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In this paper we present a computational exercise for shut-down dose rate calculations for the JET tokamak using the in-house developed JSIR2S code package as part of its validation. The computation is performed in two parts: neutron transport and transport of secondary gamma radiation. In order to calculate neutron activation reaction rates with sufficiently low variance, hybrid variance reduction techniques using the ADVANTG code have been utilized. Probability based sampling of secondary source particles was performed. Calculated gamma dose rates after shut down are compared with dose rate measurements performed on site using ionization chambers. The C/E agreement for 1st octant is between 0.8 to 1 while statistically meaningfull results for the 2nd octant are yet to be obtained.

The ionized field should be controlled in order to insure the environmental friendliness of high voltage direct current (HVDC) transmission lines. Different with traditional HVDC transmission lines, the metal return lines is first employed in Zhangbei ±500kV flexible HVDC lines. In this paper, the characteristics of ionized field with and without metal return lines are calculated on the basis of numerical method with Deutsch’s assumption. The influence factors, i.e. roughness coefficient, distance between metal return line and height of the metal return line, are analysed in detail. The results show that the metal return lines will have a shield effect on the ionized field on the ground. The distribution of ionized field is nearly independent on the height of metal return line. The shielding effect of the metal return line mainly contributes to the projection position of the metal return line. The presented results can give instructions for the design and control of the ionized field level of flexible HVDC lines with metal return lines.

Proton therapy as Radiotherapy a treatment modality to treat cancer due to the favorable ballistic properties of proton beams. The proton loses the majority of its energy in biological matter by interaction with the electrons of molecules by an inelastic coulomb process which is bigger and maximal in the end of the range causing ionization or excitation, also through the interaction with the nucleus which is a minimal process in biological matter. Otherwise the last process is the responsible of the lateral deviation of the protons from the center. Our work consists to calculate and evaluate the lateral scattering of the dose distribution of protons acceleration up to energies within the therapeutic window between 70 and 250 MeV using a voxelized water phantom as a 3D detector which detect and calculate the beam deposed energy and dose in any area of water phantom using Geant4 platform based on Monte-Carlo Method simulation. Results of our work are compared to the experimental references results and also to other methods of simulation results.

We present results of theoretical and experimental study of collisional relaxation of fast electrons energy in gas. The dependence on the gas pressurepand electron energy ε of the mean pass Λ of fast electrons injected into a gas being sufficient to spend on ionization all their initial energy ε has been calculated. It was found that Λ is directly proportional to ε2and inversely proportional to the gas pressure. To sustain glow discharge with electrostatic confinement of fast electrons, Λ should be less than the mean way to the anode of emitted by the cathode electrons.

Massive stars and their associated ionized (HII) regions could play a key role in the formation and evolution of filaments that host star formation. However, the properties of filaments that interact with H regions are still poorly known. To investigate the impact of HII regions on the formation of filaments, we imaged the Galactic HII region RCW 120 and its surroundings where active star formation takes place and where the role of ionization feedback on the star formation process has already been studied. We used the ArT\'eMiS camera on the APEX telescope and combined the ArT\'eMiS data at 350 and 450 microns with Herschel-SPIRE/HOBYS. We studied the dense gas distribution around RCW 120 with a resolution of 8 arcsec (0.05 pc at a distance of 1.34 kpc). Our study allows us to trace the median radial intensity profile of the dense shell of RCW 120. This profile is asymmetric, indicating a clear compression from the HII region on the inner part of the shell. The profile is observed to be similarly asymmetric on both lateral sides of the shell, indicating a homogeneous compression over the surface. On the contrary, the profile analysis of a radial filament associated with the shell, but located outside of it, reveals a symmetric profile, suggesting that the compression from the ionized region is limited to the dense shell. The mean intensity profile of the internal part of the shell is well fitted by a Plummer like profile with a deconvolved Gaussian FWHM of 0.09 pc, as observed for filaments in low-mass star-forming regions. This study suggests that compression exerted by HII regions may play a key role in the formation of filaments and may further act on their hosted star formation. ArT\'eMiS data also suggest that RCW 120 might be a 3D ring, rather than a spherical structure, Comment: 8 pages, 8 figures, accepted by A&A

Aims. Using the recently observed torsional Alfvén waves in solar prominences, we determine the ionisation state of the plasma by taking into account that Alfvén waves propagate in a partially ionised prominence plasma. We derive the evolutionary equation of waves and compare the analytical solutions to observations to determine the number density of neutrals. Methods. Using a single fluid plasma approximation, where the wave damping is provided by the Cowling resistivity, we study the temporal evolution of waves. By comparing the solution of equations with observational data (period, amplitude, propagation speed), we determined the value of the Cowling resistivity that led us to draw a conclusion on the amount of neutrals in the partially ionised plasma, a quantity that cannot be measured directly or indirectly. Results. Our results show that damped torsional Alfvén waves are an ideal diagnostic tool for the ionisation state of the plasma. Using a simple model, we find that at the observational temperature of torsional Alfvén waves, the number of neutrals, is of the order of 5 × 1010 cm−3.

