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A new remote sensing method for the Earth's magnetosphere is suggested. The method is based on the parametric reflection of whistler mode waves from the level in the magnetosphere where a whistler wave frequency coincides with the local lower hybrid resonance frequency. In this region a sufficiently intense whistler signal generates two electrostatic plasma waves which can produce a reflected whistler wave. The known localization of the whistler reflection leads us to suggest a new method of electron density measurements in the magnetosphere, using a grid of frequencies from a powerful ground-based VLF transmitter. Parametric reflection of whistler signals in the magnetosphere can appear from naturally occurring short-scale low frequency turbulence (ion sound or ion cyclotron waves). In this case, using this new method we can obtain important information about this turbulence. Some experimental data which demonstrate the appearance of VLF echo signals from the magnetosphere with anomalously small group time delays are discussed from this point of view.

A quantitative theory of the generation of ELF/VLF signals, which are caused by the ionospheric demodulation of modulated signals from broadcasting MF/HF transmitters, is developed. Two cases are considered when the ionospheric current, modulated by broadcasting signals, is a one-dimensional linear current (the polar electrojet), and when it is an extended two-dimensional current sheet. It is shown that the main demodulation effect is caused by the formation of an ionospheric travelling wave antenna. In the case of the polar electrojet, this antenna radiates ELF/VLF waves in two directions, one of which coincides with the line connecting the broadcasting transmitter with the ELF/VLF receiver, and the other one is in a direction which is the mirror image of this line relative to the current direction. In this case the polarisation of the ELF/VLF magnetic field component varies widely. In the case of the extended ionospheric current, the demodulation takes place along the line connecting the MF/HF transmitter with the ELF/VLF receiver, and the horizontal ELF/VLF magnetic field component is normal to this line. Amplitude and phase distortions in the ELF/VLF signal are absent below a frequency ⪅ 1 kHz and appear above ∼ 1 kHz. Quantitative estimates of the amplitude of the ELF/VLF signal give a value ∼0.15pT which is close to the experimentally observed value.

The decomposition of chloroflurocarbons (CFCs) in the troposphere with the aid of natural lightning energy is calculated. The scheme is to use the reaction of dissociative attachment of an electron to a CFC molecule, producing Cl − . An upper limit to the decomposition rate due only to natural lightning discharges is found to be ~900 kg in one year, which is only about one-millionth of the annual production rate of CFC molecules worldwide. A method to increase the efficiency of decomposition is proposed, which uses negative ion drift under the static electric field near the thundercloud. The energy consumption to decompose one CFC molecule is found to be 1 × 10 7 eV at a minimum, which leads to the maximum decomposition rate of 4 × 10 6 kg/year, almost 0.5% of the annual production rate, which, unfortunately, is still not significant.

The ISU's Master of Space Studies (MSS) programme is a new, unique and interdisciplinary postgraduate course of eleven months duration. It is designed for those who will lead and work in the international space programmes of the next century. It considers not only many aspects of the space sciences and their applications, but also most engineering, business, management, policy and law issues relevant to the activities of both space agencies and space industries. In the first term, fundamental issues are covered, and MSS participants from many countries around the world select some topics of their choice; within the sciences, attention is focused on basic physics, the space environment and life sciences. In the second and third terms, advanced subjects ranging from astronomy to planetary sciences, microgravity sciences, telecommunications and remote sensing of the Earth's surface and atmosphere are available. For two months in the second term, each participant carries out a project at an affiliate campus or an associated institution, and prepares a written report on this. Throughout the year, all participants play an active part in a team design project on a chosen theme; a substantial written report is prepared, and the results are also presented orally. Thus the aim of the MSS programme is to educate space generalists, yet generalists who are knowledgeable in all the relevant disciplines, including science.

