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<p><font face="Times New Roman, Times, serif">Dear all,</font></p>
<p><font face="Times New Roman, Times, serif"> thanks for your
reactions to this work and sorry for the late reply, this is
holidays time for me. <br>
</font></p>
<font face="Times New Roman, Times, serif">Indeed SUMER and EIS have
limitations and we tried not to over interpret the data. </font><font
face="Times New Roman, Times, serif">EIS flares lines were not
detected (apart from a too weak Fe XVII). In Figure 3 of the
paper you have the temporal information from the SUMER hot lines
(75 sec integration) where, in the selected (off disk) areas, you
don't have any detectable activity. The corrected AIA 94 channel
did not show relevant temporal variation. Maybe this channel is
also not sensitive enough to the small flares detected by RHESSI?
Or we were too high in the corona to be affected by those events.
<br>
</font>
<p><font face="Times New Roman, Times, serif">We could estimate the
EM from the RHESSI data and see how compatible it is with our
finding (included the upper limit imposed with the undetected Fe
XXIII), thanks Hugh for pointing this out. Certainly it would be
interesting to see if and how much the perturbation they cause
affects the neighboring corona (see the SUMER slit positions in
my Figure 1). <br>
</font></p>
<p><font face="Times New Roman, Times, serif">In this respect, I
don't have yet an answer to Phil's question, apart form the fact
that our results are compatible with the low frequency
nanoflares picture. To answer we would need some simulations and
to understand better the magnetic structure of the AR. <br>
</font></p>
<p><font face="Times New Roman, Times, serif">Best</font></p>
<p><font face="Times New Roman, Times, serif">Susanna<br>
</font></p>
<br>
<div class="moz-cite-prefix">Le 8/6/2017 à 8:12 AM,
<a class="moz-txt-link-abbreviated" href="mailto:hm11@damtp.cam.ac.uk">hm11@damtp.cam.ac.uk</a> a écrit :<br>
</div>
<blockquote
cite="mid:Prayer.1.3.5.1708060712370.14043@carrot.maths.cam.ac.uk"
type="cite">Hi Phil,
<br>
<br>
As always you raise some interesting questions, and yes this
region was quite active, but Susanna tried very carefully to avoid
the microflare activity, but the question remains as to whether
this is really possible.
<br>
<br>
Hugh is also right that the time resolution for spectrometers like
SUMER and CDS is not great. We generally need to combine
spectroscopic observations with those from SDO/AIA to get the best
results. IRIS of course gets around this, but does not have good
coverage of coronal ions. Plenty of results with good old FeXXI
though and TR ions. Good work by Vanessa (Polito) for example.
<br>
<br>
One of the outcomes from the Loops discussions was that we really
need another high res X-ray spectrometer like SMM BCS and FCS.
MAGIXS should provide some answers. Another result of discussions
was that flying HiC with 171 again would address several key
questions.
<br>
<br>
If you like 'discussion', as we know you do, you really should
come to the Loops meetings, or perhaps even host it in Boulder!
Jeremy Drake came to the one in Palermo and stimulated lots of new
and interesting discussions, in particular relating Solar and
stellar connections. We shall soon be seeking offers of venues for
2019. Steve Bradshaw is currently 'our Loops leader'.
<br>
<br>
Even I thought that perhaps after seven loops workshops, Loops7
being in Cambridge, the discussions might have died down, but
actually the meeting in Palermo was really good, lots of
interesting talks and posters, and much animated discussion. Also
a good mix of old hands and young enthusiastic researchers. Our
thanks of course went to Fabio, for all his hard work and
hospitality. Although the temperature outside the Loops was rather
high!
<br>
<br>
H.
<br>
<br>
On Aug 6 2017, Philip Judge wrote:
<br>
<br>
<blockquote type="cite">So my email caused a little discussion...
excellent... that was why I sent
<br>
it!
<br>
<br>
Thanks Hugh. More discussion here? I would love to hear more
insight from
<br>
interested researchers... personally, I just love the stuff that
resolutely
<br>
refuses to agree with our preconceptions... but it is quite
difficult to
<br>
come up with such things.
<br>
<br>
Thanks for the original posting, Susanna
<br>
<br>
phil
<br>
<br>
<br>
On Sat, Aug 5, 2017 at 4:07 PM, Hugh Hudson
<a class="moz-txt-link-rfc2396E" href="mailto:hhudson@ssl.berkeley.edu"><hhudson@ssl.berkeley.edu></a>
<br>
wrote:
<br>
<br>
<blockquote type="cite">Phil, in addition to exotic mechanisms
such as "long-lived reconnection", one could also look at the
Parenti et al. paper from the point of view of flare physics.
