Ion Pair Production Rate Research Articles

Empirical Model of SSUSI‐Derived Auroral Ionization Rates

AbstractWe present an empirical model for auroral (90–150 km) electron–ion pair production rates, ionization rates for short, derived from Special Sensor Ultraviolet Spectrographic Imager electron energy and flux data. Using the Fang et al. (2010, https://doi.org/10.1029/2010gl045406) parametrization for mono‐energetic electrons, and the NRLMSISE‐00 neutral atmosphere model (Picone et al., 2002, https://doi.org/10.1029/2002ja009430), the calculated ionization rate profiles are binned in 2‐hr magnetic local time and 3.6°geomagnetic latitude to yield time series of ionization rates at 5‐km altitude steps. We fit each of these time series to the geomagnetic indices Kp, PC, and Ap, the 81‐day averaged solar radio flux index, and a constant term. The resulting empirical model can easily be incorporated into coupled chemistry–climate models to include particle precipitation effects.

Activity concentration of indoor radon and its short-lived progeny (218Po, 214Pb, and 214Po) and their effect on atmospheric ionization rate in Sana'a, Yemen

Exposure to ionizing radiation inside houses, especially radionuclides of radon and its progeny, poses serious health risks that can be exacerbated when inhaled as a result of interaction with human lung tissue. Also, air ionization is mainly due to these radionuclides. Therefore, accurate measurements of radon activity concentrations and its short-lived progeny are required to assess dose and environmental pollution and estimate ionization rates in indoor environments. For this purpose, we employed a previously tested and approved reliable method, following the three-count procedure. This method is based on airborne radon progeny sampling on polycarbonate membrane filters and alpha counting using a passive α-dosimetry technique with CR-39 detectors. The method also relies on a PC-based software we developed for solving mathematical equations and calculating all the necessary physical quantities. In this study, the concentrations of radon and individual short-lived radon progeny were measured in 20 houses in Sana'a, Yemen. Measurement conditions and meteorological variables were considered. The average activity concentrations of 222Rn, Equilibrium-Equivalent Concentration (EEC), 218Po, 214 Pb, and 214Po were 73.1 ± 6.0, 29.2 ± 2.4, 44.4 ± 3.6, 30.5 ± 2.5, and 23.2 ± 1.9 Bq.m-3, respectively. The calculated average unattached fractions f1(218Po), f2(214 Pb), and fp were found to be 0.24, 0.04, and 0.07 % respectively. The annual average values of ion-pair production rate caused by 222Rn and their progeny and air ion concentration, were 27.25 ions.cm-3s-1 and 1829 ions.cm-3 respectively. The annual effective dose was estimated to be 1.93 ± 0.16 mSv.y−1, well lower than the recommended 10 mSv.y−1.

Contribution of the Photonic Component to the Ionization of the Atmosphere by Earth Crust Nuclides and Radioactive Emanations

Abstract—We investigate the contribution of gamma radiation of natural radionuclides constituting the Earth crust, radioactive emanations, and their decay product in the ground to the intensity of production of ion pairs in the atmosphere against the background of ionization of the atmosphere by radioactive gases flowing to the atmosphere from the ground and propagating together with their short-lived daughter products. The density of the radon flux to the atmosphere is estimated by three methods: the reservoir method, the integration of altitude profiles of volume activity of radon, based on gamma spectroscopic observation and diffusion model. The distribution of the gamma dose rate dose from the earth radionuclides in the soil and in the atmosphere is calculated using Gleant4 software. The propagation of the radon isotopes and their decay products in the atmosphere is calculated using large eddy simulations supplemented with kinematic simulations of the subgrid transport of a passive scalar. It is shown that depending on the specific activity of nuclides in the ground and the turbulent regime of the atmosphere, the total contribution of the γ-radiation to the ion pair production rate in the atmospheric boundary layer is approximately from 1% to 20% and increases upon a decrease in the penetrability of the upper ground layer for radioactive emanations.

