Science of the Earth, formerly Vietnam Journal of Earth Sciences, is a peer-reviewed journal to publish high-quality articles on the entire range of earth sciences and the environment, focused on the Asia Pacific region and their correlations and connections to the globe. The journal publishes fundamental and applied research in earth sciences and the environment, including geology, geophysics, geography, soil science, hydrology, meteorology, oceanography, petroleum, geohazards, environmental sciences, environmental engineering, sustainable development, geoinformatics, geodesy, GIS, and remote sensing.

Among the intermingled translational and rotational effects occurring in earthquakes, the translational effects are rather well understood. Recent experiments have been performed to investigate the rotational effects which have been observed for centuries that remain intriguing and less well understood. Although rotational seismology is of interest in a wide range of disciplines, rotational ground motions remain challenging to detect directly, especially their sense of rotation. To avoid a possible random response of a single balance, we locate two Cavendish balances in an ultra-low-noise laboratory. For the two successive 2012 Italian earthquakes in Emilia detected in exactly the same direction, opposed counterclockwise and clockwise responses of the two balances are recorded at the same site. Despite the complex combinations of Rayleigh and Love surface waves in the far-field, the two circular fundamental eigenmodes of the gravity-free torsion balances permit the determination of the ground rotation senses, which are indirectly confirmed by the phase shifted acceleration components in the balance frequency bandwidth, as well as the corresponding opposite driving angular impulses. The versatility of the Cavendish balances suggests that they could be used as inexpensive rotational sensor arrays in seismic areas to follow the propagation of ground rotations from the epicentres.

Surface waves generated by earthquakes create atmospheric waves detectable in the ionosphere using radio waves techniques: i.e., HF Doppler sounding, GPS and altimeter TEC measurements, as well as radar measurements. We present observations performed with the over-the-horizon (OTH) radar NOSTRADAMUS after the very strong earthquake (M=8.6) that occurred in Sumatra on March 28, 2005. An original method based on the analysis of the RTD (Range-Time-Doppler) image is suggested to identify the multichromatic ionospheric signature of the Rayleigh wave. The proposed method presents the advantage to preserve the information on the range variation and time evolution, and provides comprehensive results, as well as easy identification of the waves. In essence, a Burg algorithm of order 1 is proposed to compute the Doppler shift of the radar signal, resulting in sensitivity as good as obtained with higher orders. The multi-chromatic observation of the ionospheric signature of Rayleigh wave allows to extrapolate information coherent with the dispersion curve of Rayleigh waves, that is, we observe two components of the Rayleigh waves with estimated group velocities of 3.8 km/s and 3.6 km/s associated to 28 mHz (T similar to 36 s) and 6.1 mHz (T similar to 164 s) waves, respectively. Spectral analysis of the RTD image reveals anyway the presence of several oscillations at frequencies between 3 and 8 mHz clearly associated to the transfer of energy from the solid-Earth to the atmosphere, and nominally described by the normal modes theory for a complete planet with atmosphere. Oscillations at frequencies larger than 8 mHz are also observed in the spectrum but with smaller amplitudes. Particular attention is pointed out to normal modes 0S29 and 0S37 which are strongly involved in the coupling process. As the proposed method is frequency free, it could be used not only for detection of ionospheric perturbations induced by earthquakes, but also by other natural phenomena as well as volcanic explosions and particularly tsunamis, for future oceanic monitoring and tsunami warning systems. (C) 2014 Elsevier Ltd. All rights reserved.

