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Extremely low-frequency magnetic fields are thought to be capable of modulating the resistance of plants to adverse factors, particularly drought. Magnetic fields in this frequency range occur in nature in connection with so-called Schumann resonances, excited by lightning discharges in the Earth–ionosphere cavity. The aim of this work was to identify the influence of a magnetic field with a frequency of 14.3 Hz (which corresponds to the second Schumann harmonic) on the transpiration and photosynthesis of wheat plants under the influence of drought. The activity of photosynthesis processes, the crop water stress index, relative water content and leaf area were determined during drought intensification. At the end of the experiment, on the 12th day of drought, the length, and fresh and dry weight of wheat shoots were measured. The results obtained indicate a protective effect of the magnetic field on plants in unfavorable drought conditions; the magnetic field delayed the development of harmful changes in the transpiration and photosynthesis processes for several days. At the same time, in the absence of the stressor (drought), the effect of the electromagnetic field was not detected, except for a decrease in relative transpiration. In favorable conditions, there were only minimal modifications of the photosynthetic processes and transpiration by the magnetic field. [ABSTRACT FROM AUTHOR]

Thunderstorm ground enhancements (TGEs) are fluxes of energetic particles multiplied in thunderclouds, which may be registered by ground‐based detectors. Using the Weather Research and Forecasting (WRF) Model, the state of the atmosphere with a 1‐km horizontal resolution is modeled for convective events accompanied by TGEs observed at the high altitude Aragats Research Station in Armenia (40.47 N, 44.18 E, 3,200 m above sea level). By comparing the data obtained in observations with the results of simulations using a microphysical parameterization for WRF, a technique is developed for estimating charge distribution parameters. A typical charge distribution in a TGE‐producing cloud is found to be well approximated by a two‐layered charge structure with a lower positive charge region formed by graupel particles and an upper negative charge region formed by snow particles. The characteristic charge density is 0.01 nC/m3 for the graupel cluster and −0.02 nC/m3 for the snow cluster. A vertical distance of about 1–2 km between the lower positive and upper negative layers is sufficient for the development of an energetic particle avalanche. Key Points: The technique of electric cloud structure estimation based on WRF simulation of a convective event is developedA dipole structure with a positive lower layer is typical for the thunderclouds producing intense thunderstorm ground enhancements (TGEs)Snow and graupel particles are the main charge carriers in the mountain conditions of TGE occurrence [ABSTRACT FROM AUTHOR]

On the basis of a parametrization of the ionospheric potential (IP), the seasonal dynamics of the diurnal IP variation for 2016–2017 is simulated for the first time using the Weather Research and Forecasting (WRF)-Advanced Research WRF (WRF-ARW) model. The diurnal IP variation averaged over the annual simulation period shows good agreement with the classical Carnegie curve, suggesting that the proposed parametrization correctly reproduces the basic characteristics of stationary global electric circuit generators. The annual variation shows no precise repeatability from year to year, but there is a lower IP in the Northern Hemisphere winter and a higher value in the summer. The model-derived diurnal variation demonstrates stable seasonal trends, with only one distinct IP maximum of 120% of the average at 16:00 to 18:00 UTC in the Northern Hemisphere winter and two much lower maxima (~107% of the average) in the summer: a morning maximum at 08:00 to 09:00 UTC and an evening maximum at 18:00 to 20:00 UTC. The model annual dynamics of the diurnal variation agrees with the experimental data of surface field measurements in Antarctica in 2006–2011. The proposed parameterization and the modeling technique made it possible to correctly simulate the times of IP variation maxima, their seasonal variability, and а decrease in the variation amplitude during the Northern Hemisphere summer. [ABSTRACT FROM AUTHOR]

Spatial distribution of a two-photon luminescence signal when gold nanoparticles on the surface are scanned by the tip of an atomic force microscope irradiated by femtosecond laser radiation was studied in an experiment. Comparison of the experimental data with the results of numerical simulation of two-photon luminescence based on a finite-difference time-domain calculation of electric field distribution in the nanoparticle–tip system can give information on the shape and orientation of the nanoparticles. [ABSTRACT FROM AUTHOR]