by MarkBour » Fri May 01, 2015 9:37 pm
This is one beautiful APOD.
I was struck by the video that neufer posted. It appears that the coronal mass ejection was accompanied by an opposite ejection as well. Is this common? I wonder about the mechanism of an ejection, and why it would occur on opposite sides of the Sun. What very little I know about it, the gas is all flowing under the influence of massive magnetic force. Something must cause a "line of force" to "spread out" (I'm using quotes here because I'm well beyond my knowledge at this point), carrying a huge amount of mass away from the surface (the photosphere boundary). Either the magnetic force settles and stops expanding, or, in the case of a CME, it disconnects and flies on out, taking some of the gas with it. (I read the "Cause" section on the Wikipedia article on CME, which is pretty cursory.) I can imagine that when one huge magnetic loop is moving outward, that on the opposite side of the Sun, another line is likely to do the same. If anyone has further explanation to help me, I'd appreciate your sharing, it's fascinating.
Chris noted that the photosphere is the point at which the material appears opaque. True enough in this image. But, I wonder if the edge of the photosphere is actually the point at which the material becomes opaque in the usual sense, or if he is using "opaque" in a special sense here. Normally, opaque would mean that light does not pass through something. If the gas is mainly hydrogen, is there a given density at which hydrogen gas becomes opaque, and is that what causes the photosphere? It seems possible to me that light can pass through the material just fine, but since the material is a dazzling light source, we will never see light passing through the photosphere.
When the CMEs and flares occur, no doubt the sun (a) wobbles, and (b) undergoes significant changes in light output. I wonder if Kepler has ever seen such events and mistaken them for planet transits ... I seem to recall that the Kepler project looks for regularly repeated occurrences of these events, so since these flares and CMEs are evidently random in appearance, they would easily be factored out, if given a little time.