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

[Susanna Parenti]

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



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