TARANIS — Scientific payload and mission strategy

International audienceOn December 2010 the implementation phase of the TARANIS micro-satellite was authorized by the French space agency. TARANIS is dedicated to the study of impulsive transfers of energy between the Earth atmosphere and the space environment, and more precisely to the physics of the Transient Luminous Events (TLEs) and of the Terrestrial Gamma ray Flashes (TGFs). By 2015 TARANIS will provide combined Nadir observations of TLEs and TGFs, high resolution measurements of energetic electrons, and wave field measurements. The strategy adopted to maximize the scientific return of the data is presented

Midlatitude propagation of VLF to MF waves through nighttime ionosphere above powerful VLF transmitters

International audience[1] Midlatitude nighttime observations made by the DEMETER satellite in the very low frequency (VLF) to medium frequency (MF) bands (3 kHz to 3 MHz) have demonstrated the propagation of radio waves from the bottom of ionosphere up to the satellite altitude (~700 km). Propagation characteristics derived from the magneto-ionic theory [Budden, 1985] are used to explain the absence of wave observations between ~1 and 2 MHz. Under hypotheses made for the Appleton and Hartree (or Appleton and Lassen) formula, studies of the vertical variations of the real and imaginary parts of the refractive index are performed to point out modifications in the propagation characteristics of the waves: (i) at the crossing of the plasma cutoffs regions, (ii) at the crossing of the ordinary and extraordinary mode resonance regions, and (iii) in the region where the product of the collision frequency (n) and the electronic density (Ne) is maximum. It is shown that enhancements in the collision frequencies, produced by powerful VLF transmitters in the region where the product of n and Ne is maximum, open the half angle of the MF wave transmission cones and increase the power densities of those waves at the DEMETER altitude. Citation: Lefeuvre F., J. L. Pinc¸n , and M. Parrot (2013), Midlatitude propagation of VLF to MF waves through nighttime ionosphere above powerful VLF transmitters

Temporal and spatial analyses on seismo-electric anomalies associated with the 27 February 2010 M = 8.8 Chile earthquake observed by DEMETER satellite

International audienceThis paper studies seismo-electromagnetic anomalies observed by the French satellite DEMETER (Detection of ElectroMagnetic Emissions Transmitted from Earthquake Regions) during the 27 February 2010 M = 8.8 Chile earthquake. The nighttime electron density (N e), electron temperature (T e), ion density (N i), ion temperature (T i) and whistler counts (C w) are investigated. A statistical analysis of the box-and-whisker method is applied to see if data of two or more groups under study are significantly different. A cross-examination of temporal variations before and after shows that N e and N i (C w) increases (decreases) appear 10–20 days before the earthquake. A comparison of data over the epicenter and those over its reference area can be employed to discriminate the earthquake-related anomalies from global effects. Results prove that anomalous enhancements of N e , N i , and T i occur specifically around the epicenter area. The intersection of the temporal and spatial results confirms that N e and N i are useful and sensitive detecting anomalous related to the 2010 M = 8.8 Chile earthquake

Sharing and community curation of mass spectrometry data with Global Natural Products Social Molecular Networking

The potential of the diverse chemistries present in natural products (NP) for biotechnology and medicine remains untapped because NP databases are not searchable with raw data and the NP community has no way to share data other than in published papers. Although mass spectrometry techniques are well-suited to high-throughput characterization of natural products, there is a pressing need for an infrastructure to enable sharing and curation of data. We present Global Natural Products Social molecular networking (GNPS, http://gnps.ucsd.edu), an open-access knowledge base for community wide organization and sharing of raw, processed or identified tandem mass (MS/MS) spectrometry data. In GNPS crowdsourced curation of freely available community-wide reference MS libraries will underpin improved annotations. Data-driven social-networking should facilitate identification of spectra and foster collaborations. We also introduce the concept of ‘living data’ through continuous reanalysis of deposited data

Is There an Earthquake Weather?

