Hi everyone,
You might be interested in a new tool that Spiros, Durgesh, and I have developed for analyzing spectra. It can be downloaded from http://lanl.arxiv.org/abs/1506.08102. The abstract is below.
Hope to see many of you at Loops VII,
Jim
The detailed shapes of spectral line profiles provide valuable information about the emitting plasma, especially when the plasma contains an unresolved mixture of velocities, temperatures, and densities. As a result of finite spectral resolution, the intensity measured by a spectrometer is the average intensity across a wavelength bin of non-zero size. It is assigned to the wavelength position at the center of the bin. However, the actual intensity at that discrete position will be different if the profile is curved, as it invariably is. Standard fitting routines (spline, Gaussian, etc.) do not account for this difference, and this can result in significant errors when making sensitive measurements. Detection of asymmetries in solar coronal emission lines is one example. Removal of line blends is another. We have developed an iterative procedure called Intensity Conserving Spline Interpolation (ICSI) that corrects for this effect. As its name implies, it conserves the observed intensity within each wavelength bin, which ordinary fits do not. Given the rapid convergence, speed of computation, and ease of use, we suggest that ICSI be made a standard component of the processing pipeline for spectroscopic data.
********************************************************************************
James A. Klimchuk
NASA Goddard Space Flight Center
Solar Physics Lab, Code 671
Bldg. 21, Rm. 158
Greenbelt, MD 20771
USA
Phone: 1-301-286-9060
Fax: 1-301-286-7194
E-mail: James.A.Klimchuk(a)nasa.gov<mailto:James.A.Klimchuk@nasa.gov>
Homepage: http://science.gsfc.nasa.gov/sed/index.cfm?fuseAction=people.jumpBio&&iPhon…
No endorsement by NASA is implied for any correspondence related to my official role in professional organizations.
********************************************************************************
Dear colleagues,
You may be interested to look at the recently published volume of papers in "Philosophical Transactions A" (Royal Society) on "New Approaches in Coronal Heating", edited by Ineke de Moortel and myself.
http://rsta.royalsocietypublishing.org/content/373/2042
This presents an overview of the current state-of-the-art in coronal heating theory and observations, and includes articles by many notable members of the Loops mailing list.
Best regards
Philippa Browning
Dear Colleagues,
I remind you that the registration date for abstracts for Loops7 is
17th April 2015.
Please see the Loops7 website for details:
http://www.damtp.cam.ac.uk/user/astro/cl7/
Basic accommodation has been reserved at a college. If you wish to stay in
a hotel, information is provided on the website, but we strongly recommend
that you make a reservation as soon as possible, since hotels get very
busy in the summer months.
Please note that we do have some funding support available for young
researchers from the USA and Europe. A case should be made online
when submitting an abstract (deadline 17th April).
We are looking forward to welcoming you to Cambridge.
Best wishes,
helen
--
Hi all,
our paper "Stellar Activity and Coronal Heating: an overview of recent
results"
has just been accepted for publication in a special issue of Phil. Trans.
Royal Soc. A on "Coronal heating". The paper presents a brief overview
of recent stellar studies in selected topics relevant to magnetic
activity and
coronal heating in late-type stars.
In case you are interested, a preprint can be downloaded at
http://arxiv.org/abs/1502.07401
cheers,
Paola
Title: Stellar Activity and Coronal Heating: an overview of recent results
Authors: Paola Testa, Steve Saar, Jeremy Drake
(Harvard-Smithsonian Center for Astrophysics)
Abstract: Observations of the coronae of the Sun and of solar-like stars provide
complementary information to advance our understanding of stellar magnetic
activity, and of the processes leading to the heating of their outer
atmospheres. While solar observations allow us to study the corona at high
spatial and temporal resolution, the study of stellar coronae allows us to
probe stellar activity over a wide range of ages and stellar parameters.
Stellar studies therefore provide us with additional tools for understanding
coronal heating processes, as well as the long-term evolution of solar X-ray
activity. We discuss how recent studies of stellar magnetic fields and coronae
contribute to our understanding of the phenomenon of activity and coronal
heating in late-type stars.
