global distribution of nighttime medium scale traveling ionospheric disturbances seen by swarm satellites the activity of nighttime medium scale traveling ionospheric disturbance mstid in middle latitudes 25 40 magnetic latitudes is investigated using the measurements of the electron density by swarm satellites fractional electron density fluctuation is used as a proxy for mstids and the mstid distribution is derived from the observations in december 2013 january 2017 the mstid activity shows a semi annual variation in most longitudes with the primary and secondary peaks during the june and december solstices respectively the distinguishing feature in the mstid distribution is the high occurrence rate of mstids around 150 e longitude in june august the longitudinal and annual distribution of mstids shows a hemispheric symmetry which we interpret as the demonstration of conjugacy in mstids

temporal geomagnetic and related attributes of kimberlite magmatism at ekati northwest territories canada abstract this paper outlines the development of a multi disciplinary strategy to focus exploration for economic kimberlites on the ekati property high resolution aeromagnetic data provide an over arching spatial and magnetostratigraphic framework for exploration and kimberlite discovery at ekati and hence also for this investigation the temporal geomagnetic spatial and related attributes of kimberlites with variable diamond content have been constrained by judiciously augmenting the information gathered during routine exploration with detailed laboratory based or field based investigations the natural remanent magnetisation of 36 ekati kimberlites has been correlated with their age as determined by isotopic dating techniques and placed in the context of a well constrained geomagnetic polarity timescale kimberlite magmatism occurred over the period 75 to 45 ma in at least five temporally discrete intrusive episodes based on current evidence the older kimberlites 75 to 59 ma have low diamond contents and are distributed throughout the property younger kimberlites 56 to 45 ma have moderate to high diamond contents and occur in three distinct intrusive corridors with nne to ne orientations economic kimberlite pipes erupted at 55 4 0 4 ma along the a154 lynx intrusive corridor which is 7 km wide and oriented at 015 and at 53 2 0 3 ma along the panda intrusive corridor which is 1 km wide and oriented at 038 the intrusion ages straddle a paleopole reversal at chron c24n consistent with the observation that the older economic kimberlites present as aeromagnetic low anomalies while the younger economic pipes are characterised as aeromagnetic highs the aeromagnetic responses for these kimberlites are generally muted because they contain volcaniclastic rock types with low magnetic susceptibility kimberlites throughout the ekati property carry a primary natural magnetic remanence nrm vector in ti bearing groundmass magnetite and it dominates over vectors related to induced magnetisation magnetostratigraphic correlation of ekati kimberlites may therefore present a powerful adjunct to existing exploration techniques mainly because the diamond content of ekati kimberlites apparently is related more to the age of eruption than to any other parameter investigated in this work

multisensor profiling of a concentric gravity wave event propagating from the troposphere to the ionosphere in this paper we present near simultaneous observations of a gravity wave gw event in the stratosphere mesosphere and ionosphere over the south central united states and track it from its convective source region in the troposphere to the ionosphere where it appears as a traveling ionospheric disturbance tid on 4 april 2014 concentric gw ring patterns were seen at stratospheric heights in close proximity to a convective storm over north texas in the atmospheric infrared sounder data on board the nasa aqua satellite concentric gws of similar orientation and epicenter were also observed in mesospheric nightglow measurements of the day night band of the visible infrared imaging radiometer suite on the suomi national polar orbiting partnership satellite concentric tids were seen in total electron content data derived from ground based gps receivers distributed throughout the u s these new multisensor observations of tids and atmospheric gws can provide a unique perspective on ionosphere atmosphere coupling

negative estuarine circulation in the ria of pontevedra nw spain an along estuary negative circulation was measured in the ria of pontevedra nw spain on may 13 1998 this two layered circulation pattern with near bed water moving seaward and near surface water landward was generated by the existence of two different water masses at intermediate depths water in the inner part of the estuary was a mixture of estuarine water and eastern north atlantic central water enacw which had entered the estuary some days before due to an intense upwelling event water in the middle part of the estuary was a mixture of estuarine water and fresh water coming from the river discharge which had been higher during the days previous to may 13 this water mass distribution gave rise to the existence of denser water in the inner part of the estuary than in the middle one generating the observed negative circulation pattern

directivity and apparent velocity of the coseismic ionospheric disturbances observed with a dense gps array abstract coseismic disturbances in ionosphere have been observed after recent thrust earthquakes off the pacific coast of japan with a dense global positioning system array positive pulses in electron content as large as several times 10 15 electrons m 2 and as long as 4 5 min emerge 10 min after earthquakes and propagate horizontally with apparent velocity of 1 km s close to the sound velocity at the ionospheric height they may have been excited by coseismic uplifts of the sea surface initially as upward propagating compressive pulses of atmosphere which were gradually refracted to propagate horizontally in ionosphere the propagation has strong north south asymmetry and interaction between the movements of charged particles in acoustic waves and geomagnetic fields might have selectively attenuated the northward propagating disturbances

