Temporal smoothing of the electrical impulses generated by lightning and shower clouds occurs through the global atmospheric electric circuit (GEC); smoothing is quantified by the time constant of the GEC. Two new methods for calculating this time constant are presented. They are based a) on a novel global circuit capacitor model, rather than the Earth-ionosphere capacitor model, and b) on the concept of dielectric relaxation time of near-surface poorly conducting air. The new GEC model considers the contributions of stratus clouds and their changes to the electrical conductivity of the air. Using model a), the time constants for the various regions of the atmosphere, over land and oceans, are obtained and the GEC time constant is found to be similar to 10 min. This compares very favourably with the time constant derived from recent observations of the effects of sudden volcanic lightning on the GEC. The upper "pseudo-electrode" of the capacitor, the actual value of whose constant potential varies according to the conditions present, is found to be at an altitude of 1.8 km. For model b), the upper pseudo-electrode is placed at the boundary between dielectric and conducting atmospheres, i.e. where the displacement current equals the conduction current. Its altitude is 2.0 km, in the vicinity of stratiform clouds; the GEC time constant is 7.6 min. The vertical profile of air conductivity which best fits both DC GEC and AC (Schumann resonance) considerations is presented. Smoothing from the GEC's time constant provides steady background conditions for stratiform cloud edge charging which may affect their properties in the climate system; the steady conditions are also exploited biologically, e.g., by spiders and their webs. Other connections between atmospheric electricity and various living species are briefly explored.

The DC global electric circuit, GEC, was conceived by C.T.R. Wilson more than a century ago. Powered by thunderstorms and electrified shower clouds, an electric current I ~1 kA flows up into the ionosphere, maintaining the ionospheric potential V ~250 kV with respect to the Earth’s surface. The circuit is formed by the current I, flowing through the ionosphere all around the world, down through the atmosphere remote from the current sources (J ~2 pA/m2 through a resistance R ~250 Ω), through the land and sea surface, and up to the thunderstorms as point discharge currents. This maintains a downward electric field E of magnitude ~130 V/m at the Earth’s surface away from thunderstorms and a charge Q ~−6.105 C on the Earth’s surface. The theoretical modelling of ionospheric currents and the miniscule geomagnetic field perturbations (ΔB ~0.1 nT) which they cause, as derived by Denisenko and colleagues in recent years, are reviewed. The time constant of the GEC, τ = RC, where C is the capacitance of the global circuit capacitor, is estimated via three different methods to be ~7 to 12 min. The influence of stratus clouds in determining the value of τ is shown to be significant. Sudden excitations of the GEC by volcanic lightning in Iceland in 2011 and near the Tonga eruption in 2022 enable τ to be determined, from experimental observations, as ~10 min and 8 min, respectively. It has been suggested that seismic activity, or earthquake precursors, could produce large enough electric fields in the ionosphere to cause detectable effects, either by enhanced radon emission or by enhanced thermal emission from the earthquake region; a review of the quantitative estimates of these mechanisms shows that they are unlikely to produce sufficiently large effects to be detectable. Finally, some possible links between the topics discussed and human health are considered briefly.

The DC global electric circuit (GEC) distributes charge in the lower atmosphere by current flow between “generator regions” (thunderstorms and rain clouds) and “load regions” (distant conductive air), with a timescale defined by circuit properties. Previously, the load has only been modelled by assuming fair weather (FW) conditions, neglecting cloud. As stratiform clouds cover ∼30 % of the Earth’s surface, load resistance has been added to represent them, considered to provide semi fair weather (semi-FW) conditions. This increases the GEC timescale by 9 % for stratocumulus, or 33 % for stratus at a lower level. Including mutual capacitance between the outer charged layer and an electrode representing stratocumulus clouds increases the timescale by 35 %, to 8.6 minutes. These modelled results - the first including the semi-FW aspects - are demonstrated to be consistent with experimentally determined timescales of the real GEC, of between 7 and 12 minutes, derived from volcanic lightning variations associated with the May 2011 Grímsvötn eruption in Iceland. Accounting for semi-FW circumstances improves the modelled representation of the natural global circuit. Further, the GEC timescale is comparable with cloud droplet charging timescales in the updrafts of extensive layer clouds, suggesting its possible relevance to the microphysical behaviour of stratiform (layer) clouds in the climate system.

