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Coronal Mass Ejections and Forbush Decreases

Cane, Hilary V.

Coronal Mass Ejections (CMEs) are plasma eruptions from the solar atmosphere involving previously closed field regions which are expelled into the interplanetary medium. Such regions, and the shocks which they may generate, have pronounced effects on cosmic ray densities both locally and at some distance away. These energetic particle effects can …

Observations of Irradiance Variations

Fröhlich, Claus

Since November 1978 a complete set of total solar irradiance (TSI) measurements from space is available, yielding a time series of 21 years. From measurements made by different space radiometers (HF on NIMBUS-7, ACRIM I on SMM, ACRIM II on UARS and VIRGO on SOHO) a composite record of TSI can be compiled. The corrections which are needed for each …

Modelling solar irradiance variations: Comparison with observations, including line-ratio variations

Solanki, S. K.; Unruh, Y. C.; Fligge, M.

Solar irradiance variations show a strong temporal and spectral dependence. The progression of the Sun through its activity cycle as well as solar rotation are mirrored in the irradiance variations. The spectral dependence is such that the variations are several magnitudes larger in the EUV than in the visible or infrared. We present a simple 3-co…

The Morphology of the Solar Upper Atmosphere During the Sunspot Minimum

Wilhelm, K.; Dammasch, I. E.; Feldman, U.

The solar upper atmosphere (SUA) is defined as the volume above the photosphere occupied by plasmas with electron temperatures, T_e, above ~ 2×10^4 K. Until the Skylab era, only little was known about the morphology of the SUA, while the quality of the spectroscopic observations was continually improving. A spherically symmetric atmosphere was ass…

Modelling Short-Term Spectral Irradiance Variations

Solanki, S. K.; Unruh, Y. C.; Fligge, M.

On time-scales of the solar rotation most of the solar irradiance variations are caused by the changing distribution of solar surface magnetic features. We model these short-term irradiance variations using calculations of sunspot and facular contrasts as a function of wavelength and limb angle on the Sun. The position of active regions on the sol…