medium scale traveling ionospheric disturbances detected with dense and wide tec maps over north america 1 nighttime and daytime medium scale traveling ionospheric disturbances mstids are detected with dense and wide detrended total electron content tec maps over north america using multiple gps receiver networks the tec maps cover a wide region of 60 130 w and 24 54 n 30 65 n in geomagnetic latitude and have a spatial resolution of 1 05 1 05 in latitude and longitude 0 15 0 15 with 7 7 pixel smoothing and a temporal resolution of 30 seconds the tec maps reveal for the first time that the nighttime mstids propagate southwestward with 200 500 km wavelengths over north america and have wavefronts longer than 2 000 km we also observe that daytime mstids with 300 1 000 km wavelengths propagate southeastward until mid afternoon and southwestward in the late afternoon in the mid to late afternoon these mstids propagating in the different directions are superimposed the tec maps can be a new powerful tool to investigate the mstids

ionospheric holes made by ballistic missiles from north korea detected with a japanese dense gps array 1 a dense array of global positioning system gps receivers is a useful tool to study ionospheric disturbances here we report observations by a japanese gps array of ionospheric holes i e localized electron depletion they were made by neutral molecules in exhaust plumes e g water of ballistic missiles from north korea taepodong 1 and 2 launched on 31 august 1998 and 5 april 2009 respectively negative anomaly of electron density emerged 6 min after the launches in the middle of the japan sea and extended eastward along the missile tracks by comparing the numerical simulation of electron depletion and the observed change in ionospheric total electron content we suggest that the exhaust plumes from the taepodong 2 second stage effused up to 1 5 1026 water molecules per second the ionospheric hole signature was used to constrain the taepodong 2 trajectory together with other information e g coordinates of the launch pad time and coordinates of the first stage splashdown and height and time of the second stage passage over japan the taepodong 2 is considered to have reached the ionospheric f region in 6 min flown above northeastern japan 7 min after the launch and crashed to the pacific ocean without attaining the first astronautical velocity the ionospheric hole in the 1998 taepodong 1 launch was much less in size but it is difficult to compare directly the thrusts of the two missiles due to uncertainty of the taepodong 1 trajectory

concentric traveling ionosphere disturbances triggered by super typhoon meranti 2016 concentric traveling ionosphere disturbances ctids in total electron content tec triggered by super typhoon meranti on 13 september 2016 are detected using the ground based global navigation satellite system gnss network in taiwan the ctids emanated outwards before the typhoon landfall and lasted for more than 10 hours the characteristics of ctids agree with the gravity wave theory and exhibit spatial and temporal scales in wave periods of 8 30 minutes horizontal wavelengths of 160 200 km and horizontal phase velocities of 106 220 m s we also observe the ctids showing the stationary wave character broad spectra of ctids are excited after the rainbands of typhoon impinged on central mountain range cmr of taiwan the ray tracing technique confirms that the ctids were excited by convective clouds spiral rainbands and the eyewall of typhoon meranti this study provides new evidence of typhoon induced concentric gravity waves in the ionosphere

a model study of gravity waves over hurricane humberto 2001 abstract atmospheric gravity waves are known to influence global circulations understanding these waves and their sources help to develop parameterizations that include their effects in climate and weather forecasting models deep convection is believed to be a major source for these waves and hurricanes may be particularly intense sources simulations of hurricane humberto 2001 are studied using the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 humberto is simulated at both tropical storm and hurricane stages fourier transform and wavelet analysis are employed to investigate wave characteristics and their behavior in the lower stratosphere the fourier analysis gives a regional view of storm affects whereas wavelet analysis gives a local picture of isolated events analysis of the movement of convective sources and local winds gives further insight into the mechanisms that can cause gravity waves convectively generated grav

diamonds through time diamonds form in the upper mantle during episodic events and have been transported to the earth s surface from at least the archean to the phanerozoic small diamonds occur as inclusions in robust minerals in tectonically activated ultrahigh pressure metamorphosed crustal rock establishing an association with subduction processes and recycled carbon but providing no economic deposits diamonds in economic deposits are estimated to be mainly 99 derived from subcontinental lithospheric mantle and rarely approx 1 from the asthenosphere harzburgite and eclogite are of roughly equal importance as source rocks followed by lherzolite and websterite diamonds which provide evidence of extensive residence time in the mantle are with minimal exceptions smooth surfaced crystalline diamonds scd with potential commercial value the oldest prolific scd formation event documented on the world s major diamond producing cratons occurs in archean lithospheric mantle harzburgite metasomatized by likely subduction related potassic carbonatitic fluids disaggregation of the diamondiferous carbonated peridotite on decompression during volcanic transit gives rise to the association between diamonds g10 garnets and diamond inclusion type chromites well used in diamond exploration within the mantle domains of diamond stability there have been repeated episodes of further diamond crystallization and or growth these are associated with old often proterozoic subduction related melt generation metasomatic fluid migration and reaction with preexisting mantle eclogite websterite and peridotite using improved methods of isotope analysis diamond formation ages can be correlated with specific major processes such as craton accretion craton edge subduction and magmatic mantle refertilization fibrous cuboid diamond and fibrous coats on scd are rough surfaced diamonds with abundant fluid inclusions they have low mantle residence time forming rapidly from late stage metasomatic fluids in diamond stable domains that may already contain scd the symbiotic relationship between formation of fibrous diamond and magmatic sampling and transport of diamonds into the crust suggest that the associated fluids contribute diamond friendly volatile loading of the deep lithospheric mantle shortly before the triggering of a volcanic eruption continuing a process of volatile enrichment in the lithospheric mantle already identified in the archean harzburgite diamond event mantle derived scd commonly shows evidence of resorption illustrating that diamond unfriendly processes including lamproite and kimberlite generation are also active and may have a substantial negative effect in extreme cases on scd crystal size exposure of scd to a long period of changing conditions during mantle residence contributes to the difficulty of assigning specific parageneses and ages to individual inclusion free diamonds with our current state of knowledge

