EM loci
by Klimchuk, James A. (GSFC-6710)
14 Oct '10
14 Oct '10
Friends,
The EM loci technique is frequently used to access whether a plasma is isothermal. The attached paper addresses the uncertainty in this technique and proposes a way to determine the range of thermal distribution widths that are consistent with a set of emission line data.
Cheers,
Jim
********************************************************************************
James A. Klimchuk
NASA Goddard Space Flight Center
Solar Physics Lab, Code 671
Bldg. 21, Rm. 158
Greenbelt, MD …
[View More]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>
Home page: http://science.gsfc.nasa.gov/671/staff/bios/cs/James_Klimchuk_ssi.html
No endorsement by NASA is implied for any correspondence related to my role as an officer of professional organizations (American Geophysical Union, American Astronomical Society, International Astronomical Union).
********************************************************************************
[View Less]
Scott,
I agree that the real application of DEM has been disappointing (so
far). However, DEM is the one unambiguous function that can be derived
both from models and observations. It is therefore a unique point of
comparison between them; more so that the intensities of a few lines.
DEM could also in principle be defined for non-steady state ionization,
although we have not yet developed the way to treat such observations.
It is probably not applicable for non-thermal distributions.
…
[View More]Alan Gabriel
--
______________________________________________________________________
Alan GABRIEL alan.gabriel(a)ias.u-psud.fr
Institut d'Astrophysique Spatiale tel : (33) 1 69 85 85 10
Batiment 121, Universite Paris XI fax : (33) 1 69 85 86 75
91405 ORSAY Cedex mobile : (33) 6 72 14 23 89
France
_____________________________________________________________________
[View Less]
Dear all,
You may be interested in our paper, which has just been accepted for publication in ApJL and which adds to the current debate on periodic flows and waves.
Periodic spectral line asymmetries in solar coronal structures from slow magnetoacoustic waves
Verwichte, E., Marsh, M., Foullon, C., Van Doorsselaere, T., De Moortel, I., Hood, A.W. and Nakariakov, V.M.
Abstract: Recent spectral observations of upward moving quasi-periodic intensity perturbations in solar coronal structures …
[View More]have shown evidence of periodic line asymmetries near their footpoints. These observations challenge the established interpretation of the intensity perturbations in terms of propagating slow magnetoacoustic waves. We show that slow waves inherently have a bias towards enhancement of emission in the blue wing of the emission line due to in-phase behaviour of velocity and density perturbations. We demonstrate that slow waves cause line asymmetries when the emission line is averaged over an oscillation period or when a quasi-static plasma component in the line-of-sight is included. Therefore, we conclude that slow magnetoacoustic waves remain a valid explanation for the observed quasi-periodic intensity perturbations.
http://go.warwick.ac.uk/erwin_verwichte/publications/verwichte_apjl2010.pdf
Best regards,
Erwin
Dr Erwin Verwichte
Centre for Fusion, Space and Astrophysics
Department of Physics
University of Warwick
Coventry CV4 7AL, United Kingdom
Office PS1.09
tel: +44(0)2476524917
fax: +44(0)2476524887
http://www.warwick.ac.uk/go/erwin_verwichte
[View Less]