In The Lecture Hall: 5 Major Violent Activities on the Sun's Surface

"Hey! Where's the professor?" I asked as I walked into Hall 407, noting the empty chair at the front.

"He's attending a conference," the scholar replied, wiping the center whiteboard clean. "It's quite an event."

I walked to the first bench in front of the center table and dropped my backpack on the connected desk. "Sounds like fun!"

"Some are. Some are boring. Some are dreadful."

I chuckled as I sat down on the bench.

"So will we continue the discussion about the Sun's surface?" He dragged a three-legged metallic stool and sat down on its round cushioned seat.

"Yes! I was reading a few articles, but got confused about the various activities that occur on the surface."

"Ah, I see. Overall, there are five major types of activities that happen on the surface. Let's discuss them one by one."

A laptop on the center table was connected to an HDMI cable. A remote lay beside it. The scholar pressed a button and the projector that hung from the ceiling whirred into life. Its sharp light lit up the large white screen in front of me.

Activity #1 - Sunspots

"First up are the sunspots," the scholar said as he crossed his legs. "I believe they are relatively well known."

"Yes they are," I replied. "If I am not wrong, they are the cooler and darker regions on the surface."

"Correct. Do you know the reason why they appear dark?"

"No, I'm not sure."

"It's simple," he smiled. "They are cooler than the surrounding areas, which imparts a dark color."

I nodded.

"Sunspots appear in regions where the magnetic field lines are really strong. The increased strength inhibits the flow of heat and plasma from the Sun's interior. That's why they are cooler and darker than the surrounding area."

The laptop screen was mirrored onto the projector. He pressed a few keys and a picture was displayed.

"That's the Sun's surface. It has an average temperature of 5,500 C.

The dark spots that you see are the sunspots. Their temperature is around 3,500 C."

"The central region is the darkest because the temperature is the lowest there. Is that right?"

"Exactly. And that's because the magnetic field lines are the strongest there. The central region is called the umbra."

"What about the orange area around the dark regions?"

"That's the penumbra. The magnetic field is diffuse and weaker there. They are hotter than the umbra but cooler than the rest of the surface.

Alright, let's move on to the next one."

Activity #2 - Solar flares

"The second activity is a solar flare," he said as he removed the previous picture. "It is an intense burst of radiation and energy that occurs when magnetic energy builds up in the Sun's surface and gets released suddenly."

"Since strong magnetic fields are involved, are these flares connected to sunspots?"

"Good! You are catching on!" he grinned. "Yes, you are correct. When the number of sunspots increase, the likelihood of these magnetic lines getting twisted and tangled increase. That ends up releasing large amount of energy."

He brought up another picture on the screen.

"That's a solar flare. A flare always starts from a sunspot and ends up in one.

Moving on to the next one."

Activity #3 - Prominences

"Prominences are bright features extending outward from the surface. They are also formed in regions of strong magnetic activity."

"What are they made of?"

"Plasma. The magnetic fields trap and channel the plasma from the Sun's corona."

The screen became red as a photo of the Sun appeared.

"The large loop that you can see on the top right corner, is a prominence," the mouse cursor circled around that region.

"Isn't a prominence the same as a flare? What's the difference?"

"Good question. A flare is a sudden burst of energy. They are short-lived, typically lasting from minutes to hours only.

Prominences, on the other hand, are large, bright loops of plasma. These structures persist for days, weeks or even months."

"I see. And do they affect us?"

"Flares, yes. Prominences, not so much."

I rapidly nodded.

Activity #4 - Coronal Mass Ejections

"We have already covered the basics of CMEs in the previous discussion."

I nodded. "That was the Carrington event."

"Yes. Similar to solar flares, CMEs arise due to the twisting and tangling of magnetic field lines. When they snap and reconnect, they eject a large cloud of energetic particles into space."

"This photo has been captured by blocking out the Sun's glare with a coronagraph. Now we can observe the CME clearly."

"Ah, this is similar to the direct image technique of exoplanet detection."

"Exactly!"

Activity #5 - Solar Tsunamis

"There are tsunamis on the Sun's surface."

The scholar chuckled to my raised eyebrow. "No, they are not giant waves of water on the surface. And no, they are not related to quakes.

They are called Moreton waves and are related to solar flares and CMEs."

"The flares are everywhere!" I threw my hands in the air.

"Yes they are," the scholar laughed. "These waves are caused by the shocks of these explosive events. They propagate through the solar atmospheres as tsunamis."

"Here's a photo of a Moreton wave," he pointed up at the screen. "The large dark region there is a wave moving across the atmosphere."

"Wow."

"So, all of these events are connected to the magnetic activity on the surface," I said, piecing it together.

"Exactly," the scholar confirmed with a nod. "We'll discuss the details when the professor returns."

"Sounds good," I replied, already eager for the next session.

As I packed up and left Hall 407, I felt a newfound appreciation for the violent, dynamic nature of the Sun. I couldn't wait to learn more about the mysteries of our star.

Hardik Medhi

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