International audience; The French government has committed to launch the satellite TARANIS to study transient coupling processes between the Earth's atmosphere and near-Earth space. The prime objective of TARANIS is to detect energetic charged particles and hard radiation emanating from thunderclouds. The British Nobel prize winner C.T.R. Wilson predicted lightning discharges from the top of thunderclouds into space almost a century ago. However, new experiments have only recently confirmed energetic discharge processes which transfer energy from the top of thunderclouds into the upper atmosphere and near-Earth space; they are now denoted as transient luminous events, terrestrial gamma-ray flashes and relativistic electron beams. This meeting report builds on the current state of scientific knowledge on the physics of plasmas in the laboratory and naturally occurring plasmas in the Earth's atmosphere to propose areas of future research. The report specifically reflects presentations delivered by the members of a novel Franco-British collaboration during a meeting at the French Embassy in London held in November 2011. The scientific subjects of the report tackle ionization processes leading to electrical discharge processes, observations of transient luminous events, electromagnetic emissions, energetic charged particles and their impact on the Earth's atmosphere. The importance of future research in this area for science and society, and towards spacecraft protection, is emphasized.

It is shown that quasi-monochromatic whistler waves (wavelets) can be caused by the strong cyclotron instability, stimulated by hiss emissions. The hiss, generated by the cyclotron instability of an anisotropic smooth energetic electron distribution, creates a step-like deformation of the distribution function at the boundary between resonant and nonresonant electrons. This deformation leads to the strong amplification of the wavelet whose frequency corresponds to that for cyclotron resonance with electrons at the step. Analytical calculations for this amplification have been made using the rigorous theory of the cyclotron instability in an inhomogeneous magnetic field. The wave amplification can be 2 orders of magnitude greater than that for a smooth distribution function. A self-consistent computational analysis of the cyclotron instability is developed on the basis of quasi-linear theory. This confirms both the formation of the step-like deformation of the distribution function and the wavelet generation.

The contributions made by Ken Bullough (1927–1994) to space physics and conflict research are briefly summarised. This brief obituary and review of his scientific contributions is supplemented by a complete list of his publications.

Geomagnetic field variations and electromagnetic waves of different frequencies are ever present in the Earth's environment in which the Earth's fauna and flora have evolved and live. These waves are a very useful tool for studying and exploring the physics of plasma processes occurring in the magnetosphere and ionosphere. Here we present ground-based observations of natural electromagnetic emissions of magnetospheric origin at very low frequency (VLF, 3–30 kHz), which are neither heard nor seen in their spectrograms because they are hidden by strong impulsive signals (sferics) originating in lightning discharges. After filtering out the sferics, peculiar emissions are revealed in these digital recordings, made in Northern Finland, at unusually high frequencies in the VLF band. These recently revealed emissions, which are observed for several hours almost every day in winter, contain short (~1–3 min) burst-like structures at frequencies above 4–6 kHz, even up to 15 kHz; fine structure on the 1 s time scale is also prevalent. It seems that these whistler mode emissions are generated deep inside the magnetosphere, but the detailed nature, generation region and propagation behaviour of these newly discovered high latitude VLF emissions remain unknown; however, further research on them may shed new light on wave-particle interactions occurring in the Earth's radiation belts.

[1] The first measurements from a new globally distributed extremely low frequency magnetic field sensor network are presented. The recorded data demonstrate that the system observed lightning with continuing currents on a global scale with a timing accuracy of ∼30 μs. The network consists of four state of the art instruments at sites in Scotland, the United States, South Africa and Australia. Each instrument records the two horizontal magnetic field components (Bx and By) with a sampling frequency of 4 kHz. The first results show the typical electromagnetic signature of a transient airglow increase (sprite) above a thunderstorm in southern Europe which is simultaneously imaged with a video camera. A similar electromagnetic signature is recorded from a lightning discharge in central Africa, and it is also attributed to a sprite occurrence. Studies using this global network should advance lightning and sprite research considerably.

We review the global circuit driven by thunderstorms and electrified rain clouds. With the ionosphere at an equipotential of ∼ +250kV with respect to the Earth, the load in the circuit is the fair weather atmosphere; its conductivity is mainly determined by the flux of galactic cosmic rays. The circuit exhibits variability in both space and time by more than fifteen orders of magnitude. We discuss results produced by a new electrical engineering analogue model of the circuit constructed using the PSpice software package. Finally, we consider several interesting new experimental observations relating to the topic.

