ADAS analysis of the differential emission measure structure of the inner solar corona - application of the data adaptive smoothing approach to the SERTS-89 active region spectrum

A.C. Lanzafame, D.H. Brooks, J. Lang, H.P. Summers, R.J. Thomas, A.M. Thompson

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

The differential emission measure (DEM) of a solar active region is derived from SERTS-89 rocket data between 170 and 450 î.. (Thomas and Neupert 1994). The integral inversion to infer the DEM distribution from spectral line intensities is performed by the data adaptive smoothing approach (Thompson 1990, 1991). Our analysis takes into account the density dependence of both ionisation fractions and excitation coefficients according to the collisional-radiative theory as implemented in ADAS, the Atomic Data and Analysis Structure (McWhirter and Summers 1984; Summers 1994; Summers 2001). Our strategy aims at checking, using observational data, the validity and limitations of the DEM method used for analysing solar EUV spectra. We investigate what information it is possible to extract, within defined limitations, and how the method can assist in a number of cases, e.g. abundance determination, spectral line identification, intensity predictions, and validation of atomic cross-sections. Using the above data and theory, it is shown that a spurious multiple peak in the DEM distribution between and 6.7, where is the electron temperature, may derive from an inaccurate treatment of the population densities of the excited levels and ionisation fractions or from using an integral inversion technique with arbitrary smoothing. Therefore, complex DEM structures, like those proposed for solar and stellar coronae by several authors, must be considered with caution. We address also the issue of systematic differences between iso-electronic sequences and show that these cannot be unambiguously detected in the coronal lines observed by SERTS. Our results indicate that a substantial improvement is required in the atomic modelling of the complex element Fe. The elemental abundance ratio Si/Ne is found to be close to its photospheric value. The same result may be true for the Fe/Ne abundance, but this latter result is uncertain because of the problems found with Fe.
LanguageEnglish
Pages242-272
Number of pages30
JournalAstronomy and Astrophysics
Volume384
Issue number1
DOIs
Publication statusPublished - Mar 2002

Fingerprint

solar corona
smoothing
corona
summer
line spectra
ionization
stellar coronas
inversions
solar spectra
data structures
density dependence
rockets
population density
cross section
analysis
electron energy
electron
cross sections
coefficients
prediction

Keywords

  • sun
  • atmosphere
  • corona UV radiation
  • atomic data
  • data analysis
  • plasma

Cite this

@article{6fa79647890e4bf98d32365f731dc109,
title = "ADAS analysis of the differential emission measure structure of the inner solar corona - application of the data adaptive smoothing approach to the SERTS-89 active region spectrum",
abstract = "The differential emission measure (DEM) of a solar active region is derived from SERTS-89 rocket data between 170 and 450 {\^i}.. (Thomas and Neupert 1994). The integral inversion to infer the DEM distribution from spectral line intensities is performed by the data adaptive smoothing approach (Thompson 1990, 1991). Our analysis takes into account the density dependence of both ionisation fractions and excitation coefficients according to the collisional-radiative theory as implemented in ADAS, the Atomic Data and Analysis Structure (McWhirter and Summers 1984; Summers 1994; Summers 2001). Our strategy aims at checking, using observational data, the validity and limitations of the DEM method used for analysing solar EUV spectra. We investigate what information it is possible to extract, within defined limitations, and how the method can assist in a number of cases, e.g. abundance determination, spectral line identification, intensity predictions, and validation of atomic cross-sections. Using the above data and theory, it is shown that a spurious multiple peak in the DEM distribution between and 6.7, where is the electron temperature, may derive from an inaccurate treatment of the population densities of the excited levels and ionisation fractions or from using an integral inversion technique with arbitrary smoothing. Therefore, complex DEM structures, like those proposed for solar and stellar coronae by several authors, must be considered with caution. We address also the issue of systematic differences between iso-electronic sequences and show that these cannot be unambiguously detected in the coronal lines observed by SERTS. Our results indicate that a substantial improvement is required in the atomic modelling of the complex element Fe. The elemental abundance ratio Si/Ne is found to be close to its photospheric value. The same result may be true for the Fe/Ne abundance, but this latter result is uncertain because of the problems found with Fe.",
keywords = "sun, atmosphere, corona UV radiation, atomic data, data analysis, plasma",
author = "A.C. Lanzafame and D.H. Brooks and J. Lang and H.P. Summers and R.J. Thomas and A.M. Thompson",
year = "2002",
month = "3",
doi = "10.1051/0004-6361:20011662",
language = "English",
volume = "384",
pages = "242--272",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
number = "1",

}

ADAS analysis of the differential emission measure structure of the inner solar corona - application of the data adaptive smoothing approach to the SERTS-89 active region spectrum. / Lanzafame, A.C.; Brooks, D.H.; Lang, J.; Summers, H.P.; Thomas, R.J.; Thompson, A.M.

