scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Electromagnetic Atmosphere-Plasma Coupling: The Global Atmospheric Electric Circuit

01 Jun 2012-Space Science Reviews (Springer Netherlands)-Vol. 168, Iss: 1, pp 363-384
TL;DR: In this article, a description of the global atmospheric electric circuit operating between the Earth's surface and the ionosphere is given, with a huge range of horizontal and vertical spatial scales, ranging from 10−9 m to 1012 m, concerned with many important processes at work.
Abstract: 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 1012 m, concerned with the many important processes at work. A similarly enormous range of time scales is involved from 10−6 s to 109 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.

Summary (3 min read)

1. Introduction

  • This paper is concerned with atmospheric electrical coupling from near the Earth's surface up into -and down from -the ionosphere at ~ 80 km altitude and higher.
  • Fig. 2 shows the broad range of temporal scales that are involved in the many phenomena of importance.
  • The consequent large electrostatic field above the thundercloud exceeds the conventional threshold field for electrical breakdown, creating a sprite from about 80 km at the base of the ionosphere down to about 55 km (Fullekrug et al.

2. Properties of the global electric circuit

  • (a) Generator and load regions Fig. 3 is a schematic representation of the circuit taken from Rycroft et al. (2000) .
  • The lower part of Fig. 3 shows the equivalent circuit.
  • A very recent paper by Mach et al. (2011) has, for the first time, used experimental data from aircraft and satellites to deduce that thunderstorms over the land contribute 1.1 kA to the global circuit and, over the oceans, 0.7 kA.
  • The conductivity and the electric current density J z flowing in the fair weather regions determine the vertical electric field E. Near the Earth's surface away from aerosol pollution in fair weather E = -130 V/m; the minus sign indicates that the electric field is directed downwards.

(b) Vertical variations

  • The cosmic ray fluxes at different altitudes and for different rigidities (i.e. for different momenta) have been reported by Bazilevskaya et al.
  • These results are in good agrement with those presented by Rycroft et al. (2007) and Rycroft and Odzimek (2010) .
  • Fig. 3 of the Rycroft and Odzimek (2010) model considered the effect on the global circuit of reducing the conductivity within the thundercloud by a factor ranging from 2 to 29.
  • With the increase in conductivity with height, the vertical electric field becomes so small with increasing height that the potential in the model atmosphere at 60 km is only 24 V less than the 250,000 kV ionospheric potential (Rycroft et al. 2007) .
  • Stansbery et al. (1993) estimate that half of the current that reaches the ionosphere flows into the geomagnetically conjugate hemisphere.

3. Recent findings concerning the global circuit

  • (a) Source term Fig. 7 shows the position of the RHESSI satellite when it detected a TGF (taken from Smith 2009; more results are given by Smith et al. 2010 ).
  • Whilst it is not proven that TGFs play a role in maintaining the global circuit, it is important to consider the impact of relativistic processes taking place above thunderstorms on the global circuit.
  • They note that such "relativistic electron beams are a new form of impulsive energy transfer between thunderclouds and the middle atmosphere which need to be considered as a novel element in the global atmospheric electric circuit".
  • Globally, there are about 44 flashes per second, of which less than one is over the oceans.
  • Price (2006) plotted (his Fig. 8 ) the Universal Time variation of the thunderstorm area of the three tropical continental regions.

(b) Current flow and ionospheric potential

  • Integrating the vertical electric field profile measured aboard aircraft or balloons up to the troposphere essentially determines the ionospheric potential.
  • The curve closely resembles the Carnegie Curve (Markson 1986 ), which is one of the "confirming ideas" (Aplin et al, 2008) supporting the behaviour of the Earth-atmosphere global circuit system.
  • Harrison and Bennett (2007) considered the observations made on some days, in different years from 1966 to 1971, using electric field sensors carried on balloons launched from Weissenau, Germany, from which the ionospheric potential was derived by vertical integration.
  • The results were compared with fair weather observations made on the same days at the Kew observatory, on the outskirts of London.
  • This indicates that global circuit concept holds over an area at least as great as the size of Europe.