The measurements of physical parameters of the TRIGA reactor and Nuclear power plant Krško (NEK) reactor cores have been in the past performed on hand of the neutron flux signal obtained from uncompensated ionization cells and by employment of the a digital meter of reactivity (DMR). At the TRIGA reactor only one ionization cell is currently used for flux measurements. During the insertion of one control rod the neutron flux distribution is significantly altered affecting the flux measurements of inserting different control rods. The problem is presently solved by assigning a correction factor to each control rod what introduces an additional uncertainty. In the present paper the implementation of four fission cells for reactivity measurements is presented. In this way determining the correct gamma background and its subtraction, performed by DMR algorithms, becomes less important as previously by using ionization chambers. The larger number of detectors also reduces the flux redistribution effects on the signal during individual control rod movements.

To improve the performance characteristics of power and high-frequency electronics, wide bandgap semiconductors are now widely used. This paper presents consideration of features arising during exploration of electronic characteristics of wide bandgap materials. We use the admittance spectroscopy method for analyzing free carrier concentration and boron-impurity activation energy in semiconductor diamond. The special aspect that should be taken into account while studying wide bandgap materials is incomplete ionization of impurity. In this work we adjust the experimental conditions, basing on the previous experience, in particular reduce signal/noise ratio and reckon with heat capacity of the samples and substrate. As a result we obtained high quality conductance spectra and activation energy of boron impurity in low-doped diamond.

Aims and Methods. Accretion bursts triggered by the magnetorotational instability (MRI) in the innermost disk regions were studied for protoplanetary gas-dust disks formed from prestellar cores of various mass $M_{\rm core}$ and mass-to-magnetic flux ratio $\lambda$. Numerical magnetohydrodynamics simulations in the thin-disk limit were employed to study the long-term ($\sim 1.0$~Myr) evolution of protoplanetary disks with an adaptive turbulent $\alpha$-parameter, which depends explicitly on the strength of the magnetic field and ionization fraction in the disk. The numerical models also feature the co-evolution of gas and dust, including the back-reaction of dust on gas and dust growth. Results. Dead zone with a low ionization fraction $x, Comment: Accepted for publication in Astronomy & Astrophysics

Energetic particle precipitation induces ionization of the atmosphere which initiates a chain of reaction cycles affecting atmospheric composition and dynamics potentially down to surface weather systems. Ionization rates are retrieved based on yield functions or pre-calculated monoenergetic electron flux and energy spectra of precipitated energetic particles. Usually, information about energy spectra is obtained from satellites, balloons, and various ground-based observations. In all cases, some assumptions about spectral distribution for the entire energy range have to be made. As ionization rates are widely used in chemistry-climate models to estimate the atmospheric response to particle forcing, evaluation of the energy spectra is a key task in the solar-terrestrial studies. In this paper, it is shown that possible uncertainties of the ionization rates retrieval based on different spectral functions can lead to large disagreements in the ionization rates, with implications for the modelled response of atmospheric composition and dynamics to electron precipitation., E3S Web of Conferences, 196, ISSN:2267-1242

The anthropogenic impact of the megalopolis on the release of volatile matters by woody plants, air ionization in the suburban areas of the forestland for the period 1998 - 2018 was monitored. A decrease in the emission of volatile matters by woody plants, negative ions, an increase in positive ions was revealed. The composition of the air environment of a megalopolis for a long time was studied. It has been established that anthropogenic factors (dust content, gas contamination, electromagnetic radiation) increase the amount of positive ions by order of magnitude. It was revealed that the presence of electromagnetic radiation significantly affects the physical properties of air. The effect of ionization and volatile matters on the deposition rate of suspended particles was determined in laboratory conditions. Theoretical studies have been carried out, on the basis of which deterministic, differential equations of the effect of ionization on dust content, gas contamination of the air environment and the interaction of air ionization with polydisperse dust, volatile substances to produce adsorbate and its deposition rate have been obtained. The data of experimental and theoretical studies made it possible to develop measures to reduce anthropogenic environmental factors, which will improve the ecological situation and reduce the incidence of megalopolis residents.