The energetic particle environment of a GJ 436 b-like planet

ABSTRACTA key first step to constrain the impact of energetic particles in exoplanet atmospheres is to detect the chemical signature of ionization due to stellar energetic particles and Galactic cosmic rays. We focus on GJ 436, a well-studied M dwarf with a warm Neptune-like exoplanet. We demonstrate how the maximum stellar energetic particle momentum can be estimated from the stellar X-ray luminosity. We model energetic particle transport through the atmosphere of a hypothetical exoplanet at orbital distances between $a=0.01\text{ and }0.2\,$au from GJ 436, including GJ 436 b’s orbital distance (0.028 au). For these distances, we find that, at the top of atmosphere, stellar energetic particles ionize molecular hydrogen at a rate of $\zeta _{\rm StEP,H_2} \sim 4\times 10^{-10}\text{ to }2\times 10^{-13}\, \mathrm{s^{-1}}$. In comparison, Galactic cosmic rays alone lead to $\zeta _{\rm GCR, H_2}\sim 2\times 10^{-20}\!-\!10^{-18} \, \mathrm{s^{-1}}$. At 10 au, we find that ionization due to Galactic cosmic rays equals that of stellar energetic particles: $\zeta _{\rm GCR,H_2} = \zeta _{\rm StEP,H_2} \sim 7\times 10^{-18}\, \rm {s^{-1}}$ for the top-of-atmosphere ionization rate. At GJ 436 b’s orbital distance, the maximum ion-pair production rate due to stellar energetic particles occurs at pressure $P\sim 10^{-3}\,$bar, while Galactic cosmic rays dominate for $P\gt 10^2\,$bar. These high pressures are similar to what is expected for a post-impact early Earth atmosphere. The results presented here will be used to quantify the chemical signatures of energetic particles in warm Neptune-like atmospheres.

Long Short Term Memory networks (LSTM)-Monte-Carlo simulation of soil ionization using radon

Earthquake events are usually associated with atmospheric processes variations. Some of the important events in seismic periods include the atmospheric electricity/conductivity modification, which mostly depends on the ion population in the vicinity of earthquake preparation area. Radon, together with cosmic radiation are the major ionization sources in the lower troposphere. The radon induced soil ion-pair production rate was estimated for Erzincan, a city along the North Anatolian Fault Zone, Turkey. The Long Short-Term Memory networks (LSTM's) and Monte Carlo method are proposed to account for uncertainty in estimating the ion production rate. The advantage of the LSTM model is taken to study radon anomalies during the M = 5 Girlevik earthquake, Erzincan. Radon concentration is found to increase prior to the 5.0 Girlevik earthquake. According to estimations, 23 × 109 ion-pairs m−3s−1 were generated at 1 m depth from the Earth's surface during this earthquake. The soil-ion production estimation rate due to radon and its progeny in Erzincan is at the order of 109 ion-pairs m−3s−1. When these generated ions and charged aerosols reach the surface and were added to other ionization sources, parameters such as the near surface conductivity and electric field would be modified. In addition, under pronounced conditions could favor ionospheric perturbations.

The Atmospheric Radiation Interaction Simulator (AtRIS): Description and Validation

AbstractWe present the Atmospheric Radiation Interaction Simulator (AtRIS), a newly developed GEANT4‐based code tailored specifically to enable parametric studies of radiation propagation through various (exo)planetary atmospheres. Its main purpose is to model the altitude‐dependent atmospheric secondary particle environment and to calculate the ion pair production rates, which are a mandatory input for atmospheric chemistry models in order to, for example, directly characterize the habitability of the modeled planet. Similar codes have been developed previously (e.g., PLANETOCOSMICS; Desorgher, et al., ); however, until now, none possesses the necessary flexibility in the specification of the atmosphere and the regolith that is necessary to model planets outside our solar system. Here we provide a detailed description of AtRIS and its validation against earthbound measurements. For validation, we show comparisons against Earth measurements. Thereby, the focus is on the atmospheric altitude‐dependent ionization, the surface muon, and the neutron fluxes, as well as the primary proton fluxes. Furthermore, a comparison of the computed energy losses of monoenergetic protons based on AtRIS and PLANETOCOSMICS is shown. Our aim is to demonstrate the validity of AtRIS and its importance for future studies on, for example, potential (Earth‐like) exoplanets.