[1] A quantitative model of the global atmospheric electric circuit has been constructed using the PSpice electrical engineering software package. Currents (~1 kA) above thunderstorms and electrified rain/shower clouds raise the potential of the ionosphere (presumed to be an equipotential surface at 80 km altitude) to ~250 kV with respect to the Earth's surface. The circuit is completed by currents flowing down through the fair-weather atmosphere in the land/sea surface and up to the cloud systems. Using a model for the atmospheric conductivity profile, the effects of both negative and positive cloud-to-ground (CG) lightning discharges on the ionospheric potential have been estimated. A large positive CG discharge creates an electric field that exceeds the breakdown field from the ionosphere down to ~74 km, thereby forming a halo, a column sprite, and some milliseconds later, from ~67 km down to ~55 km at ~60 ms after the discharge, a "carrot" sprite. Estimates are made of the return stroke current and the thundercloud charge moment change of a +CG discharge required to exceed the threshold breakdown field, or the threshold field for creating and sustaining negative or positive streamers. The values for breakdown at 80 km altitude are 35 kA and 350 C.km, (Coulomb.kilometers), respectively, and those at 70 km altitude are 45 kA and 360 C.km, respectively. The different temporal and spatial developments of the mesospheric electric field distinguishing between column and carrot sprites agree with the latest deductions from recent observations. The current flowing in the highly conducting sprite reduces the ionospheric potential by ~1 V.

[1] Magnetospheric line radiation (MLR) events are electromagnetic waves in the frequency range between about 1 and 8 kHz that, when presented as a frequency-time spectrogram, take the form of nearly parallel and clearly defined lines, which sometimes drift slightly in frequency. They have been observed both by satellites and ground-based instruments, but their origin is still unclear. We present a survey of these MLR waves observed by the DEMETER spacecraft (at an altitude of about 700 km). Three years of VLF Survey mode data were manually searched for MLR events, creating the largest event satellite database of about 650 events, which was then used to investigate the wave properties and geographical occurrence. Finally, the most favorable geomagnetic conditions (Kp and Dst indices) for the occurrence of MLR events have been found. It is shown that MLR events occur mostly at L > 2 (upper limit is given by a limitation of the spacecraft), they occur primarily inside the plasmasphere, and there is a lower number of events occurring over the Atlantic Ocean than elsewhere on the globe. The MLR events occur more often during the day and usually during, or after, periods of higher magnetic activity. Their frequencies usually lay between about 2 and 6 kHz, with the total frequency bandwidth of an observation being below 2 kHz in the majority of cases. Moreover, it is shown that the longitudinal dimensions of the MLR events can be as large as 100° and they can last for up to a few hours. Finally, we discuss a possibility that MLR events may be triggered by power line harmonic radiation (PLHR) and we report an event supporting this hypothesis.

The AGILE Satellite [8] [9], launched the 23rd April 2007, is an italian mission devoted to high energy gamma‐ray astrophysics in the 30 MeV–50 GeV range, with a window in the hard‐X domain 18–60 keV. One of the on‐board detectors, the Mini‐Calorimeter (MCAL), was also designed to work as all sky transient monitor in the energy range 0.33–100 MeV. Though the main purpose of MCAL is the detection of cosmological Gamma‐Ray‐Bursts (GRB), MCAL detected transient events with a very brief duration, few msec, that does not match timing and spectral features of known cosmic GRB. These events more likely agree with the features of typical Terrestrial Gamma‐Ray Flashes as described in the literature and previously detected by the BATSE instrument onboard the Compton Gamma Ray Observatory and the RHESSI satellite. The characteristics of the detected TGF candidate events, as well as their geographical distribution will be presented and discussed.

This paper deals with the rare high intensity electromagnetic pulses associated with earthquakes, whose spectrum signature differs from that of atmospherics produced by lightning discharges. On the basis of actual data records, cases of the generation of anomalous seismo‐electromagnetic emissions are described. These natural sub‐millisecond electromagnetic pulses were associated with the passage of seismic waves from earthquakes to Moscow, the place where the electromagnetic field observations were made. Space‐time coupling has been revealed between exact seismic waves from the earthquakes, lightning triggering and Transient Luminous Events triggering.

