Hello Everyone.
I had a productive SHG session on 13Aug and am processing a number of images. I did notice something interesting while generating the H-alpha spectroheliogram. As shown below, there was a rapid variation in the spectrum of AR12401 which may be an observation of a loop prominence, in absorption. Here is a (line centre) H-alpha spectroheliogram of the disk:
AR12401 appears, in the spectroheliogram, as a region of bright plage with a central absorbing region. In the picture below, I've added, for comparison, a filtergram taken with my Daystar system the next day, on 14Aug. I also present two spectra, taken at different locations in the AR, which show the central absorbing gas to have a region of high outflow velocity next to a region of high inflow velocity.
My first interpretation is that this corresponds to a "top view" of streaming gas in a loop. Does H plasma actually stream this way in a loop? I'll have to research the idea further.
Cheers.
Peter.
13Aug SHG: 1st installment. Spectral study of AR12401.
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Re: 13Aug SHG: 1st installment. Spectral study of AR12401.
Peter,
very interesting....
Evershed effect??
very interesting....
Evershed effect??
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Re: 13Aug SHG: 1st installment. Spectral study of AR12401.
Excellent indeed Peter!
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Re: 13Aug SHG: 1st installment. Spectral study of AR12401.
Short answer, yes. Here is a pair of images from March 8, 2011, when AR1165 blew a bubble. The bubble is actually gas flowing downward, as seen: The two images are +/- 0.03nm from Ha line center. This was a very lucky catch, very late in the day and the Sun was getting close to the horizon. Large air mass and a lot of atmospheric scatter but the best example of counterflow I have.p_zetner wrote: My first interpretation is that this corresponds to a "top view" of streaming gas in a loop. Does H plasma actually stream this way in a loop? I'll have to research the idea further.
Cheers.
Peter.
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Re: 13Aug SHG: 1st installment. Spectral study of AR12401.
Thanks, Joe. That is a terrific catch!
If I understand your observation, the loop has a receding velocity component (red) and an approaching velocity component (green) with respect to the line of sight. But the overall flow is downwards. This makes sense and is consistent with what I expected of the behaviour of gas flow in loops (prominences in general). The prominence plasma is thought to condense in the corona and stream downwards.
In the present case, though, I'm observing the behaviour of an absorber against a plage region on the solar disk, a "view from the top", with an upwards stream and downwards stream separated by a small (angular) distance. I make the simple-minded interpretation of a flow which originates on the surface (?) flows radially outward and returns to the surface. The attached picture, borrowed from Wikipedia, seems to suggest such flow is possible, but I haven't read anything further about it.
Cheers.
Peter.
If I understand your observation, the loop has a receding velocity component (red) and an approaching velocity component (green) with respect to the line of sight. But the overall flow is downwards. This makes sense and is consistent with what I expected of the behaviour of gas flow in loops (prominences in general). The prominence plasma is thought to condense in the corona and stream downwards.
In the present case, though, I'm observing the behaviour of an absorber against a plage region on the solar disk, a "view from the top", with an upwards stream and downwards stream separated by a small (angular) distance. I make the simple-minded interpretation of a flow which originates on the surface (?) flows radially outward and returns to the surface. The attached picture, borrowed from Wikipedia, seems to suggest such flow is possible, but I haven't read anything further about it.
Cheers.
Peter.
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Re: 13Aug SHG: 1st installment. Spectral study of AR12401.
Thanks Ken, Alexandra and Mark for your comments!
Ken: My understanding of the Evershed effect is that it describes radial outflow from a sunspot's umbra, across the penumbra, to the surface. I'm pretty sure that, with a bandpass of about 0.02nm near line centre, I'm looking at exclusively chromosphere and sunspot gas dynamics are not really visible.
Cheers.
Peter.
Ken: My understanding of the Evershed effect is that it describes radial outflow from a sunspot's umbra, across the penumbra, to the surface. I'm pretty sure that, with a bandpass of about 0.02nm near line centre, I'm looking at exclusively chromosphere and sunspot gas dynamics are not really visible.
Cheers.
Peter.