(c) Global circuit modulation

  • Next, the authors investigate studies of the response of the global atmospheric electric circuit to changes of the flux of cosmic rays in order to test their understanding of the global circuit.
  • Measurements of the conduction current show a positive response to cosmic ray changes, driven by the solar cycle (Markson, 1980; Harrison and Usoskin, 2010) .
  • It shows as individual symbols the ionospheric potential observed from several different investigators on specific days; this usually lies between 150 and 300 kV.
  • This indicates the flux of galactic cosmic rays with rigidities > 3 GV.
  • The atmospheric conductivity is less at solar maximum than at solar minimum and the ionospheric potential is accordingly less.

(d) Global circuit cloud coupling

  • This modulation of the fair weather current density by solar activity and associated cosmic ray changes provides a potential mechanism whereby the properties of clouds at low heights in fair weather regions could be changed by the currents passing through them, with implications, currently not quantified, for changes in weather and climate as a result.
  • Theory indicates that, at the edge of a horizontal layer cloud, the transition from low conductivity air within a cloud to air of greater conductivity outside the cloud will be accompanied by a region of enhanced space charge, when the current flows vertically through the cloud boundary.
  • This result is not inconsistent with a cosmic ray effect on the global circuit which also influences clouds through a conduction current mechanism, and the analysis indicates rapid time scales of ~1day or less.
  • A similar periodicity is apparent in surface PG data at Nagycenk Observatory, Hungary (Harrison and Marcz 2007) , during fair weather conditions but absent during disturbed weather when global circuit influences would be masked.
  • Fig. 12 shows a combination of neutrons (a) and Lerwick cloud data (c), filtered as in Harrison (2008) , but with the short period of conduction current data available from Lerwick around the same time (Harrison and Nicoll, 2007) , panel (b).

(e) Applications of global atmospheric electricity

  • The potential gradient (PG) in surface air is sensitive to aerosol pollution, because of the removal of ions by aerosol particles.
  • In severely polluted air, the PG can be substantially raised and, since historically many measurements were made in urban regions, this provides a method by which past urban pollution information can be reconstructed (Harrison and Aplin 2002, 2003; Harrison, 2006 Harrison, , 2009)) .
  • This reduces the columnar resistance to the ionosphere and, in a fair weather region, the current to the ionosphere increases.
  • It would be interesting to observe the cut-off frequency of "tweeks" (Reeve and Rycroft 1972) , signals from distant lightning propagating at night over the earthquake-affected region in order to test the prediction of this mechanism where precursors to major earthquakes occurring over land affect the ionosphere.
  • Pulinets and Ouzounov (2010) have presented a more complex mechanism relating these observable phenomena, and others.

4. Concluding remarks

  • In this paper the authors have outlined the physical processes operating in the D.C. and A.C. global atmospheric electric circuit which rapidly couple phenomena occurring near the Earth's surface with the ionosphere and the near-Earth space environment.
  • Finally, the authors suggest some studies which could advance the subjects discussed further.
  • It seems to be desirable to: (i) investigate in more detail the relative contributions made by thunderstorm generators and by rain/shower cloud generators as drivers of the global electric circuit (Liu et al.

Figures with captions

  • The black lines represent the bandpass filtered versions of the raw data, passband 1.55 to 1.81 years with phase relationships preserved, as a percentage of the mean value of the raw data.
  • Randomly selected points from the relevant series have been substituted for missing data, and the mean filtered version (thick line) is determined from multiple realisations of the random data replacements, with 95% confidence limits shown (dashed lines).
  • Dotted thin lines show the 95% confidence limits on the variability in multiple realisations obtained by passing randomly chosen points through the bandpass filter.
  • Dashed-dotted lines show a fitted sine wave with period 1.68 years, beginning at 1981.5.