More than one hundred different transient luminous events (TLEs) i.e. sprites, sprite halos and one blue jet‐like emission have been observed in Central Europe at a new optical observation site in Sopron, Hungary, during the summer of 2007. The recently developed LINET lightning location network supplied information about the lightning activity in the region. This was the first time that data from this network was used to support TLE observations and to help interpret the results. TLE‐triggering lightning flashes were identified by their radiation in the ELF (Extremely Low Frequency) band, appearing as coherent transient signals with enhanced amplitudes in the monitored field components of the atmospheric electromagnetic field at NCK station in Hungary. Individual lightning flashes could be associated with 92% of the optically observed events. No ELF transient could be associated with the blue jet‐like emission, and for one sprite neither a corresponding transient nor any causative lightning flash could be found. Positive polarity lightning flashes were associated with almost all TLEs. In one exceptional case, a negative polarity parent lightning flash was associated with an ELF transient indicating a positive polarity source. In the present paper, the new optical observation site is introduced, the method of observation is described, and the potential role of LINET is discussed in connection with TLE research.

Fingers from ionization fronts for a hydrodynamic plasma model result from a balance between impact ionization and electron diffusion in a non‐attaching gas. An analytical estimation of the size of the fingers and its dependence on both the electric field and electron diffusion coefficient can be done when the diffusion is low and the electric field is strong.

We give a brief overview of our present understanding of the global circuit formed by the atmosphere, the ionosphere and the solid and ocean surface of the Earth. The circuit is driven by currents (∼1 kA) above both thunderstorms and electrified shower clouds up to the ionosphere, which is presumed to be an equipotential surface (∼250 kV with respect to the Earth). This large scale circuit is completed by currents (∼2 pA/m2) flowing down through the fair weather atmosphere to the Earth’s surface and up into the atmosphere below the electrically active clouds. Using a realistic profile of the atmospheric electric conductivity, we have generated a model of this equivalent circuit using the PSpice electrical engineering software package. The effects of model lightning discharges on the circuit have been estimated numerically. Model sprites exhibiting mesospheric discharge processes have been constructed, first for negative cloud‐to‐ground discharges (−CGs), then for discharges transferring positive charge to...

We report observations of lightning‐induced transient emissions (LITEs) in or below the OH airglow layer observed from the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) onboard the FORMOSAT‐II satellite. The ISUAL team conducted a nine‐day campaign in January 2007 using both the broadband and narrowband filters on the CCD imager. It is found that LITEs occur more frequently in the OH airglow layer than below. It is also found that the observations of LITEs below the OH airglow layer by the narrow‐band filter are rare. The observations of LITEs by the narrowband filter are the first of its kind in existence. Our data analysis shows that there is a significant intensity increase in the OH airglow layer when there is lightning and a residual intensity increase post the lightning activity. We propose that LITEs in the OH airglow layer could be due to OH species.

Calibrated measurements of TLE radiances are required for understanding the processes occurring at various altitudes and in order to map the spatial and temporal evolution of the optical emissions. We present a procedure for calculating the radiance of TLEs, based on observations with a calibrated Watec 902H2 Ultimate CCD camera. During the ILAN winter sprite campaign we measured the brightness of TLEs in the vicinity of Israel and the eastern Mediterranean. Calibration setup, image analysis and preliminary results are discussed.

In Russia several space missions are now planned to study transient luminous events in the atmosphere and high energy charged particles at satellite altitudes. The experimental goal is to investigate the origin of the high energy electrons and gamma‐ray quanta for specific transient luminous events (TLEs) and their role in the ionosphere‐magnetosphere system. Simultaneous measurements of electrons at the orbit of the satellite and TLE atmospheric radiation in many wavelength bands will be performed in two missions, Tatiana‐2 and RELEC. In the TUS mission UV transient event detection will be accompanied by measurements of the weak UV emission from the “seed” electrons of extensive air showers of extremely high primary energies.

