Hi Sylvie! In my opinion, everything related to the solar magnetic activity facinates me!

*The way the active regions are created, how they develop, how they release the energy in beautiful and powerful solar flares...
* The way the solar magnetic field (also known as Interplanetary Magnetic Field - IMF) changes along the solar cycle and modulate the transport of energetic particles (including the cosmic rays) inside the Heliosphere...
* The way the Earth's atmosphere (from the bottom to the top) responds to the solar variability...

All the features of the solar activity are interesting, intriguing and wonderful!

The fact that always befuddles me is that while it only takes about 8 minutes or light to get to us from the surface of the Sun, photons produced deep in the solar interior get bounced around and absorbed and re-emitted so much, due to how dense it is deep in the interior, that it takes hundreds of thousands of years for that "piece of light" (taking some poetic liberties here) to escape to the Sun's surface. So the light we see now is not just 8 minutes old, but started its journey before most of modern civilization! That just astounds me...and gives a good sense of how dense, and how different, the inside of our nearest star is compared to what I feel like I "know" in my daily life.

Hello! I think the most interesting fact about the Sun is that it has differential rotation. Planet Earth is mostly a solid body, so all points rotate about the Earth's axis in 24 hours. However, the Sun is not solid, so the Sun rotates every 25 days at the equator and takes longer to rotate at higher latitudes, up to 35 days at the poles. This is what we call differential rotation. Both the Sun and the Earth rotate in the same direction even though the Sun has differential rotation and the Earth does not. What makes the Sun's differential rotation even more interesting, is that the gas giants, Jupiter and Saturn, also have differential rotation! Here's a nifty picture:
https://www.nasa.gov/miss.../solar-rotation.html