This paper presents an estimation of the velocity of the Earth’s crust in Vietnam and the Southeast Asian region,determined from the GPS data in nearly 8 years (4/2005-11/2013) at 5 sites in Vietnam (DBIV, PHUT, VINH, HUES andHOCM) plus more than 20 ones in Southeast Asia and other regions using GAMIT software. The horizontal velocityvectors in ITRF2005 at the considered Southeast Asia stations show that they drive to the south-eastward, but theKUNM, DBIV, PHUT, VINH and HUES (with velocity of about 31-36mm/yr) move faster than the HOCM, CUSV, NTUSand BAKO (with the velocity of 21.5-25.5 mm/yr); meanwhile the PIMO drives to the northwest with the velocity of 29.8mm/yr. 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This study presents the time variations of the total electron content in the South East Asian equatorial ionization anomaly. The time variation of the TEC is analyzed through the period 2006–2011 by using a latitudinal chain of GPS stations extending in the northern and southern hemisphere. The data shows that the shape of the diurnal variation of the TEC depends on the latitude: a plateau is observed at the stations near the equator and a Gaussian at the station distant from the equator. We observe a semiannual pattern in all the stations with maxima at equinox. In both hemispheres, the amplitude of the crest is larger in spring than autumn from 2006 to 2008 and smaller in spring than in autumn from 2009 to 2011. We also observe an asymmetry between the amplitude and the position of the two crests of ionization. There is a very high level of correlation between the amplitude of the TEC at the two crests and the sunspot number: ∼0.88. During the deep solar minimum 2008–2009, the amplitude of crests of ionization becomes small during several months in summer and winter. The results show that both crests move significantly equatorward in winter than other seasons and there is a tendency for both crests to appear earlier in winter and later in summer.

This article deals with the impact of ionospheric electron density inhomogeneities on the functionality of global navigation satellite systems emphasizing positioning errors. The scintillation characteristics of transmitted signals have been obtained using data gathered in measurement campaigns. The effects on a standard receiver are then presented. Positioning errors due to scintillations were shown to be greater than 10 meters in the worst case. (c) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Les signaux radioelectriques se propageant sur un trajet Terre-satellite sont parfois perturbes par la scintillation ionospherique. Ce phenomene se traduit par l’apparition de fluctuations rapides du signal recu qui sont susceptibles d’affecter les performances du systeme. C’est en particulier le cas du GPS pour lequel les scintillations sont un sujet de preoccupation pour certaines applications exigeantes en termes de precision, de disponibilite et de fiabilite. Dans le present article, on rapporte les resultats d’une campagne de mesures de la scintillation en regions equatoriales. Cette campagne, menee dans le cadre de cooperations internationales, a permis de valider des outils specifiques de surveillance et de prevision de la scintillation.

We use observations of ionospheric scintillation at equatorial latitudes from two GPS receivers specially modified for recording, at a sampling rate of 50Hz, the phase and the amplitude of the L1 signal and the Total Electron Content (TEC) from L1 and L2. The receivers, called GISTM (GPS Ionospheric Scintillation and TEC Monitor), are located in Vietnam (Hue, 16.4°N, 107.6°E; Hoc Mon, 10.9°N, 106.6°E). These experimental observations are analysed together with the tomographic reconstruction of the ionosphere produced by the Multi-Instrument Data Analysis System (MIDAS) for investigating the moderate geomagnetic storm which occurred on early April 2006, under low solar activity. The synergic adoption of the ionospheric imaging and of the GISTM measurements supports the identification of the scale-sizes of the ionospheric irregularities causing scintillations and helps the interpretation of the physical mechanisms generating or inhibiting the appearance of the equatorial F layer irregularities. In particular, our study attributes to the turning of the IMF (Interplanetary Magnetic Field) between northward and southward direction an important role in the inhibition of the generation of spread F irregularities resulting in a lack of scintillation enhancement in the post-sunset hours.

The Mitigation of Ionospheric Effects on Radio Systems COST 296 Action is devoted to the mitigation of ionospheric effects on radio systems. It creates a platform for sharing of data, algorithms, models, and jointly developed advanced technologies, the processing chain from measurements, through algorithms, to operational knowledge. This initiative creates a unique possibility for national groups to consolidate the design of a product required for their own activity and for European assessments in the ionosphere and telecommunication area. An important part of the action is to stimulate and integrate many national and international activities which provide tools for global and regional ionospheric monitoring and modeling. The work includes the near‐Earth space plasma monitoring, modeling and forecasting, and a study of the upper atmosphere climate. Well‐defined terms of reference include developing ground‐based and space‐borne monitoring techniques and parameters describing the state of ionospheric plasma, maintaining and extending the flow of real‐time and retrospective ionospheric monitoring data to databases. To obtain adequate, high‐quality information, special attention is paid to the data ingestion and assimilation in constructing ionospheric models of different spatial and time scale perturbations, as well as storms, small variations, and irregularities. The physical origin of atmospheric/ionospheric effects and their signatures and parameters are investigated. Identification criteria are studied and formulated.

