3 ms·

why the flares slide back to were they came from as if the video was rewinding instead of falling down back as one would expect from gravity?

by gcb0 12y ago

pdx 12y ago
I saw that too, and it drove me crazy. My theory is that either it's an artifact of the lens system on the camera, or more likely, what we're actually seeing is not the flair, but a reflection of the flair on the ball of the sun. Think what it would look like if you had a shiny ball (a Christmas tree ornament), and there were flairs coming off of that. As the flair went out from the ball and fell back, you would see it's reflection in the surface of the ball, and I think it would look a lot like those flairs look.
FoeNyx 12y ago
I'm far from being an expert, but my understanding is that magnetic forces are really intense around solar spots, and that a change of polarity might channel back some ejected coronal matter. See the current magnetic field lines : http://sdo.gsfc.nasa.gov/assets/img/latest/latest_1024_0193pfss.jpg http://sdo.gsfc.nasa.gov/assets/img/latest/latest_1024_0193p...
- mturmon 12y ago
  You are quite right. The charged particles in the flare are following magnetic field lines, which run (typically) from one point on the Sun's surface, up through its atmosphere, and then back down to another point. The diagram you linked illustrates this very well. There is one other wrinkle, which is that the video shows only a relatively narrow frequency range of light. The full list is at http://aia.lmsal.com/public/instrument.htm http://aia.lmsal.com/public/instrument.htm ; the video was made from just one frequency band from that list. Each band is sensitive to plasma within one particular temperature range. So, as plasma heats or cools, it can disappear from the image even though it is still there. By combining the information from the various temperature ranges (i.e., various frequency ranges) you can reconstruct heating/cooling of packets of plasma as they travel through the solar atmosphere. The ranges were chosen to sample about equally in log(temperature) -- rightmost column of the list above. The reason this is so important is that the temperature of the atmosphere increases dramatically as you go up, and we don't understand why. This is the "coronal heating problem" (http://en.wikipedia.org/wiki/Corona#Coronal_heating_problem http://en.wikipedia.org/wiki/Corona#Coronal_heating_problem). If you look at the video, you could get the impression that the pictures are just giving a visual impression of where flaring is happening. In fact, because of the sampling process described above, they are used in a quantitative way to initialize 3D magneto-hydrodynamic models so that the flows can be modeled and predicted. It's embryonic weather forecasting, but for a different atmosphere.
  - FoeNyx 12y ago
    Very Interesting, thank you! But it seems there are several methods to create composite views on SDO website (several freq ranges used as RGB of the output composite images). I guess there isn't one easy way to visualize all of this, or is it ? Do you know if the embryonic "3D magneto-hydrodynamic models" are by any chance available on the web to play with ? :) Also, in the case of the video, I don't know the intent of the creator so it's just a supposition, but if it's for science vulgarisation rather than science exactitude, I guess a composite view, as http://sdo.gsfc.nasa.gov/assets/img/latest/f_094_335_193_1024.jpg http://sdo.gsfc.nasa.gov/assets/img/latest/f_094_335_193_102... , would have be less appealing to the targeted public, as it would look way more artificial than the red/orange sun shown in the video (though it is also a totally arbitrary colouring). The suspension of disbelief in "hey look it's our Sun!" is probably easier using those culturally accepted warm colour tones to represent it.
    - mturmon 12y ago
      I don't know of one particular way to visualize all the bands. Sometimes at conferences you will see specialists' posters with composite views like the one you linked. But usually they will show the individual bands separately, side by side. I think the colorings were chosen by the predecessor instrument to SDO/AIA, which was on SoHO, and they have just been retained. It's funny, I never thought to ask who came up with them, because AFAIK they are arbitrary. You need an expert to drive the MHD models. They are still in development, although you can find videos online. Incidentally, I notice there is a nice video showing the transit of Venus: http://sdo.gsfc.nasa.gov/assets/img/latest/mpeg/latest_1024_0131_venus.mp4 http://sdo.gsfc.nasa.gov/assets/img/latest/mpeg/latest_1024_...
robin_reala 12y ago
I’m not a physicist, but the motion of flares is governed more by eletromagnetic forces than gravity. Each flare loop tracks the Sun’s magnetic field (I believe).
Retric 12y ago
Plasma moves along magnetic field lines. Which is a really important part of how plasma containment works in a tokamak nuclear fusion reactor's. Also, these features are mind bogglingly big and gravity is only 28g's on the surface of the sun. http://www.thesuntoday.org/solar-facts/how-big-is-the-sun/ http://www.thesuntoday.org/solar-facts/how-big-is-the-sun/

why the flares slide back to were they came from as if the video was rewinding instead of falling down back as one would expect from gravity?

by gcb0 12y ago

why the flares slide back to were they came from as if the video was rewinding instead of falling down back as one would expect from gravity?

pdx 12y ago

I saw that too, and it drove me crazy. My theory is that either it's an artifact of the lens system on the camera, or more likely, what we're actually seeing is not the flair, but a reflection of the flair on the ball of the sun. Think what it would look like if you had a shiny ball (a Christmas tree ornament), and there were flairs coming off of that. As the flair went out from the ball and fell back, you would see it's reflection in the surface of the ball, and I think it would look a lot like those flairs look.

