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!!!Lunch
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** Studies of small ARs and Flares
*** Moss (Tripathi et al., 2008)
*** AR Jets (Chifor et al., 2008)
*** AR microflares and precursors to filament eruptions (Chifor et al., 2008, 2009)
*** Small flares (Del Zanna, 2008)
*** AR flows (Del Zanna, 2008)
*** AR loops: n_e, T_e and flows (Tripathi et al. 2009)
*** Small flare activity (Mitra et al., 2009)
** This presentation
Small active region close to the limb
Can take the n_e ratio as we go from the disc to off-limb.
We can also attempt to get the temperature in a simple way. Never subscribed to this before, but I'm showing a plot! We want to see how hot the temperature is. But if you take Fe XVI / Fe XV, you can see that the core is very hot around log(T) 6.7. We've done the same for Fe XIV / Fe XIII, we get a lot more, interesting structure, which we need to follow up and invesigate.
We want to look for these higher temperature lines, but must be really careful about removing blends. The Fe XVII line is a good line to use.
When looking at Ca XVII, you can't use the CHIANTI Fe XI ratio, as it's wrong. But you can do it empirically by finding the ratio on the quiet Sun and then using that to remove the blend with Ca XVII.
Then we compared the XRT and EIS data and wanted to cross-calibrate the DEMs -- but they look nothing like each other! So we can't yet use EIS and XRT to have large-T coverage DEMs that we believe.
GAD: those limb-brightening curves about the limb: do you have O IV and O V? Cos that's a check on the scattered light?
HEM: they do fall off quite sharply
PRY: For the AR, there was a paper last year that showed three separate isothermal components in the corona.
HEM: that's difficult for me to believe.
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Let's look at some CDS data taken above the limb, and it looks consistent with an isothermal plasma. Fairly well-established result. Now let's look with EIS. One of the things we found with SUMER is that the Si data seems to behave pretty well. Assume a delta-function EM and formalise the fit parameters. Get a pretty good fit. The density is being adjusted with intensity. The encouraging thing with EIS is that we get a similar result with the big strong lines that everyone includes in their studies. one thing that is unsettling is that the magnitude of the EM is different! This could mean Si / Fe ratio in the abundances of Feldman is wrong.
That's what can be done.
When you bring in Fe XIV - Fe XVI, they don't lie on the curves. So is there some dispersion in the temperature distribution? Then we end up with a fairly narrow distribution, but it doesn't account for the higher temperatures.
So another thing we've considered is MCMC used in PINTofALE. We also see a tail extending down to higher T. This accounts very well, but although tempting, it's not clear, because the ionisation fractions become very unclear as you get away from their peaks. Or maybe we really do have a tail in the DEM!
Ca XIV thru XVII help us to probe the high-T lines. Their contribution functions are narrower than the equivelant-T Fe species. Ca XIV and XV lines are fairly strong, and we should reconsider AR observations so that they include these lines.
GAD showed earlier an AR movie: I wanted to comment that the we show the Ko et al. deconvolution of Ca XVII.
As we move out from the core of the AR, we see the high-temperature emission coming down. Just because you dno't see any signal doesn't mean there's something wrong. Can still offer useful constraint for analysis. Something interesting is that the EM
Modelling evolving coronal loops with narrow-angle STEREO. Aschwanden has put a package on SSW for measuring loops' 3D geometry.
We're doing mutli-thread modelling of loops: we can calculate the expected lifetime of the loop, but it lasts much longer. We've put to gether such a multi-thread model. Good matches to TRACE loop lifetimes.
Another independent check is the DEM. Can approximate observed lifetime and DEM.
The way we motivate the heating in a loop, the higher the density, the more energy you've to put in.
We try to reproduce the XRT loops, and can't find those loops. May be that we can't find loops in XRT due to the morphology.
Would love to see the EIS slit over a post-flare loop arcade.
An important goal for the future. So, to summarise:
* QS above the limb
* AR DEMs
* Evolving loops.
HEM: I'm still confused by the isothermality... the heating models might predict a high-temperature tail.
HPW: There's no physical interpretation, that's what's so difficult to understand. Essentially indpendent of height. Maybe there is this hi-T component.
HEM: just not high-enough T lines?
HPW: We have Fe XV. There are always probs with atomic data, like Li-like lines...
KPD: One of the Fe XII lines could be being misidentified as Fe XI
HPW: It's hard to see how, because the ratio is extremely constant.
PRY: I remember fitting the lines, and the ratio was very flat.
