Starship Asterisk*

http://apod.nasa.gov/apod/ap070402.html

Can anyone tell me what the scale of the image is? How high are those gas jets we see in it?

TIA, ean

Of particular interest is erupting glowing gas that shows how the Sun's magnetic field comes right out of the spot center, but curves markedly around the spot edges.

Seems logical to me. The mass ejected from the center is at the highest velocity and goes directly away from the sun, while the other portions of the mass are affected by the extreme gravitational pull of the star. The farter from center the mass ejects from, the less force, the greater curvature due to gravity.

Yeah, I'd agree with you there... seems logical that the higher velocity matter is ejected from the center of the spot... but that's just a guess on my part

It might be fun to hear some guesses first....lol

I believe it's more complicated than that. The particles are charged, and for an electric charge to move through a region of varying magnetic field strength requires energy representing the change in electromagnetic potential.

So if the net magnetic field lines in the center are vertical, the travel path of the charged particles has a greater tendency to be vertical. If they're curved, the greater tendency is to follow the curved path.

As to what is the dominant force, gravity or magnetic field, I don't know. Given that discussions of sunspots always seem to focus on the magnetic field, I would suspect that factor.

Of course, the initial velocity angle is also important. If a particle is ejected straight away, even if it doesn't have escape velocity, it's trajectory will appear more or less straight. Think of tossing a ball straight up or slightly sideways.

So if the net magnetic field lines in the center are vertical, the travel path of the charged particles has a greater tendency to be vertical. If they're curved, the greater tendency is to follow the curved path.

But can we really tell if their trajectories are less vertical near the edge of the spot because they just happen to be, or because they initially have less kinetic energy? One things for sure: I should learn more about sunspots.

l3p3r wrote:

So if the net magnetic field lines in the center are vertical, the travel path of the charged particles has a greater tendency to be vertical. If they're curved, the greater tendency is to follow the curved path.

But can we really tell if their trajectories are less vertical near the edge of the spot because they just happen to be, or because they initially have less kinetic energy? One things for sure: I should learn more about sunspots.

Indeed. Off the top of my head I can think of at least 3 solar-observing satellites currently active, and there's numerous ground-based projects, but even the solar scientists don't claim to have a thorough understanding of sunspots. There's a lot to learn.

As far as their kinetic energy, I'd be willing to bet that can be determined fairly accurately based on either time-lapse imagery or doppler shift, but it's not something we can tell by looking at a single (but impressive) APOD.

l3p3r wrote:But can we really tell if their trajectories are less vertical near the edge of the spot because they just happen to be, or because they initially have less kinetic energy? One things for sure: I should learn more about sunspots.

APOD has a lot of very interesting images of solar flare activity. The one at http://antwrp.gsfc.nasa.gov/apod/ap030418.html shows multiple arching promentories; clearly charged particles following magnetic flux lines. The coolest (or hottest ) one in my view is at http://antwrp.gsfc.nasa.gov/apod/ap061204.html. It shows the "bubble, bubble, toil and trouble" of the Sun's surface as well as flares.

It is my understanding that the Sun's magnetic fields are the result of an extremely complex magneto-hydrodynamic system driven by the incredible energy of hydrogen fusion and motion of the plasma. It is far far from a simple dipole. (The same is true for Earth's magnetosphere but less dramatically.)