The Ly<alpha> and Ly<beta> profiles in solar prominences and prominence fine structure

We present the first combined Ly and Ly profiles in solar prominences obtained by the SOHO/SUMER instrument and discuss their important spatial variability with respect to predictions from 1D and multithread models.Comment: Accepted in Solar Physics, 14 pages with 9 figures and 3 Table

Swaying threads of a solar filament

From recent high resolution observations obtained with the Swedish 1 m Solar Telescope in La Palma, we detect swaying motions of individual filament threads in the plane of the sky. The oscillatory character of these motions are comparable with oscillatory Doppler signals obtained from corresponding filament threads. Simultaneous recordings of motions in the line of sight and in the plane of the sky give information about the orientation of the oscillatory plane. These oscillations are interpreted in the context of the magnetohydrodynamic theory. Kink magnetohydrodynamic waves supported by the thread body are proposed as an explanation of the observed thread oscillations. On the basis of this interpretation and by means of seismological arguments, we give an estimation of the thread Alfv\'en speed and magnetic field strength by means of seismological arguments.Comment: Accepted for publication in the Astrophysical Journa

Modelling the incomplete Paschen-Back effect in the spectra of magnetic Ap stars

We present first results of a systematic investigation of the incomplete Paschen-Back effect in magnetic Ap stars. A short overview of the theory is followed by a demonstration of how level splittings and component strengths change with magnetic field strength for some lines of special astrophysical interest. Requirements are set out for a code which allows the calculation of full Stokes spectra in the Paschen-Back regime and the behaviour of Stokes I and V profiles of transitions in the multiplet 74 of FeII is discussed in some detail. It is shown that the incomplete Paschen-Back effect can lead to noticeable line shifts which strongly depend on total multiplet strength, magnetic field strength and field direction. Ghost components (which violate the normal selection rule on J) show up in strong magnetic fields but are probably unobservable. Finally it is shown that measurements of the integrated magnetic field modulus $H_s$ are not adversely affected by the Paschen-Back effect, and that there is a potential problem in (magnetic) Doppler mapping if lines in the Paschen-Back regime are treated in the Zeeman approximation.Comment: 8 pages, 10 figures, to appear in MNRA

Oscillatory Modes of a Prominence-PCTR-Corona Slab Model

Oscillations of magnetic structures in the solar corona have often been interpreted in terms of magnetohydrodynamic waves. We study the adiabatic magnetoacoustic modes of a prominence plasma slab with a uniform longitudinal magnetic field, surrounded by a prominence-corona transition region (PCTR) and a coronal medium. Considering linear small-amplitude oscillations, the dispersion relation for the magnetoacoustic slow and fast modes is deduced assuming evanescent-like perturbations in the coronal medium. In the system without PCTR, a classification of the oscillatory modes according to the polarisation of their eigenfunctions is made in order to distinguish modes with fast-like or slow-like properties. Internal and external slow modes are governed by the prominence and coronal properties respectively, and fast modes are mostly dominated by prominence conditions for the observed wavelengths. In addition, the inclusion of an isothermal PCTR does not substantially influence the mode frequencies, but new solutions (PCTR slow modes) are present.Comment: Accepted for publication in Solar Physic

Physics of Solar Prominences: II - Magnetic Structure and Dynamics

Observations and models of solar prominences are reviewed. We focus on non-eruptive prominences, and describe recent progress in four areas of prominence research: (1) magnetic structure deduced from observations and models, (2) the dynamics of prominence plasmas (formation and flows), (3) Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and large-scale patterns of the filament channels in which prominences are located. Finally, several outstanding issues in prominence research are discussed, along with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape

Detection of the Neupert Effect in the Corona of an RS CVn Binary System by XMM-Newton and the VLA

The RS CVn-type binary $\sigma$ Geminorum was observed during a large, long-duration flare simultaneously with {\it XMM-Newton} and the VLA. The light curves show a characteristic time dependence that is compatible with the Neupert effect observed in solar flares: The time derivative of the X-ray light curve resembles the radio light curve. This observation can be interpreted in terms of a standard flare scenario in which accelerated coronal electrons reach the chromosphere where they heat the cool plasma and induce chromospheric evaporation. Such a scenario can only hold if the amount of energy in the fast electrons is sufficient to explain the X-ray radiative losses. We present a plausibility analysis that supports the chromospheric evaporation model.Comment: Accepted for publication in Ap

Nordic homicide report : Homicide in Denmark, Finland, Iceland, Norway and Sweden, 2007–2016