Did you find this useful? Give us your feedback

Figures (8)

Content maybe subject to copyright    Report

Electromagnetic atmosphere-plasma
coupling: the global atmospheric electric
circuit
Article
Accepted Version
Rycroft, M. J. and Harrison, R. G. (2012) Electromagnetic
atmosphere-plasma coupling: the global atmospheric electric
circuit. Space Science Reviews, 168 (1). pp. 363-384. ISSN
0038-6308 doi: https://doi.org/10.1007/s11214-011-9830-8
Available at https://centaur.reading.ac.uk/24952/
It is advisable to refer to the publishers version if you intend to cite from the
work. See Guidance on citing
.
To link to this article DOI: http://dx.doi.org/10.1007/s11214-011-9830-8
Publisher: Springer
Publisher statement: The original publication is available at www.springerlink.com
All outputs in CentAUR are protected by Intellectual Property Rights law,
including copyright law. Copyright and IPR is retained by the creators or other
copyright holders. Terms and conditions for use of this material are dened in
the End User Agreement
.
www.reading.ac.uk/centaur
CentAUR

Central Archive at the University of Reading
Readings research outputs online

1
Electromagnetic atmosphere-plasma coupling: The global electric
circuit
M.J. Rycroft
(1)
and R.G. Harrison
(2)
(1) CAESAR Consultancy, 35 Millington Road, Cambridge CB3 9HW, UK;
International Space University, 1 rue Jean-Dominique Cassini, 67400 Ilkirch-
Graffenstaden, France
(2) Department of Meteorology, University of Reading, Earley Gate, PO Box 243,
Reading, Berkshire RG6 6BB, UK
accepted for publication in Space Science Reviews doi:
10.1007/s11214-011-9830-8
Abstract
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 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.
Keywords: global circuit; thunderstorms; electrified cloud generators; cosmic rays;
atmospheric electrical conductivity profile; fair weather regions; ionospheric potential;
lightning; sprites; layer cloud electrification
1. Introduction
This paper is concerned with atmospheric electrical coupling from near the Earth’s
surface up into - and down from - the ionosphere at ~ 80 km altitude and higher. This
coupling takes place rapidly, at, or close to, the speed of light c (Rycroft 2006), as
opposed to coupling mechanisms involving mechanical waves of one type or the other
which propagate at speeds much slower than c, and which are discussed in other papers in
this volume. As outlined by Aplin et al. (2008), the subject of atmospheric electricity had
its origins in the eighteenth century, grew into the concept of the global atmospheric
electric circuit in the early twentieth century with the seminal papers of Wilson (1921,
1929, 1956), and matured considerably in the first decade of the twenty first century.

