7
$\begingroup$

What is the difference in the creation process of solar flares and CME (coronal mass ejections)? How do they relate to sunspots and coronal holes?

Here there are some good explanations about the flares' and CME's differences. But my question focuses on how each of them is created, and what are the respective conditions at the corona.

Edit: In an effort to make the questions more clear, I could add that as far as I can tell both effects result from magnetic reconnection, but in one case we have only energetic particles emitted while in the other we have whole chunks of plasma. Do we know which is the determining factor about which of the two will happen?

Also, I understand that flares are mostly related to sunspots while ejections are to coronal holes. Is this correct? If yes then it sounds like a pretty big difference.

(Please be reminded that specifying that the answer is not known yet is an answer.)

Edit #2: Please see this comment for further clarification of what the question is about.

| improve this question | |
$\endgroup$
  • $\begingroup$ I think you'll need to be more specific, you are basically asking for a summary of decades of research by a huge community that has still not completely answered all these questions. $\endgroup$ – Ken G Apr 2 '17 at 14:44
  • $\begingroup$ Specifying which parts of the questions are not answered yet is an answer :) However, it is true that I'm asking for a summary of gathered knowledge. I'll try to add a more detailed edit, but I somehow fear that it won't help much. $\endgroup$ – Helen - down with PCorrectness Apr 2 '17 at 18:06
5
$\begingroup$

The point of my comment was that the connection between CMEs and flares would make for a good 20 page research paper in a college course. The connections are still only understood at a kind of cartoon level, after decades of concerted research. But I can tell you what the basic cartoon is, and you can think of that as a kind of operating hypothesis that helps organize many of the observations, but is still a long way from a predictive model. The basic idea is that the energy for flares and for CMEs both seem to come from magnetic free energy stored in the corona due to the magnetic and turbulent nature of the convection zone. The magnetic field is capable of trapping pockets of hot gas that has been energized by this magnetic activity, but then when the field lines get significantly twisted up they reach a point where they can release that energy and relax to a smoother configuration. This relaxation does two things-- it releases energy, and it reconfigures the field such that it can release these pockets of trapped plasma. The former is the solar flare, the latter is the CME, and that's why the two often come together.

However, there seems to be a full range of weak to strong flares, and weak ones would not be associated with CMEs. On top of all that, there may be other processes that heat the corona, and other processes that lead to the solar wind, so one big question is if the heating of the corona is mostly from lots and lots of small flares, and the solar wind is lots and lots of small CMEs, or if the general heating of the corona and general driving of the wind are separate processes from flares and CMEs.

Also, you mention closed and open field regions, so these questions can be asked separately in those two domains. But CMEs would normally come from closed field regions that open up when the field reconfiguration occurs, I believe open field regions tend to be rather sedate and not associated with either strong flares or CMEs, but rather a more steady wind. In the closed field regions, CMEs are often associated with features called "helmet streamers," which are regions of trapped plasma that are kind of combed out at their highest point by the solar wind, creating an interface between closed and open fields that is a good setup for getting field reconfiguration that could launch out some plasma.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Thanks, honestly, for the explanations which are both useful and show where to look. But allow me to say that I'm asking for less things than you thought I do :) A hypothetical answer of the kind I was hoping for would be something like "solar flares are observed to come from less twisted lines than CME; CME can only come from coronal holes". (Again, I just made these up, no claim to have put any thought in this example; it is just in order to show what I was looking for. If what I look for is a misinterpretation and doesn't make sense, please let me know.) $\endgroup$ – Helen - down with PCorrectness Apr 3 '17 at 17:59
  • $\begingroup$ I think the key you are looking for is that CMEs come from fairly large magnetic structures that trap a lot of plasma, and this plasma gets spat out when the magnetic fields reconfigure in a very significant way, releasing a lot of energy. So by and large, CMEs are not associated with open fields,those tend to be simple and not twisted and strong. Instead, if you want to know where the next CME is likely to come from, look for regions with lots of hot plasma and strong fields, likely in the vicinity of sunspots, especially if the fields seem tangled and interacting with other structures. $\endgroup$ – Ken G Apr 4 '17 at 0:10
  • $\begingroup$ Also, if you have access to an H-alpha picture of the Sun, look for "prominences", regions of H-alpha emission (or absorption) that look like long sausages hanging in space above the surface. Those are indicators of strong twisted fields, likely a site for strong flares and CMEs. $\endgroup$ – Ken G Apr 4 '17 at 0:12
  • 1
    $\begingroup$ Or, if you have a picture of the corona and you want to know where CMEs might happen, look for "helmet streamers," which are regions of trapped plasma that are kind of combed out by the solar wind, creating an interface between closed and open fields that is a good setup for getting field reconfiguration that could launch out some plasma. $\endgroup$ – Ken G Apr 4 '17 at 0:16
  • $\begingroup$ (Getting back at this just now,) maybe your new information could be worked into an answer / addition? $\endgroup$ – Helen - down with PCorrectness May 4 '17 at 17:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.