December 2020


2020-Dec-01

"Solar space elevator" event

Blob B1

Decay time

A very rough estimate of the size of B1 (based on counting IRIS pixels in the sliding-tile aligned movie from 2020-Nov-19) yields a lengthwise dimension of 10 pixels, or L ~ 10 pixel * 0.167 arcsec/pixel * 730 km/arcsec ~ 1200 km.

If we assume a coronal environment of T ~ 1 MK, then the sound speed would be ~170 km/s, and the characteristic HD pressure decay time would be of order 7 s.  Thus, given the apparent (minimum) B1 lifetime of 220 s, the blob persists for a least 30 decay times.

However, if we assume a TR temperature of T ~ 80,000 K (0.08 MK) characteristic of Si IV (which is, after all, what we're observing it in!), then the sound speed is closer to ~48 km/s, which gives a decay time of ~25 s, and the blob persists for ~9 decay times.

Either of these results is significantly better than the 650x decay times I found above.  30x still seems a bit high, but plausible.  9x is very reasonable, although it is not clear to me how the 0.08 MK temperature would be the relevant temperature for the blob (even given that it appears in Si IV).  Indeed, it isn't clear to me how Si IV even survives in the loop environment, especially since B1 does show earlier emission in significantly hotter channels (such as AIA 94 Å at several MK).

Finally, in the context of the loop sims, the original estimate of 650x still applies, since that's the time scaling for the non-dim sims.  So, however I construct the model blob, it must survive for at least several hundred coronal sound transit times.

Loop sims

Same as above.  Need to set up loop sim with a model blob that can survive for >>100x coronal sound transit times.

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2020-Dec-13

IRIS calibrations

Still need to follow up with Ryan re: extra SJI 2796 flat.

SJI flats

SJI flats displayed odd "darkening" during processing, some sub-flats seemed very dark compared to normal.  Final flats are not significantly different than normal, however.  May just be a scaling issue in the display.

Missing sub-flat 1 for 1330?  Not clear where the data went for that...

Unusual number of rejected sub-flats for SJI 1400.


1
2
3
4
5
5
1330
missing?
X
1400
X
X
X
2796
N/A
N/A
N/A
2832
N/A
N/A N/A

SG flats

NUV: 0 incomplete images

FUV: 0 incomplete images

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2020-Dec-14

"Solar space elevator" event

Stable blob HD

Based on the ~1200 km size for the blob B1 stated above, and the 58.5 km coronal MFP size at 1 MK and 1e9 cm^-3, the scaled bob size is ~20 MFPs.

loopsim test "blob_comov_001" indicates that, even starting in pressure equilibrium, a blob will blow itself apart within <100 t_cor.  This is much too short a time.

http://solar.physics.montana.edu/sbrannon/research/plots/20201214/blob_comov_001_density

Undoubtedly, I will need to institute a radiative loss term, as discussed with CCK.

Also, I am noting that the RHS boundary, which as I recall was designed to operate as a Neumann BC (i.e. derivatives held at zero, quantities allowed to float).


FURST group meeting

ZEROTH baffles may require some trimming to allow desired rays to get through.

Reviewed "Skylar's FURST Shutter Control System" document


Research meeting w/ CCK

How to create a blob in the comoving frame?


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End of document.