We investigate the relation between the detection of the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature in the nuclear (∼24-230 pc) regions of 22 nearby Seyfert galaxies and the properties of the cold molecular gas. For the former we use ground-based (0.3-0.6″ resolution) mid-infrared (mid-IR) spectroscopy. The cold molecular gas is traced by ALMA and NOEMA high (0.2-1.1″) angular resolution observations of the CO(2-1) transition. Galaxies with a nuclear detection of the 11.3 μm PAH feature contain more cold molecular gas (median 1.6 × 107 MO ) and have higher column densities (N(H2) = 2 × 1023 cm-2) over the regions sampled by the mid-IR slits than those without a detection. This suggests that molecular gas plays a role in shielding the PAH molecules in the harsh environments of Seyfert nuclei. Choosing the PAH molecule naphthalene as an illustration, we compute its half-life in the nuclear regions of our sample when exposed to 2.5 keV hard X-ray photons. We estimate shorter half-lives for naphthalene in nuclei without a 11.3 μm PAH detection than in those with a detection. The Spitzer/IRS PAH ratios on circumnuclear scales (∼4″ ∼ 0.25-1.3 kpc) are in between model predictions for neutral and partly ionized PAHs. However, Seyfert galaxies in our sample with the highest nuclear H2 column densities are not generally closer to the neutral PAH tracks. This is because in the majority of our sample galaxies, the CO(2-1) emission in the inner ∼4″ is not centrally peaked and in some galaxies traces circumnuclear sites of strong star formation activity. Spatially resolved observations with the MIRI medium-resolution spectrograph on the James Webb Space Telescope will be able to distinguish the effects of an active galactic nucleus (AGN) and star formation on the PAH emission in nearby AGN., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

We present observations obtained with the VLT/MUSE optical integral field spectrograph of the radio source 3C277.3, located at a redshift of 0.085 and associated with the galaxy Coma A. An emission line region fully enshrouds the double-lobed radio source, which is ~60 kpc x 90 kpc in size. Based on the emission line ratios, we identified five compact knots in which the gas ionization is powered by young stars located as far as ~60 kpc from the host. The emission line filaments surrounding the radio emission are compatible with ionization from fast shocks (with a velocity of 350-500 km/s), but a contribution from star formation occurring at the edges of the radio source is likely. Coma A might be a unique example in the local Universe in which the expanding outflow triggers star formation throughout the whole radio source., Pre-proofs version - Accepted for publication in A&A

The shape of the ionising spectra of galaxies is a key ingredient to reveal their physical properties and to our understanding of the ionising background radiation. A long-standing unsolved problem is the presence of HeII nebular emission in many low-metallicity star-forming galaxies. This emission requires ionising photons with energy >54 eV, which are not produced in sufficient amounts by normal stellar populations. To examine if high mass X-ray binaries and ultra-luminous X-ray sources (HMXB/ULX) can explain the observed HeII nebular emission and how their presence alters other emission lines, we compute photoionisation models of galaxies including such sources. We combine spectral energy distributions (SEDs) of integrated stellar populations with constrained SEDs of ULXs to obtain composite spectra with varying amounts of X-ray luminosity, parameterised by Lx/SFR. With these we compute photoionisation models to predict the emission line fluxes of the optical recombination lines of H and He+, and the main metal lines of OIII, OII, OI, and NII. The predictions are then compared to a large sample of low-metallicity galaxies. We find that it is possible to reproduce the nebular HeII and other line observations with our spectra and with amounts of Lx/SFR compatible with the observations. Our work suggests that HMBX/ULX could be responsible for the observed nebular HeII emission. However, the strengths of the high and low ionisation lines, such as HeII and OI, depend strongly on the X-ray contribution and on the assumed SEDs of the high energy source(s); the latter are poorly known., Accepted by A&A on 13/09/2021

Partially ionized plasmas are found in many different astrophysical environments. The study of partially ionized plasmas is of great interest for solar physics because some layers of the solar atmosphere (photosphere and chromosphere) as well as solar structures, such as spicules and prominences, are made of these kinds of plasmas. To our knowledge, despite it being known that the adiabatic coefficient,γ, or the first adiabatic exponent, Γ1, depend on the ionization degree, this fact has been disregarded in all the studies related to magnetohydrodynamic waves in solar partially ionized plasmas. However, in other astrophysical areas, the dependence ofγor Γ1on the plasma ionization degree has been taken into account. Therefore, our aim here is to study how, in a plasma with prominence physical properties, the joint action of the temperature, density, and ionization degree modifies the numerical values of the first adiabatic exponent Γ1which affects the adiabatic sound speed and the period of slow waves. In our computations, we have used two different approaches; first of all, we assume local thermodynamic equilibrium (LTE) and, later, we consider a non-local thermodynamic equilibrium (non-LTE) model. When comparing the results in the LTE and non-LTE cases, the numerical values of Γ1are clearly different for both and they are probably strongly dependent on the assumed model which determines how the ionization degree evolves with temperature. Finally, the effect of the ionization degree dependence of Γ1on the period of slow waves has been determined showing that it can be of great importance for seismological studies of partially ionized solar structures.