Although the authors have done careful work on the time
series, the time resolution of the SUMER and EIS data is not
great. During the interval 27-Apr-2012 16:00 through
28-apr-2012 10:00, I count 25 flare triggers in the RHESSI
catalog, just for those located in the SW limb region. RHESSI
has excellent time resolution, good sensitivity, and less
temporal confusion because of the shorter time scales of hard
X-rays. The total of 25 is many more than GOES reports, and
our past experience with events at this level is that - though
weak - they really look like ordinary flares. Given the
power-law distribution of flare magnitudes, it is highly
likely that many more true flare events below even the RHESSI
threshold may have occurred during this active period.
<br>
<br>
You ask "Can you rule out any heating mechanisms?" and I'd be
delighted to see a RHESSI Science Nugget on this topic!
<br>
<br>
Hugh
<br>
<br>
> On Aug 4, 2017, at 9:06 PM, Philip Judge
<a class="moz-txt-link-rfc2396E" href="mailto:judge@ucar.edu"><judge@ucar.edu></a> wrote:
<br>
>
<br>
>
<br>
> This looks very nice. Can you rule out any heating
mechanisms? Is the
<br>
> really hot stuff (in)consistent with the emergence and
dissipation of
<br>
new magnetic field from below via a long-lived reconnection
due to the
<br>
underlying continuous emergence of flux?
<br>
>
<br>
>
<br>
>
<br>
> On Thu, Jul 27, 2017 at 3:18 AM, Susanna Parenti <
<br>
<a class="moz-txt-link-abbreviated" href="mailto:susanna.parenti@ias.u-psud.fr">susanna.parenti@ias.u-psud.fr</a>> wrote:
<br>
> Dear all,
<br>
>
<br>
> here is a new paper just accepted for publication on
the ApJ. It
<br>
provides evidence for very hot plasma above the limb observed
for an AR using spectroscopic observations from Fe X to Fe
XIX. We quantify the spatial and temporal properties of this
plasma. Main results: the hot plasma is detected in various
places above the limb which are at different heights; its
thermal properties are not changing much over the duration of
the observations (17h) .
<br>
>
<br>
> Regards,
<br>
>
<br>
> Susanna Parenti
<br>
>
<br>
>
<br>
> <a class="moz-txt-link-freetext" href="http://arxiv.org/abs/1707.08445">http://arxiv.org/abs/1707.08445</a>
<br>
>
<br>
> Spectroscopy of very hot plasma in non-flaring parts of a
solar limb
<br>
active region: spatial and temporal properties.
<br>
>
<br>
> In this work we investigate the thermal structure of an
off-limb active
<br>
region in various non-flaring areas, as it provides key
information on the way these structures are heated. In
particular, we concentrate in the very hot component (>3
MK) as it is a crucial element to discriminate between
different heating mechanisms. We present an analysis using Fe
and Ca emission lines from both SOHO/SUMER and HINODE/EIS. A
dataset covering all ionization stages from Fe X to Fe XIX has
been used for the thermal analysis (both DEM and EM). Ca XIV
is used for the SUMER-EIS radiometric cross-calibration. We
show how the very hot plasma is present and persistent almost
everywhere in the core of the limb AR. The off-limb AR is
clearly structured in Fe XVIII. Almost everywhere, the EM
analysis reveals plasma at 10 MK (visible in Fe XIX emission)
which is down to 0.1% of EM of the main 3 MK plasma. We
estimate the power law index of the hot tail of the EM to be
between -8.5 and -4.4. However, we leave an open question on
the possible existence of a small minor peak at around 10 MK.
The absence in some part of the AR of Fe XIX and Fe XXIII
lines (which fall into our spectral range) enables us to
determine an upper limit on the EM at such temperatures. Our
results include a new Ca XIV 943.59 \AA~ atomic model
<br>
>
<br>
>
<br>
>
<br>
>
<br>
>
<br>
> _______________________________________________
<br>
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<br>
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<br>
>
<br>
>
<br>
>
<br>
>
<br>
> --
<br>
> Philip Judge 303-775-9863
<br>
> Senior Scientist, HAO, NCAR
<br>
> Editor-in Chief, Open Astronomy
<br>
>
<br>
> <a class="moz-txt-link-freetext" href="https://www.degruyter.com/view/j/astro">https://www.degruyter.com/view/j/astro</a>
<br>
> <a class="moz-txt-link-freetext" href="http://people.hao.ucar.edu/judge/homepage/">http://people.hao.ucar.edu/judge/homepage/</a>
<br>
>
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>
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>
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>
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>
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</blockquote>
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<br>
<br>
</blockquote>
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