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The presence of small ions influences the growth dynamics of a size distribution of aerosols. Specifically the often neglected mass of small ions influences the aerosol growth rate, which may be important for terrestrial cloud formation. To this end, we develop a numerical model to calculate the growth of a species of aerosols in the presence of charge, which explicitly includes terms for ion-condensation. It is shown that a positive contribution to aerosol growth rate is obtained by increasing the ion-pair concentration through this effect, consistent with recent experimental findings. The ion-condensation effect is then compared to aerosol growth from charged aerosol coagulation, which is seen to be independent of ion-pair concentration. The model source code is made available through a public repository.

One hundred and ten direct measurements of aerosol nucleation rate at high ionization levels were performed in an 8 m3 reaction chamber. Neutral and ion-induced particle formation from sulfuric acid (H2SO4) was studied as a function of ionization and H2SO4 concentration. Other species that could have participated in the nucleation, such as NH3 or organic compounds, were not measured but assumed constant, and the concentration was estimated based on the parameterization by Gordon et al. (2017). Our parameter space is thus [H2SO4] = 4×106 − 3×107 cm−3, [NH3+ org] = 2.2 ppb, T = 295 K, RH = 38 %, and ion concentrations of 1700–19 000 cm−3. The ion concentrations, which correspond to levels caused by a nearby supernova, were achieved with gamma ray sources. Nucleation rates were directly measured with a particle size magnifier (PSM Airmodus A10) at a size close to critical cluster size (mobility diameter of ∼ 1.4 nm) and formation rates at a mobility diameter of ∼ 4 nm were measured with a CPC (TSI model 3775). The measurements show that nucleation increases by around an order of magnitude when the ionization increases from background to supernova levels under fixed gas conditions. The results expand the parameterization presented in Dunne et al. (2016) and Gordon et al. (2017) (for [NH3 + org] = 2.2 ppb and T = 295 K) to lower sulfuric acid concentrations and higher ion concentrations. The results make it possible to expand the parameterization presented in Dunne et al. (2016) and Gordon et al. (2017) to higher ionization levels.

Here we combine observations of open clusters (OCs) with single- and binary population synthesis models and a Galactic potential to reconstruct the SN activity of these OCs during the past 35 Myr. We find that several OCs potentially hosting SN progenitors have passed within 100 pc of the Sun during the past 35 Myr. In particular we find that ASCC 19, NGC 1981, and NGC 1976 are likely to have hosted one or more SNe while passing within 200 pc of the solar system in the period 17 - 12 Myr BP which might have affected Earths' geology and climate. Besides the stellar history of the individual OCs we also compute 1) a spatial and temporal 2D-probability density map showing the most likely position and time of SN from our sample of OCs within 1 kpc during the past 35 Myr, 2) the time series of the SN rate per volume and 3) the relative SN rate compared with today and corrected for OC evaporation of older generations. The SN rate today from core collapse is estimated to be 37.8$\pm$6.1$\rm kpc^{-3} Myr^{-1}$. During the past 35 Myr we find a peak SN rate around 10 Myr before present (BP) where the rate was 40% higher relative to the past 1 Myr. Finally we discuss possible effects of binary stellar evolution in relation to the history of SN production in the solar neighbourhood and the detected $\rm ^{60}Fe$ signal in terrestrial geological samples induced between $\sim$2.2 - 2.8Myr BP., Submitted to MNRAS. 14 pages, 3 tables, 8 figures

An ab initio study of gaseous clusters of O2− and O2− with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find that anionic O2−(H2O)n and O3−(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding. Although clustering up to 12 H2O, we find that the O2 and O3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O2− and O3− speicies are thus accessible for further reactions. Finally, the thermodynamics of a few relevant cluster reactions are considered.

An ab initio study of gaseous clusters of O-2(-) and O-3(-) with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find that anionic O-2(-)(H2O)n and O-3(-)(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding. Although clustering up to 12 H2O, we find that the O-2 and O-3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O-2(-) and O-3(-) speicies are thus accessible for further reactions. We consider the distributions of cluster sizes as function of altitude before finally, the thermodynamics of a few relevant cluster reactions are considered.

Based on density functional theory calculations we present a study of the gaseous oxidation of SO2 to SO3 by an anionic O3−(H2On cluster, n=0–5. The configurations of the most relevant reactants, transition states, and products are discussed and compared to previous findings. Two different classes of transition states have been identified. One class is characterized by strong networks of hydrogen bonds, very similar to the reactant complexes. The other class is characterized by loose structures of hydration water and is stabilized by high entropy. At temperatures relevant for atmospheric chemistry, the most energetically favorable class of transition states vary with the number of water molecules attached. A kinetic model is utilized, taking into account the most likely outcomes of the initial SO2O3−(H2O)n collision complexes. This model shows that the reaction takes place at collision rates regardless of the number of water molecules involved. A lifetime analysis of the collision complexes supports this conclusion. Hereafter, the thermodynamics of water and O2 condensation and evaporation from the product SO3−O2(H2O)n cluster is considered and the final products are predicted to be O2SO3− and O2SO3−(H2O)1. The low degree of hydration is rationalized through a charge analysis of the relevant complexes. Finally, the thermodynamics of a few relevant reactions of the O2SO3− and O2SO3−(H2O)1 complexes are considered.