Intense X-ray and ultraviolet stellar irradiation can heat and inflate the atmospheres of closely orbiting exoplanets, driving mass outflows that may be significant enough to evaporate a sizable fraction of the planet atmosphere over the system lifetime. The recent surge in the number of known exoplanets, together with the imminent deployment of new ground and space-based facilities for exoplanet discovery and characterization, requires a prompt and efficient assessment of the most promising targets for intensive spectroscopic follow-ups. To this purpose, we developed ATES (ATmospheric EScape); a new hydrodynamics code that is specifically designed to compute the temperature, density, velocity and ionization fraction profiles of highly irradiated planetary atmospheres, along with the current, steady-state mass loss rate. ATES solves the one-dimensional Euler, mass and energy conservation equations in radial coordinates through a finite-volume scheme. The hydrodynamics module is paired with a photoionization equilibrium solver that includes cooling via bremsstrahlung, recombination and collisional excitation/ionization for the case of a primordial atmosphere entirely composed of atomic hydrogen and helium, whilst also accounting for advection of the different ion species. Compared against the results of 14 moderately-to-highly irradiated planets simulated with The PLUTO-CLOUDY Interface (TPCI), ATES yields remarkably good agreement at a significantly smaller fraction of the computational time. A convergence study shows that ATES recovers stable, steady-state hydrodynamic solutions for systems with $\log(-\phi_p) \lesssim 12.9 + 0.17\log F_{\rm XUV}$. Incidentally, atmospheres of systems above this threshold are generally thought to be undergoing Jeans escape. The code, which also features a user-friendly graphic interface, is available publicly as an online repository., Comment: 17 pages, 11 figures. Revised version. Accepted by A&A. Minor changes only; this new version includes a convergence study. Comments are welcome

Aims. The primary motivation for this paper is to provide accurate data for the photoionisation of the CH radical, including the absolute total photoionisation cross-section, partial cross-sections, and photoelectron angular distribution. In addition, the near threshold features in the photoionisation curve (which are absent in previous studies) are produced with high precision. Methods. A multichannel wavefunction based on the R-matrix approach, which uses the configuration interaction (CI) method to describe electronic correlation, is carried out in the present calculations. A set of B-spline orbitals is employed to represent the accurate continuum. The distinctive feature of the present calculations allows us to generate a more accurate description of the bound and continuum states than those employed before. Results. Total photoionisation cross-sections from the ground state of CH radicals and partial cross-sections corresponding to 1π, 3σ, and 2σ states of CH+ ions are presented for photon energies ranging from threshold to 80 eV. Extensive resonance structures, which are absent in previous studies, are observed for the first time near the ionisation threshold. The cross-section dataset obtained from the present calculations is expected to be sufficiently accurate and comprehensive for most current modelling applications involving the photon and CH radical scattering system.

The magnetic fields of accretion disks play an important role in studying their evolution. We may assume that its generation is connected to the dynamo mechanism, which is similar with that in the galactic disks. Here, we propose a model of the magnetic field of the accretion disk that uses the same approaches that have been used for galaxies. It is necessary to obtain the field, which is expected to be less than the equipartition value, and without destroying the disk. To do so, it is necessary to formulate the basic properties of the ionized medium and to estimate the parameters governing the dynamo. We used the no-z approximation that has been developed for thin disks. We also take different boundary conditions that can change the value of the field significantly. We show that the magnetic field strictly depends on the boundary conditions. Taking zero conditions and the fixed magnetic field condition on the inner boundary, which are connected to the physical properties of the accretion disk, we can avoid solutions that are greater than the equipartition field., Comment: 9 pages, 9 figures, accepted for publication in Astronomy & Astrophysics

Ionized interstellar gas is an important component of the interstellar medium and its lifecycle. The recent evidence for a widely distributed highly ionized warm interstellar gas with a density intermediate between the warm ionized medium (WIM) and compact HII regions suggests that there is a major gap in our understanding of the interstellar gas. Here we investigate the properties of the dense warm ionized medium (D-WIM) in the Milky Way using spectrally resolved SOFIA GREAT [NII] 205 micron line emission and Green Bank Telescope hydrogen radio recombination lines (RRL) data, supplemented by Herschel PACS [NII] 122 micron data, and spectrally resolved 12CO. We observed eight lines of sight in the 20deg 50% of the observed [CII] intensity along these LOS. The kinetic temperatures we derive are too low to explain the presence of N+ resulting from electron collisional ionization and/or proton charge transfer of atomic nitrogen. Rather, these regions most likely are ionized by extreme ultraviolet radiation., Comment: 16 pages, 10 figures

