Search Publications
Modelling irradiance variations from the surface distribution of the solar magnetic field
Solanki, S. K.; Unruh, Y. C.; Fligge, M.
An important question in solar physics is to what extent solar surface magnetism affects the solar irradiance. Previous attempts to answer this question have employed proxies of the magnetic field to reconstruct the irradiance and compare it with observations. Here we present the first model calculations of solar irradiance variations based on var…
Slow magnetoacoustic waves in coronal loops
Berghmans, D.; Nakariakov, V. M.; Verwichte, E. +1 more
A theoretical model interpreting propagating disturbances of EUV emission intensity, recently observed in coronal loops, is constructed in terms of slow magnetoacoustic waves. The model is one-dimensional and incorporates effects of nonlinearity, dissipation due to finite viscosity and thermal conduction, and gravitational stratification of plasma…
A spectroscopic study of coronal dimming associated with a coronal mass ejection
Harrison, R. A.; Lyons, M.
Extreme ultraviolet spectroscopic observations of one coronal mass ejection event are used to examine the onset phase of the eruption. We find significant dimming of million K plasmas in the low corona under the ascending CME, the activation of an adjacent prominence and 2 million K `hot spots' which may be associated with the CME footpoints. In p…
On the source regions of the fast solar wind in polar coronal holes
Wilhelm, K.; Marsch, E.; Dammasch, I. E. +1 more
Fast streams of the solar wind with speeds of up to ~ 800 km s-1 at a distance of 1 AU (astronomical unit) from the Sun are known to originate in solar coronal holes. With the Solar and Heliospheric Observatory (SOHO) detailed studies of the solar wind source regions have been made possible for the first time. We show images of solar po…
Solar spicules and macrospicules observed by SUMER
Wilhelm, K.
Motivated by recent observations of spicules and macrospicules in the far-ultraviolet (FUV) wavelength range with the Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) on the Solar and Heliospheric Observatory (SOHO), a generation mechanism for spicules and macrospicules is outlined which deviates significantly from most of …
Characteristics of solar coronal streamers. Element abundance, temperature and density from coordinated CDS and UVCS SOHO observations
Bromage, G. E.; Parenti, S.; Raymond, J. C. +3 more
This paper presents the results from coordinated observations of streamers acquired by the SOHO Coronal Diagnostic Spectrometer (CDS) and UltraViolet Coronograph Spectrometer (UVCS) experiments. Data from different altitudes within the solar corona were taken, with the purpose of determining their physical parameters - densities, electron temperat…
Multi-component structure of solar and stellar transition regions
Peter, H.
Emission lines from the solar transition region between the chromosphere and the corona often show a two Gaussian component profile with a core and a broad second component contributing up to 25% to the total intensity. For the first time a systematic study of the broadening and Doppler shift of the second weaker components is performed using SUME…
On the origin of the fast solar wind in polar coronal funnels
Mann, G.; Marsch, E.; Hackenberg, P.
Funnels are open magnetic structures connecting the chromosphere with the solar corona ( \cite{Axf97,Mar97,Hac99}). We investigate the stationary plasma flow out of funnels with a flux-tube model. The funnel area function is derived from an analytical 2-D magnetic field model. Since the funnel height is only approximately 15 Mm, the area function …
Low-frequency p- and g-mode solar oscillations
Provost, J.; Berthomieu, G.; Morel, P.
In order to help the detection and identification of low-frequency p- and g-modes in the solar spectrum observed by ground-based networks and SoHO experiments, we study the properties of low degree (l=0 - 6) low-frequency (100 - 2000 mu Hz) solar oscillations. The frequencies of p- and g-modes have been computed for a set of solar models with upda…
Evaluation of solar energetic Fe charge states: effect of proton-impact ionization
Torsti, J.; Kocharov, L.; Kovaltsov, G. A. +1 more
We present the energy-dependent rates of ionization and recombination of energetic Fe ions in solar coronal plasma for the energy range from 0.01 to above 100 MeV nucleon-1. For the > 0.1 MeV n-1 ions, the energy dependencies become essential for both ionization and recombination processes. Ionization of the Fe projectile …