Anton Artamonov

Model CRAC:EPII for atmospheric ionization due to precipitating electrons: Yield function and applications

A new model of the family of CRAC models, CRAC:EPII (Cosmic Ray Atmospheric Cascade: Electron Precipitation Induced Ionization), is presented. The model calculates atmospheric ionization induced by precipitating electrons and uses the formalism of ionization yield functions. The CRAC:EPII model is based on a full Monte Carlo simulation of electron propagation and interaction with the air molecules. It explicitly considers various physical processes, namely, pair production, Compton scattering, generation of bremsstrahlung high-energy photons, photoionization, annihilation of positrons, and multiple scattering. The simulations were performed using GEANT 4 simulation tool PLANETOCOSMICS with NRLMSISE 00 atmospheric model. The CRAC:EPII model is applicable to the entire atmosphere. The results from the simulations are given as look-up table representing the ionization yield function. The table allows one to compute ionization due to precipitating electrons for a given altitude and location considering a given electron spectrum. Application of the model for computation of ion production during electron precipitation events using spectra from balloon-borne measurements is presented.

Neutron monitor yield function for solar neutrons: A new computation

A new yield function of a standard neutron monitor 6NM64 for solar neutrons is presented and tabulated in the attached lookup tables. It corresponds to a wide range of altitudes of the neutron monitor locations and angles of incidence for neutrons entering the Earth’s atmosphere. The computations were made by Monte Carlo using the GEANT4-based PLANETOCOSMICS tool. The yield function was validated against the measured data for solar neutron events of 3 June 1982 and 24 May 1990, and good agreement was found within a wide range of the altitudes of the neutron monitor location and angles of incidence of solar neutron arrival. The sensitivity of the world neutron monitor network for registration of solar neutron events was reassessed. The neutron monitor network is shown to be, in addition to other methods, a sensitive tool for monitoring of high-energy solar-flare neutrons with ≈95% probability to detect statistically significantly (> 5σ) a solar neutron event similar to that of 3 June 1982.

Comparative investigation of antioxidant activity of human serum blood by amperometric, voltammetric and chemiluminescent methods

Introduction A blood test can provide important information about the functional state of the antioxidant system. Malfunction of this system increases the concentration of free radicals and can cause oxidative stress. A difficulty in assessing oxidative stress is the lack of a universal method for determining the antioxidant activity (AOA) of blood components, because of their different nature. Material and methods The objects of investigation were sera of 30 male patients with a diagnosis of alcohol dependence syndrome and healthy donors. Comparative investigation of total antioxidant activity (TAA) of human serum blood was carried out by voltammetric (VA), amperometric (AM) and chemiluminescent (HL) methods. Results All applied methods revealed that serum TAA of the patients with alcoholism is lower than TAA of healthy donors (control group); according to amperometric method the average value of serum TAA was 850 ±210 nA × s, and 660 ±150 nA × s for healthy donors and alcoholics respectively (p < 0.05). Similar trend was revealed by chemiluminescence and voltammetry methods. The results confirm that thiol compounds make a significant contribution to the antioxidant activity of serum. The average thiol concentrations were 0.94 ±0.34 mmol/l and 1.21 ±0.36 mmol/l (p < 0.05) for alcoholics and healthy donors respectively. Decreasing thiol concentration in blood of alcoholics leads to depletion of antioxidant systems of blood. However, the differences between the results of AM, VA and HL methods were significant, because they reflected different aspects of antioxidant activity. Conclusions For objective assessment of antioxidant activity of biological objects, we suggest using methods based on different model systems.

Updated model CRAC : HEPII of atmospheric ionization due to high energy protons

An extension of the CRAC model - CRAC:HEPII (Cosmic Ray Atmospheric Cascade: High Energy Proton Induced Ionization) is presented. The model allows one to compute the ion production by high energy protons entering the Earth’s atmosphere. The model is an extension of the CRAC:CRII model and it is focused on the upper part of the stratosphere and mesosphere. The model is also applicable in the low termosphere. The model is based on pre-computed with high statistics ionization yield functions. Therefore, the CRAC:HEPII model is based on a full Monte Carlo simulation of primary proton propagation and interaction with the atmosphere and explicitly considers various physical processes involved in ion production. All simulations were performed using the GEANT 4 simulation tool PLANETOCOSMICS with NRLMSISE 00 atmospheric model. The ionization yield function allows one to compute ion production due to various populations of primary protons in a wide energy range 100 keV –- 20 GeV/nucleon for a given altitude, from about 6.5×10

Computation of electron precipitation atmospheric ionization: updated model CRAC-EPII

^{−9}

Balloon measurements of the vertical ionization profile over southern Israel and comparison to mid-latitude observations

g/cm

Atmospheric ionization induced by precipitating electrons: Comparison of CRAC:EPII model with a parametrization model

^2

Calculation of atmospheric ionization induced by electrons with non-vertical precipitation: Updated model CRAC-EPII

(about 200 km a.s.l.) to the sea level considering a given primary proton spectrum. The spacial and height resolution of the model is improved compared to CRAC model. An application of the model for computation of ion production during ground level enhancement events is demonstrated. A quasi-analytical approach, which allows one to compute the ionization yields for events with arbitrary incidence is also presented.

Response of the total ozone to energetic electron precipitation events

A new model of the CRAC family, CRAC:EPII (Cosmic Ray Atmospheric Cascade: Electron Precipitation Induced Ionization) is presented. The model allows one to calculate atmospheric ionization induced by precipitating electrons. The model is based on pre-computed with highprecision ionization yield functions, which are obtained using full Monte Carlo simulation of electron propagation and interaction in the Earth’s atmosphere, explicitly considering all physical processes involved in ion production. The simulations were performed using GEANT 4 simulation tool PLANETOCOSMICS with NRLMSISE 00 atmospheric model. A quasi-analytical approach, which allows one to compute the ionization yields for events with arbitrary incidence is also presented. It is compared with Monte Carlo simulations and good agreement between Monte Carlo simulations and quasi-analytical approach is achieved.