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.

Data on the atmospheric fair weather electric field obtained during Carnegie cruise VII are plotted as a two dimensional map in Universal Time and month coordinates to show both time and seasonal variations. The maximum of the field is observed at a time around 18 UT in January. For this point in time a model is created for the thunderstorm-related ionospheric part of the global electric circuit in January. The obtained current system consists of both mid-latitude currents and equatorial electrojets, day-time and night-time, westward and eastward, up to 120 A.

Observed responses of the AC and DC parts of the Global Electric Circuit (GEC) to the large eruption of the Hunga Tonga - Hunga Ha’apai (HT-HH) volcano on 15 January, 2022 are presented. The AC-related investigation is based on Schumann resonance (SR) measurements from the Nagycenk Geophysical Observatory (NCK), Hungary as well as from distant stations on the globe belonging to the HeartMath Institute (https://www.heartmath.org/gci/). The DC-related investigation is based on atmospheric electric potential gradient measurements (PG) from six recording stations in Europe and in the USA. The GLD360 and the WWLLN lightning detection networks were used to characterize lightning activity in the vicinity of the HT-HH island on the investigated day. The peak lightning stroke rate reached 80/s (5000/minute), whereas the average global rate is ~44/s. Lightning discharges occurred in rings around the vent of the volcano. Peak currents and the diameter of the ring of positive and negative polarity lightning strokes varied differently in the main phase of the eruption. At its peak, negative lightning dominated the electric activity in the volcanic cloud.A global intensification of SR is apparent in connection with the enhanced lightning activity caused by the eruption. The SR data together with the global network observations indicate that the lightning activity in the eruption dominates the naturally occurring global activity for a period of at least one hour. The highly localized increase in lightning activity over HT-HH provides a unique point source of excitation for the SR.In contrast with the dramatic response of the AC global circuit, the response of the DC GEC to this exceptional eruption is not readily unambiguous in the PG measurements. The observations suggest that impulse-like charging of the GEC by ~15% via -CG lightning strokes took place two times during the eruption. A time constant of 7 or 8 minutes has been inferred for near-surface electric field changes from these enhancements. This could be the first direct measurement of the time constant of the GEC near the Earth’s surface, as well as the first observation of the direct charging of the DC GEC by a single atmospheric electrified source.

Responses of the AC and DC global electric circuits (GECs) to the large eruption of the Hunga Tonga‐Hunga Ha'apai (HT‐HH) volcano on 15 January 2022 are discussed. The AC‐related investigation is based on Schumann resonance (SR) measurements from six stations on four continents. The DC‐related investigation utilizes atmospheric electric field (potential gradient, PG) measurements from six recording stations in Europe and the USA. According to data from the GLD360 and WWLLN lightning detection networks, the peak lightning stroke rate, 83/s, was dominated by negative polarity lightning, but the distributions of positive and negative lightning discharges in latitude and longitude around the volcano differed. A global intensification of SR is apparent in connection with the enhanced lightning activity caused by the eruption. SR data‐based results confirm that the lightning activity in the eruption dominated the naturally occurring global activity for a period of about 1 hr. The highly localized increase in lightning activity over HT‐HH was a unique point source of SR excitation. PG measurements suggest that impulse‐like charging of the DC GEC, by ∼15%, via negative cloud‐to‐ground lightning strokes took place twice during the eruption. A time constant of 7 or 8 min has been inferred for near‐surface PG changes due to these enhancements. This could be the first direct measurement of the time constant of the GEC near the Earth's surface, as well as the first observation of the direct charging of the DC GEC by a unique atmospheric electrified source.

The articles mentioned in this Correction were published under category “Original Paper”. However, their correct category should be “Review Paper.”

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 twodimensional 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.