2
The global circuit is formed between the surface of the Earth and the ionosphere, both of
which are good electrical conductors in comparison with the insulating atmosphere
between them. D.C. and A.C. electric generators exist in the atmosphere, for example in
thunderstorms, creating currents flowing up to the ionosphere. The current circuit closes
through fair weather parts of the atmosphere that are remote from the generators. Useful
background papers on different aspects of the global atmospheric electric circuit have
been written by Vonnegut (1973), Makino and Ogawa (1984, 1985), Roble and Tzur
(1986), Volland (1987), Hays and Roble (1979), Roble aand Hays (1979), Roble (1991),
Bering et al. (1998), Rycroft et al. (2000, 2007, 2008), Williams (2002, 2009), Harrison
(2004), Siingh et al. (2005, 2007, 2011), Aplin (2006), Markson (2007), Tinsley et al.
(2007), Harrison et al. (2008) and Tinsley (2008). The present paper complements these
papers and those which they cite. The D.C. global atmospheric electric circuit has been
considered in the context of the changing climate of planet Earth by Williams (1992),
Price (1993), Tinsley et al. (1994), Gray et al. (2010) and Siingh et al. (2011).
When considering a subject in physics, and its mathematical representation, the treatment
conventionally begins simply, using linear theory. However, as the subject develops, it is
usually appreciated that a more complex representation is appropriate. At larger
amplitudes nonlinearities can arise and the system may even become chaotic on the small
scale, or on the local, moderate (regional) or largest (global) scales. An important
characteristic of such complex systems is that they simultaneously need to consider a
wide range of spatial scales and temporal scales. Up to the present, the treatment of
atmospheric electricity has remained linear, whereas nowadays climate studies often
involve multi-scale and nonlinear behaviour (Donner et al. 2009; Slingo et al. 2009;
Palmer and Williams 2010). The global electric circuit may be involved in climate
change via non-linear electrical effects on cloud microphysical processes (Aplin et al.
2008; Carslaw 2009; Harrison and Ambaum 2008, 2010; Nicoll and Harrison 2010), as
discussed later in this paper.
Fig. 1 shows the huge range of horizontal and vertical scales involved in the diverse
phenomena and processes of interest which occur in the atmosphere and in the near-Earth
space environment (Rycroft 2010). The horizontal scale extends over 18 orders of
magnitude, and the vertical scale over 12 orders. At the Earth’s surface, point discharge
currents (Chalmers 1962; Ette and Utah 1973; Marcz and Bencze 1998) emanate from
sharp-ended vertical conductors, such as grass and the spiky needles of coniferous trees,
which have scales of millimetre size. Pointed hills and ridges have scales of kilometres to
hundreds of kilometres, and the oceans longer scales, although sea spray has dimensions
of millimetres.
In the lowest part of the atmosphere over continental surfaces, ionisation is generated
from the escape of radon isotopes (Harrison et al. 2010) and by galactic cosmic rays
arriving from beyond the solar system (Bazilevskaya et al. 2000, 2008; Velinov et al.
2009). In clean air, water vapour condenses onto these ions to form cluster ions ~ 1 nm in
size (Aplin et al. 2008, Rycroft et al. 2008). Some cluster ions are removed by ion-ion
recombination and others are lost to aerosol particles (Harrison and Tammet 2008,

3
Hirsikko et al. 2011). In some circumstances in which condensable vapours such as
sulphuric acid are abundant, the cluster ions may eventually grow into ~ 100 nm sized
cloud condensation nuclei (CCN) onto which cloud droplets can form; raindrops, which
are up to three orders of magnitude larger, result from coalescence of the cloud droplets.
It is worth mentioning here that Enghoff et al. (2011) have recently studied sulphuric acid
aerosol nucleation in an atmospheric pressure reaction vessel where a 580 MeV electron
beam has ionised the gas. They found clear evidence for an ion-induced effect on aerosol
nucleation under conditions which resemble those of the Earth’s atmosphere.
Also shown in Fig. 1 are low level stratiform clouds (SCs) such as stratocumulus, where
the electric charges at the cloud edges are important (Nicoll and Harrison 2009, 2010),
and thunderstorm cells (TCs) which can grow into large thunderstorms (Williams and
Yair 2006), termed mesoscale convective systems (MCSs). Thunderstorms produce
lightning discharges which radiate electromagnetic waves across a broad range of
frequencies; these constitute the A.C. part of the global electric circuit, discussed later.
Above large thunderstorms transient luminous events (TLEs), such as sprites, elves and
blue jets (Fullekrug et al. 2006), may occur just below the ionosphere. The lower
ionosphere responds to activity from above, in the form of wave-particle interactions
between whistler-mode waves from lightning and energetic electrons trapped in the
magnetosphere (Rycroft 2010); extra ionization is then produced in the lowest ionosphere
(Rodger et al. 2001). The magnetosphere is stimulated by activity on the Sun, that
information travelling through interplanetary space in the form of coronal mass ejections
(CMEs); these phenomena are generically termed space weather (Bothmer and Daglis
2007). Such phenomena (Rycroft 2010) are important in terms of possible damage to
satellites and other assets in space and to humans aboard spacecraft.
Fig. 2 shows the broad range of temporal scales that are involved in the many phenomena
of importance. On the shortest time scales of microseconds are electrical discharge
phenomena. These are leader processes which occur as a lightning discharge progresses
in steps from a thundercloud towards the ground, the cloud-to-ground (CG) return stroke
which is a large (~ 30 kA) current to the cloud, and intra-cloud (IC) discharges (Rakov
and Uman 2003). Lightning radiates all radio frequencies from MHz (associated with
leader processes) to ~ 10 kHz (where the spectrum peaks (Smith et al. 2010)) to “slow
tails” (~ 100 Hz, Mullayarov et al. 2010), and to the longest wavelength electromagnetic
waves occurring in the Earth’s environment (~ 10 Hz). These latter waves excite
Schumann resonances of the spherical shell cavity between the good conducting Earth
and ionosphere, the fundamental of which is at 8 Hz (Williams 1992; Price et al. 2007;
Simoes et al. 2008; Yang et al. 2009; Shvets et al. 2010; Nickolaenko et al. 2010;
Golkowski et al. 2011).
A few stations around the world can record the radiation of various frequencies generated
by lightning and by sprites in order to find their location. Williams et al. (2010) did this
for radio signals produced over Africa, investigating their dependence on the charge
moment changes of the parent lightning. Whitley et al. (2011) have recently shown that
with four stations around the world sources can be geolocated to an accuracy of ~ 10 km,

