Search Publications
Solar cycle variation of the radiance and the global electron density of the solar corona
Llebaria, A.; Quemerais, E.; Lamy, P.
The question of the global activity of the solar corona, as a function of time and distance from the center of the Sun, is considered by analyzing SOHO/LASCO-C2 daily polarized images over four years, i.e., from the minimum to the rising phase of the 23rd solar cycle. After proper correction for instrumental polarization, they are combined to prod…
The SOHO CELIAS/SEM EUV database from SC23 minimum to the present
Judge, D. L.; Ogawa, H. S.; Pap, J. M. +2 more
The SOHO Solar EUV Monitor has been in operation since December 1995 onboard the SOHO spacecraft. This instrument is a highly stable transmission grating solar extreme ultraviolet spectrometer. It has made nearly continuous full disk solar irradiance measurements both within an 8 nm bandpass centered at 30.4 nm and throughout the 0.1 to 50 nm sola…
How much of the solar irradiance variations is caused by the magnetic field at the solar surface?
Solanki, S. K.; Fligge, M.
The contribution to total solar irradiance variations by the magnetic field at the solar surface is estimated. Detailed models of the irradiance changes on the basis of magnetograms show that magnetic features at the solar surface account for over 90% of the irradiance variations on a solar rotation time scale and at least 70% on a solar cycle tim…
Total solar and spectral irradiance variations from solar cycles 21 to 23
Fröhlich, C.; Pap, J. M.; Floyd, L. +2 more
Total solar and UV irradiances have been measured from various space platforms for more than two decades. More recently, observations of the "Variability of solar IRradiance and Gravity Oscillations" (VIRGO) experiment on SOHO provided information about spectral irradiance variations in the near-UV at 402 nm, visible at 500 nm, and near-IR at 862 …
Variability and dynamic state of active region loops
Gurman, J. B.; Wilhelm, K.; Fredvik, T. +3 more
A set of 218 consecutive CDS rasters taken at the solar limb on October 26-28 1999 has been used to investigate the variability and plasma dynamics of active region loops. Each raster contains simultaneous images in 6 different lines, covering the full temperature range of CDS, 10 000 K (He I) to 2.7 MK (Fe XVI). Activity is seen to go on without …
Slow and fast solar wind acceleration near solar maximum
Breen, A. R.; Moran, P. J.; Tappin, S. J. +4 more
2-site measurements of interplanetary scintillation (IPS) provide measurements of solar wind speed in regions of the heliosphere which are otherwise inaccessible. We present results from co-ordinated observations made with the EISCAT and MERLIN facilities during 1999 and 2000, covering heliocentric distances from 7 to 80 solar radii (R) predominan…
Active longitudes and coronal structures during the rising phase of the solar cycle
Kosovichev, A. G.; Benevolenskaya, E. E.; Scherrer, P. H.
The longitudinal structure of the solar corona has been investigated during the transition period between solar cycles 22 and 23 and at the beginning of the current cycle 23 using the SOHO/EIT data obtained in 171 Å, 195 Å, 284 Å and 304 Å EUV lines. The EIT images were transformed into synoptic maps for each of the spectral lines, and for the 195…
Variability in the solar constant from irradiances shortward of Lyman-Alpha
Tobiska, W. Kent
The variation in the solar constant, S(t), is reproduced by the SOLAR2000 Research Grade v1.05 empirical solar irradiance model and is described for 5 solar cycles between cycles 18 and 23 (February 14, 1947 through May 31, 2000). This solar constant variation is dependent upon the derivation data sets and the formulation of SOLAR2000 which are de…
The solar corona in cycle 23
Del Zanna, G.; Fludra, A.; Thompson, W. T. +1 more
The Coronal Diagnostic Spectrometer (CDS) on SOHO has been recording EUV spectra and monitoring time variability of EUV line intensities, electron temperature and density in the low solar corona during the rising part of Cycle 23. The four-year data set includes daily synoptic observations in four EUV lines along the central meridian since April 1…
An investigation into instrumental nonlinear effects
Walker, S. N.; Balikhin, M. A.; Huff, R. +1 more
High order spectral techniques are one of the most powerful tools for the identification of non-linear processes in space plasma turbulence. Without such tools it is impossible to determine, for example, the occurrence of non-linear interactions between spectral components. However, since the observations made by an instrument involve some interna…