Solar prominences are formed by partially ionized plasma with inter-particle collision frequencies generally warranting magnetohydrodynamic treatment. In this work we explore the dynamical impacts and observable signatures of two-fluid effects in the parameter regimes when ion-neutral collisions do not fully couple the neutral and charged fluids. We perform 2.5D two-fluid (charges-neutrals) simulations of the Rayleigh-Taylor instability (RTI) at a smoothly changing interface between a solar prominence thread and the corona. The purpose of this study is to deepen our understanding of the RTI and the effects of the partial ionization on the development of RTI using nonlinear two-fluid numerical simulations. Our two-fluid model takes into account neutral viscosity, thermal conductivity, and collisional interaction between neutrals and charges: ionization–recombination, energy and momentum transfer, and frictional heating. In this paper, the sensitivity of the RTI dynamics to collisional effects for different magnetic field configurations supporting the prominence thread is explored. This is done by artificially varying, or eliminating, effects of both elastic and inelastic collisions by modifying the model equations. We find that ionization and recombination reactions between ionized and neutral fluids do not substantially impact the development of the primary RTI. However, such reactions can impact the development of secondary structures during the mixing of the cold prominence and hotter surrounding coronal material. We find that collisionality within and between ionized and neutral particle populations plays an important role in both linear and nonlinear development of RTI; ion-neutral collision frequency is the primary determining factor in development or damping of small-scale structures. We also observe that the degree and signatures of flow decoupling between ion and neutral fluids can depend on the inter-particle collisionality and on the magnetic field configuration of the prominence thread.

We have used the Multi-Unit Spectroscopic Explorer (MUSE) to study the circumgalactic medium (CGM) of a z = 2.92 radio galaxy, MRC 0943-242 by parametrising its emitting and absorbing gas. In both Ly$\alpha$ $\lambda$1216 and He II $\lambda$1640 lines, we observe emission with velocity shifts of $\Delta v \simeq-1000$ km s$^{-1}$ from the systemic redshift of the galaxy. These blueshifted components represent kinematically perturbed gas that is aligned with the radio axis, which we interpret as jet-driven outflows. Three of the four known Ly$\alpha$ absorbers are detected at the same velocity as C IV $\lambda\lambda1548,1551$ and N V $\lambda\lambda1239,1243$ absorbers, proving that the gas is metal enriched more so than previously thought. At the velocity of a strong Ly$\alpha$ absorber with an HI column of $N_{\rm HI}/{\rm cm}^{-2} = 10^{19.2}$ and velocity shift of $\Delta v \simeq -400$ km s$^{-1},$ we also detect Si II $\lambda$1260 and Si II $\lambda$1527 absorption, which suggests that the absorbing gas is ionisation bounded. With the added sensitivity of this MUSE observation, we are more capable of adding constraints to absorber column densities and consequently determining what powers their ionisation. To do this, we obtain photoionisation grid models in \pkg{cloudy} which show that AGN radiation is capable of ionising the gas and producing the observed column densities in a gas of metallicity of Z/Z$_\odot \simeq$ 0.01 with a nitrogen abundance a factor of 10 greater than that of hydrogen. This metal-enriched absorbing gas, which is also spatially extended over a projected distance of $r \gtrsim 60$ kpc, is likely to have undergone chemical enrichment through stellar winds that have swept up metals from the interstellar-medium and deposited them in the outer regions of the galaxy's halo., Comment: 21 pages, 20 figures, accepted for publication in A&A

Aims. In the context of black-hole accretion disks, the main goal of the present study is to estimate the plasma environment effects on the atomic structure and radiative parameters associated with the K-vacancy states in ions of the oxygen isonuclear sequence. Methods. We use a time-averaged Debye-Huckel potential for both the electron-nucleus and the electron-electron interactions implemented in the fully relativistic multiconfiguration Dirac-Fock (MCDF) method. Results. Modified ionization potentials, K thresholds, Auger widths and radiative transition wavelengths and rates are reported for O I - O VII in plasma environments with electron temperature and density ranges 10E5 - 10E7 K and 10E18 - 10E22 cm-3 ., 8 pages, 6 figures, to be published in A&A