Two new submodels for the Modular Earth Submodel System (MESSy): New Aerosol Nucleation (NAN) and small ions (IONS) version 1.0

Abstract. Two new submodels for the Modular Earth Submodel System (MESSy) were developed. The New Aerosol Nucleation (NAN) submodel includes new parameterisations of aerosol particle formation rates published in recent years. These parameterisations include ion-induced nucleation and nucleation of pure organic species. NAN calculates the rate of new particle formation based on the aforementioned parameterisations for aerosol submodels in the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The ion pair production rate, needed to calculate the ion-induced or ion-mediated nucleation, is described using the new submodel IONS, which provides ion pair production rates for other submodels within the MESSy framework. Both new submodels were tested in EMAC simulations. These simulations showed good agreement with ground-based observations.

A model for charge transfer in ultracold Rydberg ground-state atomic collisions

In excited molecules, the interaction between the covalent Rydberg and ion-pair channels forms a unique class of excited states, in which the infinite manifold of vibrational levels are the equivalent of atomic Rydberg states with a heavy electron mass. Production of the ion-pair states usually requires excitation through one or several interacting Rydberg states; these interacting channels lead to loss of flux, diminishing the rate of ion-pair production. Here, we develop an analytical, asymptotic charge-transfer model for the interaction between ultracold Rydberg molecular states, and employ this method to demonstrate the utility of off-resonant field control over the ion-pair formation, with near unity efficiency.

On the variation of the ionospheric potential due to large‐scale radioactivity enhancement and solar activity

AbstractSensitivity of the global electric circuit (GEC) to variations of atmospheric conductivity and current sources is analyzed and discussed. When the undisturbed exponential conductivity profile is assumed all over the Earth, the most substantial changes in the ionospheric potential (IP) are caused by conductivity perturbations inside thunderstorms; if, in addition, conductivity reduction inside thunderstorms and nonelectrified clouds is assumed, the IP becomes less sensitive to conductivity perturbations; besides, the IP is even more sensitive to source current variations than to conductivity. Current source and voltage source descriptions of GEC generators are compared; it is shown that the IP variation may critically depend on the chosen description. As an application, the IP variation due to nuclear weapons testing is studied; it is shown that neither local nor global increase of conductivity in the stratosphere could alone explain the observed 40% IP increase in the 1960s; at the same time this increase might be accounted for by a 40% increase in the source current density or a 46% reduction of the conductivity inside thunderstorms, provided that it was not reduced initially. The IP variation due to solar activity and, in particular, due to solar modulation of galactic cosmic ray flux is also discussed and modeled, which required an adequate parameterization of the rate of atmospheric ion pair production over the solar cycle. It is estimated that the maximum IP variation on the scale of the solar cycle does not exceed 5% of the mean value, unless source current perturbations are taken into account.

Diurnal variations of 218Po, 214Pb, and 214Po and their effect on atmospheric electrical conductivity in the lower atmosphere at Mysore city, Karnataka State, India