Dear Colleagues,
We have just published a new paper using EIS/Hinode data titled
'Spectroscopic Observations of a Coronal Loop: Basic Physical Plasma
Parameters Along the Full Loop Length', Gupta, G. R.; Tripathi, Durgesh;
Mason, Helen, 2015, ApJ, *800* 140 (arXiv:1412.7428)
Article can be found here:
http://iopscience.iop.org/0004-637X/800/2/140/article
Abstract: Coronal loops are the basic structures of the solar transition
region and corona. Understanding of the physical mechanisms behind the loop
heating, plasma flows, and filling are still considered a major challenge
in solar physics. The mechanism(s) should be able to supply mass to the
corona from the chromosphere and to heat the plasma over 1 MK within a
small distance of a few hundred kilometers from the chromosphere to the
corona. This problem makes coronal loops an interesting target for detailed
study. In this study, we focus on spectroscopic observations of a coronal
loop observed in its full length in various spectral lines as recorded by
the Extreme-ultraviolet Imaging Spectrometer on board Hinode. We derive
physical plasma parameters such as electron density, temperature, pressure,
column depth, and filling factors along the loop length from one footpoint
to the another. The obtained parameters are used to infer whether the
observed coronal loop is overdense or underdense with respect to
gravitational stratification of the solar atmosphere. These new
measurements of physical plasma parameters, from one footpoint to another,
provide important constraints on the modeling of the mass and energy
balance in coronal loops.
With Regards,
Girjesh R. Gupta
-----------------------------------------------------------------------------------------
*Girjesh R. Gupta*
DST-INSPIRE Faculty Fellow
Inter-University Centre for Astronomy & Astrophysics (IUCAA)
Ganeshkhind, Pune University Campus
Pune 411007 India
*Tel.* : +91 20 2560 4208
*Fax *: +91 20 2560 4699
*homepage: *http://www.iucaa.ernet.in/~girjesh
-----------------------------------------------------------------------------------------
Coronal Loop Workshop VII - Heating of the Magnetically Closed Corona
DAMTP, CMS, University of Cambridge, 21-23 July 2015
SECOND ANNOUNCEMENT
Dear colleagues,
we are pleased to announce that the online registration and abstract submission
for the 7th Coronal Loops Workshop to be held at the Centre for Mathematical
Science, University of Cambridge, from 21-23 July 2015 will be open on February
4th. The workshop is expected to extend over three full days. A reception will
take place on the evening of Monday, 20th July. A conference dinner will be
held at St Edmund's College on Wednesday 22nd July.
A limited amount of funds may be available to support students and early
post-docs. Requests for financial support should be made via the comments
section when submitting an abstract.
Conference website: http://www.damtp.cam.ac.uk/user/astro/cl7/index.html
Registration and Deadlines:
* All abstracts due by 17 Apr 2015
* Financial support request (via abstract submission form) deadline: 17 Apr 2015
* Registration deadline: 1 June 2015 (100 GBP),reduced for students (50 GBP).
After this deadline please email loopworkshop(a)damtp.cam.ac.uk to check
availability to attend this workshop. The SOC intends to limit the number of
participants to ensure focused discussions.
Accommodation
We have made a block booking of 60 en-suite rooms at Gonville and Caius
college, a few minutes walking distance from the conference location. Bookings
for these rooms can be made via the registration form on the conference
website. The cost is 66 GBP per night (including breakfast). The rooms are
basic student-type accommodation and will be allocated on a first come first
served basis.
Hotels are available in the area (see links on the conference website), but we
strongly advise early booking, since Cambridge gets very busy in the
summertime, and it may not be possible to find a room if you leave it too late.
Hotels should be booked directly, not via the conference organisers.
Scientific Programme
The loops workshops are a series of highly focused workshops dealing with the
observation and modeling of magnetically confined plasma in active regions. The
programme and invited speakers are as follows:
Session 1 - Coronal Heating: Global Active Region Models and Mechanisms
- Heating mechanisms (reconnection vs waves vs spicules)
Mahboubeh Asgari-Targhi
- Global AR models (visualizations etc.)