morphological features of ionospheric response to typhoon couplings between the ionosphere and meteorological events have been studied widely however most of them are individual case studies or correlation analyses and few are aiming at the full morphological features of the ionospheric response processes in this paper complete records of 24 strong typhoons from 1987 to 1992 were collected and comparison was made with corresponding ionospheric hf doppler shift data the main purpose of the present work is to find the temporal evolution of these responses and their common features by the merit of the continuities of hf doppler shift observation in time on the basis of the statistical analyses this paper reveals the common features of ionospheric responses to typhoon a summary of these characteristics is as follows 1 during the existing time of a typhoon there are almost always medium scale traveling ionospheric disturbances tids in the ionosphere especially when a strong typhoon is landing or near the coast of a mainland 2 these tids show quite clear periodicity and their periods vary with time and gradually grow longer 3 after sunset the wavelike disturbances with large magnitudes often excite the midlatitude spread f 4 the intense typhoon can cause the wavelike records of the doppler shift to show the s shaped echo tracing which means that the amplitudes of those waves are sufficiently large and 5 the sunrise like phenomena often appear in nonsunrise time during the period the typhoon exists the phenomena mentioned above are generally in agreement with the linear propagation theories of the acoustic gravity waves agws in the atmosphere a typhoon is surely one of the important ground sources of the wavelike disturbances in troposphere this source is very effective especially when a typhoon is landing on or near a mainland coast of course the morphological details of the ionospheric response to typhoon can by no means be completely identical every time in this study except for tids that almost always appear during all the typhoon events the other common features are not seen every time however we are certain that the phenomena summarized above are statistically the manifestation of the ionospheric response to typhoon since they appear much more frequently during periods influenced by typhoon

isotopic and geochemical characteristics of groundwater in the senegal river delta aquifer implication of recharge and flow regime groundwater and surface water samples were collected to improve understanding of the senegal river lower valley and delta system which is prone to salinization inorganic ion concentrations and environmental isotopes 18o 2h and 3h in groundwater river lake and precipitation were investigated to gain insight into the functioning of the system with regard to recharge sources and process groundwater renewability hydraulic interconnection and geochemical evolution the geochemical characteristics of the system display mainly cation ca2 and or na bicarbonated waters which evolve to chloride water type this occurs during groundwater flow in the less mineralized part of the aquifer in contrast saline intrusion and secondary brines together with halite dissolution are likely to contaminate the groundwater to na cl type halite gypsum and calcite dissolution determine the major ion na cl ca2 mg2 so42 and hco3 chemistry but other processes such as evaporation salt deposition ion exchange and reverse exchange reactions also control the groundwater chemistry both surface water and groundwater in the system show an evaporation effect but high evaporated signatures in the groundwater may be due to direct evaporation from the ground infiltration of evaporated water or enriched rainwater in this region the stable isotopes also reveal two types of groundwater in this system which geomorphologically are distributed in the sand dunes depleted isotopes and in the flood plain enriched isotopes consideration of the 3h content reinforces this grouping and suggests two mechanisms of recharge contribution of enriched surface water in recharging the flood plain groundwater and in the sand dunes area where water table is at depth between 8 and 13 m slow recharge process characterized the submodern to mixed water

arecibo observations of ionospheric perturbations associated with the passage of tropical storm odette 1 a suite of instruments including incoherent scatter radar ionosonde and a satellite bourne gps receiver observed the ionosphere immediately following the passage of a tropical storm tropical storm odette formed on 4 december 2003 and proceeded northeasterly over the next 4 days passing within 600 km of the arecibo observatory ao on the night of 7 8 december ao measured f region plasma densities and velocities nearly coincident with the storm large velocity variations 10 80 m s are evident in the plasma drift components the variations appear wave like with an average period of 90 min at 367 km zonal drifts were observed with magnitudes significantly greater than commonly observed for similar geomagnetic conditions the ramey ionosonde observed intense midlatitude spread f on the night following the closest passage of the storm gps occultations within the storm path showed an increase in gravity wave activity and f region scintillation combining the local increase in gravity wave activity with the large drift variations and dominant meridional electric field observed immediately following the storm s traversal of the flux tube coincident with the ao observing volume provide insight into coupling between mesoscale weather systems and the ionosphere

