Ionospheric Potential Research Articles

Моделирование суточной вариации атмосферного электрического поля в турбулентном приземном слое

An electrodynamic model of the electric field dynamics behavior in the atmospheric surface layer due to the action of local factors is presented. The model was obtained by reducing the differential equations system of the electrode effect to the so-called total current equation, which is a second-order equation of parabolic type, considered in a two-dimensional space-time region. The total current equation allows us to connect the set of main factors influencing on the atmospheric surface layer electric field state: conduction current, turbulent current and current arising as a result of convective processes in the atmosphere with the so-called total current in the nearground layer, reflecting changes in the ionospheric potential. The described method provides significant advantages in research, since within the framework of one model it allows the formulation of various problems of electrodynamics of the surface layer and a comparative analysis of the influence on the behavior of the electric field in the surface layer of both individual factors and their combinations. Based on meteorological data at the Peak Cheget mountain station in the Elbrus region, a daily variation in the values of the turbulent diffusion coefficient was constructed. The resulting analytical dependence was used to solve the equation for the total current in the surface layer, provided that it is constant at the upper boundary of the turbulent electrode layer. Solutions obtained by the Fourier method describe the daily variation of the electric field strength depending on the degree of turbulent mixing in the atmosphere. The appearance of a time shift in daily extrema, a change in their amplitude, and the appearance of additional extrema depending on the elec-tric field values have been established. All of these effects are comparable to the global unitary variation and increase with increasing electric field.

The influence of the solar wind electric and magnetic fields on the latitude and temporal variations of the current density, JZ, of the global electric circuit, with relevance to weather and climate

Observations have shown small day-to-day stratiform cloud opacity and atmospheric dynamical responses to variations in the ionosphere-earth current density (JZ). We model the day-to-day and seasonal/bi-decadal changes in the area-integrals of ionospheric potential (Vi) near the magnetic poles due to solar wind electric field inputs. The overhead value of Vi, divided by the local column resistance (R) determines JZ, where the conductivity of the column is the result of ionization by galactic cosmic rays (GCRs) and solar and magnetospheric energetic particle precipitation. These vary with time, due to varying solar wind magnetic field inputs, not only on the day-to-day timescale (e.g., Forbush decreases) but also on the decadal and bi-decadal and century timescales. The GCR and energetic particle inputs vary with latitude, due to filtering of particle energies in the geomagnetic field. We compare area-integrals of the amplitude of the JZ variations due to Vi changes to those due to the R changes, for evaluating their global effectiveness in affecting cloud microphysics and weather and climate changes. The day-to-day and bi-decadal correlated weather and climate variations indicate JZ rather than other solar forcings as mainly responsible for the correlations. The decadal and longer climate responses to space weather are not large; however, understanding them could help improve predictions of future climate change due to greenhouse gases.

Calculating the High‐Latitude Ionospheric Electrodynamics Using a Machine Learning‐Based Field‐Aligned Current Model

AbstractWe introduce a new framework called Machine Learning (ML) based Auroral Ionospheric electrodynamics Model (ML‐AIM). ML‐AIM solves a current continuity equation by utilizing the ML model of Field Aligned Currents of Kunduri et al. (2020, https://doi.org/10.1029/2020JA027908), the FAC‐derived auroral conductance model of Robinson et al. (2020, https://doi.org/10.1029/2020JA028008), and the solar irradiance conductance model of Moen and Brekke (1993, https://doi.org/10.1029/92gl02109). The ML‐AIM inputs are 60‐min time histories of solar wind plasma, interplanetary magnetic fields (IMF), and geomagnetic indices, and its outputs are ionospheric electric potential, electric fields, Pedersen/Hall currents, and Joule Heating. We conduct two ML‐AIM simulations for a weak geomagnetic activity interval on 14 May 2013 and a geomagnetic storm on 7–8 September 2017. ML‐AIM produces physically accurate ionospheric potential patterns such as the two‐cell convection pattern and the enhancement of electric potentials during active times. The cross polar cap potentials (ΦPC) from ML‐AIM, the Weimer (2005, https://doi.org/10.1029/2004ja010884) model, and the Super Dual Auroral Radar Network (SuperDARN) data‐assimilated potentials, are compared to the ones from 3204 polar crossings of the Defense Meteorological Satellite Program F17 satellite, showing better performance of ML‐AIM than others. ML‐AIM is unique and innovative because it predicts ionospheric responses to the time‐varying solar wind and geomagnetic conditions, while the other traditional empirical models like Weimer (2005, https://doi.org/10.1029/2004ja010884) designed to provide a quasi‐static ionospheric condition under quasi‐steady solar wind/IMF conditions. Plans are underway to improve ML‐AIM performance by including a fully ML network of models of aurora precipitation and ionospheric conductance, targeting its characterization of geomagnetically active times.

