Radio sky mapping from satellites at very low frequencies

Wave Distribution Function (WDF) analysis is a procedure for making sky maps of the sources of natural electromagnetic waves in space plasmas, given local measurements of some or all of the three magnetic and three electric field components. The work that still needs to be done on this subject includes solving basic methodological problems, translating the solution into efficient algorithms, and embodying the algorithms in computer software. One important scientific use of WDF analysis is to identify the mode of origin of plasmaspheric hiss. Some of the data from the Japanese satellite Akebono (EXOS D) are likely to be suitable for this purpose

Low frequency seismogenic electromagnetic emissions as precursors to earthquakes and volcanic eruptions in Japan

A multipoint network was constructed in the Tokyo area for earthquake prediction using seismogenic electromagnetic emissions. The network consists of eight observation points within 50 km of each other.Each point has a digital direction-finding detector with two loop sensors tuned to 82 kHz. The output signals of the receivers are added into a digital vector composition circuit to obtain the direction angle of the source point,and this signal is telemetered to the central computer.To protect from false alarms caused by local man-made noise interference,the warning is announced only when there is a high cross-correlation between almost all detectors pointing to one small area. The mechanism of these earthquake precursors can be explained as electromagnetic emissions from the rocks around the focus when they are crushed completely by the distortion pressure. These emissions propagate along the fault plane as an EM surface wave mode and radiate from the slit antenna formed by the intersection of the fault plane and ground surface.In the last five years, we have detected impulsive noise bursts of seismogenic emissions at 82 kHz, 1.525 kHz, and 36 Hz using our multipoint detection network around the Tokyo region and Izu peninsula. This system has recorded EM signals prior to the following events: volcanic eruptions on November 15 and 2 1, 1986 at Mt. Mihara on Ohshima Island, and on July 12, 1989 in Itoh Bay in the Izu peninsula region, and also a minor earthquake on October 14, 1989 at Ohshima Island

Sferics

The properties of sferics (the electric and magnetic fields generated by electrified clouds and lightning flashes) are briefly surveyed; the source disturbance and the influence of propagation being examined. Methods of observing sferics and their meteorological implications are discussed. It is concluded that close observations of electrostatic and radiation fields are very informative, respectively, upon the charge distribution and spark processes in a cloud; that ground-level sferics stations can accurately locate the positions of individual lightning flashes and furnish valuable knowledge on the properties of the discharges; but that satellite measurements only provide general information on the level of thundery activity over large geographical regions

Automated tracking of the Florida manatee (Trichechus manatus)

The electronic, physical, biological and environmental factors involved in the automated remote tracking of the Florida manatee (Trichechus manatus) are identified. The current status of the manatee as an endangered species is provided. Brief descriptions of existing tracking and position locating systems are presented to identify the state of the art in these fields. An analysis of energy media is conducted to identify those with the highest probability of success for this application. Logistic questions such as the means of attachment and position of any equipment to be placed on the manatee are also investigated. Power sources and manateeborne electronics encapsulation techniques are studied and the results of a compter generated DF network analysis are summarized

Electro-Magnetic Earthquake Bursts and Critical Rupture of Peroxy Bond Networks in Rocks

We propose a mechanism for the low frequency electromagnetic emissions and other electromagnetic phenomena which have been associated with earthquakes. The mechanism combines the critical earthquake concept and the concept of crust acting as a charging electric battery under increasing stress. The electric charges are released by activation of dormant charge carriers in the oxygen anion sublattice, called peroxy bonds or positive hole pairs (PHP), where a PHP represents an $O_3X/^{OO}\backslash YO_3$ with $X,Y = Si^{4+}, Al^{3+}...$, i.e. an $O^-$ in a matrix of $O^{2-}$ of silicates. We propose that PHP are activated by plastic deformations during the slow cooperative build-up of stress and the increasingly correlated damage culminating in a large ``critical'' earthquake. Recent laboratory experiments indeed show that stressed rocks form electric batteries which can release their charge when a conducting path closes the equivalent electric circuit. We conjecture that the intermittent and erratic occurrences of EM signals are a consequence of the progressive build-up of the battery charges in the Earth crust and their erratic release when crack networks are percolating throughout the stressed rock volumes, providing a conductive pathway for the battery currents to discharge. EM signals are thus expected close to the rupture, either slightly before or after, that is, when percolation is most favored.Comment: 17 pages with 3 figures, extended discussion with 1 added figure and 162 references. The new version provides both a synthesis of two theories and a review of the fiel

Multi-instrumental analysis of large sprite events and their producing storm in southern France