GAD: Helen, you didn't get this isothermal plasma, but was it in an AR?
HPW: I thought it was in an AR?
Discussion continued....!
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Seems like almost everyone has spoken about outflows!
Seems a correlation between outflow speed and line widths. Can these widths be attributed to multiple components with different speeds? One such AR, we have observations as the AR rotates from east to west across the disc. The dominant outflow region seems to change position, but this could be a geometric effect.
Fit Fe XII 195, Fe XII 192, Fe XIII 202. Have used one of PRY's codes to fit a double Gaussian. Correlation between width and velocity remains, although it's not quite so clear for the smaller component at larger blue-shifts. These data are taken from each pixel in a box around the outflow region. Only done for the one active region, because the Gaussians were well separated.
LKH: does it change with time in the series of rasters you showed.
PB: not by much
KPD: The interesting thing is in the change of one flow region from redshifts to blueshifts.
In the core of the AR, the blend to the red side of the line becomes more important at higher densities.
GAD: how did you determine your zero velocity?
PB: Took a horizontal slice along the bottom
JTM: based on muliple simulations of loop flow problems, you have to be careful when fitting that if you choose two lumps of plasma: one moving and another static. I think Ken had the right idea when he used moments because you could use things like skew. that might be what this is telling you.
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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.
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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.
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There have actually been a couple of flares observed with both RHESSI and EIS. Primarily interested in evaporation.
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!Science with other, non-Hinode instruments
I’d also like to solicit talks on any of the wealth of cross-observatory data taken over Hinode’s life so far (Hinode-SUMER campaigns, regular CDS co-observing, TRACE co-observing, WHI 2008, etc.) What projects do we have (under-way or recently completed) with these multi-instrument observations that couldn’t otherwise be tackled?
%%
*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
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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.
HEM: can you do densities? wouldn't that be helpful?
RM: Have done the analysis but not the interpretation.
PRY: is the break to do with the detector you're looking at?
RM: don't think so... but it's all in the paper.
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* HEM would be interested to put together a joint EIS XRT temperature distribution.
* LKH thinks there's a disconnect between horizontal magnetic fields
** EIS could potentially do something there
* GAD: SOT discovered spicular material that's moving at very high
* JTM we have great difficulty at getting quantitative information
** JLC is the filter ratio method working quantitatvely
*** think the XRT filter ratio people have confidence, but when you compare that with EIS
** JTM: I just want to know where the hot plasma is
** JLC: if you see it at all in XRT, it's hot, but that's qualitative
** HPW in principle should be able to put these things together. We w
* LKH: Outflow areas: what does Ca II H look like?
* HPW: could SOT provide a measure of the vector magnetic field
* LKH: how do the horizontal magnetic fields impact on heating the atmosphere
* GAD: how accurate are the XRT filter ration?
** And do we know what their temperature responses. We should get XRT to explain how they're getting these.
* HPW: think we should do what Helen has done and get cross-calibrated joint observations
* JTM: does unusual flux emergence have correspondence in EIS data.
* GAD: any energetic stuff seen in SOT: flux cancellation, we could try to tie in with something we see in EIS.
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* 15:30 Line identifications with EIS and CHIANTI (Peter Young)
* 15:50 Diagnostics with the slot (Ignacio Ugarte)
* 16:20 Line identifications with EIS and CHIANTI (Peter Young)
The chances are in the last few years that if you've observed Fe XI 188.8, yo've probabluy also picked up 188.5 in the same window, so it's a little messy in that region of the spectrum.
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If my ident of Fe IX 197 is correct, it's probably a good line for temperature diagnostics.
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Can also "fix" the TRACE temperature response, so it's an important role for EIS to help better science from the imagers.
** Fe VII: normally see that 195 towers above the rest of the spectrum. The Fe VII data most commonly used are normally in the optical, but now working on the EUV lines.
Based on the current ion-balance calculations, it puts Fe VII at logT 5.4. But it's clear that __missed this__
# 11 new line IDs made from EIS spectra (mainly in the LW band)
# 16 new or revised energy levels
*** Diagnostics
Unfortunately no density sensitivity below log ne = 9.0
If you want to put Fe VII in your study, 196.22 is probably the best, and then 195.39 is a factor of two even stronger. Unfortunately, there are a lot of data which have problems and can be out by a factor of two between theory and observations.
Pretty fantastic that you can see 11 consecutive Fe ionisation stages from VII through XVII.