Citations
More filters
Journal ArticleDOI
TL;DR: In this article, the authors identified future research areas in relation to Task Group 4 of the Climate and Weather of the Sun-Earth System (CAWSES-II) programme, 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.

141 citations


Cites background from "Electromagnetic Atmosphere-Plasma C..."

  • ...3(b); the topic is covered briefly in Section 3.1 of Rycroft and Harrison (2011)....

    [...]

  • ...Combining these data sets with optical lightning counts made from space (see Christian et al., 2003; Rycroft and Harrison, 2011), Mach et al. (2011) concluded that the mean contributions to the global electric circuit from land and ocean thunderstorms are 1.1 kA and 0.7 kA, respectively....

    [...]

  • ...…mass ejections (CMEs) and other space weather effects, (e) auroral activity and (f) gigantic jets (as discussed briefly, but with more references, in Rycroft and Harrison (2011)), (viii) the effects of gigantic jets (see Chou et al., 2010) on the global circuit—they short circuit the 5% of the…...

    [...]

  • ...The topic of the global atmospheric electric circuit has been recently reviewed by Rycroft and Harrison (2011), which thoroughly discussed the background to the subject, and gave a large number of key references to the literature going back more than a hundred years....

    [...]

  • ...3(a) (Rycroft and Harrison, 2011)....

    [...]

Journal ArticleDOI
TL;DR: A review of research work on the global electrical circuit (GEC) is presented in this paper, with an emphasis on the period since the last International Conference on Atmospheric Electricity (ICAE) in Beijing, China in 2007.

109 citations

Journal ArticleDOI
TL;DR: In this paper, the temporal and spatial development of sprite-producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system (MCS) on 29 June 2011 near the Oklahoma Lightning Mapping Array (LMA).
Abstract: [1] The temporal and spatial development of sprite-producing lightning flashes is examined with coordinated observations over an asymmetric mesoscale convective system (MCS) on 29 June 2011 near the Oklahoma Lightning Mapping Array (LMA). Sprites produced by a total of 26 lightning flashes were observed simultaneously on video from Bennett, Colorado and Hawley, Texas, enabling a triangulation of sprites in comparison with temporal development of parent lightning (in particular, negatively charged stepped leaders) in three-dimensional space. In general, prompt sprites produced within 20 ms after the causative stroke are less horizontally displaced (typically 30 km). However, both prompt and delayed sprites are usually centered within 30 km of the geometric center of relevant LMA sources (with affinity to negative stepped leaders) during the prior 100 ms interval. Multiple sprites appearing as dancing/jumping events associated with a single lightning flash could be produced either by distinct strokes of the flash, by a single stroke through a series of current surges superposed on an intense continuing current, or by both. Our observations imply that sprites elongated in one direction are sometimes linked to in-cloud leader structure with the same elongation, and sprites that were more symmetric were produced above the progression of multiple negative leaders. This suggests that the large-scale structure of sprites could be affected by the in-cloud geometry of positive charge removal. Based on an expanded dataset of 39 sprite-parent flashes by including more sprites recorded by one single camera over the same MCS, the altitude (above mean sea level, MSL) of positively charged cloud region tapped by sprite-producing strokes declined gradually from ~10 km MSL (−35°C) to around 6 km MSL (−10°C) as the MCS evolved through the mature stage. On average, the positive charge removal by causative strokes of sprites observed on 29 June is centered at 3.6 km above the freezing level or at 7.9 km above ground level.