In: Astronomy and Astrophysics, Vol. 384, No. 1, 03.2002, p. 242-272.

Research output: Contribution to journalArticle

TY - JOUR

T1 - ADAS analysis of the differential emission measure structure of the inner solar corona - application of the data adaptive smoothing approach to the SERTS-89 active region spectrum

AU - Lanzafame, A.C.

AU - Brooks, D.H.

AU - Lang, J.

AU - Summers, H.P.

AU - Thomas, R.J.

AU - Thompson, A.M.

PY - 2002/3

Y1 - 2002/3

N2 - The differential emission measure (DEM) of a solar active region is derived from SERTS-89 rocket data between 170 and 450 î.. (Thomas and Neupert 1994). The integral inversion to infer the DEM distribution from spectral line intensities is performed by the data adaptive smoothing approach (Thompson 1990, 1991). Our analysis takes into account the density dependence of both ionisation fractions and excitation coefficients according to the collisional-radiative theory as implemented in ADAS, the Atomic Data and Analysis Structure (McWhirter and Summers 1984; Summers 1994; Summers 2001). Our strategy aims at checking, using observational data, the validity and limitations of the DEM method used for analysing solar EUV spectra. We investigate what information it is possible to extract, within defined limitations, and how the method can assist in a number of cases, e.g. abundance determination, spectral line identification, intensity predictions, and validation of atomic cross-sections. Using the above data and theory, it is shown that a spurious multiple peak in the DEM distribution between and 6.7, where is the electron temperature, may derive from an inaccurate treatment of the population densities of the excited levels and ionisation fractions or from using an integral inversion technique with arbitrary smoothing. Therefore, complex DEM structures, like those proposed for solar and stellar coronae by several authors, must be considered with caution. We address also the issue of systematic differences between iso-electronic sequences and show that these cannot be unambiguously detected in the coronal lines observed by SERTS. Our results indicate that a substantial improvement is required in the atomic modelling of the complex element Fe. The elemental abundance ratio Si/Ne is found to be close to its photospheric value. The same result may be true for the Fe/Ne abundance, but this latter result is uncertain because of the problems found with Fe.

AB - The differential emission measure (DEM) of a solar active region is derived from SERTS-89 rocket data between 170 and 450 î.. (Thomas and Neupert 1994). The integral inversion to infer the DEM distribution from spectral line intensities is performed by the data adaptive smoothing approach (Thompson 1990, 1991). Our analysis takes into account the density dependence of both ionisation fractions and excitation coefficients according to the collisional-radiative theory as implemented in ADAS, the Atomic Data and Analysis Structure (McWhirter and Summers 1984; Summers 1994; Summers 2001). Our strategy aims at checking, using observational data, the validity and limitations of the DEM method used for analysing solar EUV spectra. We investigate what information it is possible to extract, within defined limitations, and how the method can assist in a number of cases, e.g. abundance determination, spectral line identification, intensity predictions, and validation of atomic cross-sections. Using the above data and theory, it is shown that a spurious multiple peak in the DEM distribution between and 6.7, where is the electron temperature, may derive from an inaccurate treatment of the population densities of the excited levels and ionisation fractions or from using an integral inversion technique with arbitrary smoothing. Therefore, complex DEM structures, like those proposed for solar and stellar coronae by several authors, must be considered with caution. We address also the issue of systematic differences between iso-electronic sequences and show that these cannot be unambiguously detected in the coronal lines observed by SERTS. Our results indicate that a substantial improvement is required in the atomic modelling of the complex element Fe. The elemental abundance ratio Si/Ne is found to be close to its photospheric value. The same result may be true for the Fe/Ne abundance, but this latter result is uncertain because of the problems found with Fe.

KW - sun

KW - atmosphere

KW - corona UV radiation

KW - atomic data

KW - data analysis

KW - plasma

UR - http://dx.doi.org/10.1051/0004-6361:20011662

U2 - 10.1051/0004-6361:20011662

DO - 10.1051/0004-6361:20011662

M3 - Article

VL - 384

SP - 242

EP - 272

JO - Astronomy and Astrophysics

T2 - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 1

ER -