Generation of internal gravity vortices in the high-latitude ionosphere     

V.M. Chmyrev  V.M. Sorokin 《Journal of Atmospheric and Solar》2010,72(13):992-996

It is shown that ionosphere heating by DC electric field leads to instability of acoustic-gravity waves and to the formation of solitary internal gravity vortex structures. These dipole type vortices with characteristic transverse size of the order of several kilometers are propagated in the lower ionosphere with subsonic velocity. The threshold values of the electric field needed to suppress the wave damping caused by the interaction of induced current with the geomagnetic field and to provide the vortex generation are found. The considered physical mechanism is applicable to the generation of internal gravity vortices and related ionospheric disturbances when the ionosphere is influenced by the electric field of seismic origin exceeding the threshold value.  相似文献   

Project TWINSAT: Development of Integrated Aerospace and Ground-Based Early Warning and Monitoring Technologies for Precursors to Large-Scale Natural Disasters     

E. A. Rogozhin  V. M. Chmyrev  O. A. Pokhotelov  B. F. Nesterov 《Seismic Instruments》2018,54(5):521-530

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The fine structure of intensive small-scale electric and magnetic fields in the high-latitude ionosphere as observed by Intercosmos-Bulgaria 1300 satellite     

V.M. Chmyrev  V.N. Oraevsky  S.V. Bilichenko  N.V. Isaev  G.A. Stanev  D.K. Teodosiev  S.I. Shkolnikova 《Planetary and Space Science》1985,33(12):1383-1388

The data on intensive small-scale electric fields and related transverse magnetic disturbances observed from Intercosmos-Bulgaria 1300 satellite at altitudes of 800–900 km in the auroral ionosphere are presented here. The typical time scale of the phenomena is of the order of 1 s, the amplitudes reach 250 mV m⁻¹ in electric field and up to 300 nT in magnetic field. A detailed correlation between the variations of electric and magnetic fields in such structures is shown. Some peculiarities are presented which show that the observed electric jumps are transient electromagnetic disturbances rather than steady electrostatic structures.  相似文献   

Spatial and seasonal patterns of European short-snouted seahorse Hippocampus hippocampus distribution in island coastal environments     

F Otero-Ferrer  R Herrera  VM Tuset  J Socorro  L Molina 《African Journal of Marine Science》2015,37(3):395-404

This study represents the first report on seahorses in the Macaronesian islands (North-East Atlantic), determining the spatial and seasonal abundance, population structure and physical appearance of European short-snouted seahorse Hippocampus hippocampus. Animals were surveyed off Gran Canaria Island in two bays, Melenara and Sardina del Norte, within three habitats: rocky bottom, artificial substrata and seagrass. Populations were monitored over a 5-year period (spring 2006–winter 2011) using 15-minute visual fast count (VFC) surveys. Seahorses were characterised by low abundances, small proportions of subadults and roughly equal sex ratios at each site. We aimed to determine whether environmental conditions and geographical position could explain differences in seahorse abundance and population structure between the study sites. Melenara Bay (mean sighting rate = 0.44 individuals VFC–¹; SD 0.72) offered protected environments where seahorse distribution varied with substratum type, irrespective of season. Strong hydrodynamic forces in winter affected abundance and size at exposed locations in Sardina del Norte Bay (mean sighting rate=0.21 individuals VFC^?1; SD 0.52). Our findings contribute to the scarce available knowledge about this Data Deficient species (IUCN Red List), helping to establish future conservation strategies and management recommendations for the preservation of H. hippocampus populations around Gran Canaria Island and other localities with similar coastal environments.  相似文献