The short-lived radon daughters (218Po, 214Pb, 214Bi and 214Po) are natural tracers in the troposphere, in particular near the ground surface. They are electrically charged particles and are chemically reactive. As soon as they are formed they get attached to the aerosol particles of the atmosphere. The behavior of radon daughters is similar to that of aerosols with respect to their growth, transport and removal processes in the atmosphere. The electrical conductivity of the atmosphere is mainly due to the presence of highly mobile ions. Galactic cosmic rays are the main source of ionization in the planetary boundary layer; however, near the surface of the earth, ions are produced mainly by decays of natural radioactive gases emanating from the soil surface and by radiations emitted directly from the surface. Hence the electrical conductivity of air near the surface of the earth is mainly due to radiations emitted by 222Rn, 218Po, 214Pb, 214Bi and 214Po, and depends on aerosol concentrations and meteorological parameters. In the present work the diurnal and seasonal variations of radon and its progeny concentrations are studied using Low Level Radon Detection System and Airflow Meter respectively. Atmospheric electrical conductivity of both positive and negative polarities is measured using a Gerdien Condenser. All the measurements were carried out simultaneously at one location in Mysore city (12°N, 76°E), India. The diurnal variation of atmospheric electrical conductivity was found to be similar to that of ion pair production rate estimated from radon and its progeny concentrations with a maximum in the early morning hours and minimum during day time. The annual average concentrations of 222Rn, 218Po, 214Pb, and 214Po at the study location were found to be 21.46, 10.88, 1.78 and 1.80 Bq m−3 respectively. The annual average values of positive and negative atmospheric electrical conductivity were found to be 18.1 and 16.6 f S m−1 respectively. The radon and its progeny concentrations are higher in winter than in summer and rainy season.

Population Balances of Micron-Sized Aerosols in a Bipolar Ion Environment

The present work re-examines the assumptions that are required for a steady-state charge distribution analysis to be valid. First, the common approximation that there are only 11 charge states available to the distribution is relaxed to allow for 201 charge states to be available to the particle distribution. This is found to have large repercussions on the behavior of the distribution for radii greater than 0.5 μm. The steady-state assumption itself is then re-examined by calculating the time required to reach steady state for many different ion-pair production rates and initial particle charge states as a function of radius. In the steady-state model, the ion populations are often assumed to decouple completely from the aerosol; this is shown to be false throughout the troposphere. Finally, the number of positive and negative charge states needed to accurately model a particle population of a given size is determined. © 2013 American Association for Aerosol Research

Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation

Atmospheric aerosols exert an important influence on climate through their effects on stratiform cloud albedo and lifetime and the invigoration of convective storms. Model calculations suggest that almost half of the global cloud condensation nuclei in the atmospheric boundary layer may originate from the nucleation of aerosols from trace condensable vapours, although the sensitivity of the number of cloud condensation nuclei to changes of nucleation rate may be small. Despite extensive research, fundamental questions remain about the nucleation rate of sulphuric acid particles and the mechanisms responsible, including the roles of galactic cosmic rays and other chemical species such as ammonia. Here we present the first results from the CLOUD experiment at CERN. We find that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100-1,000-fold. Time-resolved molecular measurements reveal that nucleation proceeds by a base-stabilization mechanism involving the stepwise accretion of ammonia molecules. Ions increase the nucleation rate by an additional factor of between two and more than ten at ground-level galactic-cosmic-ray intensities, provided that the nucleation rate lies below the limiting ion-pair production rate. We find that ion-induced binary nucleation of H(2)SO(4)-H(2)O can occur in the mid-troposphere but is negligible in the boundary layer. However, even with the large enhancements in rate due to ammonia and ions, atmospheric concentrations of ammonia and sulphuric acid are insufficient to account for observed boundary-layer nucleation.

Model for induced ionization by galactic cosmic rays in the Earth atmosphere and ionosphere

The ionization profiles produced by galactic cosmic rays in the Earth atmosphere and ionosphere are obtained on the basis of Monte Carlo simulations. Cascade processes in the atmosphere are simulated using CORSIKA 6.52 code with FLUKA 2006 and QGSJET II hadronic interaction subroutines. Proton induced showers are considered using a realistic atmospheric model (US Standard Atmosphere). The energy deposit from different components is taken into account, namely electromagnetic, hadron and muon components. The curvature of the atmosphere is considered in the computer code. On the basis of the computed ionization yield function the ion pair production rate in the atmosphere is obtained for different conditions and locations. The model is applicable to the entire atmosphere, from ground level to upper atmosphere. Several applications of the obtained results are discussed. The Monte Carlo simulation model considers nuclear interactions below the altitude of 35 km. It is compared with analytical–numerical electron production rate model. The latter model which takes into account the electromagnetic interactions above altitudes of 35 km has two main regions of application: above 50 km (thin target model) and between 35 and 50 km (intermediate target model). A good agreement between the CORSIKA results and analytical–numerical model results is found above altitude of 35 km.