82 citations


Cites background from "Electromagnetic Atmosphere-Plasma C..."

  • ...[2] Understanding of lightning effects in near Earth’s space has progressed substantially by studying associated transient luminous events (TLEs) in the mesosphere [Rodger, 1999; Pasko et al., 2011; Rycroft and Harrison, 2011]....

    [...]

Journal ArticleDOI
TL;DR: The basic structure and dynamics of the primary electric current systems in the Earth's magnetosphere is presented and discussed in this paper, and the implications of understanding magnetospheric current systems are discussed, including paths forward for new investigations with the robust set of observations being produced by the numerous scientific and commercial satellites orbiting Earth.
Abstract: The basic structure and dynamics of the primary electric current systems in the Earth's magnetosphere is presented and discussed. In geophysics, the word current is used to describe the flow of mass from one location to another, and its analogue of electric current is a flow of charge from one place to another. An electric current is associated with a magnetic field, and they combine with the Earth's internally-generated dipolar magnetic field to form the topology of the magnetosphere. The concept of an electric current is reviewed and compared with other approaches to investigating the physics of the magnetosphere. The implications of understanding magnetospheric current systems is discussed, including paths forward for new investigations with the robust set of observations being produced by the numerous scientific and commercial satellites orbiting Earth.

82 citations

References
More filters
Book
28 Jun 2010
TL;DR: In this paper, the authors present a model of lightning and its effects in the atmosphere and the distant lightning electromagnetic environment: atmospherics, Schumann resonances and whistlers.
Abstract: Preface 1. Introduction 2. Incidence of lightning 3. Electrical structure of lightning-producing clouds 4. Downward negative lightning discharges to ground 5. Positive and bipolar lightning discharges to ground 6. Upward lightning initiated by ground-based objects 7. Artificial initiation (triggering) of lightning by ground-based activity 8. Winter lightning in Japan 9. Cloud discharges 10. Lightning and airborne vehicles 11. Thunder 12. Modelling of lightning processes 13. The distant lightning electromagnetic environment: atmospherics, Schumann resonances and whistlers 14. Lightning effects in the middle and upper atmosphere 15. Lightning effects on the chemistry of the atmosphere 16. Extraterrestrial lightning 17. Lightning locating systems 18. Deleterious effects of lightning and protective techniques 19. Lightning hazards to humans and animals 20. Ball lightning, bead lightning, and other unusual discharges Appendix. books on lightning and related subjects Subjects Index.

1,715 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the OTD measurements to construct lightning climatology maps that demonstrate the geographical and seasonal distribution of lightning activity for the globe, and found that lightning occurs mainly over land areas, with an average land/ocean ratio of 10:1.
Abstract: of uncertainty for the OTD global totals represents primarily the uncertainty (and variability) in the flash detection efficiency of the instrument The OTD measurements have been used to construct lightning climatology maps that demonstrate the geographical and seasonal distribution of lightning activity for the globe An analysis of this annual lightning distribution confirms that lightning occurs mainly over land areas, with an average land/ocean ratio of 10:1 The Congo basin, which stands out year-round, shows a peak mean annual flash density of 80 fl km 2 yr 1 in Rwanda, and includes an area of over 3 million km 2 exhibiting flash densities greater than 30 fl km 2 yr 1 (the flash density of central Florida) Lightning is predominant in the northern Atlantic and western Pacific Ocean basins year-round where instability is produced from cold air passing over warm ocean water Lightning is less frequent in the eastern tropical Pacific and Indian Ocean basins where the air mass is warmer A dominant Northern Hemisphere summer peak occurs in the annual cycle, and evidence is found for a tropically driven semiannual cycle INDEX TERMS: 3304 Meteorology and Atmospheric Dynamics: Atmospheric electricity; 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3324 Meteorology and Atmospheric Dynamics: Lightning; 3394 Meteorology and Atmospheric Dynamics: Instruments and techniques;