the geology and mineralogy of the anuri kimberlite nunavut canada abstract the 613 6 ma anuri kimberlite is a pipelike body comprising two lobes with a combined surface area of approximately 4 5 ha the pipe is infilled with two contrasting rock types volcaniclastic kimberlite vk and less common hypabyssal kimberlite hk the hk is an archetypal kimberlite composed of macrocrysts of olivine spinel mica rare eclogitic garnet and clinopyroxene with microphenocrysts of olivine and groundmass spinel phlogopite apatite and perovskite in a serpentine calcite phlogopite matrix the ba enrichment of phlogopite the compositional trends of both primary spinel and phlogopite as well as the composition of the mantle derived xenocrysts are also characteristic of kimberlite the present day country rocks are granitoids however the incorporation of sedimentary xenoliths in the hk shows that the archean granitoid basement terrain at least locally was capped by younger proterozoic sediments at the time of emplacement the sediments have since been removed by erosion hk is confined to the deeper eastern parts of the anuri pipe it is suggested that the hk was emplaced prior to the dominant vk as a separate phase of kimberlite the hk must have ascended to high stratigraphic levels to allow incorporation of proterozoic sediments as xenoliths most of the anuri kimberlite is infilled with vk which is composed of variable proportions of juvenile lapilli discrete olivine macrocrysts country rock xenoliths and mantle derived xenocrysts it is proposed that the explosive breakthrough of a second batch of kimberlite magma formed the western lobe resulting in the excavation of the main pipe much of the resulting fragmented country rock material was deposited in extra crater deposits pyroclastic eruption s of kimberlite must have occurred to form the common juvenile lapilli present in the vks the vk is variable in nature and can be subdivided into four types volcaniclastic kimberlite breccia magmaclast rich volcaniclastic kimberlite breccia finer grained volcaniclastic kimberlite breccia and lithic rich volcaniclastic kimberlite breccia the variations between these subtypes reflect different depositional processes these processes are difficult to determine but could include primary pyroclastic deposition and or resedimentation there is some similarity between anuri and the lac de gras kimberlites with variable types of vk forming the dominant infill of small steep sided pipes excavated into crystalline archean basement and sedimentary cover

ionospheric ripples excited by superimposed wave fronts associated with rayleigh waves in the thermosphere 1 coseismic ionospheric disturbances cids associated with the 2011 tohoku earthquake off the pacific coast mw 9 0 tohoku eq were examined using total electron content and seismic wave data a faster cid propagated at 3 0 km s only in the west southwest while a slower cid propagated concentrically at 1 2 km s or slower from the tsunami source area taking the propagation speed and oscillation cycle into account the faster cid was associated with a rayleigh wave but the slower cid was associated with an acoustic or gravity wave the north south asymmetry of the cid associated with the rayleigh wave suggests that the rayleigh wave did not act as a point source of the acoustic wave because a point source propagating in all directions must produce symmetric cid in all directions therefore a superimposed wave front of acoustic waves was excited by the rayleigh wave and produced the north south asymmetry of the faster cid due to the magnetic inclination effect which is different from a well known north south asymmetry of cid excited at the epicenter on the other hand above and south of the tsunami source area the cid with a period of 4 min was excited by a point source located at the tsunami source area because atmospheric waves propagating from a point source produce north south asymmetry in the resulting cid

ionospheric disturbances triggered by the 11 march 2011 m9 0 tohoku earthquake 1 an earthquake of magnitude 9 0 occurred near the east coast of honshu tohoku area japan producing overwhelming earth surface motions and inducing devastating tsunamis which then traveled into the ionosphere and significantly disturbed the electron density within it hereafter referred to as seismotraveling ionospheric disturbances stids the total electron content tec derived from nationwide gps receiving networks in japan and taiwan is employed to monitor stids triggered by seismic and tsunami waves of the tohoku earthquake the stids first appear as a disk shaped tec increase about 7 min after the earthquake occurrence centered at about 200 km east of the epicenter near the west edge of the japan trench fast propagating disturbances related to rayleigh waves quickly travel away from the epicenter along the main island of japan with a speed of 2 3 3 3 km s accompanied by sequences of concentric circular tec wavefronts and followed by circular ripples close to a tsunami speed of about 720 800 km h that travel away from the stid center these are the most remarkable stids ever observed where signatures of rayleigh waves tsunami waves etc simultaneously appear in the ionosphere

global survey of concentric gravity waves in airs images and ecmwf analysis concentric gravity waves cgws are atmospheric phenomena with ring shape perturbations originating in the troposphere they can propagate up to the ionosphere and thermosphere and dynamically couple the lower and upper atmosphere in this study we developed a novel ring detection algorithm to extract cgws from the atmosphere infrared sounder airs radiance data and the european center for medium range weather forecasting ecmwf analysis temperature in the stratosphere to produce the first global maps of such phenomena the algorithm is capable of estimating wave amplitude wavelength propagation direction and source location both airs and ecmwf data show a significant diurnal variation in wave propagation direction and generation in addition to strong seasonal variations in wavelength and amplitude occurrence of these ring waves is associated not only with tropical deep convections but also with summertime midlatitude convection wintertime extratropical jets and topography such as islands the high resolution ecmwf analysis data capture most of the cgw features but the wave amplitude is significantly weaker than airs observations showing few convectively generated cgws