Aims. Hydrogen Lyman continuum emission is greatly enhanced in the impulsive kernels of solar flares, with observations of Lyman lines showing impulsive brightening and both red and blue wing asymmetries, based on the images with low spatial resolution. A spate of proposed instruments will study Lyman emission in more detail from bright, impulsive flare kernels. In support of new instrumentation we aim to apply an improved interpretation of Lyman emission with the hydrodynamic radiative code, HYDRO2GEN, which has already successfully explained Hαemission with large redshifts and sources of white light emission in solar flares. The simulations can interpret the existing observations and propose observations in the forthcoming missions.Methods. A flaring atmosphere is considered to be produced by a 1D hydrodynamic response to injection of an electron beam, defining depth variations of electron and ion kinetic temperatures, densities, and macro-velocities. Radiative responses in this flaring atmosphere affected by the beams with different parameters are simulated using a fully non-local thermodynamic equilibrium (NLTE) approach for a five-level plus continuum model hydrogen atom with excitation and ionisation by spontaneous, external, and internal diffusive radiation, and by inelastic collisions with thermal and beam electrons. Integral radiative transfer equations for all optically thick transitions are solved using the L2 approximation simultaneously with steady state equations.Results. During a beam injection in the impulsive phase there is a large increase of collisional ionisation and excitation by non-thermal electrons that strongly (by orders of magnitude) increases excitation and the ionisation degree of hydrogen atoms from all atomic levels. These non-thermal collisions combined with plasma heating caused by beam electrons lead to an increase in Lyman line and continuum radiation, which is highly optically thick. During a beam injection phase the Lyman continuum emission is greatly enhanced in a large range of wavelengths resulting in a flattened distribution of Lyman continuum over wavelengths. After the beam is switched off, Lyman continuum emission, because of its large opacity, sustains, for a very long time, the high ionisation degree of the flaring plasma gained during the beam injection. This leads to a long enhancement of hydrogen ionisation, occurrence of white light flares, and an increase of Lyman line emission in cores and wings, whose shapes are moved closer to those from complete redistribution (CRD) in frequencies, and away from the partial ones (PRD) derived in the non-flaring atmospheres. In addition, Lyman line profiles can reflect macro-motions of a flaring atmosphere caused by downward hydrodynamic shocks produced in response to the beam injection reflected in the enhancements of Ly-line red wing emission. These redshifted Ly-line profiles are often followed by the enhancement of Ly-line blue wing emission caused by the chromospheric evaporation. The ratio of the integrated intensities in the Lyαand Lyβlines is lower for more powerful flares and agrees with reported values from observations, except in the impulsive phase in flaring kernels which were not resolved in previous observations, in which the ratio is even lower. These results can help observers to design the future observations in Lyman lines and continuum emission in flaring atmospheres.

We demonstrate two-dimensional control over the chargelocalization in H2 dissociation using elliptically polarized laser pulses. The influences of the CEP and the laser phase at the instant of ionization are investigated.

XXI International Conference on Ultrafast Phenomena 2018 (UP 2018), Hamburg, Germany, 15 Jul 2019 - 20 Jul 2019; The European physical journal / Web of Conferences Web of Conferences : proceedings proceedings 205, 06009 - (2019). doi:10.1051/epjconf/201920506009, We simulated the multi-photon multi-ionization dynamics of an iodomethane molecule, CH3I, exposed to ultraintense and ultrashort x-ray pulses. The strong ionization causes electronic charge rearrangement in the molecule that leads to an enhanced total charge., Published by EDP Sciences, Les Ulis

Ultrafast dissociation dynamics in bromoform molecules initiated by UV (263 nm) excitation and by strong-field ionization are explored using femtosecond XUV transient absorption spectroscopy.

XXI International Conference on Ultrafast Phenomena 2018, UP 2018, Hamburg, Germany, 15 Jul 2018 - 20 Jul 2018; The European physical journal / Web of Conferences 205, 07002 (2019). doi:10.1051/epjconf/201920507002, Laser-aligned carbonyl-sulfide molecules were strong-field ionized using mid-infrared light. Investigating the strong-field effects in the molecular frame allowed to add novel facets to the understanding of the intrinsic nature of strong-field physics., Published by EDP Sciences, Les Ulis

Methods for calculation of specific conductance of ions and micelles and the degree of micelle ionization using conductometric data in various approximations of the Debye – Hückel – Onsager theory were considered. The analysis of the existing calculation methods was carried out to identify their drawbacks and to suggest ways of their elimination. The calculation method of the micellar parameters on the basis of conductometric data using micellar size was modified, and a new formula for determining the degree of micelle ionization was obtained. All calculations using the modified method were performed in the first and the second approximations, and the newly obtained values of the micellar parameters are in greater agreement with the results of other studies. Based on the calculations performed, it was shown that the contribution of micelles to the total conductivity of micellar solution cannot be neglected, since at high concentrations the contribution of micelles exceeds the contribution of counterions and can exceed 50%.

Using asymmetric two-color laser fields composed of 1800 and 900nm, we have simultaneously controlled four well identified fragmentation channels in dissociative ionization of the hydrogen molecule, resulting in enhanced electron-localization sensitivities of up to 65%.

We introduce and employ the molecular attoclock method. This allows us to simultaneously trace the nuclear and electron dynamics during H2 fragmentation, and to CEP-control the two-electron emission dynamics on sub-cycle time scales., High Intensity Lasers and High Field Phenomena, 26–28 March, 2018, Strasbourg, France

The unprecedented combination of transient absorption and ion mass spectroscopy with attosecond resolution is used to study and control the complex multidimensional excitation and decay cascade of an ultrafast Auger process in krypton.