FoeNyx 12y ago

I'm far from being an expert, but my understanding is that magnetic forces are really intense around solar spots, and that a change of polarity might channel back some ejected coronal matter. See the current magnetic field lines : http://sdo.gsfc.nasa.gov/assets/img/latest/latest_1024_0193pfss.jpg http://sdo.gsfc.nasa.gov/assets/img/latest/latest_1024_0193p...

mturmon 12y ago
You are quite right. The charged particles in the flare are following magnetic field lines, which run (typically) from one point on the Sun's surface, up through its atmosphere, and then back down to another point. The diagram you linked illustrates this very well. There is one other wrinkle, which is that the video shows only a relatively narrow frequency range of light. The full list is at http://aia.lmsal.com/public/instrument.htm http://aia.lmsal.com/public/instrument.htm ; the video was made from just one frequency band from that list. Each band is sensitive to plasma within one particular temperature range. So, as plasma heats or cools, it can disappear from the image even though it is still there. By combining the information from the various temperature ranges (i.e., various frequency ranges) you can reconstruct heating/cooling of packets of plasma as they travel through the solar atmosphere. The ranges were chosen to sample about equally in log(temperature) -- rightmost column of the list above. The reason this is so important is that the temperature of the atmosphere increases dramatically as you go up, and we don't understand why. This is the "coronal heating problem" (http://en.wikipedia.org/wiki/Corona#Coronal_heating_problem http://en.wikipedia.org/wiki/Corona#Coronal_heating_problem). If you look at the video, you could get the impression that the pictures are just giving a visual impression of where flaring is happening. In fact, because of the sampling process described above, they are used in a quantitative way to initialize 3D magneto-hydrodynamic models so that the flows can be modeled and predicted. It's embryonic weather forecasting, but for a different atmosphere.
- FoeNyx 12y ago
  Very Interesting, thank you! But it seems there are several methods to create composite views on SDO website (several freq ranges used as RGB of the output composite images). I guess there isn't one easy way to visualize all of this, or is it ? Do you know if the embryonic "3D magneto-hydrodynamic models" are by any chance available on the web to play with ? :) Also, in the case of the video, I don't know the intent of the creator so it's just a supposition, but if it's for science vulgarisation rather than science exactitude, I guess a composite view, as http://sdo.gsfc.nasa.gov/assets/img/latest/f_094_335_193_1024.jpg http://sdo.gsfc.nasa.gov/assets/img/latest/f_094_335_193_102... , would have be less appealing to the targeted public, as it would look way more artificial than the red/orange sun shown in the video (though it is also a totally arbitrary colouring). The suspension of disbelief in "hey look it's our Sun!" is probably easier using those culturally accepted warm colour tones to represent it.
  - mturmon 12y ago
    I don't know of one particular way to visualize all the bands. Sometimes at conferences you will see specialists' posters with composite views like the one you linked. But usually they will show the individual bands separately, side by side. I think the colorings were chosen by the predecessor instrument to SDO/AIA, which was on SoHO, and they have just been retained. It's funny, I never thought to ask who came up with them, because AFAIK they are arbitrary. You need an expert to drive the MHD models. They are still in development, although you can find videos online. Incidentally, I notice there is a nice video showing the transit of Venus: http://sdo.gsfc.nasa.gov/assets/img/latest/mpeg/latest_1024_0131_venus.mp4 http://sdo.gsfc.nasa.gov/assets/img/latest/mpeg/latest_1024_...

robin_reala 12y ago

I’m not a physicist, but the motion of flares is governed more by eletromagnetic forces than gravity. Each flare loop tracks the Sun’s magnetic field (I believe).

Retric 12y ago

Plasma moves along magnetic field lines. Which is a really important part of how plasma containment works in a tokamak nuclear fusion reactor's. Also, these features are mind bogglingly big and gravity is only 28g's on the surface of the sun. http://www.thesuntoday.org/solar-facts/how-big-is-the-sun/ http://www.thesuntoday.org/solar-facts/how-big-is-the-sun/