Dear Colleagues,
The following paper on EIS+XRT coronal loop DEM analysis has just been published in ApJ:
Deeper by the Dozen: Understanding the Cross-Field Temperature Distributions of Coronal Loops
by Schmelz, J.T., Pathak, S. Jenkins, B.S., Worley, B.T. 2013, ApJ, 764, 53.
https://umdrive.memphis.edu/jschmelz/public/Loops/Dozen_SchmelzEtAl_2013.pdf
Abstract: Spectroscopic analysis of coronal loops has revealed a variety of cross-field temperature distributions. Some loops appear to be isothermal while others require multithermal plasma. The EUV Imaging Spectrometer on Hinode has the spatial resolution and temperature coverage required for differential emission measure (DEM) analysis of coronal loops. Our results also use data from the X-Ray Telescope on Hinode as a high-temperature constraint. Of our 12 loops, two were post-flare loops with broad temperature distributions, two were narrow but not quite isothermal, and the remaining eight were in the mid range. We consider our DEM methods to be a significant advance over previous work, and it is also reassuring to learn that our findings are consistent with results available in the literature. For the quiescent loops analyzed here, 10 MK plasma, a signature of nanoflares, appears to be absent at a level of approximately two orders of magnitude down from the DEM peak. We find some evidence that warmer loops require broader DEMs. The cross-field temperatures obtained here cannot be modeled as single flux tubes. Rather, the observed loop must be composed of several or many unresolved strands. The plasma contained in each of these strands could be cooling at different rates, contributing to the multithermal nature of the observed loop pixels. An important implication of our DEM results involves observations from future instruments. Once solar telescopes can truly resolve X-ray and EUV coronal structures, these images would have to reveal the loop substructure implied by our multithermal results.
Regards,
Joan
>
>
> Subject: new paper on loops
>
> Folks,
>
> The following paper has now been accepted by ApJ. The conclusion
> goes rather against the current consensus: our observations show that at least some coronal separator surfaces and separators are *darker*
> than the corona around them. We have no explanation yet.
>
> Download the paper from: http://solar.physics.montana.edu/martens/Darkbands_Scott_revisions_20130111…
>
> Cheers,
>
> Piet Martens
>
> OUTFLOWS AND DARK BANDS AT ARCADE-LIKE ACTIVE REGION CORE BOUNDARIES
> J. T. Scott, P.C.H. Martens, L. Tarr Dept. of Physics, Montana State
> University Bozeman MT 59717 USA
>
> ABSTRACT
> Observations from the EUV Imaging Spectrometer (EIS) on board Hinode have revealed outflows and non-thermal line broadening in low intensity regions at the edges of active regions (ARs). We use data from Hinode′s EIS, SDO’s AIA and HMI, and the TRACE instrument to investigate the boundaries of arcade like AR cores for NOAA ARs 11112, 10978, and 9077. A narrow, low intensity region that is observed at the core’s periphery as a dark band shows outflows and increased spectral line broadening. This dark band is found to exist for days and appears between the bright coronal loop structures of different coronal topologies. We find a case where the dark band region is formed between magnetic field from emerging flux and the field of the pre-existing flux. A magnetic field extrapolation indicates this dark band is coincident with the spine lines or magnetic separatricies in the extrapolated field. This occurs over unipolar regions where the brightened coronal field is separated in connectivity and topology. This separation does not appear to be infinitesimal and an initial estimate of the minimum distance of separation is found to be ≈ 1.5-3.5 Mm.
>
> Subject headings: Solar Corona, Spectral Line Broadening, Coronal Topology, Coronal Loops
>
>
-------------------------------------------------------------------------------------
Dr. Henry (Trae) Winter III
Astrophysicist Tel: 617-495-7400
Center for Astrophysics Fax: 617-496-7577
60 Garden Street, MS 58 Cell: 617-755-7967
Cambridge, MA 02138 hwinter(a)cfa.harvard.edu
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Hi everyone,
In the spirit of a number of recent papers that have been focused on trying
to determine the dominant components of the emission in the wavelength
channels of imaging instruments (AIA, in particular), Jim and I would like
to share with you all a link to a paper on this very topic that was recently
published in the ApJ Supplement Series:
http://iopscience.iop.org/0067-0049/194/2/26/pdf/apjs_194_2_26.pdf
Our aim in carrying out the work described in this paper was to provide a
large amount of quantitative data from our modeling studies that we hope
will be of use in the analysis of observationally gathered data.
Best wishes,
Steve
-----Original Message-----
From: loops-bounces(a)solar.physics.montana.edu
[mailto:loops-bounces@solar.physics.montana.edu] On Behalf Of Paola Testa
Sent: Tuesday, September 20, 2011 10:00 AM
To: A mailing list for scientists involved in the observation and modeling
of solar loop structures
Cc: Juan Martinez Sykora
Subject: [Loops] Forward modeling of emission in SDO/AIA passbands from
dynamic 3D simulations
Hello all,
here is a link to a preprint of a paper, accepted for publication on ApJ,
that is also discussing issues related to the interpretation of AIA
observations:
http://adsabs.harvard.edu/abs/2011arXiv1109.0704M
cheers,
Paola
On 9/9/11 12:03 PM, Giulio Del Zanna wrote:
>
> Dear colleagues,
>
> here is a link to a preprint that discusses various
> (important) issues related to the interpretation of AIA data:
>
> http://solar.physics.montana.edu/cgi-bin/eprint/index.pl?entry=15555
>
> Those of you that were present at the excellent Mallorca meeting might
> recall the issues we raised there. The paper, which follows on from
> O'Dwyer et al., contains more.
>
> I encourage all to follow the example in the Appendix to calculate
> your own AIA responses using CHIANTI. We will soon release v.7, but do
> not expect huge differences.
> We are working to try and improve the atomic data for AIA, more to come.
>
>
> best wishes,
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