This report compares the trends and patterns of lethal violence in from 2007 to 2016, in five Nordic countries: Denmark, Finland, Iceland, Norway and Sweden. The report is a product of the “Nordic Homicide from Past to Present” research project, funded by the Scandinavian Research Council for criminology. The main findings include: * Based on homicide mortality rates, the Nordic countries form currently three groups: compared to the rates in Denmark and Sweden, the homicide mortality rate is about 30 per cent higher in Finland and 30 per cent lower in Norway and Iceland. However, by global standards, all the countries have extremely low rates of homicide mortality. * In Denmark, Iceland, Norway, and Sweden, the hotspots of lethal violence are the metropolitan areas of the largest cities; in Finland, the rural areas and small towns in the eastern and northern provinces. In this respect, the situation in Scandinavia and Iceland resembles that in Western Europe, in Finland again, it resembles that in some of the eastern European countries. * In all five countries, non-working working-age male substance abusers are hugely over-represented among homicide offenders and victims. * In the three Scandinavian countries, immigrants make up to 25 to 40 per cent of homicide offenders, while in Iceland and Finland their proportion is about 10 per cent. While this difference reflects the sizes of the immigrant populations, differential risks are also involved. In all Nordic countries, the homicide offending rates of immigrants are higher than those of native residents, but this difference is substantially larger in Scandinavia than in Iceland or Finland. * The role of alcohol and drinking situations in lethal violence is central in Finland, Iceland and Sweden, but only moderate in Denmark and insignificant in Norway. This is reflected in the temporal distribution of homicide incidents; and to the lower percentage of crimes in near relations and the higher percentage of male victims in Finland, Iceland and Sweden. * Concerning firearm homicides, Sweden is currently a clear outlier in the region with every fourth homicide being perpetrated by firearms. The firearm homicide rate in Sweden is the highest of all the Nordic countries. The situation has deteriorated fast in the last few years. Firearm homicides are concentrated in the metropolitan areas of Stockholm, Gothenburg and Malmö and to a large extent are linked to gang violence in a few residential districts. * Nordic homicide clearance rates are among the highest in the world; offenders are caught and sentenced almost without exception. The official control policies are effective and arguably contribute to very low homicide rates in the region when compared with the global situation

Physics of Solar Prominences: I - Spectral Diagnostics and Non-LTE Modelling

This review paper outlines background information and covers recent advances made via the analysis of spectra and images of prominence plasma and the increased sophistication of non-LTE (ie when there is a departure from Local Thermodynamic Equilibrium) radiative transfer models. We first describe the spectral inversion techniques that have been used to infer the plasma parameters important for the general properties of the prominence plasma in both its cool core and the hotter prominence-corona transition region. We also review studies devoted to the observation of bulk motions of the prominence plasma and to the determination of prominence mass. However, a simple inversion of spectroscopic data usually fails when the lines become optically thick at certain wavelengths. Therefore, complex non-LTE models become necessary. We thus present the basics of non-LTE radiative transfer theory and the associated multi-level radiative transfer problems. The main results of one- and two-dimensional models of the prominences and their fine-structures are presented. We then discuss the energy balance in various prominence models. Finally, we outline the outstanding observational and theoretical questions, and the directions for future progress in our understanding of solar prominences.Comment: 96 pages, 37 figures, Space Science Reviews. Some figures may have a better resolution in the published version. New version reflects minor changes brought after proof editin

The Paschen-Back effect in the Li I 6708 A line and the presence of lithium in cool magnetic Ap stars

A number of cool magnetic Ap stars show a prominent feature at lambda 6708 A. Its identification with Li I remains controversial due to a poor knowledge of the spectra of rare-earth elements that are strongly enhanced in peculiar stars and can potentially provide an alternative identification. We suggest to investigate the 6708 line in Ap stars with strong magnetic fields. In these objects the magnetic broadening and splitting provides an additional powerful criterium for line identification, allowing to use the whole line profile instead of a mere coincidence of the observed and predicted wavelength. Due to a small separation of the Li I doublet components, their magnetic splitting pattern deviates from the one expected for the Zeeman effect even in relatively weak fields. We carry out detailed calculations of the transition between the Zeeman and Paschen-Back regimes in the magnetic splitting of the Li I line and compute polarized synthetic spectra for the range of field strength expected in Ap stars. Theoretical spectral synthesis is compared with the high-resolution observations of cool Ap stars HD 116114, HD 166473 and HD 154708, which have a mean field strength of 6.4, 8.6 and 24.5 kG, respectively, and show a strong 6708 A line. High-resolution spectra for the 6708 A region are analysed for 17 magnetic Ap stars. The presence of the 6708 A line is confirmed in 9 stars and reported for the first time in 6 stars. We demonstrate that the observed profiles of the 6708 A line in the strong field stars HD 116114, HD 166473 and HD 154708 correspond rather well to the theoretical calculations assuming the Li I identification. Inclusion of the Paschen-Back effect improves the agreement with observations, especially for HD 154708. Results of our study confirm the Li I identification proposed for the 6708 A line in cool Ap stars.Comment: 11 pages, 7 figures; accepted for publication in Astronomy & Astrophysic

Prominence-cavity regions observed using SWAP 174A filtergrams and simultaneous eclipse flash spectra

Images from the SWAP (Proba 2 mission) taken at 174A in the Fe IX/X lines are compared to simultaneous slitless flash spectra taken during the last solar total eclipse of July, 11th 2010. Many faint low excitation emission lines together with the HeI and HeII Paschen Alpha chromospheric lines are recorded on eclipse spectra where regions of limb prominences are obtained with space-borne imagers. We consider a deep flash spectrum obtained by summing 80 individual spectra to show the intensity modulations of the continuum. Intensity depressions are observed around the prominences in both eclipse and SWAP images. The prominence cavities are interpreted as a relative depression of plasma density, produced inside the corona surrounding the prominences. Photometric measurements are shown at different scales and different, spectrally narrow, intervals for both the prominences and the coronal background.Comment: 22 pages, 14 figures, accepted to publish in Sol. Phy