[Loops] Very hot plasma above the limb using spectroscopic observations up to Fe XIX

Sun Aug 6 00:12:37 MDT 2017

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
>>
>>
>
>
>