows us the different solar flare classes:

Class	W/m2 between 1 & 8 Ångströms
A	<10-7
B	≥10-7 <10-6
C	≥10-6 <10-5
M	≥10-5 <10-4
X	≥10-4

• An X2 flare is twice as powerful as an X1 flare, and is four times more powerful than an M5 flare.
• The X-class class category is slightly different and doesn’t stop at X9 but continues on. Solar flares of X10 or stronger are sometimes also called “Super X-class solar flares.”

A & B-class solar flares

• The A & B-class are the lowest class of solar flares. The background flux (amount of radiation emitted when there are no flares) is often in the B-range during solar maximum and in the A-range during solar minimum.

C-class solar flares

• C-class solar flares are minor solar flares that have little to no effect on Earth.
• Only C-class solar flares which are long in duration might produce a coronal mass ejection but they are usually slow, weak and rarely cause a significant geomagnetic disturbance here on Earth.
• The background flux (amount of radiation emitted when there are no flares) can be in the lower C-class range when a complex sunspot region inhabits the Earth-facing solar disk.

M-class solar flares

• M-class solar flares are what we call the medium-large solar flares. They cause small (R1) to moderate (R2) radio blackouts on the daylight side of the Earth.
• Some eruptive M-class solar flares can also cause solar radiation storms. Strong, long-duration M-class solar flares are likely candidates to launch a coronal mass ejection. If the solar flare takes place near the center of the Earth-facing solar disk and launches a coronal mass ejection towards our planet, there is a high probability that the resulting geomagnetic storm is going to be strong enough for aurora on the middle latitudes.

X-class solar flares

• X-class solar flares are the biggest and strongest of them all. On average, solar flares of this magnitude occur about 10 times a year and are more common during solar maximum than solar minimum.
• Strong to extreme (R3 to R5) radio blackouts occur on the daylight side of the Earth during the solar flare.
• If the solar flare is eruptive and takes place near the center of the Earth-facing solar disk, it could cause a strong and long-lasting solar radiation storm and release a significant coronal mass ejection that can cause severe (G4) to extreme (G5) geomagnetic storming at Earth.
• X-class flares can trigger planet-wide radio blackouts and long-lasting radiation storms.

’Super X-class’’ solar flares

• The X-class solar flare is divided into nine subdivisions. For example, X1 to X9. After X9 instead of getting a new letter and these solar flares are often referred to as ‘’Super X-class’’ solar flares. 
• An X10 solar flares equals an X-ray flux of 0.001 Watts/m2 while an X20 solar flare equals 0.002 Watts/m2 in the 1-8 Ångstrom wavelength.
• The largest solar flare ever recorded since satellites started to measure them in 1976 was estimated to be an X28 solar flare.

Read about Solar Cycle: https://www.iasgyan.in/blogs/solar-cycle

Corona: https://www.iasgyan.in/daily-current-affairs/solar-corona

Geomagnetic Storm: https://www.iasgyan.in/daily-current-affairs/geomagnetic-storm

MUSE and Helioswarm: https://www.iasgyan.in/daily-current-affairs/muse-and-helioswarm

PRACTICE QUESTION Q. What are Solar Flares? Write a detailed note on the classification of Solar Flares and their plausible impact on Earth.

https://indianexpress.com/article/technology/science/powerful-x-class-solar-flare-radio-blackout-8531613/