early mississippian evaporites of coastal tropical wetlands extensive evaporites in lower mississippian successions from palaeoequatorial regions are commonly used as evidence for an arid to semi arid palaeoclimate however in this study detailed studies of evaporites and their context refute this interpretation detailed sedimentological and petrographical analysis of the lower mississippian of northern britain is combined with archived log data from more than 40 boreholes across southern scotland northern england and northern ireland and published literature from canada two key cores from the tweed basin and the northern margin of the northumberland solway basin contain 178 evaporite intervals and reveal twelve distinct forms of gypsum and anhydrite across seven facies that are associated with planar laminated siltstone and intercalated thin beds of ferroan dolostone nodular gypsum and anhydrite typically in intervals less than 1 to 2 m thick are integral components of the succession nodular evaporite occurs within about 1 m of a palaeosurface but most evaporite deposits represent ephemeral brine pans to semi permanent hypersaline lakes or salinas on a floodplain that was subjected periodically to storm surges introducing marine waters formation of evaporites under a strongly seasonal climate in a coastal wetland is supported by palaeosol types and geochemical proxies and from palaeobotanical evidence published previously although 65 of modern equatorial areas experience a strongly seasonal climatic regime salinas and sabkhas are a minor component today in comparison with the evidence from these lower mississippian successions this implies that the earliest terrestrial environments were complex and dynamic providing a diverse range of habitats in which the early tetrapods became terrestrialized and represent a setting that is rarely preserved in the geological record

medium scale traveling ionospheric disturbances triggered by super typhoon nepartak 2016 two remarkable typhoon induced traveling ionospheric disturbances tids with concentric and northwest southeast nw se alignments respectively associated with concentric gravity waves cgws and ionosphere instabilities possibly seeded by cgws were observed in total electron content tec derived from ground based gnss networks in taiwan and japan when the category 5 super typhoon nepartak approached taiwan on 7 july 2016 the concentric tids ctids first appear with horizontal phase velocities of 161 200 m s horizontal wavelengths of 160 270 km and periods of 15 22 min during 08 00 11 20 ut following the ctids the nw se aligned nighttime medium scale tids mstids are formed on the west edge of the ctids over the taiwan strait during 11 30 14 00 ut it is suggested that the mstids are produced by the electrodynamical coupling of perkins instability and cgw induced polarization electric fields this study proposes connections of typhoon induced ctids and subsequently occurring mstids in the low latitude ionosphere

u pb dating of perovskite by la icp ms an example from the oka carbonatite quebec canada abstract the potential for u pb dating of the mineral perovskite using laser ablation inductively coupled plasma mass spectrometry la icp ms has been evaluated perovskite can have relatively elevated u and th contents making it a potentially useful geochronometer kimberlite lamprophyre and carbonatite intrusions are prone to alteration and typically contain abundant xenocrysts thus standard techniques for dating the magmatic emplacement of these rocks becomes highly problematic perovskite however is commonly present as a primary magmatic mineral in these rocks and has been used to constrain the timing of kimberlite and lamprophyre emplacement the main limitations to the production of accurate la icp ms u pb ages for perovskite are the lack of suitable standards coupled with the large common pb correction required 204 hg can produce large isobaric interference on the non radiogenic 204 pb isotope and methods based on 208 pb 206 pb and u th ratios are hampered by the enhanced th content present in most perovskite crystals after careful calibration using zircon reference materials common pb corrected 206 pb 238 u ages can be determined on each individual la icp ms analysis by using the measured 207 pb 206 pb ratio which is dominated by the common pb proportion in phanerozoic rocks this method assumes that the perovskite crystals analyzed are cogenetic and have the same initial pb ratios the la icp ms method has been applied to data collected on two large single perovskite crystals from the oka carbonatite complex quebec canada the weighted mean 206 pb 238 u age of 131 7 ma n 25 mswd 0 42 is consistent with published geochronology data from the region and suggests that la icp ms dating of perovskite could be a useful low cost alternative to compliment existing techniques

traveling ionospheric disturbances observed in the oi 630 nm nightglow images over japan by using a multipoint imager network during the front campaign pilot observations using a network of five all sky imagers asis were conducted during the new moon period of may 19 22 1998 as part of the f region radio and optical measurement of nighttime tid front campaign the network observation enabled us to track propagation of medium scale traveling ionospheric disturbances tids in the oi 630 nm nightglow over a distance of more than 2500 km the tids were observed every night during the campaign period but occurrence was limited from evening to midnight they have horizontal wavelengths of 200 600 km travel a horizontal distance of more than 1000 km and last for more than three hours in every case the tids moved southwestward with a velocity of 83 137 m s using dual site tid images the altitude of the tid structures in the 630 nm nightglow was calculated to be 260 km which corresponds to the bottom side of the mid latitude ionospheric f layer