Detectors on the “Universitetsky‐Tatiana” satellite measured a smoothly varying intensity of UV radiation from the night‐time atmosphere in the nadir direction and the intensity of the energetic electron flux at the orbit. At high latitudes the UV intensity in the auroral oval is interpreted as being due to electrons penetrating into the atmosphere. At middle latitudes the UV intensity is an order of magnitude less and more data are needed to reveal the origin of this radiation. Millisecond flashes of UV radiation were observed. The flashes’ energy, temporal profile and global distribution are similar to these parameters for Transient Luminous Events (TLEs). These studies will be continued aboard the next satellite “Tatiana‐2”.

High‐altitude discharges driven by runaway electron avalanches were simulated for moderate or even small thundercloud dipole moments, and the characteristics of the terrestrial γ‐ray and photo‐neutron flashes were calculated. The γ‐ray numbers and spectra fit observational data obtained from satellites. The calculated neutron numbers are large enough for detection by satellites in low Earth orbit.

Terrestrial gamma‐ray flash (TGF) emissions are predicted to be accompanied by energetic electron emissions. These electrons have been suggested to explain several anomalous TGF observations by the RHESSI and BATSE spacecraft. These electrons additionally provide a new window for study of TGFs as they carry additional information about the source through their pitch angle / arrival time distributions and confinement by the geomagnetic field. This information could prove very useful for analysis of TGF source mechanisms.We present results of simulations of electron and photon emissions and describe the implications of these results for inferences about the TGF source. We also present the results of a search of data from the SAMPEX satellite for these electrons and discuss in particular two events with multiple strong pulses of electrons.

We study the “local” distribution of lightning activity on the Earth calculated from Extremely Low Frequency (ELF) magnetic field variations. Lightning generates strong electromagnetic impulses recorded in the ELF band as short signal spikes. Using two perpendicular magnetic antennas at our Hylaty station, we calculate the azimuths of the sources of such spikes. These ELF data are compared with selected satellite measurements available on NASA and BADC web centres. For the winter period January 8 to 9, 2006, analysed in detail, a large cyclone was observed over the Mediterranean Sea (MS). The cyclone was created in the western part of the MS and then moved eastwards along the North coast of Africa. The absence of lightning activity nearer our station allowed us to compare the ELF measurements with observations of this cyclone made from the TRMM and Meteosat‐7 satellites, using Lightning Imaging Sensor observations and full Earth disk images, respectively. The analysis proves that ELF measurements can be used for on‐line monitoring of lightning activity in the vicinity of the measuring ELF station, with the radius of effective observations being more than 2000 km. This inexpensive method can easily be used in areas without other lightning monitoring systems, or it can supplement existing ones.

Based on the first four years of the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) experiment onboard the FORMOSAT‐2 satellite, ELVEs are found to be the most abundant type (∼80%) of TLEs (transient luminous events), whereas sprites and halos only combine to account for ∼20%. The distribution of sprites and halos closely resemble that of the cloud‐to‐ground lightning. However, nearly 60% of ELVEs occurred over the ocean, a feature indicating that the high peak current lightning is more abundant over the ocean. The global TLE occurrence rates are inferred to be 72, 3.7, and ∼1 events/minute, respectively, for ELVEs, halos, and sprites. Comparing with the results from the first three years of the ISUAL experiment reported by Chen et al. [1], the global occurrence rates for ELVEs and halos are higher due to the adoption of different correction factors. Using these updated TLE rates, the free electron content over an ELVE hot zone is estimated to be elevated by more than 10%. From analyzing ISUAL ...