GAD: there's an Fe XXI and XXII line as well as Fe XXIII and XXIV
Also found there are Cr lines, too. Large EM between 5.5 and 5.8 enhances lines in this temperature range. have ID'd Cr VII and Cr VIII
** EIS is very important for doing basic spectroscopy
*** testing atomic data
*** making new identifications
*** benefits existing and upcoming missions' science
* 16:40 Diagnostics with the slot (Ignacio Ugarte)
Wanted to see what else we could get out of the slots.
Compared consecutive slot and slit rasters: similar but different.
Tried to reconstruct 40 gaussians from the slit profile. A LOT of free parameters.
Each of these 40 gaussians has an amplitude, a width, a centroid, and a (constant) background. So I had to fix the parameters. I'm going to assume the same width because they all have the same temperature (it's just an assumption). Also assume that there are no Doppler shifts, that they're centred. So I just fit the amplitudes (justified on the basis of the consecutive raster).
So, we have the raster simulated from the slot. There are differences, but remember that the raster took time to make, and the differences could be of solar origin.
* 17:05 Velocities with the slot (Louise Harra)
Using the slot plus ''TRACE'' and employing a MOSES-like technique. The velocities are very encouraging.
HEM: so it's important that TRACE co-ordinates with EIS?
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What we’ve learned to date on observing with the S-band antenna
* 16:10 Some techniques for observing (David Williams)
* 16:20 Raster stitching (David Brooks)
** Problems
** Some examples of studies that have proven useful in overcoming these problems
** Prospects & challenges for the future:
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** 16:25 Flares (Ryan Milligan)
** 16:45 Very active regions (Harry Warren / John Mariska)
* 17:05 Observation Planning - Core Team proposals and HOPS (Len Culhane)
** 17:00 Flares (Ryan Milligan)
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Small-FOV, high-cadence spectral images are key for good physics.
*** Line profiles from FPs during impulsive phase
*** Measure Doppler and nonthermal velocities as functions of time and temperature
*** How are line profiles related to electron beam parameters
*** n_e measurements.
Wish list:
# < 4-min cadence rasters
# moderate FOV 100 x 100
# fast exposures < 5 seconds
## (originally advertised 1 second exposures)
# line selections:
Core lines, Fe species, at least one n_e sensitive pair
# long duration observations >16 hours per day
# Max millennium ToOs
# not using the flare trigger to increase chance of catching the very early conditions
## what latency is there using the trigger anyway?
## ''seems like it's a second or two from XRT's trigger to EIS
# for RHESSI-specific observations, running EIS only during RHESSI's day?
*** People often write that a spectral window is centred on a given line. Maybe junk the red side of the window, because most high-T lines have blue shifts, but not high redshifts.
*** Are coronal HXR sources the reconnection site? EIS could measure the differences in the pre- and post-flare densities. Perhaps detect reconnection inflows around the source.
*** Observe regions __after__ they've rotated beyond the limb.
*** Impulsive EUV emission
high-cadence (1-second) 266" slot observations
*** resonant absorption of MHD waves
** 17:15 Very active regions (Harry Warren / John Mariska)
Commuted to a discussion about how we might co-ordinate prime flare observations as a test case for prime observations for all major targets.
PRY: if EIS puts a strong message that we want to do one kind of obserbvation
HPW: how do we prioritise our observations when the ARs come back?
PRY: would be good if we came up with an observation
Needs to be freedom -- want to run for long periods of time
Could there be working groups on how to build active region observations, for example? Does there need to be a meeting?
* Active regions
* Quiet Sun
* Observation Planning - Core Team proposals and HOPS (Len Culhane)
''Thursday'' 09:15
Len listed the kinds of class of observation that are proposed by the SSCs after they're gathered from proposers.
Discussions between the EIS SSCs, a more aggressive pursuit of what
HEM: I think what you said about getting feedback is important. One might think of a quick response to the data. ''Good idea''
JLC: there may be a very good reason to run a study several
AI: try to link the eis_plan file into the Wiki so that there's an RSS feed to tell people what EIS is doing.
PRY: is it worth time-limiting these plans? I've probably got enough data.
JTM: I'm a little reluctant to prioritise the 2nd tier, but run numbers would be useful. that would be self-prioritising. A little worried also about polluting the e-mail and webspace with another source of information.
''Suggest somehow placing these files on the Wiki automatically''
HEM would like to know the channel for feedback from proposers.
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17:15
17:30
This page (revision-83) was last changed on 02-Feb-2017 13:19 by David R WilliamsTop