bow and stern waves triggered by the moon s shadow boat 1 it has been predicted that the moon s shadow the cooling region sweeping over the earth s atmosphere with a supersonic speed could trigger bow waves since 1970 the longest total solar eclipse within next hundred years occurring on 22 july 2009 sweeps over the eastern asia region during the noontime period an analysis of the hilbert huang transform hht is applied to study ionospheric tec total electron content derived from ground based gps receivers in taiwan and japan we not only find the feature of the predicted bow wave but also the stern wave on the equator side of the eclipse path as well as the stern wake right behind the moon s shadow boat the bow and stern waves are formed by acoustic gravity waves of periods about 3 and or 5 minutes traveling equatorward with a phase speed of about 100 m s in the ionosphere

holocene deltaic sequence in the saloum estuary senegal abstract the 2250 km2 saloum delta south of dakar senegal consists of a holocene sedimentary sequence deposited during five evolutionary stages submerged postglacial ria funnel like estuary barred estuary cuspate delta and reverse estuary the passage from one stage to another was marked by the deposition of sedimentary units consisting of shelly sands silty or sandy clays and an extensive thick green mud muds in the lower strata dating between 6130 and 3500 yr b p were deposited on a subtidal mudflat while fine sands and silty clays characterize intertidal deposits a drastic change in sedimentation patterns resulting in the accumulation of a series of beach barriers likely was associated with a major climatic change the regional climate was then very dry and silt and sand were trapped in the water behind the barriers in two stages from 1990 to 1510 and 1020 to 600 yr b p each event was accompanied by construction of shell middens that demonstrate the presence of humans who exploited newly available shallows and banks relative sea level did not change significantly between 6000 yr b p and the present morphological and sedimentological changes observed in the late holocene sequences were apparently induced by a constraining climatic background

high resolution mapping of tec perturbations with the gsi gps network over japan two dimensional total electron content tec perturbations over japan are mapped with the geographical survey institute gsi gps network geonet gps earth observation network its spatial resolution is 0 15 latitude 0 15 longitude and temporal resolution is 30 seconds two dimensional tec observations with these high resolutions revealed spatial structures and temporal evolutions of traveling ionospheric disturbances tids in the nighttime mid latitude ionosphere on july 03 1997 a preliminary result of the tec perturbation mapping indicates that it would be a strong tool to investigate the ionospheric structures in detail coordinated observations with other ionospheric observation techniques such as incoherent scatter is radars airglow imagers and ionosondes are needed to clarify the vertical structure of the ionosphere

macrocrystal phlogopite rb sr dates for the ekati property kimberlites slave province canada evidence for multiple intrusive episodes in the paleocene and eocene abstract new rb sr age determinations using macrocrystal phlogopite are presented for 27 kimberlites from the ekati property of the lac de gras region slave province canada these new data show that kimberlite magmatism at ekati ranges in age from at least late paleocene 61 ma to middle eocene time 45 ma older perovskite bearing kimberlites from ekati extend this age range to late cretaceous time 74 ma within this age range emplacement episodes at 48 51 53 55 56 and 59 61 ma can be recognized middle eocene kimberlite magmatism of the previously dated mark kimberlite 47 5 ma is shown to include four other pipes from the east central ekati property a single kimberlite aaron may be younger than the 47 5 ma mark kimberlite the economically important panda kimberlite is precisely dated in this study to be 53 3 0 6 ma using the phlogopite isochron method and up to six additional kimberlites from the central ekati property have early eocene ages indistinguishable from that of panda including the koala and koala north occurrences late paleocene 55 56 ma kimberlite magmatism represented by the diavik kimberlite pipes adjacent to the southeastern ekati property is shown to extend onto the southeastern ekati property and includes three and possibly four kimberlites a precise eight point phlogopite isochron for the cobra south kimberlite yields an emplacement age of 59 7 0 4 ma eight other kimberlites from across the ekati property have similar late paleocene rb sr model ages the addition of 27 new emplacement ages for kimberlites from the ekati property confirms that kimberlite magmatism from the central slave province is geologically young despite ages ranging back to cambrian time from elsewhere in the slave province with the available geochronologic database lac de gras kimberlites with the highest diamond potential are currently restricted to the 51 53 and 55 56 ma periods of kimberlite magmatism

ionospheric bow waves and perturbations induced by the 21 august 2017 solar eclipse u s national science foundation grant ags 1242204 nasa grant nnx17ah71g nasa lws muri grant onr15 foa 0011 onr n00014 17 1 2186

msx satellite observations of thunderstorm generated gravity waves in mid wave infrared images of the upper stratosphere data from the midcourse space experiment msx has provided the first observations of thunderstorm generated gravity waves imaged from space gravity wave theory predicts that isolated sufficiently convective thunderstorms can launch waves and create a unique intensity pattern of concentric circles on a radiating surface of constant altitude above such a storm among the msx constant nadir angle mid wave infrared mwir observations two instances of such patterns have been identified it was confirmed from meteorological satellite images that highly convective isolated thunderstorms occurred at the locations and times expected

