This page (revision-83) was last changed on 02-Feb-2017 13:19 by David R Williams

This page was created on 27-Jan-2009 03:17 by David R Williams

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At line 441 added one line
You can model an active region from the potential field. For SXT or XRT it works quite well hydrostatically. But in TRACE, all the emission is concentrated in the footpoints, but the model shows that there aren't loops. The intensities in the moss match, though, even if the warm, over-dense loops don't.
At line 443 added 24 lines
Antiochos & co. suggest that the moss emission in large active regions is consistent with steady heating.
One thing I wanted to do is to look at dynamic active regions to see if there are any signatures of dynamics in the moss?
Use EIS at high-cadence to look at variation in the moss AR 10960. There were 15 M-class flares, 27 C-class flares. So the region is very flare-productive. I've made a movie of the moss region. It's not like the flares are happening away from the moss, they're happening close to or in the core of the region. But the pattern of the moss is very stable. De Pontieu et al. would argue that any variation in the moss is spicules in front of them. We used a study designed with 1-second exposures for a 75-second cadence. Have looked at the properties in little boxes in moss regions.
See that Vnt is very stable, as is the Doppler velocity and intensity. The flare doesn't really disturb the moss.
PRY: what's the cadence again?
DHB: 75 seconds
HEM: do you have enough counts to pick out changes in the moss?
DHB: you do, yes.
*Looking at the intensities in these boxes: less than 10% but so small that you can see residual orbital variation!
*The velocity doesn't vary by more than 2 km/s over 16 hours
*Non-thermal velocity variation is less than 5% over 16 hours.
Intensities are consistent with a steady or pseudo-steady heating, so the question is, is it showing contribution from steady heating?
HH: you mean the fluctuation of non-thermal velocity is very large?
I would like to show a different result.
Hara: (Small-scale motions at footpoints: signature of coronal heating site)
See large fluctuations in the line width map, where it is dark in TRACE. This region is quiescent, so there is no flaring happening at all.
At line 469 added one line
There have actually been a couple of flares observed with both RHESSI and EIS. Primarily interested in evaporation.
At line 471 added 21 lines
*BCS: Was often thought that the stationary component was collected material at the loop top from previous reconnection.
*CDS: Fe XIX, cooler than Ca XIX often showed much slower footpoint velocities
two scenarios for two diff't electron beam strengths:
# small blueshifts with gentle evaporations
# chromospheric recoil with explosive evaporation caused by much stronger electron beams.
EIS observations, fast rasters.
Part of the loop has only filled at the Fe XXIII and XXIV temperatures. Only above 2MK do we see the blueshifted material. This shift increases with temperature. Fe XXIII may have an Ar blend, but the Fe XXIV seems okay.
Each line profile is symmetric and shifted, except for Fe XXIII and XXIV which still seem to have a dominant stationary component, plus a strong blue-shifted component.
Think there's a small loop with a much larger overlying loop. This paper was submitted about a month ago, and I've just focused on the impulsive phase and the Doppler velocities.
Was interested in looking at flow v as a function of temperature. This is a considerable progression from CDS. First, there's a linear dependence on temperature, and there is a very narrow-T divide between the blue and red-shifted components. The red-shifts are seen up to 2MK, much higher than before. Wei Liu took the Fisher model of a single burst of non-thermal electrons, where as Wei looked at more continuous dumping of energy, and also predicts high-temperature downflows.
In a previous micro-flare observation (B flare) published last year, we also see a high-T downflow. So this high-temperature downflow may be a regular feature in flares; more observations may help us answer this, or whether there's some spectral index dependence.
Outstanding issues:
explosive
This page (revision-83) was last changed on 02-Feb-2017 13:19 by David R WilliamsTop