Dear all,
you might be interested in our new paper Lörinčík et al. 2020:
Title: Plasma Diagnostics from Active Region and Quiet-Sun Spectra
Observed by Hinode/EIS: Quantifying the Departures from a Maxwellian
Distribution
Abstract: We perform plasma diagnostics, including that of the
non-Maxwellian κ-distributions, in several structures observed in the
solar corona by the Extreme-Ultraviolet Imaging Spectrometer (EIS) on
board the Hinode spacecraft. To prevent uncertainties due to the
in-flight calibration of EIS, we selected spectral atlases observed
shortly after the launch of the mission. One spectral atlas contains an
observation of an active region, while the other is an off-limb
quiet-Sun region. To minimize the uncertainties of the diagnostics, we
rely only on strong lines and average the signal over a spatial area
within selected structures. Multiple plasma parameters are diagnosed,
such as the electron density, the differential emission measure, and the
non-Maxwellian parameter κ. To do that, we use a simple, well-converging
iterative scheme based on refining the initial density estimates via the
differential emission measure (DEM) and κ. We find that while the
quiet-Sun spectra are consistent with a Maxwellian distribution, the
coronal loops and moss observed within the active region are strongly
non-Maxwellian with κ lap 3. These results were checked by calculating
synthetic ratios using DEMs obtained as a function of κ. Ratios
predicted using the DEMs assuming κ-distributions converged to the
ratios observed in the quiet Sun and coronal loops. To our knowledge,
this work presents a strong evidence of the presence of different
electron distributions between two physically distinct parts of the
solar corona.
Links:
https://arxiv.org/abs/2003.07091https://iopscience.iop.org/article/10.3847/1538-4357/ab8010
Sincerely,
Juraj Lörinčík
Hello Everyone,
I've been administering the Loops mailing list since its inception, but as
I will be leaving the field soon it is time to find someone else to take
over.
Being the list admin doesn't require much work. Just the occasional
addition of new members to the list or rejection of SPAM.
Please consider volunteering for this important, and incredibly easy,
task. Volunteers can contact me directly.
Thanks!
Trae
--
Henry “Trae” Winter III
Astrophysicist
SAO: Solar Stellar X-Ray Group
Center for Astrophysics | Harvard & Smithsonian
Office: (617) 495-7400
FAX: (617) 496-7577
60 Garden Street | MS 58 | Cambridge, MA 02138
cfa.harvard.edu | Facebook <http://cfa.harvard.edu/facebook> | Twitter
<http://cfa.harvard.edu/twitter> | YouTube <http://cfa.harvard.edu/youtube>
| Newsletter <http://cfa.harvard.edu/newsletter>
All,
You may be interested in a paper we've just had published, Knizhnik & Reep 2020:
https://link.springer.com/article/10.1007/s11207-020-1588-2
Title: The Distribution of Time Delays Between Nanoflares in Magnetohydrodynamic Simulations
Abstract: Nanoflares are thought to be an important energy source for heating the solar corona. The exact amount of heating contributed by nanoflares depends, in part, on the frequency of the heating and the time interval between nanoflares. Several numerical models have attempted to constrain the frequency of the heating by fitting to observed emission measures. To date, however, no physically motivated value for the time interval between nanoflares has been obtained. In this paper, we calculate a physically motivated distribution of time intervals between successive “nanoflare” reconnection events in driven magnetohydrodynamic simulations. We show that this distribution follows a power law with a slope near −1, much shallower than previously inferred from observations and determined from loop model comparisons with observations. We show that the energy flux injected into the corona in our model is of order 10^7 erg/cm^2/s, and that the heating rate due to these reconnection events reaches values of order 1 -- 10 erg/cm^3/s. Additionally, we show that this power law slope is dependent only weakly on the amount of magnetic helicity injected into the solar magnetic field by the photospheric motions, but the rate of reconnection is about 45% higher if no magnetic helicity is injected.
Cheers,
Jeff
Hi Loops friends,
Attached is a paper just accepted by Solar Physics entitled "The Distinction Between Thermal Nonequilibrium and Thermal Instability," a topic which has caused some confusion.
Abstract:
For some forms of steady heating, coronal loops are in a state of thermal nonequilibrium and evolve in a manner that includes accelerated cooling, often resulting in the formation of a cold condensation. This is frequently confused with thermal instability, but the two are in fact fundamentally different. We explain the distinction and discuss situations where they may be interconnected. Large-amplitude perturbations, perhaps associated with MHD waves, likely play a role in explaining phenomena that have been attributed to thermal nonequilibrium but also seem to require cross-field communication.
Best wishes,
Jim
********************************************************************************
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/bio/james.a.klimchuk<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 all,
related with the issue reported in the email "[Loops] WARNING people using Loops Workshop contact details
to request money”, we have removed all the contact details from the Fifth Coronal Loops webpage. Regards
Prof. J. L. Ballester
Departament de Física & IAC3-UIB
Universitat Illes Balears
E-07122 Palma de Mallorca (Spain)
phone: 34 971 172832
Fax: 34 971 173426
joseluis.ballester(a)uib.es
directorIAC3(a)uib.es
https://joseluisballester.wixsite.com/pershttp://solar.uib.es
Dear All,
someone is using the email distribution and contact details from the
"5th coronal loops workshop", they use an alias from someone at the
meeting, and then when you respond they ask for money. Check the email
address if you receive emails about a Loops Workshop.
I assume the contact details are from this webpage:
http://www.uibcongres.org/paginasCongresos/pagina_205_6.en.html?cc=205
Kind regards,
Matt
P.s. As a matter of practice it might be best to check your webpages in
general, the lawyers at ROB have asked us to remove everyones contact
details due to liability under the General Data Protection Regulation.
---
Matthew J West
PROBA2 Technical Coordinator
Physicist & Space Weather Forecaster
Royal Observatory of Belgium
Ringlaan - 3 – Avenue Circulaire
B – 1180 Brussels, Belgium
---
Hello all,
I hope those of you at Loops IX this week are enjoying the workshop. In a
convenient bit of timing, a new paper investigating the inter-dependencies
of various loop plasma properties in several different regimes of thermal
conduction has just been accepted for publication in ApJ. I've uploaded a
copy to the arXiv if you would like a sneak preview.
http://arxiv.org/abs/1906.03332
Best wishes,
Steve
Dr. Stephen J. Bradshaw
(Associate Professor of Physics and Astronomy / Chair of the Undergraduate
Program)
Department of Physics and Astronomy (MS 108)
Rice University,
6100 Main Street,
Houston,
TX 77005,
USA.
Tel: +1 713 348 4045
Email: stephen.bradshaw(a)rice.edu <mailto:stephen.bradshaw@rice.edu>
Web: solar.rice.edu