Solar influences on the Earth’s atmosphere: solved and unsolved questions

Solar influences on the Earth’s atmosphere: solved and unsolved questions

Solar Activity, Weather, and Climate: The Elusive Connection

Abstract The search for an explanation of correlations of weather and climate with solar activity has uncovered some subtle effects of the varying solar inputs, which include irradiance, energetic particles, electric fields induced by the solar wind, and the modulation of the galactic cosmic ray flux. Relevant phenomena have been identified in stratospheric chemistry and dynamics and in aerosols, atmospheric electricity, and clouds. The effects are small and appear intermittently in statistical analyses of observations. Correlations and theory permit responses to several solar inputs effective on the decadal time scales, making it difficult to distinguish them observationally. No mechanism for tropospheric decadal change can be considered to be definitely established, but for the day-to-day time scale there is clear observational evidence for clouds responding to solar wind–induced current flow (JZ) in the global electric circuit, due to changes in ionospheric potential, and independently from Forbush decreases of the cosmic ray flux. The responses to JZ also correlate separately with ionospheric potential changes due to changes in day-to-day thunderstorm activity. The identified mechanism is for electric charge effects on in-cloud scavenging, and this implies a decadal response, in view of decadal changes in JZ. However, a complete and quantitative model of the inferred electrically induced changes in cloud microphysics is not yet available. The failures, successes, and controversies of the search illustrate the somewhat chaotic process of scientific discovery.

Quantifying the ability of magnetohydrodynamic models to reproduce observed Birkeland current and auroral electrojet magnitudes

Although global magnetohydrodynamic (MHD) models have increased in sophistication and are now at the forefront of modeling Space Weather, there is still no clear understanding of how well these models replicate the observed ionospheric current systems. Without a full understanding and treatment of the ionospheric current systems, global models will have significant shortcomings that will limit their use. In this study we focus on reproducing observed seasonal interhemispheric asymmetry in ionospheric currents using the Space Weather Modeling Framework (SWMF). We find that SWMF does reproduce the linear relationship between the electrojets and the FACs, despite the underestimation of the currents’ magnitudes. Quantitatively, we find that at best SWMF is only capturing approximately 60% of the observed current. We also investigate how varying F10.7 effects the ionospheric potential and currents during the summer and winter. We find that simulations ran with higher F10.7 result in lower ionospheric potentials. Additionally, we find that the models do not always replicate the expected behavior of the currents with varying F10.7. This work points to a needed improvement in ionospheric conductance models.