High energy radiation from tens of keV to tens of MeV in energy, the transition region from x‐rays to gamma rays, has been observed in association with high electric fields in air in many contexts: from the ground, associated with thunderstorms and with individual flashes of natural and rocket‐triggered lightning [1, 2, 3, 4, 5, 6, 7, 8] from sparks in the laboratory [9, 10, 11, 12], from Earth orbit in the form of millisecond Terrestrial Gamma‐ray Flashes (TGFs) [13, 14], and at intermediate altitudes from aircraft and balloons [15, 16, 17, 18, 19]. The gamma radiation in all cases is almost certainly bremsstrahlung generated by the collision of accelerated electrons with nuclei in the atmosphere. The penetrating gamma‐rays can provide a mechanism for coupling between the troposphere, mesosphere, ionosphere and magnetosphere in the form of energetic particles and ionization.

An experimental Very Low Frequency (VLF) World‐Wide Lightning Location Network (WWLLN) is being developed through collaborations with research institutions across the globe. In this paper we report on the steady improvement in the Detection Efficiency (DE) of the WWLLN due to increasing station number, which led to a doubling in locations provided from 2003–2007. In addition, a new algorithm has recently been implemented which leads to DE improvements of 63%.

Sprites, jets and elves, also referred to as “Transient Luminous Events (TLEs)”, are phenomena well‐suited for educational purposes as well as for public outreach activities. This paper gives an introduction to what is meant by “Education and Public Outreach (EPO)”, and emphasizes the usefulness and effectiveness of such activities in scientific projects. In 2002 the “Coupling of Atmospheric Layers (CAL)” research training project was funded by the European Commission to study TLEs. CAL consisted of ten scientific work‐packages and two work‐packages specifically dedicated to the training and outreach program of the project. CAL is an example and inspiration of how a scientific research project can be a unique opportunity to provide EPO learning activities to both young and senior scientists.

Synoptic, long-term observational programmes provide a wide diversity of information on the solar-terrestrial environment. Such data sets are particularly valuable in certain locations, on the ground, or in space. Further, such data sets are necessary for identifying the baseline from which anthropogenic changes may occur, for characterising transient events, for placing the results of short-term experiments in context, and also for carrying out statistical analyses. Results for all of these four examples can be interpreted according to present understanding of the physics of solar-terrestrial phenomena. Inadequacies are identified and understanding is thereby improved. New hypotheses are put forward and tested; new modelling schemes and new observational techniques are devised.Some examples are presented, dealing with different physical parameters of solar, interplanetary, magnetospheric, ionospheric, thermospheric and geomagnetic phenomena. Considerations of mass, momentum and energy transfer across the magnetopause, and of energy dissipation in the polar, auroral and midlatitude upper atmosphere are emphasised, on time scales ranging from a few minutes to a century. Such studies are essential for the success of the Solar Terrestrial Energy Programme, STEP, the research aspects of which are underpinned by synoptic programmes. They will open the door to more successful predictions of the solar-terrestrial environment, an ever-developing requirement for mankind at the end of the twentieth century.

The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as "central tenets", for example, the importance of radio science in establishing the conducting upper layer. The central tenets are distinguished from additional findings that merely corroborate, or are explained by, the global circuit model. Using this analysis it is possible to specify which observations are preferable for detecting global circuits in extraterrestrial atmospheres. Schumann resonances, the extremely low frequency signals generated by excitation of the surface-ionosphere cavity by electrical discharges, are identified as the most useful single measurement of electrical activity in a planetary atmosphere. © 2008 Springer Science+Business Media B.V.

The paper reviews recent advances in studies of electric discharges in the stratosphere and mesosphere above thunderstorms, and their effects on the atmosphere. The primary focus is on the sprite discharge occurring in the mesosphere, which is the most commonly observed high altitude discharge by imaging cameras from the ground, but effects on the upper atmosphere by electromagnetic radiation from lightning are also considered. During the past few years, co-ordinated observations over Southern Europe have been made of a wide range of parameters related to sprites and their causative thunderstorms. Observations have been complemented by the modelling of processes ranging from the electric discharge to perturbations of trace gas concentrations in the upper atmosphere. Observations point to significant energy deposition by sprites in the neutral atmosphere as observed by infrasound waves detected at up to 1000 km distance, whereas elves and lightning have been shown significantly to affect ionization and heating of the lower ionosphere/mesosphere. Studies of the thunderstorm systems powering high altitude discharges show the important role of intracloud (IC) lightning in sprite generation as seen by the first simultaneous observations of IC activity, sprite activity and broadband, electromagnetic radiation in the VLF range. Simulations of sprite ignition suggest that, under certain conditions, energetic electrons in the runaway regime are generated in streamer discharges. Such electrons may be the source of X- and Gamma-rays observed in lightning, thunderstorms and the so-called Terrestrial Gamma-ray Flashes (TGFs) observed from space over thunderstorm regions. Model estimates of sprite perturbations to the global atmospheric electric circuit, trace gas concentrations and atmospheric dynamics suggest significant local perturbations, and possibly significant meso-scale effects, but negligible global effects.

