Related papers: Non-equilibrium helium ionization in an MHD simula…
The ionization of hydrogen in the solar chromosphere and transition region does not obey LTE or instantaneous statistical equilibrium because the timescale is long compared with important hydrodynamical timescales, especially of…
Helium ionization plays an important role in the energy balance of the upper chromosphere and transition region. Helium spectral lines are also often used as diagnostics of these regions. We carry out 1D radiation-hydrodynamics simulations…
The thermal structure of the chromosphere is regulated through a complex interaction of various heating processes, radiative cooling, and the ionization degree of the plasma. Here we study the impact on the thermal properties of the…
Detailed numerical models of chromosphere and corona are required to understand the heating of the solar atmosphere. An accurate treatment of the solar chromosphere is complicated by the effects arising from Non Local Thermodynamic…
A new generation of coronagraphs to study the solar wind and CMEs are being developed and launched. These coronagraphs will heavily rely on multi-channel observations where visible light (VL) and UV-EUV observations provide new plasma…
Understanding the dynamics of the solar chromosphere is crucial to understanding energy transport across the solar atmosphere. The chromosphere is optically thick at many wavelengths and described by non-local thermodynamic equilibrium…
We investigate the ionization of hydrogen in a dynamic Solar atmosphere. We show that the time scale for ionization/recombination can be estimated from the eigenvalues of a modified rate matrix where the optically thick Lyman transitions…
An approximate method for solving the rate equations for the hydrogen populations was extended and implemented in the three-dimensional radiation (magneto-)hydrodynamics code CO5BOLD. The method is based on a model atom with six energy…
We investigate a non-equilibrium ionization state and an electron-ion two-temperature structure of the intracluster medium (ICM) in merging galaxy clusters using a series of N-body and hydrodynamic simulations. Mergers with various sets of…
During transient events such as major solar eruptions, the plasma can be far from the equilibrium ionization state because of rapid heating or cooling. Non-equilibrium ionization~(NEI) is important in rapidly evolving systems where the…
Simulations of the formation of galaxies, as well as ionisation models used to interpret observations of quasar absorption lines, generally either assume ionisation equilibrium or ignore the presence of the extra-galactic background (EGB)…
The solar chromosphere is weakly ionized and interactions between ionized particles and neutral particles likely have significant consequences for the thermodynamics of the plasma. We investigate the importance of introducing neutral…
Models of the solar transition region made from lines other than those of helium cannot account for the strength of the helium lines. However, the collisional excitation rates of the helium resonance lines are unusually sensitive to the…
Our aim is to determine the dominant processes and timescales for the ionisation equilibrium of calcium under solar chromospheric conditions. The study is based on numerical simulations with the RADYN code, which includes hydrodynamics,…
An initial theoretical attempt to explain the observed decrease of the polytropic/adiabatic index $\gamma$ in the solar corona has been accomplished. The chemical reactions of the ionization-recombination processes in local thermodynamic…
The Sun is moving through a warm ($\sim$6500 K) and partly ionized local interstellar cloud (LIC) with a velocity of $\sim$26 km/s. Recent measurements of the ionization of the LIC (Wolff et al., 1999) suggest that interstellar helium in…
Recent observations and theoretical investigations of neutron stars indicate that their atmospheres consist not of hydrogen or iron but possibly other elements such as helium. We calculate the ionization and dissociation equilibrium of…
Non-equilibrium ionization effects are important in cosmological hydrodynamical simulations but are computationally expensive. We study the effect of non-equilibrium ionization evolution and UV ionizing background (UVB) generated with…
Magnetic flux emergence has been shown to be a key mechanism for unleashing a wide variety of solar phenomena. However, there are still open questions concerning the rise of the magnetized plasma through the atmosphere, mainly in the…
The temperature and density conditions in the magnetized photosphere and chromosphere of the Sun lead to a very small degree of atomic ionization. In addition, at particular height, the magnetic field may be strong enough to give rise to a…