- ID:
- ivo://CDS.VizieR/J/A+A/578/A137
- Title:
- Solar acoustic modes in period 1996-2014
- Short Name:
- J/A+A/578/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar activity has significantly changed over the last two Schwabe cycles. After a long and deep minimum at the end of Cycle 23, the weaker activity of Cycle 24 contrasts with the previous cycles. In this work, the response of the solar acoustic oscillations to solar activity is used in order to provide insights into the structural and magnetic changes in the sub-surface layers of the Sun during this on-going unusual period of low activity. We analyze 18 years of continuous observations of the solar acoustic oscillations collected by the Sun-as-a-star GOLF instrument on board the SoHO spacecraft. From the fitted mode frequencies, the temporal variability of the frequency shifts of the radial, dipolar, and quadrupolar modes are studied for different frequency ranges that are sensitive to different layers in the solar sub-surface interior. The low-frequency modes show nearly unchanged frequency shifts between Cycles 23 and 24, with a time evolving signature of the quasi-biennial oscillation, which is particularly visible for the quadrupole component revealing the presence of a complex magnetic structure. The modes at higher frequencies show frequency shifts that are 30% smaller during Cycle 24, which is in agreement with the decrease observed in the surface activity between Cycles 23 and 24. The analysis of 18 years of GOLF oscillations indicates that the structural and magnetic changes responsible for the frequency shifts remained comparable between Cycle23 and Cycle 24 in the deeper sub-surface layers below 1400km as revealed by the low-frequency modes. The frequency shifts of the higher-frequency modes, sensitive to shallower regions, show that Cycle 24 is magnetically weaker in the upper layers of Sun
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- ID:
- ivo://CDS.VizieR/J/A+AS/126/281
- Title:
- Solar disk spectrum (660-1175A)
- Short Name:
- J/A+AS/126/281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The near-limb quiet-Sun spectrum recorded on January 25, 1996 near the solar North pole is presented in tabular form and in graphical form. Table 1 - the line list - lists all lines found in the spectrum providing absolute peak intensities, measured and literature wavelengths, identification, and classification of the transition. Fig. 4 is a display the composite spectrum. The most prominent lines are labelled. In this figure intensities are given in instrumental units and logarithmic scale.
- ID:
- ivo://CDS.VizieR/J/A+A/422/337
- Title:
- Solar EUV Post-Eruptive Arcades
- Short Name:
- J/A+A/422/337
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) spacecraft provides unique observations of dynamic processes in the low corona. The EIT 195{AA} data taken from 1997 to the end of 2002 were investigated to study the basic physical properties of post-eruptive arcades (PEAs) and their relationship with coronal mass ejections (CMEs) as detected by SOHO/LASCO (Large Angle Spectrometric Coronagraph). Over the investigated time period, 236 PEA events have been identified in total. For each PEA, its EUV lifetime as derived from the emission time at 195{AA}, its heliographic position and length, and its corresponding photospheric source region inferred from SOHO/MDI (Michelson Doppler Imager) data has been studied, as well as the variation of these parameters over the investigated phase of solar cycle 23.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A26
- Title:
- Solar Lyman irradiance line profiles
- Short Name:
- J/A+A/581/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate hydrogen spectra emitted by the entire solar disc in the Ly-{alpha} and Ly-{beta} lines are valuable for deriving the distribution and the behaviour of atomic hydrogen in the heliosphere, for understanding the UV emissions of solar type stars better, and finally for estimating the solar energy input that mainly initiates the chemical processes occurring in the planetary and cometary outer atmospheres. In this paper we want to accurately determine the irradiance solar spectral profiles of Ly-{alpha} and Ly-{beta} and their evolution through the solar activity cycle 23. The SUMER/SOHO spectrometer is a slit spectrometer that is only able to analyse a small part of the solar image. Consequently, we used the scattered light properties of the telescope to obtain average spectra over the solar disc. Then the profile is calibrated using the SOLSTICE/UARS and TIMED/SEE irradiance spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/375/591
- Title:
- SUMER Spectral Atlas of Solar Disk Features
- Short Name:
- J/A+A/375/591
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- List of spectral lines in the wavelength range from 668{AA} to 1611{AA} identified in SUMER (Solar Ultraviolet Measurements of Emitted Radiation, spectrograph on the spacecraft SOHO) spectra of the average quiet Sun (QS), a coronal hole (CH) and a sunspot on disk (SS). Spectral lines observed in second order of diffraction which are also given here, extend the lower wavelength limit to below 500{AA}. For each entry we give the observed wavelengths in angstrom, the identification, the transition, the peak of spectral radiance, L^peak^, in mW/(sr*m^2^*{AA}) (incl. background), and a cross-reference to other line lists available in the literature (cf., Sect. 5.1). For second-order lines radiance entries are generally not provided, since the background separation in both orders of diffraction is a non-trivial task, which can not be automated. Only a few radiance values of strong second-order lines with negligible first-order contribution are given, which are marked by an asterisk (*).