Ignaki Ugarte-Urra
- Beyond hydro or MHD modeling
Tony Arber
Session 2 - Transition Region-Corona Connection
- Observations (IRIS, Hi-C, AIA, CRISP etc) vs theory; chromosphere
Bart De Pontieu
- Classical TR vs low lying cool loops
Pia Zacharis
- Role of spicules
Tiago Pereira
Session 3 - Fine Scale Structure and Non-equilibrium Processes
- Fine-scale structure of loops, and/or braiding (observations vs modeling)
Patrick Antolin
- Current sheets and turbulence
Bruno Coppi
- Diagnostics - developments and limitations
Peter Young
- Advances in treating non-equilibrium processes
Jaroslav Dudik
Session 4 - Wrap up session
- What doesn't match up between theory and observations?
Philippa Browning and Harry Warren
The review talks will introduce these topics, highlighting recent progress and
unresolved questions. Both observational and theoretical aspects will be
covered during each session by contributed talks and discussion.
The workshop's main goal is to encourage discussion among the participants. For
this reason the number of talks will be limited, while the poster sessions will
be long enough to allow time to view and discuss the others participants' work.
We strongly encourage young researchers to participate.
PLEASE NOTE: Only abstracts (and registrations of participants) directly
relevant to the main focus of the workshop will be accepted by the SOC.
For further information please check the web site:
http://www.damtp.cam.ac.uk/user/astro/cl7/index.html
Scientific Organising Committee
Helen Mason (chair)
Caroline Alexander
Inigo Arregui
Stephen Bradshaw
David Brooks
Leon Golub
Viggo Hansteen
Susanna Parenti
Local Organising Committee
Giulio Del Zanna (Chair)
Helen Mason
Andrew Hillier
Vanessa Polito
Stephen Bradshaw
Jaroslav Dudik
Durgesh Tripathi
Virginia Mullins (Administrative Assistant)
--
Dear all,
some of you might find the following paper interesting:
Title: The Evolution of the EM Distribution in the Core of an Active Region
Authors: Giulio Del Zanna, Durgesh Tripathi, Helen Mason, Srividya
Subramanian, Brendan O'Dwyer A&A, in press.
Available on Astro-Ph:
http://arxiv.org/abs/1411.0128
or via ADS:
http://adsabs.harvard.edu/abs/2014arXiv1411.0128D
best wishes,
Giulio
Dear all,
please find a preprint of a paper recently accepted for publication in A&A at the link:
http://arxiv.org/abs/1402.6554
Best regards
Fabio & Antonino
Thermal structure of hot non-flaring corona from Hinode/EIS
A. Petralia, F. Reale, P. Testa, G. Del Zanna
Abstract
In previous studies a very hot plasma component has been diagnosed in solar active regions through the images in three different narrow-band channels of SDO/AIA. This diagnostic from EUV imaging data has also been supported by the matching morphology of the emission in the hot Ca XVII line, as observed with Hinode/EIS. This evidence is debated because of unknown distribution of the emission measure along the line of sight. Here we investigate in detail the thermal distribution of one of such regions using EUV spectroscopic data. In an active region observed with SDO/AIA, Hinode/EIS and XRT, we select a subregion with a very hot plasma component and another cooler one for comparison. The average spectrum is extracted for both, and 14 intense lines are selected for analysis, that probe the 5.5 < log T < 7 temperature range uniformly. From these lines the emission measure distributions are reconstructed with the MCMC method. Results are cross-checked with comparison of the two subregions, with a different inversion method, with the morphology of the images, and with the addition of fluxes measured with from narrow and broad-band imagers. We find that, whereas the cool region has a flat and featureless distribution that drops at temperature log T >= 6.3, the distribution of the hot region shows a well-defined peak at log T = 6.6 and gradually decreasing trends on both sides, thus supporting the very hot nature of the hot component diagnosed with imagers. The other cross-checks are consistent with this result. This study provides a completion of the analysis of active region components, and the resulting scenario supports the presence of a minor very hot plasma component in the core, with temperatures log T > 6.6.