A fair-weather electric field has been observed near the Earth's surface for over two centuries. The field is sustained by charge generation in distant disturbed weather regions, through current flow in the global electric circuit. Conventionally, the fair-weather part of the global circuit has disregarded clouds, but extensive layer clouds, important to climate, are widespread globally. Such clouds are not electrically inert, becoming charged at their upper and lower horizontal boundaries from vertical current flow, in a new electrical regime-neither fair nor disturbed weather; hence it is described here as semi-fair weather. Calculations and measurements show the upper cloud boundary charge is usually positive, the cloud interior positive and the lower cloud boundary negative, with the upper charge density larger, but of the same magnitude (similar to nCm(-2)) as cloud base. Globally, the total positive charge stored by layer clouds is approximately 10(5)C, which, combined with the positive charge in the atmospheric column above the cloud up to the ionosphere, balances the total negative surface charge of the fair-weather regions. Extensive layer clouds are, therefore, an intrinsic aspect of the global circuit, and the resulting natural charging of their cloud droplets is a fundamental atmospheric feature.

There is an increasing interest to study the interactions between atmospheric electrical parameters and living organisms at multiple scales. So far, relatively few studies have been published that focus on possible biological effects of atmospheric electric and magnetic fields. To foster future work in this area of multidisciplinary research, here we present a glossary of relevant terms. Its main purpose is to facilitate the process of learning and communication among the different scientific disciplines working on this topic. While some definitions come from existing sources, other concepts have been re-defined to better reflect the existing and emerging scientific needs of this multidisciplinary and transdisciplinary area of research.

A model for the distribution of the ionospheric electric potential which drives the currents which close the global electric circuit is constructed. Only the internal electric fields and currents generated by thunderstorms are studied. 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 large conductivities along the geomagnetic field; the Pedersen and Hall conductivity distributions are calculated using the empirical models IRI, MSIS and IGRF. The maximum calculated voltage difference in the ionosphere under typical conditions for July, under low solar activity, at 19:00 UT, is about 85 V. In our model the potential has identical values at ionospheric conjugate points. With our more realistic ionospheric model, the electric fields are found to be an order of magnitude smaller than those of the well-known model of Hays and Roble [9].

A description is given of the global atmospheric electric circuit operating between the Earth’s surface and the ionosphere. Attention is drawn to the huge range of horizontal and vertical spatial scales ranging from 10 m to 10m, concerned with the many important processes at work. A similarly enormous range of time scales is involved from 10>s to 10s, in the physical effects and different phenomena that need to be considered. The current flowing in the global circuit is generated by disturbed weather such as thunderstorms and electrified rain/shower clouds, mostly occurring over the Earth's land surface. The profile of electrical conductivity up through the atmosphere, determined mainly by galactic cosmic ray ionisation, is a crucial parameter of the circuit. Model simulation results on the variation of the ionospheric potential, ~ 250kV positive with respect to the Earth's potential, following lightning discharges and sprites are summarized. Recent experimental results comparing global circuit variations with the neutron rate recorded at Climax, Colorado, are then discussed. Within the return (load) part of the circuit in the fair weather regions remote from the generators, charge layers exist on the upper and lower edges of extensive layer clouds; new experimental evidence for these charge layers is also reviewed. Finally, some directions for future research in the subject are suggested.

Our colleague A. P. Nickolaenko has pointed out an unfortunate, and obvious, misprint in our paper. The error is in line 5 of page 12 showing values for s 0 , which corresponds to the value of the surface conductivity in units of S/m. These values should not be negative.

This paper examines whether the Earth-ionosphere capacitor (EIC) model is correct, by comparing observed atmospheric electrical properties with those expected for a spherical capacitor, as defined in electrostatics. The comparisons suggest that the EIC concept cannot be reconciled with, and hence cannot account for, the observations, particularly the rapid reduction of the atmospheric electric field with height that is measured. This means that the spherical EIC concept is incorrect by being too simplistic; it is thus misleading. The reason for this flawed concept is simple: the model disregards the non-uniform conductivity of the atmosphere which requires the presence of a net positive charge in the lower atmosphere that equals in magnitude the Earth's negative charge. This positive charge shields the action of the Earth's negative charge from polarizing the ionosphere positively. Thus, the lower D region ionosphere remains electrically neutral, which makes the EIC concept inappropriate.