Seasonal dependence of the equatorial electrojets generated by thunderstorms

A model for the distribution of the ionospheric potential which drives the ionospheric currents closing the electric currents from/to the atmosphere is constructed. It is a part of the global electric circuit (GEC). Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric or ionospheric generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth’s surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on high conductivity along the geomagnetic field. The model of the global distribution of thunderstorms obtained from the ground-based World Wide Lightning Location Network is used as a proxy for the electric currents to the ionosphere from the atmosphere above thunderstorm regions. The global distributions of the electric potential in the ionosphere are calculated for twelve months during a year with low solar activity. The designed models contain the equatorial electrojets. There are day-time electrojets, the strengths of which are up to 200 A, and night-time ones (which are up to only half this value), while the total current of the GEC is taken equal between 1.5 and 2.5 kA in our model to satisfy the Carnegie data for the simulated dates and UT. The results are presented as diagrams of the currents in the electrojets depending on the geomagnetic longitude and month for 04 and 18 UT. These times are chosen to be the times of minimum and maximum fair weather electric field in accordance with the Carnegie results. The diagrams could help us to choose optimal conditions for measurements of the magnetic perturbations observed on the ground or by satellites to find the electrojets of the GEC which are obtained in our simulations.

The effect of the Madden–Julian Oscillation on the global electric circuit

The Madden–Julian Oscillation (MJO) is the most dominant component of the climate variability in the tropics on the timescale of tens of days. Occurring irregularly, the MJO consists of an eastward propagation of certain large-scale coupled structures in atmospheric circulation and deep convection. Here we investigate the effect of the MJO on the direct current global electric circuit (GEC), using both numerical simulations and the results of electric field measurements. We have reproduced the atmospheric dynamics for 1980–2020 with the help of the Weather Research and Forecasting model and meteorological reanalysis data; this allowed us to simulate 41 years of the GEC variation by parameterising contributions to the ionospheric potential (IP) in terms of precipitation and convection. Besides, we have analysed the results of surface potential gradient (PG) measurements at the Vostok station in Antarctica during 2006–2020. When averaged over many days, both the simulated IP and measured fair-weather PG show sinewave-like variations with the MJO phase, which manifest a statistically significant correlation with the MJO cycle. A more elaborate investigation involving an application of empirical orthogonal functions shows that the dynamics of contributions to the IP follows the patterns of variability of deep convection typical for the MJO. The variation of the IP on the MJO scale can largely be represented as a superposition of two basic oscillating patterns of convection, one of which is located over the Maritime Continent and its surrounding seas and the other is located over the Indian Ocean and part of South-East Asia. These oscillating patterns together describe the eastward progression of perturbations and can be naturally associated with the two components of the Real-time Multivariate MJO index, widely used to describe the MJO. Together with earlier results about links between the GEC and the El Niño—Southern Oscillation, the results concerning the MJO obtained in this study indicate that the GEC is an important part of the Earth system, which reflects climate variability on different timescales.

WWLLN Data Used to Model the Global Ionospheric Electric Field Generated by Thunderstorms

Electric currents flowing in the atmospheric global electric circuit (GEC) are closed by ionospheric currents. The physical and mathematical approach to simulate the ionospheric potential which drives these currents has been described in our previous papers. Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric current sources or generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth’s surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on the high conductivity along the geomagnetic field; the Pedersen and Hall conductivities are calculated using empirical models. The potentials in the E- and F-layers of the ionosphere are considered to be constant along each magnetic field line. The main progress in comparison with previous versions of the model is obtained through applying the global distribution of thunderstorms obtained from the ground-based World Wide Lightning Location Network. Under typical conditions for July, under low solar activity in 2008, at 18:00 UTC, the calculated maximum potential difference in the ionosphere is 54 V. This newest version of our model contains the equatorial electrojets. There are day-time electrojets, the strengths of which are up to 65 A, and night-time ones (of up to 40 A), while the total current flowing in the GEC is taken to be equal to 1.43 kA in our model to satisfy the Carnegie curve, i.e. the diurnal variation of the vertical electric field at ground level with UTC. The maximum of the electric potential is shifted from Africa to South-East Asia in the new model. The equatorial electrojets also change their position, direction and intensity.

