Click here for a list of SERTS related publications.
The primary strength of the SERTS data is the fact that this spectral range is rich with emission lines. Over 240 lines are seen in the SERTS active Sun spectrum, from 57 different ions. Multiple lines are observed for all ionization states of iron from Fe IX to Fe XVII. Because of this, SERTS provides a unique opportunity to study the temperature and density of coronal features using multiple line ratios from several ions of the same element. This provides a large number of internal self-consistency checks which help to minimize the impact of instrument calibration or atomic physics errors. SERTS data have become the standard for the wavelength range of 170-450 Å for both the active and the quiet Sun.
Data from SERTS have been used to address a large number of important scientific problems. Click on any of the following links to obtain more information about the scientific discoveries and advances that have been obtained using SERTS measurements.
Summary of the Most Significant SERTS Scientific Discoveries and Accomplishments
Calibrated spectra/linelists -- A major product of the SERTS program has been the calibrated emission line catalogs obtained from the data. These catalogs provide fundamental scientific information which has been used to verify and check atomic physics data, to obtain better atmospheric models for the Sun, to help plan the TRACE and SOLAR-B missions, and to understand the spectra obtained from other stars.
Differential Emission Measure (DEM) Analysis -- The solar corona is not isothermal. SERTS data hav been used to calculate the temperature distribution of emitting plasma, i.e., the DEM, for both active and quiet Sun regions. This information is useful for diverse topics such as coronal heating, coronal magnetography, and understanding the DEM of other stars.
Coronal Magnetography -- It is widely believed that the Sun's magnetic field drives coronal heating, flares, and solar wind. Therefore it is essential to measure coronal magnetic fields in order to fully understand these important phenomena which occur on the Sun. Active region and plage coronal magnetograms have been derived by combining EUV data from SERTS, and radio observations from the Very Large Array (VLA).
Spatially Resolved Active Region Spectra -- SERTS obtains a complete EUV spectrum in each spatial resolution element along its 5-arcminute slit, yielding a total of 64 spectra from each of two different pointing positions during each flight. These provide information about the structure and properties of the corona at different locations on the Sun.
Doppler Shifts -- The SERTS spectral resolution (instrumental FWHM) is about 55 milli-Angstroms in first order, and about 30 milli-Angstroms in second. Spatially resolved SERTS spectra reveal very small wavelength shifts at every position along the slit, indicating Doppler velocities less than 10 km/sec.
Density Measurements -- Density scans derived with intensity ratios from spatially resolved SERTS-93 spectra of NOAA region 7563 reveal neither systematic nor significant variations along the slit. This, combined with measured intensity variations along the slit, indicates variations in the product of the volume filling factor and the path length (fL).
SOHO CDS Cross-calibration -- The SERTS instrument underwent an end-to-end calibration in the Blue Tank at Rutherford Appleton Laboratory, Abbington, UK (the same facility used to calibrate CDS prior to the SOHO launch). Simultaneous SERTS and CDS observations taken during the 1997 flight allow an important verification of the CDS calibration.
Yohkoh/SERTS Joint Observing Results -- Simultaneous SERTS and Yohkoh observations enable consistency checks on temperatures derived from SXT filter ratios and from emission line intensity ratios. SERTS images in "coronal" ions (Fe XV and XVI) are structurally very similar to Yohkoh SXT images, tracing out hot coronal loops; SERTS images in cooler ions (He II and Mg IX) are structurally different from SXT images, delineating loop footpoints and possibly cool loops.
Coronal Heating Constraints -- SERTS off-limb spectroheliograms were used to demonstrate that significant heating is required in the quiet Sun corona below 1.2 R_sun. This places severe constraints on competing wave and current heating models.
Coronal Abundance variations -- The aluminum abundance was found to deviate most from its photospheric value. However, observations taken during the various flights indicate that the abundance anomalies vary strongly either temporally or spatially among similar solar features.
Last Revised: Wednesday, 29-Nov-2006 07:36:52 EST
Responsible NASA Official: joseph.davila@gsfc.nasa.gov
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