Often accompanied by coronal mass ejection.
1400 years ago people thought that the sun was static, that is, it didn't eject anything. However today we know that this is false. The sun ejects coronal mass.
A solar flare is a sudden flash of increased brightness on the Sun, usually observed near its surface and in close proximity to a sunspot group. Powerful flares are often, but not always, accompanied by a coronal mass ejection. Even the most powerful flares are barely detectable in the total solar irradiance (the "solar constant").
Wikipedia, Solar Flare, 2019.
The sun ejects coronal mass but this is impossible to see in the naked eye.
However this was portrayed in the Quran 1400 years before it was discovered. Hell has three suns so any object would have three shadows:
[Quran 77:30-33] Proceed to a shadow of three branches. No shade, and no protection from the flames. It throws sparks like castles. As if they were yellow camels.
"As if they were yellow camels" camels are known for their humps. It turned out that our sun throws sparks like yellow hump of a camel.
How could an illiterate man who lived 1400 years ago have known how a coronal mass ejection looks like?