Study of the Ground Level Enhancements effect on atmospheric electric properties and mineral dust particle charging

The effect of Ground Level Enhancements (GLEs) on the atmospheric and dust particles electrical properties is studied. It has been found that in the case of fair weather conditions, GLE events enhance the atmospheric electrical conductivity, reduce the columnar resistance, and modify the fair weather electric field, air–earth conduction current, and possibly the Ionospheric Potential (IP) in a way that depends on the geomagnetic cut-off rigidity of the location and the altitude. If a dust particle layer is present, GLE events tend to cancel its electrical effects in the ambient atmosphere. This means that the enhancement of the electric field and the reduction of atmospheric electrical conductivity, caused by the ion attachment to dust particles, not only tend to return to their ambient fair weather values, but they can be further modified as if the dust layer was not present. Finally, in terms of dust particles’ electrical properties, GLE events tend to modify the ion attachment mechanism, and in principle, the particle net charge, and the electric field “sensed” by them, increase. Nevertheless, since the electrical force magnitude is up to six orders of magnitude less than gravity, the increase of the particles’ electrical properties is not sufficient to modify the particle settling dynamics and settling velocities.

Atmosphere-ionosphere coupling induced by volcanoes eruption and dust storms and role of GEC as the agent of geospheres interaction

In this publication we demonstrate how interdependent are our geophysical shells. The large-scale air pollution provided by the intensive volcano eruptions and dust storms from desert areas modify the electric properties of the troposphere creating the low conducting layers and increasing the column resistance for the vertical current flowing between the ionosphere and ground within the Global Electric Circuit (GEC). This modification leads to the local modulation of the ionospheric potential (IP) magnitude and hence to formation of the large-scale irregularities of electron concentration in the ionosphere. To reveal these phenomena, we use the differential GIM TEC mapping procedure showing specific features of the ionosphere reaction. In low latitude and equatorial regions we observe the formation of positive TEC anomalies not only over the area of air pollution but in the magnetically conjugated area as well. We can conclude that these phenomena pose the double error for Precise Point Positioning (PPP). To the danger of aircraft engines destroying is added the increase of navigational PPP errors due to sharp TEC gradients on the borders of the formed large-scale positive irregularities of electron concentration.

An electrodynamics model for Data Interpretation and Numerical Analysis of ionospheric Missions and Observations (DINAMO)

We introduce a new numerical model developed to assist with Data Interpretation and Numerical Analysis of ionospheric Missions and Observations (DINAMO). DINAMO derives the ionospheric electrostatic potential at low- and mid-latitudes from a two-dimensional dynamo equation and user-specified inputs for the state of the ionosphere and thermosphere (I–T) system. The potential is used to specify the electric fields and associated F-region E × B plasma drifts. Most of the model was written in Python to facilitate the setup of numerical experiments and to engage students in numerical modeling applied to space sciences. Here, we illustrate applications and results of DINAMO in two different analyses. First, DINAMO is used to assess the ability of widely used I–T climatological models (IRI-2016, NRLMSISE-00, and HWM14), when used as drivers, to produce a realistic representation of the low-latitude electrodynamics. In order to evaluate the results, model E × B drifts are compared with observed climatology of the drifts derived from long-term observations made by the Jicamarca incoherent scatter radar. We found that the climatological I–T models are able to drive many of the features of the plasma drifts including the diurnal, seasonal, altitudinal and solar cycle variability. We also identified discrepancies between modeled and observed drifts under certain conditions. This is, in particular, the case of vertical equatorial plasma drifts during low solar flux conditions, which were attributed to a poor specification of the E-region neutral wind dynamo. DINAMO is then used to quantify the impact of meridional currents on the morphology of F-region zonal plasma drifts. Analytic representations of the equatorial drifts are commonly used to interpret observations. These representations, however, commonly ignore contributions from meridional currents. Using DINAMO we show that that these currents can modify zonal plasma drifts by up to ~ 16 m/s in the bottom-side post-sunset F-region, and up to ~ 10 m/s between 0700 and 1000 LT for altitudes above 500 km. Finally, DINAMO results show the relationship between the pre-reversal enhancement (PRE) of the vertical drifts and the vertical shear in the zonal plasma drifts with implications for equatorial spread F.

