E-Print Archive

There are 4353 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
Tomography of the Soft X-Ray Corona: Measurements of Electron Densities, Temperatures, and Differential Emission Measure Distributions above the Limb View all abstracts by submitter

Markus J Aschwanden   Submitted: 2000-05-04 16:02

We analyze long-exposure and off-pointing {sl Yohkoh/SXT} data of the solar corona observed on 1992 Aug 26. We develop a new tomographic method which is based on a forward-fitting method of a 4-parameter model to the observed soft X-ray fluxes F_1(h) and F_2(h) of two {sl SXT} wavelength filters as function of height h. The model is defined in terms of a {sl differential emission measure (DEM)} distribution dEM(h, T)/dT, which includes also a temperature dependence of density scale heights {lambda}_n(T) =qlambda {lambda}_T and allows to quantify deviations (qlambda eq 1) from hydrostatic equilibrium, i.e. {lambda}_n(T)={lambda}_T. This parametrization faciliates a proper line-of-sight integration and relates the widely-used filter-ratio temperature TFR to the peak of the DEM distribution. A direct consequence of the multi-scale-height atmosphere is that the filter ratio temperature TFR(h) is predicted to increase with height, even if all magnetic field lines are isothermal. Our model-fitting reveals that coronal holes and Quiet Sun regions are in perfect hydrostatic equilibrium, but that coronal streamers have a scale height that exceeds the hydrostatic scale height by a factor of up to qlambdalapprox 2.3, which underscores the dynamic nature of coronal streamers. Our density measurements in coronal holes are slightly lower than most of the white-light polarized brightness inversions, and seem to come closer to the requirements of solar wind models. Our DEM model provides also a physical framework for the semi-empirical {sl Baumbach-Allen formula}, and quantifies the temperature ranges and degree of hydrostaticity of the {sl K-, L-, } and {sl F-corona}.

Authors: Markus J. Aschwanden and Loren W. Acton

Publication Status: ApJ 550, 475-492
Last Modified: 2001-04-09 07:52
  Quasi-separatrix layers: refined theory and its application to solar flares
  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Go to main E-Print pageGo to main E-Print page.
Previous AbstractPrevious Abstract.
Next AbstractNext Abstract.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
View All Abstracts By SubmitterView all abstracts by submitter.
Delete AbstractDelete abstract.

Latest Entries
The role of non-axisymmetry of magnetic flux rope in constraining solar eruptions
Energy budget of plasma motions, heating, and electron acceleration in a three-loop solar flare
Space weather: the solar perspective - an update to Schwenn (2006)
Mixed properties of slow magnetoacoustic and entropy waves in a plasma with heating/cooling misbalance
The morphology of average solar flare time profiles from observations of the Sun's lower atmosphere
Indications of stellar coronal mass ejections through coronal dimmings
Could switchbacks originate in the lower solar atmosphere? II. Propagation of switchbacks in the solar corona
Solar large-scale magnetic field and cycle patterns in solar dynamo
Three-dimensional magnetic reconnection in astrophysical plasmas
Energy partition in a confined flare with an extreme-ultraviolet late phase
Alfvén wave heating in partially ionized thin threads of solar prominences
He I 10830 Dimming During Solar Flares, I: The Crucial Role of Non-Thermal Collisional Ionisations
Separating aa-index into Solar and Hale Cycle Related Components Using Principal Component Analysis
Inward Propagating Plasma Parcels in the Solar Corona: Models with Aerodynamic Drag, Ablation, and Snowplow Accretion
Energetics and 3-D Structure of Elementary Events in Solar Coronal Heating
Stellar Superflares Observed Simultaneously with Kepler and XMM-Newton
Medium-term predictions of F10.7 and F30 cm solar radio flux with the adaptive Kalman filter
Resonances in a Coronal Loop Driven by Torsional Alfvén Waves Propagating from the Photosphere
Effects of external flow on resonant absorption of coronal loop kink oscillations driven by an external fast wave: Selective excitation problem
Emerging Dimming as Coronal Heating Episodes

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey

© 2000-2020 Solar Physics Group - Montana State University