A brief summary is given here of the major achievements of the COST 296 Action MIERS.

radio systems. From the point of view Working Group 2 of the COST 296 Action, interest lies with effects associatedwith propagation via the ionosphere of signals within the HF band. Several aspects are covered in this paper:a) The directions of arrival and times of flight of signals received over a path oriented along the trough havebeen examined and several types of propagation effects identified. Of particular note, combining the HF observationswith satellite measurements has identified the presence of irregularities within the floor of the trough thatresult in propagation displaced from the great circle direction. An understanding of the propagation effects thatresult in deviations of the signal path from the great circle direction are of particular relevance to the operationof HF radiolocation systems.b) Inclusion of the results from the above mentioned measurements into a propagation model of the northerlyionosphere (i.e. those regions of the ionosphere located poleward of, and including, the mid-latitude trough)and the use of this model to predict the coverage expected from transmitters where the signals impinge on thenortherly ionosphere.c) Development of inversion techniques enabling backscatter ionograms obtained by an HF radar to be usedto estimate the ionospheric electron density profile. This development facilitates the operation of over the horizonHF radars by enhancing the frequency management aspects of the systems.d) Various propagation prediction techniques have been tested against measurements made over the troughpath mentioned above, and also over a long-range path between Cyprus and the UK.e) The effect of changes in the levels of ionospheric disturbances on the operational availability at variousdata throughput rates has been examined for the trough path mentioned earlier.The topics covered in this paper are necessarily brief, and the reader is referred to full papers referenced

The COST 296 Action MIERS (Mitigation of Ionospheric Effects on Radio Systems) within the ionosphericcommunity has the objectives, embodied in the Memorandum of Understanding (MoU), to develop an increasedknowledge of the effects imposed by the ionosphere on practical radio systems, and the development and implementationof techniques to mitigate the deleterious effects of the ionosphere on such systems. This introductorypaper summarizes briefly the background and historical context of COST 296 and outlines the main objectives,working methods and structure. It also lists the participating countries and institutions, the Management Committee(MC) Meetings, the Workshops, Short-term Scientific Missions. In addition, the paper discusses the disseminationactivities and the collaboration among the participating institutions and researchers, before outliningthe content of the Final Report.

This paper presents a review of the ionospheric scintillation monitoring and modelling by the European groupsinvolved in COST 296. Several of these groups have organized scintillation measurement campaigns at low andhigh latitudes. Some characteristic results obtained from the measured data are presented. The paper also addresses the modeling activities: four models, based on phase screen techniques, with different options and application domains are detailed. Finally some new trends for research topics are given. This includes the wavelet analysis, the high latitudes analysis, the construction of scintillation maps and the mitigation techniques.

The objective of the COST296 Action MIERS (Mitigation of Ionospheric Effects on Radio Systems) is to develop an increased knowledge of the effects imposed by the ionosphere on practical radio systems, and for the development and implementation of techniques to mitigate the deleterious effects of the ionosphere on such systems ("http://www.cost296.rl.ac.uk"). The COST296 Community contributes to the international efforts of IHY with scientific and outreach activities as well. After the realization of a web site hosted by Istituto Nazionale di Geofisica e Vulcanologia (INGV), developed also to promote the ionospheric physics to the open public, the COST296 Community supported an initiative addressed to the pupils of the primary school of several European Countries: the realization of a school-calendar dedicated to the Sun and to the Sun-Earth connections.

Telecommunications via ionospheric reflection of radio signals of ground-based transmitters are a traditional area. However, this technique is still in use in telecommunications, broadcasting, etc. Various problems have not yet been solved and some of them were studied in Working Group 3 (WG3). Structure of WG 3 and the terms of reference of its four working packages are described in the introductory paper by Zolesi and Cander (2004). Here we describe the main results achieved in COST 271 in the following areas: i) large-scale fluctuations of planetary and gravity waves; ii) development of a new type of HF channel simulator; iii) geomagnetic storm effects on the F1-region ionosphere; iv) the sporadic E-layer and spread-F phenomena; v) the HF radio wave propagation over northerly paths; vi) how to increase the bit rate in ionospheric radio links. In general, substantial progress was achieved but some problems remain open for future investigations.