The Global Electric Circuit and Global Seismicity

Basing on the catalogue of earthquakes with a magnitude of M ≥ 4.5 for the period 1973–2017, a UT variation with an amplitude of ~10% in the number of earthquakes is revealed and compared with a UT variation in the ionospheric potential (IP) with an amplitude of ~18%. We demonstrate that the amplitude of the UT variation in the number of deep-focus earthquakes is greater compared with that of crustal earthquakes, reaching 19%. The UT of the primary maxima of both the IP (according to modern calculations) and of earthquake incidence coincides (near 17:00 UT) and is, by 2 h, ahead of the classical Carnegie curve representing the UT variation in the atmospheric electric field on the ground surface. The linear regression equation between these UT variations in the number of deep-focus earthquakes and the ionospheric potential is obtained, with a correlation coefficient of R = 0.97. The results support the idea that the processes of earthquake preparation are coupled to the functional processes of the global electric circuit and the generation of atmospheric electric fields. In particular, the observed increase in thunderstorm activity over earthquake preparation areas, provided by air ionization due to radon emanation, yields a clue as to why the global thunderstorm distribution is primarily continental. Another important conclusion is that, in observing the longitudinal distributions of earthquakes against the IP distribution, we automatically observe that all such events occur in local nighttime hours. Considering that the majority of earthquake precursors have their maximums at local night and demonstrating the positive deviation from the undisturbed value, we obtain a clue as to its positive correlation with variations in the ionospheric potential.

The ionospheric equatorial electrojets generated by low latitude thunderstorms

A mathematical model is constructed of the equatorial electrojets flowing in the ionosphere which are generated by thunderstorms occurring at low latitudes. We use the narrow definition of the global electric circuit (GEC) that includes only atmospheric and ionospheric electric fields and currents generated by thunderstorms, and ignores the contributions of all ionospheric and magnetospheric generators. The ionospheric currents which distribute charges from the thunderstorm areas to the fair weather parts of the Earth are largest in the vicinity of the geomagnetic equator. They form the specific electrojets discussed here which are in addition to the electrojets formed by the wind dynamo. A model of the ionospheric potential which drives these currents was developed earlier and this is suitably modified here. We use an empirical model of the diurnal variation of the number of lightning strikes to define the currents up to the ionosphere from the main thunderstorm areas. A two-dimensional approximation of the ionospheric conductor is based on its high conductivity along the magnetic field. The Pedersen and Hall conductivity distributions are calculated using empirical ionospheric models; the Pedersen and Hall conductances are calculated by integration along magnetic field lines and these are used in the 2-D model of the ionospheric conductor. The spatial distributions of the ionospheric electric fields and currents are obtained by numerical solution of the 2-D ionospheric current continuity equation. The positions and the directions of the electrojets are defined by the global distribution of the main thunderstorm areas, as well as of the ionospheric conductivity, and so they strongly vary with Universal Time. As far as the generation of the equatorial electrojets is concerned, the African and Asian thunderstorm areas are more effective than the American ones since they are closest to the geomagnetic equator. There are day-time electrojets, the strength of which may be up to 175 A, and night-time ones (of up to 60 A), while the total current flowing in the GEC is not larger than 1400 A at any moment of time in our model. Usually the electrojets are a few times weaker in the night-time ionosphere because of its smaller conductivity. The equatorial electrojets of the GEC thus produce magnetic perturbations on the ground, which are in the 0.1 nT range, while there are one hundred times stronger, wind dynamo-driven electrojets and other larger, space weather-associated magnetic perturbations. Nevertheless, using their specific features these magnetic perturbations could be measured, especially at the night-time geomagnetic equator when and where they are not so disguised by other ionospheric currents.

