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<TITLE>RE: [Loops] loops and thermal nonequilibrium</TITLE>
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<P><FONT SIZE=2>Dear Leon and all,<BR>
<BR>
It is interesting to see the reanimation of the discussion which<BR>
I considered closed about 10 years ago :).<BR>
There is a very clear observational evidence of the propagating slow<BR>
magnetoacoustic waves in the magnetic fans above sunspots and other<BR>
magnetic elements. The observed (or deduced) disbalance of the blue and<BR>
red shifts can be explained by a number of causes, e.g. the stratification<BR>
of the medium. Hopefully, AIA will shed some additional light on this issue.<BR>
<BR>
Concerning the need for the separation of the "periodic upflows" (nonlinear<BR>
waves?) and "waves" in the automated detection, I am not sure that such<BR>
a separation is important. If detected, such phenomena attract our attention<BR>
anyway. The main task of the automated detection is to process the data much faster<BR>
than they are accumulated, not missing important events. In other words, in<BR>
my opinion, automated detection software should not be meant to produce<BR>
a research paper about the detected event, but to attract researcher's attention<BR>
to it, specifying its spatial location and time interval. I believe that our<BR>
periodmapping approach does it sufficiently well. (By the way, last week we applied it<BR>
to the preprocessing of the TESIS data obtained with the Russian CORONAS-PHOTON<BR>
satellite).<BR>
<BR>
All the best,<BR>
<BR>
Valery<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: loops-bounces@mithra.physics.montana.edu on behalf of Leon Golub<BR>
Sent: Tue 22/12/2009 08:10<BR>
To: A mailing list for scientists involved in the observation and modeling ofsolar loop structures<BR>
Subject: Re: [Loops] loops and thermal nonequilibrium<BR>
<BR>
Dear Tongjiang,<BR>
<BR>
I see that this subject is going to be debated for many years to come,<BR>
which is good. We'll have to discuss this in person some time, where we<BR>
show each other the observations and both be looking at the same thing.<BR>
In particular, it is exactly in those fan-like features that we see the<BR>
clearest flows, and indeed there is some question about the temperature.<BR>
We need simultaneous observations, in the same spectral lines, with EIS<BR>
and AIA. These should be available in a few months, once SDO launches.<BR>
Since TRACE sees upflows at both ends of the large loop systems, it<BR>
seems likely that there are interlaced loops (or threads) and that the<BR>
flows go up warm and are cooler coming down. With low-resolution (~1")<BR>
imaging, it would seem as if the blue shifts and red shifts are on top<BR>
of each other, but this is an illusion cause by failure to resolve the<BR>
different structures.<BR>
<BR>
Leon<BR>
<BR>
Tongjiang Wang wrote:<BR>
> Dear Leon,<BR>
><BR>
> I just would like to remind you that the regions showing tens of km/s<BR>
> upflows seen in EIS coronal lines are typically for weak or dark fan<BR>
> structure in TRACE and XRT, while the propagating wave features are<BR>
> often seen in bright fan-like loops (like those shown in my paper,<BR>
> where the brighter part of fan loops show RED-SHFIT!). Indeed there are<BR>
> other EIS observations show bright fan-like loops show redshift while<BR>
> not blue shifts. Moreover, as you mentioned the steady flow is not<BR>
> possibly seen in imaging observations, that means that the moving brobs<BR>
> features correspond to episodic jets or pulsive flows, thus Doppler<BR>
> shift fluctuations of tens of km/s amplitudes are expected for a upflow<BR>
> of 100-120 km/s for fan-like loops with a typical inclination of 50-60<BR>
> deg (see Marsh et al. 2009 who derived the inclination from STEREO/EUVI<BR>
> obs), but my study did not<BR>
> show this is the case. Finally, in the dark region showing tens of km/s<BR>
> EIS blue shifts, the waves may co-exist with upflows, therefore, the<BR>
> upwards moving blobs are not necessary to be the upflows. I'll try to<BR>
> look for more examples to support my view. Thank you for your discussions.<BR>
><BR>
> Best Regards<BR>
><BR>
> Tongjiang<BR>
><BR>
> On Mon, 21 Dec 2009, Leon Golub wrote:<BR>
><BR>
>> Dear Tongjiang,<BR>
>><BR>
>> This is exactly the "argument" I've been having for the past ten<BR>
>> years, starting with Nakariakov in 1999. I've been waiting for the<BR>
>> Doppler data since then, because where I see flows, other people see<BR>
>> waves. I do think that the EIS results are now showing higher<BR>
>> velocities of some tens of km/sec, and in TRACE the flows do start out<BR>
>> slow at the footpoints, so there's no inconsistency with what you're<BR>
>> saying about the speeds. There is a difference in that EIS sees the<BR>
>> upflows at somewhat higher temperatures than we do with TRACE, and XRT<BR>
>> sees them too, meaning higher T. I'm hoping that AIA will help sort<BR>
>> this out.<BR>
>><BR>
>> What I can tell you is that when we see waves in the corona, they are<BR>
>> quite clearly periodic and there's no doubt about it. Just look at any<BR>
>> movie (with high time cadence) taken above sunspots: it looks like a<BR>
>> loudspeaker pulsing away. These fans are different, and if you look<BR>
>> closely at your time-distance plots, you'll see the lower portions<BR>
>> curving upward, as the flows accelerate on their way up.<BR>
>><BR>
>> Leon<BR>
>><BR>
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