Study of atmospheric electrical conductivity, SO2, NO2, aerosols SPM (>10 μ) and RSPM (

It is well known that atmospheric electrical conductivity is mainly due to the presence of small ions. Near the surface of the earth, radon and its daughter products predominantly produce small ions. In the presence of aerosol particles, the small ion concentration is reduced due to attachment of small ions to aerosol particles which decreases mobility and conductivity in the atmosphere. The ion pair production rate is estimated from the measured radon and its progeny concentrations and correlated with electrical conductivity of the atmosphere. Measurement of concentrations of suspended particulate matter (SPM), SO2, and NO2 of air was also carried out. Data showed that reduced electrical conductivity was related to concentration of airborne SPM.

Electrical conductivity near the Earth's surface: Ion–aerosol model

An ion–aerosol model for the electrical conductivity of the lower atmosphere is developed. Ion-pair production rate, obtained from the concentrations of radon and its progeny; aerosol number density; and the meteorological parameters such as temperature, pressure and relative humidity are the input parameters to the model. Diurnal values of conductivity computed on this model are compared with the experimentally measured conductivity. The model values show good agreement with the experimental values of total conductivity.

Energy deposition and middle atmosphere electrodynamic response to a highly relativistic electron precipitation event

Rocket data have been used to evaluate the characteristics of precipitating relativistic electrons and their effects on the electrodynamic structure of the middle atmosphere. These data were obtained at Poker Flat, Alaska, on May 13 and 14, 1990, during a midday, highly relativistic electron (HRE) precipitation event. Solid state detectors were used to measure the electron fluxes and their energy spectra. An X ray scintillator was included on each flight to measure brems Strahlung X rays produced by energetic electrons impacting on the upper atmosphere. However, these were found to be of negligible importance for this particular event. The energy deposition by the electrons has been determined from the flux measurements and compared with in situ measurements of the atmospheric electrical response. The electrodynamic measurements were obtained by the same rockets and additionally on May 13, with an accompanying rocket. The impacting flux was highly irregular, containing short‐lived bursts of relativistic electrons, mainly with energies below 0.5 MeV and with fluxes most enhanced between pitch angles of 0°–20°. Although the geostationary counterpart of this measured event was considered to be of relatively low intensity and hardness, energy deposition peaked near 75 km with fluxes approaching an ion pair production rate in excess of 100/cm3 s. This exceeds peak fluxes in relativistic electron precipitation (REP) events as observed by us in numerous rocket soundings since 1976. Conductivity measurements from a blunt probe showed that negative electrical conductivities exceeded positive conductivities down to 50 km or lower, consistent with steady ionization by precipitating electrons above 1 MeV. These findings imply that the electrons from the outer radiation zone can modulate the electrical properties of the middle atmosphere to altitudes below 50 km. During the decline and activity minimum of the current solar cycle, we anticipate the occurrence of similar events but with fluxes 1–2 orders of magnitude above that reported here, based on studies of earlier solar cycles (e.g., Baker et al., 1993).

Relaxation of transient lower ionospheric disturbances caused by lightning‐whistler‐induced electron precipitation bursts

A quantitative model of the relaxation of transient lower ionospheric (D region) disturbances caused by lightning‐induced electron precipitation is developed, taking advantage of known particular features of the lightning‐induced disturbances, such as the fact that they are produced in typically <1 s and decay over 10–100 s. The model represents the nighttime D region as consisting of only four kinds of charged particles (electrons, positive ions, negative ions, and positive cluster ions) and is particularly suited for description of the detailed behavior of the electron density. Application of the model to some previously modeled disturbances indicates that some of the least known chemical reaction rates in the nighttime D region altitudes may be measurable using subionospheric VLF data. In the production of secondary ionization by precipitating electron bursts, the model calculations indicate the presence of a saturation effect such that the number density of the secondary electrons is not simply equal to the ion pair production rate times the burst duration. In some cases involving precipitation of ∼1‐MeV electrons, the model predicts the formation of new layers of ionization at 50–70 km altitude that represent a different attachment‐detachment quasi‐equilibrium value from that of the unperturbed ambient. Such new layers may exist for up to ∼105 s following electron precipitation bursts.