stratosphere perturbed by the 2011 mw9 0 tohoku earthquake this study examined the formosat 3 cosmic radio occultation soundings of total electron content in the ionosphere from 150 to 550 km and refractivity index in the lower atmosphere from 0 to 60 km after during the 2011 mw9 0 tohoku earthquake tsunami the refractivity index observations show the first evidence of the tohoku earthquake tsunami induced vertical oscillations in the lower atmosphere the atmospheric oscillations with vertical wavelength ranging from 0 5 to 8 km and from 10 to 40 km respectively appear in the stratosphere and ionosphere after the earthquake onset the short vertical wavelengths suggest that the oscillations are the atmospheric oscillatory tail due to the wavefront of the earthquake tsunami the radio occultation technique is a tool for detecting the atmospheric waves induced by earthquake or some other sources plain language summary it has been well known that the sudden uplift of the earth s surface due to earthquake tsunami significantly disturbs the upper atmosphere and ionosphere however the evidence of earthquake tsunami induced waves in the lower atmosphere is insufficient due to the lack of observation supporting here the formosat 3 cosmic f3 c radio occultation refractivity index is for the first time to capture the tohoku earthquake induced vertical oscillations at the stratosphere altitudes from 30 to 40 km the results in this study not only shed lights on understanding of earthquake tsunami waves perturbing the whole atmosphere but also suggest that the radio occultation technique can benefit to the earthquake tsunami warning system

a rb sr isochron age for a kimberlite from the recently discovered lac de gras field slave province northwest canada a rb sr phlogopite macrocryst whole rock isochron age of 47 5 0 5 ma is reported for a kimberlite from the recently discovered lac de gras field in the slave province northwestern canada this is the youngest reliably dated kimberlite occurrence in the world and correlates closely in time with emplacement of kimberlites in tanzania and yakutia indicating a widespread kimberlite emplacement event on three different cratons in the eocene

simultaneous observations of convective gravity waves from a ground based airglow imager and the airs satellite experiment 1 we report the first joint observations of convectively generated gravity waves gws using an oh airglow imager in colorado and the atmospheric infrared sounder airs onboard the aqua satellite convective gws appearing as concentric rings are observed over the western great plain regions of north america in the evening of 3 june 2008 in the airglow images inspecting both weather radars and airs radiances at 8 1 m strong convective clouds are found near the center of the concentric rings the airs data at 4 3 m show semicircular gws with horizontal wavelengths of 60 80 km at 0900 ut whereas the airglow imager observed circular gws with horizontal wavelengths of 44 km and airglow emission perturbation of 6 at the same geographic location at 0910 ut large scale gws horizontal wavelengths greater than 100 km emanating northwestward can be seen in both airs data and airglow images at different times the imager observed small scale ripples associated with unstable concentric gws in the mesopause in the early evening given that the brightness temperature perturbation of the gws in the airs data is about 0 16 k and assuming that the gws propagate without dissipation from the stratosphere to the upper mesosphere the expected airglow emission perturbation caused by the gws would be 4 17 ray tracing simulations are performed to demonstrate that the gws seen in airs and in the imager were likely excited by the same convective system

evidence of dynamics reversal in tropical estuaries geomorphological and sedimentological consequences salum and casamance rivers senegal south dakar senegambian estuaries are subject to an unusual hydrodynamical regime caused by weak or absent run off in the salum delta each distributary lacks fresh water during most of the year only the tidal flows arc responsible for geomorphological and sedimentological effects the current distribution shows a net discharge upstream due to the extensive evaporation and evapotranspiration in mangrove swamps and tidal flats consequently the salinity is always higher towards the river than near the sea a high salinity bottom layer suggests the occurrence of a supersaline wedge of reverse sense to the salt wedge of a normal estuary such an inverse pattern is similarly displayed by sedimentological features double upstream tumed spits and by the external location of the turbidity maximum a coherent reverse estuary model is suggested from our field observations

first spaceborne observation of the entire concentric airglow structure caused by tropospheric disturbance spaceborne imagers are able to observe the airglow structures with wide field of views regardless of the tropospheric condition that limits the observational time of the ground based imagers concentric wave structures of the o2 airglow in 762 nm wavelength were observed over north america on 1 june 2013 from the international space station this was the first observation in which the entire image of the structure was captured from space and its spatial scale size was determined to be 1200 km radius without assumptions the apparent horizontal wavelength was 80 km and the amplitude in the intensity was approximately 20 of the background intensity the propagation velocity of the structure was derived as 125 62 m s and atmospheric gravity waves were estimated to be generated for 3 5 1 7 h concentric structures observed in this event were interpreted to be generated by super cells that caused a tornado in its early phase

traveling ionospheric disturbances over the united states induced by gravity waves from the 2011 tohoku tsunami and comparison with gravity wave dissipative theory