Recently, there has been an increased interest in the study of the generation of low-energy cosmic rays (CRs; < 1 TeV) in shocks situated on the surface of a protostar or along protostellar jets. These locally accelerated CRs offer an attractive explanation for the high levels of non-thermal emission and ionisation rate, $\zeta$, observed close to these sources. The high $\zeta$ observed in some protostellar sources is generally attributed to shock-generated UV photons. The aim of this article is to show that when synchrotron emission and a high $\zeta$ are measured in the same spatial region, a locally shock-accelerated CR flux is sufficient to explain both phenomena. We assume that relativistic particles are accelerated according to the first-order Fermi acceleration mechanism and compute $\zeta$ and the non-thermal emission at cm wavelengths. We then apply our model to the star-forming region OMC-2 FIR 3/FIR 4. Using a Bayesian analysis, we constrain the parameters of the model and estimate the spectral indices of the non-thermal radio emission. We demonstrate that the local CR acceleration model makes it possible to simultaneously explain the synchrotron emission along the HOPS 370 jet within the FIR 3 region and $\zeta$ observed near the FIR 4 protocluster. Our model constrains the magnetic field strength (~250-450$~\mu$G), its turbulent component (~20-40$~\mu$G), and the jet velocity in the shock reference frame for the three non-thermal sources of the HOPS 370 jet (~350-1000 km s$^{-1}$). Beyond the modelling of the OMC-2 FIR 3/FIR 4 system, we show how the combination of continuum observations at cm wavelengths and molecular transitions is a powerful new tool for the analysis of star-forming regions: these two types of observations can be simultaneously interpreted by invoking only the presence of locally accelerated CRs, without having to resort to shock-generated UV photons., Comment: 10 pages, 6 figures, accepted by A&A

Protoplanetary disks are thought to evolve viscously, where the disk mass - the reservoir available for planet formation - decreases over time as material is accreted onto the central star. Observations show a correlation between dust mass and the stellar accretion rate, as expected from viscous theory. However, the gas mass inferred from 13CO and C18O line fluxes, which should be a more direct measure, shows no such correlation. Using thermochemical DALI models, we investigate how 13CO and C18O J=3-2 line fluxes change over time in a viscously evolving disk. We also investigate if the chemical conversion of CO through grain-surface chemistry combined with viscous evolution can explain the observations of disks in Lupus. The 13CO and C18O 3-2 line fluxes increase over time due to their optically thick emitting regions growing in size as the disk expands viscously. The C18O 3-2 emission is optically thin throughout the disk for only a subset of our models (Mdisk (t = 1 Myr) < 1e-3 Msun). For these disks the integrated C18O flux decreases with time, similar to the disk mass. The C18O 3-2 fluxes for the bulk of the disks in Lupus (with Mdust < 5e-5 Msun) can be reproduced to within a factor of ~2 with viscously evolving disks in which CO is converted into other species through grain-surface chemistry driven by a cosmic-ray ionization rate zeta_cr ~ 5e-17 - 1e-16 s^-1. However, explaining the stacked C18O upper limits requires a lower average abundance than our models can produce and they cannot explain the observed 13CO fluxes, which, for most disks, are more than an order of magnitude fainter than what our models predict. Reconciling the 13CO fluxes of viscously evolving disks with the observations requires either a combination of efficient vertical mixing and a high zeta_cr or low mass disks (Mdust < 3e-5 Msun) being much thinner and/or smaller than their more massive counterparts., 21 pages, 14 figures, accepted in A&A

We discuss the possible origin of the double-peaked profiles recently observed in Lyman-Alpha Emitters (LAEs) at the epoch of reionization ($z \gtrsim 6.5$) from obscured active galactic nuclei (AGN). Combining the extent of the Lyman-$\alpha$ near-zones estimated from the blue peak velocity offset in these galaxies, with the ionizing emissivity of quasars at $z \gtrsim 6$, we forecast the intrinsic UV and X-ray luminosities of the AGN needed to give rise to their double-peaked profiles. We also estimate the extent of the obscuration of the AGN by comparing their luminosities to those of similar quasar samples at these epochs. Future X-ray and radio observations, as well as those with the ${James \ Webb \ Space \ Telescope}$, will be valuable tools to test the AGN contribution to the intergalactic-scale ionization zones of high-redshift LAEs., Comment: 4 pages, 1 figure; accepted for publication in A&A Letters

Low-energy cosmic rays (LECRs) contribute substantially to the energy balance of the interstellar medium. They play also significant role in the heating and chemistry of gas, and, consequently, on the star formation process. Because of the slow propagation coupled with enhanced energy losses of subrelativistic particles, LECRs are concentrated around their acceleration sites. LECRs effectively interact with the ambient gas through nuclear reactions. Although these processes are energetically less effective compared to heating and ionization, they are extremely important from the point of view of nuclear de-excitation lines, which carry unique information about LECRs. We present results on production of de-excitation lines combining the numerical treatment of nuclear reactions using the code TALYS, with the propagation and energy losses of LECRs., Comment: Accepted for publication in Astronomy & Astrophysics

