[Loops] Very hot plasma above the limb using spectroscopic observations up to Fe XIX
Susanna Parenti
susanna.parenti at ias.u-psud.fr
Sun Aug 6 07:37:52 MDT 2017
Dear all,
thanks for your reactions to this work and sorry for the late reply,
this is holidays time for me.
Indeed SUMER and EIS have limitations and we tried not to over interpret
the data. 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.
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).
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.
Best
Susanna
Le 8/6/2017 à 8:12 AM, hm11 at damtp.cam.ac.uk a écrit :
> Hi Phil,
>
> 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.
>
> 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.
>
> 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.
>
> 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'.
>
> 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!
>
> H.
>
> On Aug 6 2017, Philip Judge wrote:
>
>> So my email caused a little discussion... excellent... that was why I
>> sent
>> it!
>>
>> Thanks Hugh. More discussion here? I would love to hear more
>> insight from
>> interested researchers... personally, I just love the stuff that
>> resolutely
>> refuses to agree with our preconceptions... but it is quite difficult to
>> come up with such things.
>>
>> Thanks for the original posting, Susanna
>>
>> phil
>>
>>
>> On Sat, Aug 5, 2017 at 4:07 PM, Hugh Hudson <hhudson at ssl.berkeley.edu>
>> wrote:
>>
>>> 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.
>>>
>>> You ask "Can you rule out any heating mechanisms?" and I'd be
>>> delighted to see a RHESSI Science Nugget on this topic!
>>>
>>> Hugh
>>>
>>> > On Aug 4, 2017, at 9:06 PM, Philip Judge <judge at ucar.edu> wrote:
>>> >
>>> >
>>> > This looks very nice. Can you rule out any heating mechanisms?
>>> Is the
>>> > really hot stuff (in)consistent with the emergence and dissipation of
>>> new magnetic field from below via a long-lived reconnection due to the
>>> underlying continuous emergence of flux?
>>> >
>>> >
>>> >
>>> > On Thu, Jul 27, 2017 at 3:18 AM, Susanna Parenti <
>>> susanna.parenti at ias.u-psud.fr> wrote:
>>> > Dear all,
>>> >
>>> > here is a new paper just accepted for publication on the ApJ. It
>>> 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) .
>>> >
>>> > Regards,
>>> >
>>> > Susanna Parenti
>>> >
>>> >
>>> > http://arxiv.org/abs/1707.08445
>>> >
>>> > Spectroscopy of very hot plasma in non-flaring parts of a solar limb
>>> active region: spatial and temporal properties.
>>> >
>>> > In this work we investigate the thermal structure of an off-limb
>>> active
>>> 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
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > _______________________________________________
>>> > Loops mailing list
>>> > Loops at solar.physics.montana.edu
>>> > https://mithra.physics.montana.edu/mailman/listinfo/loops
>>> >
>>> >
>>> >
>>> >
>>> > --
>>> > Philip Judge 303-775-9863
>>> > Senior Scientist, HAO, NCAR
>>> > Editor-in Chief, Open Astronomy
>>> >
>>> > https://www.degruyter.com/view/j/astro
>>> > http://people.hao.ucar.edu/judge/homepage/
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > _______________________________________________
>>> > Loops mailing list
>>> > Loops at solar.physics.montana.edu
>>> > https://mithra.physics.montana.edu/mailman/listinfo/loops
>>>
>>>
>>
>>
>>
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