During the night of 01-02 September, 2009, seventeen distinct sprite events including 3 halos were observed above a storm in north-western Mediterranean Sea, with a video camera at Pic du Midi (42.93N; 0.14E; 2877m). The sprites occurred at distances between 280 and 390km which are estimated based on their parent CG location. The MCS-type storm was characterized by a trailing-stratiform structure and a very circular shape with a size of about 70,000km2 (cloud top temperature lower than -35°C) when the TLEs were observed. The cloud to ground (CG) flash rate was large (45min-1) one hour before the TLE observation and very low (<5min-1) during it. Out of the 17 sprite events, 15 parent+CG (P+CG) strokes have been identified and their average peak current is 87kA (67kA for the 14 events without halo), while the associated charge moment changes (CMC) that could be determined, range from 424 to 2088±20%Ckm. Several 2-second videos contain multiple sprite events: one with four events, one with three events and three with two events. Column and carrot type sprites are identified, either together or separately. All P+CG strokes are clearly located within the stratiform region of the storm and the second P+CG stroke of a multiple event is back within the stratiform region. Groups of large and bright carrots reach ~70km height and ~80km horizontal extent. These groups are associated with a second pulse of electric field radiation in the ELF range which occurs ~5ms after the P+CG stroke and exhibits the same polarity, which is evidence for current in the sprite body. VLF perturbations associated with the sprite events were recorded with a station in Algiers. © 2012 Elsevier B.V

Electronic structure of crystalline binary and ternary Cd-Te-O compounds

The electronic structure of crystalline CdTe, CdO, $\alpha$-TeO$_2$, CdTeO$_3$ and Cd$_3$TeO$_6$ is studied by means of first principles calculations. The band structure, total and partial density of states, and charge densities are presented. For $\alpha$-TeO$_2$ and CdTeO$_3$, Density Functional Theory within the Local Density Approximation (LDA) correctly describes the insulating character of these compounds. In the first four compounds, LDA underestimates the optical bandgap by roughly 1 eV. Based on this trend, we predict an optical bandgap of 1.7 eV for Cd$_3$TeO$_6$. This material shows an isolated conduction band with a low effective mass, thus explaining its semiconducting character observed recently. In all these oxides, the top valence bands are formed mainly from the O 2p electrons. On the other hand, the binding energy of the Cd 4d band, relative to the valence band maximum, in the ternary compounds is smaller than in CdTe and CdO.Comment: 13 pages, 15 figures, 2 tables. Accepted in Phys Rev

Audiomagnetotelluric sounding using the Schumann resonances

The Schumann resonance waveforms in the lower ELF band (5-100 Hz) are produced within the Earth-ionosphere cavity by distant lightning discharges; they provide a useful source field for shallow audiomagnetotclluric (AMT) crustal sounding. In this study we investigate their waveform characteristics that are important to the assumptions of AMT sounding. A time-domain polarization analysis technique is applied to a variety of examples of Schumann resonance waveforms. The multiplicity of worldwide thunderstorm centres provides a background activity which is generally incoherent and, accordingly, displays incoherent polarization characteristics. Superimposed on the back­ground are larger-amplitude transient events (sferics) from individual thunderstorm centres; they represent the response of the Earth-ionosphere cavity to very large lightning discharges and are generally linearly polarized at a given azimuth. The analysis indicates that the Schuman resonance waveforms provide a plane-wave source field, as required for electromagnetic crustal sounding. The differences in the "received" characteristics between the two waveform types prompted an investigation of the extent to which the waveform type and its particular polarization characteristics influence the determination of a geoelectric sounding curve. A detailed study, carried out with a multivariate maximum entropy spectral analysis algorithm, indicates that the two types of Schumann resonance waveform provide repeatable and consistent results at the 95% confidence level and that the linear polarizations associated with the sferics do not influence the estimation of the Earth response

Phenomena of electrostatic perturbations before strong earthquakes (2005–2010) observed on DEMETER

International audienceDuring the DEMETER operating period in 2004– 2010, many strong earthquakes took place in the world. 69 strong earthquakes with a magnitude above 7.0 during January 2005 to February 2010 were collected and analysed. The orbits, recorded in local nighttime by satellite, were chosen by a distance of 2000 km to the epicentres during the 9 days around these earthquakes, with 7 days before and 1 day after. The anomaly is defined when the disturbances in the electric field PSD increased to at least 1 order of magnitude relative to the normal median level about 10 −2 µV 2 /m 2 /Hz at 19.5–250 Hz frequency band, and the starting point of perturbations not exceeding 10 • relative to the epicentral latitude. Among the 69 earthquakes, it is shown that electrostatic perturbations were detected at ULF-ultra low frequency and ELF-extremely low frequency band before the 32 earthquakes, nearly 46 %. Furthermore, we extended the searching scale of these perturbations to the globe, and it can be found that before some earthquakes, the electrostatic anomalies were distributed in a much larger area a few days before, and then they concentrated to the closest orbit when the earthquake would happen one day or a few hours later, which reflects the spatial developing feature during the seismic preparation process. The results in this paper contribute to a better description of the electromagnetic (EM) disturbances at an altitude of 660– 710 km in the ionosphere that can help towards a further understanding of the lithosphere-atmosphere-ionosphere (LAI) coupling mechanism