[1] We present ground-based observations of banded structures (BS) in auroral hiss. This BS hiss was detected at Porojarvi station in Northern Finland, mainly in the local evening from 19 to 23 MLT, during magnetically quiet periods; half of all the events observed corresponded to AE < 50 nT. The structures, which resemble those observed by low-altitude satellites, can be related to the cyclotron resonant interaction of VLF waves at frequencies near the lower-hybrid resonance with suprathermal protons in the upper ionosphere and magnetosphere. The maximum probability distribution of band spacing for the events observed at Porojarvi is reached in the frequency range 200–300 Hz, which corresponds to proton gyrofrequencies at L ∼ 6 at altitudes of 4000–3000 km. We found that the BS hiss was detected in the region of evening-side downward field-aligned currents and rather intense precipitation of ions with energies 1–30 keV, detected by DMSP spacecraft. We propose that the observed BS hiss can be formed not only due to absorption at the proton gyroharmonics, as is usually assumed for similar structures observed onboard satellites, but also due to generation by energetic protons with an anisotropic velocity distribution.

[1] The dependence of the frequency spectrum of individual chorus elements on the position of the observation point in and near the generation region is analyzed using recent Cluster data obtained on two different geomagnetically active days. The source of night-side chorus is localized using multicomponent measurements of the wave electric and magnetic fields. We have revealed that the spectrum of the chorus elements lacks the lower frequencies at the center of the source region. One possible explanation of this effect is provided by applying the backward wave oscillator model of chorus generation to these data. According to this model, the chorus frequency is determined by the parallel velocity corresponding to a steplike deformation in the distribution function of resonant electrons. This velocity decreases during the generation of an element as the electrons move through the source region. Thus, only a part of a chorus element is visible inside this region. For the typical case of rising-tone chorus elements, the lower frequencies are generated downstream with respect to the chorus propagation and, hence, disappear as a receiver is moved upstream towards the center of the source region. Citation: Trakhtengerts, V. Y., A. G. Demekhov, E. E. Titova, B. V. Kozelov, O. Santolik, E. Macusova, D. Gurnett, J. S. Pickett, M. J. Rycroft, and D. Nunn (2007), Formation of VLF chorus frequency spectrum: Cluster data and comparison with the backward wave oscillator model, Geophys. Res. Lett., 34, L02104, doi:10.1029/2006GL027953.

Several processes acting below, in and above thunderstorms and in electrified shower clouds drive upward currents which close through the global atmospheric electric circuit. These are all simulated in a novel way using the software package PSpice. A moderate negative cloud-to-ground lightning discharge from the base of a thunderstorm increases the ionospheric potential above the thundercloud by 0.0013%. Assuming the ionosphere to be an equipotential surface, this discharge increases the current flowing in the global circuit and the fair-weather electric field also by 0.0013%. A moderate positive cloud-to-ground lightning discharge from the bottom of a thunderstorm decreases the ionospheric potential by 0.014%. Such a discharge may trigger a sprite, causing the ionospheric potential to decrease by ∼ 1 V . The time scales for the recovery of the ionospheric potential are shown to be ∼ 250 s , which is of the same order as the CR time constant for the global circuit. Knowing the global average rate of lightning discharges, it is found that negative cloud-to-ground discharges increase the ionospheric potential by only ∼ 4 % , and that positive cloud-to-ground discharges reduce it by ∼ 3 % . Thus, overall, lightning contributes only ∼ 1 % —an almost insignificant proportion—to maintaining the high potential of the ionosphere. It is concluded that the net upward current to the ionosphere due to lightning is only ∼ 20 A . Further, it is concluded that conduction and convection currents associated with “batteries” within thunderclouds and electrified shower clouds contribute essentially equally ( ∼ 500 A each) to maintaining the ionospheric potential.