Nitric oxide and lower ionosphere quantities during solar particle events of October 1989 after rocket and ground-based measurements

The most dramatic demonstrations of solar activity are solar proton flares. One such very strong flare, accompanied by a solar proton event (SPE) and a large ground level enhancement of cosmic rays on Earth, was observed in October 1989. During this SPE, ion density and nitric oxide concentration profiles were measured by rockets launched from the Soviet research vessel ‘ Akademik Shirshov’ in the southern part of the Indian Ocean. The rocket experiment yielded the first in-situ measurement of NO concentration increased by SPE. The NO concentrations estimated from ion-pair production rates due to measured fluxes of high energy particles agree fairly well with the observed NO concentrations in the stratopause region. The results of rocket measurements are compared with measurements of the radio wave absorption in the lower ionosphere performed at similar latitudes in central Europe. Model calculations of absorption show that while the night-time enhancement of absorption can be explained by increased electron density related to the measured increase of ion density as a consequence of enhanced penetration of high energy particles, the daytime increase of absorption needs to be explained mainly in terms of the observed increase of nitric oxide concentration.

Effect of solar proton events on the middle atmosphere during the past two solar cycles as computed using a two‐dimensional model

Daily average solar proton flux data for the years 1963–1984 (two solar cycles) have been used in a proton energy degradation scheme to derive ion pair production rates and, subsequently, HOx (H, OH, HO2) and NOx (N, NO, NO2) production rates. These HOx and NOx production rates are computed in a form suitable for inclusion in an atmospheric two‐dimensional time‐dependent photochemical model. The HOx increases, although large for certain solar proton events (SPEs), are relatively short‐lived because the HOx species have lifetimes of only hours in the middle atmosphere. For longer‐lived NOx species, increases are important for 2–4 months past the more intense SPEs but are generally negligible 6 months after the SPE. The only exception to this scenario was the gigantic August 1972 SPE, whose stratospheric effects lasted about a year past the event. Comparisons of model results with the ozone data from the Nimbus 4 backscattered ultraviolet (BUV) instrument indicate relatively good agreement in the time dependence and magnitude of the ozone depletion for the middle stratosphere between the model and measurements for the August 1972 SPE and for 2 months past the event. The model predictions for the August 1972 SPE indicate at most a 1% decrease in total ozone at the highest latitudes with a significant interhemispheric difference. The model predicts a larger middle latitude stratospheric ozone change in the southern than the northern hemisphere caused by the difference in seasons between the two hemispheres. The computed ozone decreases associated with the HOx and NOx increases are substantial in the upper stratosphere at high latitudes for only a few SPEs in the 22 years studied. A mechanism is presented for transport of NOy from the stratosphere to the ground, which may be involved in the enhancements in nitrate fluxes noticed in Antarctic deposition data. Our computations, however, indicate that the SPE contributions to these nitrate fluxes (even for the August 1972 SPE) are probably small.

Electrical conductivities, ion densities and mobilities in the middle atmosphere over India—balloon measurements

Polar conductivities, ion densities and mobilities measured in three balloon experiments are reported here. Of these, two were made with self-aspirated and one with pumped Gerdien condensers. These measurements were carried out over the period 1985–1986. Both positive and negative ion data were obtained only in the first flight. Positive ions were not collected in the other two flights. The conductivity profiles obtained from the self-aspirated condensers showed fluctuations around the tropopause. These were not seen when the pumped condenser was used. Reduced mobilities of both positive and negative ions agree well with those reported by other experimenters. The ion density profile from the pumped condenser measurement showed a broad maximum around 15 km, as expected from theory. The values were less than what are obtained using available ion pair production rates and recombination coefficients.