1,117 citations

Journal ArticleDOI
25 Aug 2011-Nature
TL;DR: First results from the CLOUD experiment at CERN are presented, finding that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100–1,000-fold and ion-induced binary nucleation of H2SO4–H2O can occur in the mid-troposphere but is negligible in the boundary layer.
Abstract: Atmospheric aerosols exert an important influence on climate through their effects on stratiform cloud albedo and lifetime and the invigoration of convective storms. Model calculations suggest that almost half of the global cloud condensation nuclei in the atmospheric boundary layer may originate from the nucleation of aerosols from trace condensable vapours, although the sensitivity of the number of cloud condensation nuclei to changes of nucleation rate may be small. Despite extensive research, fundamental questions remain about the nucleation rate of sulphuric acid particles and the mechanisms responsible, including the roles of galactic cosmic rays and other chemical species such as ammonia. Here we present the first results from the CLOUD experiment at CERN. We find that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100–1,000-fold. Time-resolved molecular measurements reveal that nucleation proceeds by a base-stabilization mechanism involving the stepwise accretion of ammonia molecules. Ions increase the nucleation rate by an additional factor of between two and more than ten at ground-level galactic-cosmic-ray intensities, provided that the nucleation rate lies below the limiting ion-pair production rate. We find that ion-induced binary nucleation of H_(2)SO_(4)–H_(2)O can occur in the mid-troposphere but is negligible in the boundary layer. However, even with the large enhancements in rate due to ammonia and ions, atmospheric concentrations of ammonia and sulphuric acid are insufficient to account for observed boundary-layer nucleation.

1,071 citations

Journal ArticleDOI
TL;DR: In this paper, the development of this review article has evolved from work carried out by an international team of the International Space Science Institute (ISSI), Bern, Switzerland, and from work performed under the auspices of Scientific Committee on Solar Terrestrial Physics (SCOSTEP) regarding climate and weather of the Sun-Earth System (CAWSES).
Abstract: The development of this review article has evolved from work carried out by an international team of the International Space Science Institute (ISSI), Bern, Switzerland, and from work carried out under the auspices of Scientific Committee on Solar Terrestrial Physics (SCOSTEP) Climate and Weather of the Sun‐Earth System (CAWSES‐1). The support of ISSI in providing workshop and meeting facilities is acknowledged, especially support from Y. Calisesi and V. Manno. SCOSTEP is acknowledged for kindly providing financial assistance to allow the paper to be published under an open access policy. L.J.G. was supported by the UK Natural Environment Research Council (NERC) through their National Centre for Atmospheric Research (NCAS) Climate program. K.M. was supported by a Marie Curie International Outgoing Fellowship within the 6th European Community Framework Programme. J.L. acknowledges support by the EU/FP7 program Assessing Climate Impacts on the Quantity and Quality of Water (ACQWA, 212250) and from the DFG Project Precipitation in the Past Millennium in Europe (PRIME) within the Priority Program INTERDYNAMIK. L.H. acknowledges support from the U.S. NASA Living With a Star program. G.M. acknowledges support from the Office of Science (BER), U.S. Department of Energy, Cooperative Agreement DE‐FC02‐97ER62402, and the National Science Foundation. We also wish to thank Karin Labitzke and Markus Kunze for supplying an updated Figure 13, Andrew Heaps for technical support, and Paul Dickinson for editorial support. Part of the research was carried out under the SPP CAWSES funded by GFG. J.B. was financially supported by NCCR Climate–Swiss Climate Research.