The global electric circuit land–ocean response to the El Niño—Southern Oscillation

It is known that the global electric circuit (GEC) intensity can be characterised by a single global index, namely the ionospheric potential (IP), made up of contributions from electrified clouds all over the globe. Using the Weather Research and Forecasting model, we have reproduced the atmospheric dynamics for 2008–2018 and simulated the variation of the GEC by parameterising regional contributions to the IP in terms of convection and precipitation. Considering that the El Niño—Southern Oscillation (ENSO) can be quantitatively characterised by sea surface temperatures (SSTs) in the Niño 3.4 region, this allowed us to identify and study in detail the effect of ENSO on regional contributions to the GEC. Our simulations have shown that contributions to the GEC from the land and oceanic parts of the Earth's surface respond oppositely to the ENSO cycle. The oceanic contribution is positively correlated with the Niño 3.4 SST, largely owing to increases in convection over the Pacific Ocean. In contrast to the oceans, the land contribution shows a negative correlation with ENSO due to decreases in convection over the Maritime Continent and South America. The observed correlations are statistically significant and are clearly seen on the decadal timescale; at the same time contributions to the IP for individual years do not always clearly reflect the corresponding Niño 3.4 SST anomalies. During the two El Niños and two La Niñas that occurred between 2008 and 2018, the oceanic contribution always changed in phase with ENSO, increasing in El Niño years and decreasing in La Niña years; on the other hand, the contribution of land showed a clear variation in antiphase with ENSO only for the 2015/16 El Niño and 2010/11 La Niña, characterised by extremely large SST anomalies, with a small and indefinite effect for the two lesser events. When summing the contributions of land and ocean, two strong effects of opposite signs nearly counterbalance each other and we obtain a much less pronounced effect of ENSO on the total IP. This effect is generally positive since land and ocean provide nearly equal contributions to the GEC during Northern Hemisphere winters and, according to our analysis, the contribution of ocean is slightly more sensitive to ENSO than that of land.

A new link between El Niño—Southern Oscillation and atmospheric electricity

The global electric circuit (GEC) is a unique atmospheric system driven by the global distribution of thunderstorms and electrified shower clouds. The GEC unites electric fields and currents in the entire atmosphere and is characterized by the permanent production and dissipation of huge amounts of electrical energy. In this study, aimed at investigating the links between the GEC and El Niño—Southern Oscillation (ENSO), the GEC variability during 2008–2018 is simulated on the basis of reanalysis meteorological data using the Weather Research and Forecasting model and a parameterization of the ionospheric potential (IP), which is a natural measure of the GEC intensity. Modelling shows that strong El Niño and La Niña events influence the global distribution of electrified clouds over the Earth’s surface, thereby consistently affecting the shape of the diurnal variation of the GEC. Further analysis shows that anomalies in the Niño 3.4 sea surface temperature, which characterize the ENSO phase, and anomalies in the relative IP are positively correlated at 9:00–15:00 UTC and negatively correlated at 18:00–23:00 UTC. This correspondence between ENSO and the GEC is most prominent at 13:00 UTC and 21:00 UTC, and most pronounced anomalies in the relative IP around these hours are precisely associated with strong El Niño and La Niña events. In particular, during strong El Niños the relative IP is larger than usual around 13:00 UTC and smaller than usual around 21:00 UTC, whereas during strong La Niñas it behaves oppositely.

Seasonal and Solar Wind Sector Duration Influences on the Correlation of High Latitude Clouds With Ionospheric Potential

AbstractIrradiances from long‐lived stratus‐type clouds at Alert (Canada), Summit (Greenland), and South Pole, previously measured, show correlations with the day‐to‐day input to the global atmospheric electric circuit from the solar wind, as well as with the inputs of low‐ and mid‐latitude thunderstorms and shower clouds. We analyze the measured Alert cloud irradiances, and find differences in the responses to 2, 4, or more solar wind sectors per 27‐days solar rotation. We find seasonal variations in the correlations, with sign reversal in the summer. The correlation coefficients that were found previously for all‐year, all sector types show further increases for just winter months and in addition, for just 2‐sector intervals. At high magnetic latitudes, the ionospheric potential correlates strongly with the solar wind sector structure, and determines the flow of current density (JZ) to the Earth's surface that passes through clouds and modifies space charge in them. Parameterizations of the potential distribution near the magnetic pole are used in the correlations. The daily average values depend mainly on the solar wind (interplanetary) magnetic field (IMF) BY component, with lesser influence of the solar wind speed and IMF BZ. Mechanisms by which space charge in clouds can affect cloud microphysics and cloud opacity are described and are qualitatively consistent with the correlations, but need quantitative testing.