This chapter introduces the fundamentals of the subject, the laboratory for which is the Earth’s atmosphere. All of its important physical properties vary significantly with altitude; its electrical conductivity varies greatly with altitude and also with latitude. The modus operandi of the global atmospheric electric circuit, in part powered by thunderstorms, is outlined. Some observations of transient luminous events, which occur above certain energetic thunderstorm systems just after a strong lightning discharge (the effect of which is usually to take positive charge to the ground), are introduced and their characteristics mentioned. Different theoretical ideas that have been put forward to explain crucial aspects of these phenomena are introduced, and some relevant numerical simulations are briefly discussed. 1.1 Basic Properties of the Atmosphere 1.1.1 Global Scale Variations (Horizontal Scale greater than 10 km) The Earth’s atmosphere is bound gravitationally to our home planet. The pressure and density of the air decrease exponentially upwards from the surface, the scale height being ∼7 km (Rycroft, 2003). This scale height varies slightly through the atmosphere because it is not isothermal. Relatively, the hottest regions of the Earth’s neutral atmosphere are at its surface (global average temperature T=288 K, pressure p=1013 hPa, density =1.2 kg/m3), at the stratopause (∼250 K, near 50 km altitude) and in the thermosphere (above ∼110 km, from where the temperature rises rapidly up to ∼2000 K at ∼300 km altitude), depending on the phase of the cycle of solar activity, with successive maxima ∼11 years apart. About half of the atmosphere resides at and below an altitude of 5 km; 90% of the atmosphere lies below an altitude of ∼15 km. The pressure of the air at 32 km altitude is ∼1% of its surface value and, at 100 km altitude, it is about one millionth of its surface value. The coldest regions are at the top of the troposphere, termed the tropopause (at 18 km

Science fiction gave us the idea of space as the final frontier. Strongly supported by the pioneers of spaceflight, this was first questioned in the 1970s. The Apollo landings on the Moon did not lead to a permanent human presence on our satellite, the environment of even the most Earth-like planet (Mars) turned out to be more hostile, and the technical difficulties and the cost of spaceflight were worse than expected. So humankind seemed for ever to be bound to its own planet. These rather pessimistic views are re-examined here, in the light of recent technological advances, scientific discoveries and new perspectives. It is suggested that they result from a lack of vision. Thus the ‘final frontier’ myth is found still to hold, but with a much more stretched out timetable for future space programmes that was envisaged in the 1960s. The present generation can take its first faltering steps on the path towards a spacefaring civilization, but the outcome will depend on social, political and economic issues rather than technological and scientific ones.

Recent advances in personal computer technology have led to the development of relatively low-cost software to generate high-resolution three-dimensional images. The capability both to rotate and zoom in on these images superposed on appropriate background images enables high-quality movies to be created. These developments have been used to produce realistic simulations of the International Space Station on CD-ROM. This product is described and its potentialities demonstrated. With successive launches, the ISS is gradually built up, and visualised over a rotating Earth against the star background. It is anticipated that this product’s capability will be useful when training astronauts to carry out EVAs around the ISS. Simulations inside the ISS are also very realistic. These should prove invaluable when familiarising the ISS crew with their future workplace and home. Operating procedures can be taught and perfected. “What if” scenario models can be explored and this facility should be useful when training the crew to deal with emergency situations which might arise. This CD-ROM product will also be used to make the general public more aware of, and hence enthusiastic about, the International Space Station programme.

An ISU global education program linked to the International Space Station (ISS) is proposed in this paper. The aim of this program is to improve access by the general public to the results of research carried out aboard the International Space Station and thus to receive more support for space programmes.