1,045 citations


"Electromagnetic Atmosphere-Plasma C..." refers background in this paper

  • ...The D.C. global atmospheric electric circuit has been considered in the context of the changing climate of planet Earth by Williams (1992), Price (1993), Tinsley et al. (1994), Gray et al. (2010) and Siingh et al. (2011)....

    [...]

Book
01 Jan 1969
TL;DR: In this article, a book on ionospheric physics covering neutral atmosphere and photochemical processes, morphology, phenomena, geomagnetism, storms and geomagnetic storms is presented.
Abstract: Book on ionospheric physics covering neutral atmosphere, ionospheric measurements, photochemical processes, morphology, phenomena, geomagnetism, storms, etc

981 citations


"Electromagnetic Atmosphere-Plasma C..." refers background in this paper

  • ...It is even true through the ionospheric dynamo field region at ~ 100 to ~ 130 km altitude (Rishbeth and Garriott 1969; Kelley 2009)....

    [...]

Frequently Asked Questions (16)
Q1. What are the contributions in "Electromagnetic atmosphere-plasma coupling: the global atmospheric electric 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. Finally, some directions for future research in the subject are suggested. 

The contributions to the global circuit made by rain/shower clouds are 0.22 kA for ocean storms and 0.04 kA for storms over the land. 

Carlson et al. (2009, 2010) suggest that TGF production is associated with current pulses (~ 1 ms) in lightning leader channels and runaway processes, and they have produced promising simulations. 

Other than cosmic ray step changes, an alternative method of identifying cloud and global circuit responses to cosmic rays is to use spectral analysis methods to identify periodicities which are unique to cosmic rays. 

The global electric circuit may be involved in climate change via non-linear electrical effects on cloud microphysical processes (Aplin et al. 

In the troposphere the cosmic ray flux at high latitudes is typically ~ 20% larger in solar minimum conditions that near solar maximum; it is ~ 10% larger at 33 degrees magnetic latitude. 

The difficulty in determining the sensitivity of clouds to such changes, empirically at least, is the need to remove the substantial natural variability commonly present in cloud and clearly evident from satellite images of planet Earth. 

The ion-pair production rate at different altitudes varies by ~ 2.5 as one moves from the geomagnetic equator to the magnetic poles. 

Most of the resistance is near the surface, due to the exponential distribution of the atmospheric density with a scale height H of ~ 7 km. 

Inside an active thundercloud, the electrical conductivity is not well-constrained, but observations discussed by Rycroft et al. (2007) show that it is at least a factor of six less than its value in the clear air surrounding the thundercloud; Rycroft et al. (2007, 2008) showed values for a model thundercloud. 

If the conductivity varies as the square root of the ion production rate (Rycroft et al. 2008), as expected in marine air where there is no radon contribution, nor appreciable ion removal by aerosol, it will be ~ 6% less near solar maximum. 

These are leader processes which occur as a lightning discharge progresses in steps from a thundercloud towards the ground, the cloud-to-ground (CG) return stroke which is a large (~ 30 kA) current to the cloud, and intra-cloud (IC) discharges (Rakov and Uman 2003). 

This modulation of the fair weather current density by solar activity and associated cosmic ray changes provides a potential mechanism whereby the properties of clouds atlow heights in fair weather regions could be changed by the currents passing through them, with implications, currently not quantified, for changes in weather and climate as a result. 

Mechanical (i.e. acoustic or gravity wave, or tidal, mechanisms to account for such effects have been considered by Hayakawa (2011). 

This is believed to be created as upward-going Bremsstrahlung radiation when the electrons collide with the nuclei of atmospheric atoms. 

A very recent paper by Mach et al. (2011) has, for the first time, used experimental data from aircraft and satellites to deduce that thunderstorms over the land contribute 1.1 kA to the global circuit and, over the oceans, 0.7 kA.