International audience; In a recent work [1], we demonstrated how laser-dressed ionization can be harnessed to control with attosecond accuracy the time delay between an extreme-ultraviolet (XUV) attosecond pulse train and an infrared (IR) femtosecond pulse. In this case, the comb-like photoelectron spectrum obtained by ionizing a gas target with the two superimposed beams exhibits peaks oscillating with the delay. Two of them can be found to oscillate in phase quadrature, allowing an optimal measurement and stabilization of the delay over a large range. Here we expand this technique to isolated attosecond pulses, by taking advantage of the delay-modulation of attosecond streaking traces. Although the photoelectron spectrum contains no peaks in that case, it is possible to reconstruct the pump-probe delay by simply monitoring the mean energy of the spectrum and the amplitude at this energy. In general, we find that active delay stabilization based on laser-dressed ionization is possible as long as the XUV pulses are chirped.

High ionisation lines in the soft X-ray band are generally associated to either interstellar hot gas along the line of sight or to photoionised gas intrinsic to the source. In the low-mass X-ray binary 4U 1820-30, the nature of these lines is not well understood. We characterised the ionised gas present along the line of sight towards the source producing the X-ray absorption lines of Mg XI, Ne IX, Fe XVII, O VII, and O VIII. We analysed all the observations available for this source in the XMM-Newton and Chandra archives, taken with the RGS, HETG, and LETG spectrometers. The high-resolution grating spectra have been accurately examined through a standard X-ray analysis based on the $C$-statistic and through the Bayesian parameter inference. We tested two physical models which describe a plasma in either collisional ionisation or photoionisation equilibrium. We adopted the Bayesian model comparison to statistically compare the different combinations of the models used for the analysis.} We found that the lines are consistent with hot gas in the interstellar medium rather than being associated with the intrinsic gas of the X-ray binary. Our best-fit model reveals the presence of a collisionally ionised plasma with a temperature of $T=(1.98\pm0.05)\times10^6 $ K. The photoionisation model fails to fit the Fe XVII line (which is detected with a significance of $6.5\sigma$) due to the low column density predicted by the model. Moreover, the low inclination of the binary system is likely the reason for the non-detection of ionised gas intrinsic to the source.}, Comment: 13 pages, 7 Figure, Accepted for publication in A&A

Recent quantitative experiments on the ionization potential depression (IPD) in dense plasma show that the observational results are difficult to explain with the widely used analytical models for plasma screening. Here, we investigate the effect of plasma screening on the IPD and ionization balance of dense carbon plasma under solar and stellar interior conditions using our developed consistent nonanalytical model. The screening potential can be primarily attributed to the free electrons in the plasma and is determined by the microspace distribution of these free electrons. The ionization balance is determined by solving the Saha equation, including the effect of IPD. The predicted IPD and average ionization degree are larger than those obtained using the Stewart–Pyatt model for mass densities that are greater than 3.0 g cm−3. Under solar interior conditions, our results are in better agreement with the Ecker–Kröll model at electron temperatures and densities lower than 250 eV and 2.1 × 1023 cm−3 and in the best agreement with the ion-sphere model at 303 eV and 4.3 × 1023 cm−3. Finally, our results are compared with those obtained via a recent experiment on a CH-mixture plasma that has been compressed six times. The predicted average ionization degree of C in a CH mixture agrees better with the experiment than the Stewart–Pyatt and Thomas–Fermi models when the screening from free electrons contributed by hydrogen atoms is included. Our results provide useful information concerning the ionization balance and can be applied to investigate the opacity and equations of state for dense plasma under the solar and stellar interior conditions.

Context.Interstellar gas is in a highly turbulent dynamic state driven by successive supernova explosions and stellar winds, while its electron distribution is determined by microscopic processes such as ionization and recombination. In order to understand the properties of the electrons in the interstellar medium (ISM) it is necessary to follow numerically the nonlinear spatial and temporal evolution of the gas, its ionization structure, and its emission properties.Aims.We study the time evolution of the electrons in the ISM and how line of sight observations compare to volume analysis of the simulated medium populated with atoms and ions of the ten most abundant species. In particular, we make quantitative predictions about the occupation fractions and averaged densities of electrons, the dispersion measures, and their vantage point dependence.Methods.We carried out state-of-the-art adaptive mesh refinement simulations of the supernova-driven interstellar gas tracing the evolution of 112 ions and atoms of H, He, C, N, O, Ne, Mg, Si, S, and Fe and their emissivities in a time-dependent fashion. The gas is followed with the magnetohydrodynamical adaptive mesh refinement parallel code coupled with the Collisional + Photo Ionization Plasma Emission Software to trace the ionic structure and radiative emission of the plasma.Results.We show that more than 60% of the electrons are in thermally unstable regimes: about 50% at 200