Measuring Global Signals in the Potential Gradient at High Latitude Sites

Previous research has shown that the study of the global electrical circuit can be relevant to climate change studies, and this can be done through measurements of the potential gradient near the surface in fair weather conditions. However, potential gradient measurements can be highly variable due to different local effects (e.g., pollution, convective processes). In order to try to minimize these effects, potential gradient measurements can be performed at remote locations where anthropogenic influences are small. In this work we present potential gradient measurements from five stations at high latitudes in the Southern and Northern Hemisphere. This is the first description of new datasets from Halley, Antarctica; and Sodankyla, Finland. The effect of the polar cap ionospheric potential can be significant at some polar stations and detailed analysis performed here demonstrates a negligible effect on the surface potential gradient at Halley and Sodankyla. New criteria for determination of fair weather conditions at snow covered sites is also reported, demonstrating that wind speeds as low as 3 m/s can loft snow particles, and that the fetch of the measurement site is an important factor in determining this threshold wind speed. Daily and seasonal analysis of the potential gradient in fair weather conditions shows great agreement with the “universal” Carnegie curve of the global electric circuit, particularly at Halley. This demonstrates that high latitude sites, at which the magnetic and solar influences can be present, can also provide globally representative measurement sites for study of the global electric circuit.

Mid-latitude convective boundary-layer electricity: A study by large-eddy simulation

This paper reports the first investigations of the mid-latitude convective boundary layer (CBL) electricity above the homogeneous land surface using a large-eddy simulation (LES). Our approach uses LES together with a subgrid kinematic model for relative dispersion of scalar to calculate Lagrangian trajectories of notional particles carrying radioactive nuclei, small atmospheric ions, and charged aerosol particles. This technique opens up new possibilities for quantifying the influence of various environmental conditions on the formation of the electrical state of the undisturbed lower atmosphere. We examine the altitude distribution of principal atmospheric electrical quantities in the CBL and lower free weakly stable atmosphere without clouds depending on surface turbulent heat flux, geostrophic wind speed, mixed-layer height, ionospheric potential, and various ion production rates due to cosmic rays and radioactive gases.

Toward a Realistic Representation of Global Electric Circuit Generators in Models of Atmospheric Dynamics

AbstractThe diurnal variation of the global electric circuit (GEC) is simulated using the Weather Research and Forecasting model by estimating contributions of grid columns to the ionospheric potential (IP). A parameterization based on cutting off the grid columns with shallow convection and estimating the area covered by GEC generators (electrified clouds) in each column from the amount of precipitation yields the IP variation of the same shape as the classical Carnegie curve with a correlation coefficient of 0.97, although with a smaller peak‐to‐peak amplitude (18% against 34% of the mean) and maxima and minima shifted by 1–2 hr. It is shown that omission in the IP parameterization of either convective activity or the area covered by electrified clouds (estimated using the calculated precipitation) would result in poor similarity between the modeled IP variation and the classical Carnegie curve. The results of simulation show the best agreement with the Carnegie data during Northern Hemisphere winters; the shape of the simulated diurnal variation of the IP substantially changes throughout the year owing to the decrease of South America's contribution and the increase of Southern Asia's contribution in summer. The discrepancies between the results of modeling and the results of observations are probably caused by the limited ability of large‐scale models to differentiate between electrified and nonelectrified clouds. Further improvement of the parameterization of the IP in models of atmospheric dynamics requires using finer grids, which should allow computing microphysical characteristics of clouds and estimating source currents more accurately.