International audienceThe aim of this study is to check if there is a relationship between the seismic activity and the whistlers observed by the micro-satellite DEMETER. Whistlers are the waves emitted by lightning strokes during thunderstorm activity. They use to propagate in the Earth-ionosphere waveguide but also in the ionosphere and the magnetosphere mainly along the magnetic field lines. Due to this reason we have checked the whistler occurrence not close to earthquake epicenters but close to the magnetically conjugate point of these epicenters at the satellite altitude. The number of whistlers is given by a neural network in operation onboard the satellite. It appears that the whistler amplitude is attenuated at the satellite altitude around the magnetic equator. It is why we have removed the earthquakes occurring at low geomagnetic latitudes in the statistic. The whistler rate is normalized with a background value to take into account the seasons and the epicenter locations. A superposed epoch method is used to display the results between −15 and +5 days around the earthquake day and up to 1000 km from the conjugate point of the epicenters. It is shown that the whistler rate is higher the day before the earthquake at a distance less than 200 km. It would be unrealistic to believe in the possibility to use this study for earthquake prediction because everyday thunderstorm activity reliably masks seismic effects. But it is further evidence that there is a lithosphere-atmosphere-ionosphere coupling at the time of the seismic activity

Variations of the main nighttime ionospheric density anomalies observed by DEMETER during the descending phase of solar cycle 23

International audienceThis paper is related to analysis of the Weddell Sea Anomaly (WSA) and the Mid-latitude Summer Nighttime Anomaly (MSNA) observed by the low altitude satellite DEMETER during nighttime between 2004 and 2010. This time interval corresponds to the decrease of the solar cycle 23 which was unusually long. It appears that, if these two anomalies have a peak in local summer (December in the Southern hemisphere for the WSA, June in the Northern hemisphere for the MSNA), the anomalies are also observed during the months around December and June with a decreased intensity. But at the end of the solar cycle 23 the summer peaks dramatically decrease and even relatively more quickly than the solar index F10.7. This phenomenon is much more significant for the WSA. It is shown that the mechanism producing the two anomalies (thermospheric neutral winds and magnetic declination effects) is strengthened by the solar ionization which is active during the night above the WSA and the MSNA areas. But at solar minimum, this mechanism is weakened. These results are valid at the satellite altitude (660 km) and may vary at lower altitudes

Complete wave-vector directions of electromagnetic emissions: Application to INTERBALL-2 measurements in the nightside auroral zone

International audienceWe present several newly developed methods for wave propagation analysis. They are based on simultaneous measurement of three magnetic field components and one or two electric field components. The purpose of these techniques is to estimate complete wave vector direction and the refractive index. All the analysis results are validated by well defined simulated data. Propagation analysis of natural emissions in the night-side auroral zone at high altitudes is done using the data of the MEMO (Mesures Multicomposantes des Ondes) experiment onboard INTERBALL-2. The results show that a bursty whistler mode emission propagates toward the Earth near the resonance cone. Upward propagating auroral kilometric radiation in the R-X mode represents another example demonstrating the potential of such analysis for future applications

Propagation of Z-mode and whistler-mode emissions observed by Interball 2 in the nightside auroral region

International audienceA case study of VLF (very low frequency) natural emissions propagating at high altitude above the nightside auroral zone is presented. The analysis is based on data of the MEMO experiment on board the Interball 2 spacecraft. In its VLF band the device records waveforms of three magnetic and two electric field components covering a frequency range 1-20 kHz. Several analysis methods are applied in order to obtain the details on the wave propagation and mode structure and to identify possible source regions. We demonstrate that observed band-limited emission consists of Z-mode and whistler-mode waves. Downgoing Z-mode waves are found just above the lower cutoff at the L=0 frequency. A possible source may be connected with the electron cyclotron resonance mechanism taking place in the nightside sector at altitudes above 21,000 km. Upgoing whistler-mode waves with upper cutoff at the local plasma frequency are probably generated by upgoing electrons in the auroral region at altitudes lower than the actual satellite position, i.e., below 18,000 km

A statistical study over Europe of the relative locations of lightning and associated energetic burst of electrons from the radiation belt

International audienceThe DEMETER (Detection of ElectroMagnetic Emissions Transmitted from Earthquake Regions) spacecraft detects short bursts of lightning-induced electron precipitation (LEP) simultaneously with newly injected upgoing whistlers. The LEP occurs within < 1 s of the causative lightning discharge. First in situ observations of the size and location of the region affected by the LEP precipitation are presented on the basis of a statistical study made over Eu-rope using the DEMETER energetic particle detector, wave electric field experiment, and networks of lightning detection (Météorage, the UK Met Office Arrival Time Difference network (ATDnet), and the World Wide Lightning Location Network (WWLLN)). The LEP is shown to occur significantly north of the initial lightning and extends over some 1000 km on each side of the longitude of the lightning. In agreement with models of electron interaction with obliquely propagating lightning-generated whistlers, the distance from the LEP to the lightning decreases as lightning proceed to higher latitudes. Keywords. Ionosphere (particle precipitation; wave– particle interactions) – meteorology and atmospheric dynamics (lightning