Center-to-Limb Variation in the Solar HeII 30.4 nm Emission Line from STEREO EUVI

Details Center-to-Limb Variation in the Solar HeII 30.4 nm Emission Line from STEREO EUVI Center-to-Limb Variation in the Solar HeII 30.4 nm Emission Line from STEREO EUVI

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsh31c1803f&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SH31C-1803

Astronomy and Astrophysics

Astrophysics

[7537] Solar Physics, Astrophysics, And Astronomy / Solar And Stellar Variability, [7546] Solar Physics, Astrophysics, And Astronomy / Transition Region, [7549] Solar Physics, Astrophysics, And Astronomy / Ultraviolet Emissions, [7594] Solar Physics, Astrophysics, And Astronomy / Instruments And Techniques

Scientific paper

The variation of radiant energy that emerges from the each portion of the solar surface depends on the temperature and density structure of the solar atmosphere in those emitting regions. For wavelengths where the opacity is sufficiently large, some of the emissions are blocked by overlying plasma. HeII 30.4 nm (optically thick) solar emissions fall into this category. Accordingly, the center-to-limb (C2L) brightness variation across the solar disk will differ from that of optically thin emissions. Knowledge of the C2L variation provides important constraints on solar radiative transfer models in the lower transition region where these emissions are formed. Images from the EUVI instruments aboard the two STEREO spacecraft for the first time provide direct measurements of the C2L variation, especially in the channel centered on the strong HeII 30.4 nm emission. In general, comparisons of simultaneous images taken from different viewing angles in the ecliptic plane where the same regions of the Sun are measured provide the basis for C2L estimates. After 4 years of the STEREO mission, the increasing satellite separation provides the baseline dataset for sampling at nearly all angles. Simultaneous images are corrected for instrumental responsivity degradation and converted to purely HeII 30.4 nm radiation using a DEM model (ref needed). The C2L is expressed as parameterized models whose specific values are determined via iteration with the initial estimate based on pre-DEM images. Solar surface region types are segregated into different parameter sets by the implied intensity at disk center. Validation of the responsivity model is provided by measurements along the meridian halfway between the two satellites and through intercomparisons with simultaneous images from similar EIT instrument aboard SOHO. Validation of the model and approach are provided through similar calculations obtained for optically thin coronal lines such as FeXV.

Affiliated with

Also associated with

No associations

Rating

Center-to-Limb Variation in the Solar HeII 30.4 nm Emission Line from STEREO EUVI does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Center-to-Limb Variation in the Solar HeII 30.4 nm Emission Line from STEREO EUVI, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Center-to-Limb Variation in the Solar HeII 30.4 nm Emission Line from STEREO EUVI will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1509163