Time filter

Source Type

Millington, United Kingdom

Rycroft M.J.,CAESAR Consultancy | Harrison R.G.,University of Reading
Space Science Reviews | Year: 2012

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 -9 m to 10 12 m, concerned with the many important processes at work. A similarly enormous range of time scales is involved from 10 -6 s to 10 9 s, 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 ionization, is a crucial parameter of the circuit. Model simulation results on the variation of the ionospheric potential, ∼250 kV positive with respect to the Earth's potential, following lightning discharges and sprites are summarized. 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. © 2011 Springer Science+Business Media B.V.

Harrison R.G.,University of Reading | Aplin K.L.,Clarendon Laboratory | Rycroft M.J.,CAESAR Consultancy | Rycroft M.J.,University of Bath
Natural Hazards and Earth System Sciences | Year: 2014

We illustrate how coupling could occur between surface air and clouds via the global electric circuit-through Atmospheric Lithosphere-Ionosphere Charge Exchange (ALICE) processes-in an attempt to develop a physical understanding of the possible relationships between earthquakes and clouds. © 2014 Author(s).

Rycroft M.J.,CAESAR Consultancy | Rycroft M.J.,University of Bath | Nicoll K.A.,University of Reading | Aplin K.L.,University of Oxford | Harrison R.G.,University of Reading
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2012

The global atmospheric electric circuit is driven by thunderstorms and electrified rain/shower clouds and is also influenced by energetic charged particles from space. The global circuit maintains the ionosphere as an equipotential at~+250 kV with respect to the good conducting Earth (both land and oceans). Its "load"is the fair weather atmosphere and semi-fair weather atmosphere at large distances from the disturbed weather "generator"regions. The main solar-terrestrial (or space weather) influence on the global circuit arises from spatially and temporally varying fluxes of galactic cosmic rays (GCRs) and energetic electrons precipitating from the magnetosphere. All components of the circuit exhibit much variability in both space and time. Global circuit variations between solar maximum and solar minimum are considered together with Forbush decrease and solar flare effects. The variability in ion concentration and vertical current flow are considered in terms of radiative effects in the troposphere, through infra-red absorption, and cloud effects, in particular possible cloud microphysical effects from charging at layer cloud edges. The paper identifies future research areas in relation to Task Group 4 of the Climate and Weather of the Sun-Earth System (CAWSES-II) programme. © 2012 Elsevier Ltd.

The last forty years have seen remarkable developments in our understanding of the Doppler-shifted cyclotron resonance interactions between ducted whistler-mode radio signals travelling in one direction along a dipolar geomagnetic fluxtube (1.5 < L < ~ 6) and Van Allen radiation belt electrons travelling in the other. These signals range from natural whistlers generated by lightning discharges and sweeping in frequency to (apparently) spontaneously generated hiss and chorus, and to single frequency signals from ground-based VLF radio transmitters. In these interactions, whistler-mode waves of audio frequency are amplified and the electrons' pitch angles are reduced, some being pushed into the loss cone to perturb the lower ionosphere at the foot of the flux tube where the interaction has taken place. The plasma instability is established at or close to the equatorial plane of the magnetosphere. With feedback mechanisms, cyclotron maser action, therefore, takes place. In many cases, this action produces signals of rising frequency (and occasionally of falling frequency). Observations have been made of aspects of these interactions on rockets and on Earth-orbiting satellites, complemented by radio observations made on the ground. Such observations are reviewed for naturally occurring whistlers, chorus and man-made signals, e.g. from the Siple transmitter in Antarctica and the NWC transmitter in Australia. Selfconsistent nonlinear theoretical analyses of these interactions, involving broad electron distribution functions, have been undertaken and numerical simulations performed. An overview of these recent developments is also provided.

Tacza J.,Mackenzie Presbyterian University | Raulin J.-P.,Mackenzie Presbyterian University | Macotela E.,Mackenzie Presbyterian University | Norabuena E.,Instituto Geofisico del Peru | And 5 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2014

In this paper we present the capability of a new network of field mill sensors to monitor the atmospheric electric field at various locations in South America; we also show some early results. The main objective of the new network is to obtain the characteristic Universal Time diurnal curve of the atmospheric electric field in fair weather, known as the Carnegie curve. The Carnegie curve is closely related to the current sources flowing in the Global Atmospheric Electric Circuit so that another goal is the study of this relationship on various time scales (transient/monthly/seasonal/annual). Also, by operating this new network, we may also study departures of the Carnegie curve from its long term average value related to various solar, geophysical and atmospheric phenomena such as the solar cycle, solar flares and energetic charged particles, galactic cosmic rays, seismic activity and specific meteorological events. We then expect to have a better understanding of the influence of these phenomena on the Global Atmospheric Electric Circuit and its time-varying behavior. © 2014.

Discover hidden collaborations