Dear all,
you might be interested in the following paper that has just been
published on Science:
"Evidence of non-thermal particles in coronal loops heated impulsively
by nanoflares"
It can be downloaded from astro-ph: http://arxiv.org/abs/1410.6130 or
directly
from the Science pages: http://www.sciencemag.org/content/346/6207/1255724
The abstract is below.
cheers,
Paola
Abstract:
The physical processes causing energy exchange between the Sun's hot
corona and its
cool lower atmosphere remain poorly understood. The chromosphere and
transition region
(TR) form an interface region between the surface and the corona that is
highly sensitive to
the coronal heating mechanism. High-resolution observations with the
Interface Region
Imaging Spectrograph (IRIS) reveal rapid variability (~20 to 60 seconds)
of intensity and
velocity on small spatial scales (?500 kilometers) at the footpoints of
hot and dynamic
coronal loops. The observations are consistent with numerical
simulations of heating by
beams of nonthermal electrons, which are generated in small impulsive
(?30 seconds)
heating events called "coronal nanoflares." The accelerated electrons
deposit a sizable
fraction of their energy (?10^25 erg) in the chromosphere and TR. Our
analysis provides tight
constraints on the properties of such electron beams and new diagnostics
for their
presence in the nonflaring corona.
2nd SOLARNET MEETING:
Solar and stellar magnetic activity
Grand Hotel Piazza Borsa, Via dei Cartari, 18 Palermo
Palermo, 2 - 5 February 2015
Second Announcement
The second SOLARNET meeting on Solar Physics will take place in Palermo, at the Grand Hotel Piazza Borsa, from 2nd to 5th February 2015. This is the second meeting in the framework of the EU-FP7 funded project SOLARNET (Capacities Program, Grant Agreement number 312495).
The meeting has the purpose to put in contact different solar physics communities and researchers involved in different fields and to foster collaborations between ground and space solar projects, in order to
- provide a forum to discuss the use of current and future observational solar facilities, and how to optimise their scientific returns;
- identify the potentially paradigm-shifting observations that will become possible with the next generation ground - and space-based solar telescopes and their advanced instrumentation;
- create synergies between research programs at different wavelength bands.
Specific aims of this meeting are to review the current understanding of magnetic fields in the Sun and similar stars and to discuss future directions of research.
The scientific program includes the following topics:
1) Global properties of the solar magnetic field;
2) Solar dynamo and its applications to other stars;
3) Solar differential rotation and meridional flow, stellar rotation;
4) Solar and stellar magnetic fields;
5) Activity and stellar properties;
6) Stellar activity derived from high accuracy photometry;
7) Sources of spectral and total solar irradiance variations.
and two splinter sessions:
S1) Effect of magnetic activity and internal rotation on solar and stellar pulsations
S2) Synergies between solar and stellar research
Meeting website: http://www.astropa.unipa.it/Solarnet2015/Solarnet2015.html
There you can find a preliminary program, important dates, the abstract submission form, information about the registration, contacts, financial support, the venue and the social program.
Registrations will be accessible online by credit card in due corse.
Dates:
November 30 - abstract submission deadline;
November 30 - grant request deadline;
December 31 - early registration deadline;
Meeting: Monday February 2, 9 a.m. - Thursday February 5, 5 p.m. ;
Welcome reception: Sunday, February 1, 7 p.m.
Conference dinner: Wednesday, February 4, 8 p.m.
Registration fee: The registration fee is eu. 250 if paid no later than December 31, Eu. 300 thereafter. This includes the welcome reception, the conference dinner and coffee breaks. For the registration and payment you will be redirected to a secure website. Credit cards are accepted.
Financial support: Some grants will be available to reduce or waive the registration fee, mainly for young researchers. Applicants must submit an abstract for a talk or a poster and the applications will selected by the SOC depending on the abstract and on the relevance to the meeting topics. Applications should be sent to daric(a)astropa.inaf.it no later than November 30.
Fabio Reale