E-Print Archive

There are 4290 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
* News 04/04/20 * The archive is using a new backend database. This has thrown up a few SQL errors in the last few days. If you have any issues please email adavey@nso.edu with either the number of eprint you are trying to edit or a link to your preprint.

Subject will be restored when possible View all abstracts by submitter

Steven R Cranmer   Submitted: 2008-02-06 08:08

We present a detailed analysis of oxygen ion velocity distributions in the extended solar corona, based on observations made with the Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO spacecraft. Polar coronal holes at solar minimum are known to exhibit broad line widths and unusual intensity ratios of the O VI 1032, 1037 emission line doublet. The traditional interpretation of these features has been that oxygen ions have a strong temperature anisotropy, with the temperature perpendicular to the magnetic field being much larger than the temperature parallel to the field. However, recent work by Raouafi and Solanki suggested that it may be possible to model the observations using an isotropic velocity distribution. In this paper we analyze an expanded data set to show that the original interpretation of an anisotropic distribution is the only one that is fully consistent with the observations. It is necessary to search the full range of ion plasma parameters to determine the values with the highest probability of agreement with the UVCS data. The derived ion outflow speeds and perpendicular kinetic temperatures are consistent with earlier results, and there continues to be strong evidence for preferential ion heating and acceleration with respect to hydrogen. At heliocentric heights above 2.1 solar radii, every UVCS data point is more consistent with an anisotropic distribution than with an isotropic distribution. At heights above 3 solar radii, the exact probability of isotropy depends on the electron density chosen to simulate the line-of-sight distribution of O VI emissivity. The most realistic electron densities (which decrease steeply from 3 to 6 solar radii) produce the lowest probabilities of isotropy and most-probable temperature anisotropy ratios that exceed 10. We also use UVCS O VI absolute intensities to compute the frozen-in O5+ ion concentration in the extended corona; the resulting range of values is roughly consistent with recent downward revisions in the oxygen abundance.

Authors: Steven R. Cranmer, Alexander V. Panasyuk, and John L. Kohl
Projects: None

Publication Status: ApJ, in press (v. 679; May 20, 2008), arXiv:0802.0144
Last Modified: 2008-02-06 13:42
Go to main E-Print page  Subject will be restored when possible  Subject will be restored when possible  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
Proper Orthogonal and Dynamic Mode Decomposition of Sunspot Data.
Statistical Properties of Superflares on Solar-type Stars: Results Using All of the Kepler Primary Mission Data
Turbulent viscosity and effective magnetic Prandtl number from simulations of isotropically forced turbulence
Time and Charge-Sign Dependence of the Heliospheric Modulation of Cosmic Rays
Bayesian Analysis of Quasi-periodic Pulsations in Stellar Flares
Cause and Kinematics of a Jetlike CME
The role of small-scale surface motions in the transfer of twist to a solar jet from a remote stable flux rope
Sub-second time evolution of Type III solar radio burst sources at fundamental and harmonic frequencies
Magnetically coupled atmosphere, fast sausage MHD waves, and forced magnetic field reconnection during the SOL2014-09-10T17:45 flare
Differential rotation of the solar corona: A new data-adaptive multiwavelength approach
Magnetic Helicity Flux across Solar Active Region Photospheres: I. Hemispheric Sign Preference in Solar Cycle 24
Seismological constraints on the solar coronal heating function
The Coronal Global Evolutionary Model: Using HMI Vector Magnetogram and Doppler Data to Determine Coronal Magnetic Field Evolution
Radio and X-ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare
Research progress based on observations of the New Vacuum Solar Telescope
Dynamics evolution of a solar active-region filament from quasi-static state to eruption: rolling motion, untwisting motion, material transfer, and chirality
Microwave Study of a Solar Circular Ribbon Flare
Precise Formation-Flying Telescope in Target-Centric Orbit: the Solar Case
Propagation Effects in Quiet Sun Observations at Meter Wavelengths
Twin Null-Point-Associated Major Eruptive Three-Ribbon Flares with Unusual Microwave Spectra

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