Time series analysis of long term full disk observations of the Mn i 539.4 nm solar line

The equivalent width and central depth data of Mn 539.4 nm solar spectral line, observed in the period from 1979 to 1992 at Kitt Peak Observatory, was analyzed in pursuit for periodic changes. As the observations are highly unevenly sampled, test if the periods really exist in the observed data was needed. Two different methods for spectral analysis were applied to synthesized data sampled in the same way as observations. Comparation of these results with results obtained from the observed data showed that the parameters display at least three periodic changes with the periods of: 11years, quasi-biannual and 27 days. .

SOLAR g-MODE OSCILLATIONS: EXPERIMENTAL DETECTION EFFORTS AND THEORETICAL ESTIMATES

In the early days of helioseismology, around 1975, independent detections of an oscillation with a period of 160 min in solar spectral line-shift data caused very substantial interest: it was suggested that this resulted from a solar g mode, whose frequency would then provide a tight constraint on the structure of the solar core. Also, it was noted that such modes, which involve a substantial fraction of the solar mass, might lead to a detectable gravitational-wave signal. Later observations have, however, failed to confirm the solar nature of the originally detected oscillation. Extensive data on the low-frequency part of the solar oscillation spectrum have been obtained from several experiments over the last decade, including instruments on the SOHO spacecraft. These have provided stringent limits on amplitudes of solar g modes and a few tentative detections, although so far not independently confirmed. Theoretical estimates of g-mode amplitudes, while highly uncertain, suggest that direct detection of the modes on the solar surface may be difficult. However, detection with the ASTROD mission may be possible, although identification of the solar signal will require careful analysis.

Spectroscopic Diagnostics for Ions Observed in Solar and Cosmic Plasmas

The X-ray wavelength region (1-200Å) is rich in spectral lines from highly ionised systems. Spectra from the solar atmosphere have been studied extensively with various instruments covering different wavelength regions. In this paper, we discuss the solar spectral line emission with particular reference to iron ions and helium like ions observed during solar flares. The atomic processes involved in the calculation of theoretical intensities for low density plasmas are outlined together with the diagnostic properties of the emission lines. Comparisons are made with available cosmic X-ray spectra and predicted spectra for future projects, such as AXAF.

Observed Solar Spectral Line Asymmetries and Wavelength Shifts Due to Convection

Convective motions are manifest in the solar spectrum as slight spectral line asymmetries and wavelength shifts. These have been studied for 311 Fe I lines. Most lines are blueshifted because the larger contribution of blueshifted photons from bright and rising granules statistically dominates over the contribution from dark and sinking intergranular lanes. Fainter lines (formed deeper) show larger blueshifts than strong lines; high-excitation lines usually are more blueshifted (preferentially formed in the hotter granules) and short-wavelength lines are more blueshifted because of increased granulation contrast there. Detailed studies of line bisector behavior as function of line parameters permit the construction of model atmospheres incorporating convective hydrodynamics. The method does not require spatially resolved observations and can be extended to studies of stellar convection.