characteristics of nighttime medium scale traveling ionospheric disturbances observed over alaska 1 we focused on propagating wave like structures which frequently appeared in the o i 630 0 nm airglow images obtained by an all sky imager installed at poker flat research range 65 1 n 147 4 w magnetic latitude 65 6 in alaska these events are classified as medium scale traveling ionospheric disturbances mstids on the basis of the wavelength and propagating speed the unique points of our observation are 1 the two dimensional structures of mstids in the subauroral region are revealed 2 the horizontal direction of the electric field can be estimated from the motion of the evening co rotating patch ecp aurora appearing simultaneously and 3 neutral winds are simultaneously observed by a fabry perot spectrometer statistical study of these mstid events from november 2001 to april 2002 indicates the following characteristics the mstids were observed almost every evening and sometimes in the morning but were not observed at midnight typical propagating speed direction and wavelength of the wave phenomena were about 135 m s southwestward and about 250 km respectively when the mstids appeared northward neutral winds and westward plasma drifts were dominant this indicates that the perkins instability does not contribute to the development of mstids in the alaska region the vertical wavelength analysis using the dispersion relation of gravity waves with the observed wave parameters and background winds suggests that the observed mstids over alaska are the atmospheric gravity waves agws as a case study temporal variation of an mstid event on 21 december 2001 is shown results of a ray tracing analysis of this event suggest that the agws come from the equatorward edge of the auroral oval

vertical structure of the ionospheric response following the m w 7 9 wenchuan earthquake on 12 may 2008 the response of the vertical ionospheric electron density structure to the mw 7 9 wenchuan earthquake on 12 may 2008 was recorded by the formosat 3 cosmic f3 c radio occultation ro precise orbit determination pod total electron content tec the horizontal propagation characteristics of the seismo traveling ionospheric disturbances were identified by combining ground based global navigation satellite system gnss tec data and ro tec data the postseismic ionospheric infrasound wavefront with wavelength of around 80 km at altitude of 150 350 km was scanned vertically by an individual ro tec profile a large amount of tec profiles around the epicenter from 0000 to 1200 ut provide evidence of continental earthquake induced vertical oscillations that lasted in the ionosphere for several hours ro observed vertical perturbations appear on both the southward and northward sides of the epicenter the vertical structure of the ionospheric oscillations with wavelength ranging from 10 to 80 km increased with altitude between 230 and 650 km

concentric waves and short period oscillations observed in the ionosphere after the 2013 moore ef5 tornado 1 we detected clear concentric waves and short period oscillations in the ionosphere after an enhanced fujita scale ef 5 tornado hit moore oklahoma u s on 20 may 2013 using dense wide coverage ionospheric total electron content tec observations in north america these concentric waves were nondispersive with a horizontal wavelength of 120 km and a period of 13 min they were observed for more than 7 h throughout north america tec oscillations with a period of 4 min were also observed to the south of moore for more than 8 h a comparison between the tec observations and infrared cloud image from the goes satellite indicates that the concentric waves and short period oscillations are caused by supercell induced atmospheric gravity waves and acoustic resonances respectively this observational result provides the first clear evidence of a severe meteorological event causing atmospheric waves propagating upward in the upper atmosphere and reaching the ionosphere

reconstructing the duration of the west african monsoon season from growth patterns and isotopic signals of shells of anadara senilis saloum delta senegal abstract long term reconstructions of the seasonality of the west african monsoon are limited by the lack of seasonally resolved paleoclimate archives in this region we present an application based on the growth patterns and monthly resolved 18o profiles of anadara senilis bivalve shells to quantitatively estimate the duration of the rainy and dry seasons in the hypersaline saloum delta senegal fortnightly growth patterns are used to estimate changes of the growth rate and to place the shell isotope record into a temporal context based on fortnightly growth patterns and sharply declining 18o values the duration of the rainy season was estimated as an illustrative example we quantitatively estimated the duration of two rainy seasons and two dry seasons that occurred about 1500 years ago from a fossil shell of the dioron boumak archaeological site to the nearest month this precision can be statistically improved by the analysis of a larger shell number or by higher resolution isotope sampling our results open the possibility of using large fossil shell accumulations in the saloum delta for quantitative studies of the long term variability of the west african monsoon seasonality

gnss based statistical analysis of ionospheric anomalies during typhoon landings in taiwan japan using the global navigation satellite system gnss differenced total electron content dtec series the traveling ionosphere disturbances tids of 22 typhoons registered in taiwan japan between 2013 and 2016 were studied the horizontal speed of the first tid during a typhoon landing can be estimated by a two station method with the ionosphere anomaly indicator in total electron count units tecus dtec 0 15 tecu the horizontal speed of the tids was from 155 to 210 m s and with an average speed of 168 70 m s the estimated tid speeds of typhoons soudelor 205 93 m s and megi 158 47 m s are not consistent with each other even though they had very similar trajectories when cross through taiwan island moreover the propagation velocity of the typhoon ionospheric anomaly showed a significant positive correlation r 0 78 0 05 with the change rate of the typhoon central air pressure and a negative correlation r 0 52 0 05 with the central pressure before landing gravity waves were generated by land friction terrain blocking and strong wind shear transport energy into the atmosphere from the near surface to the mesosphere and thermosphere which is the main cause of ionosphere disturbances during typhoon landing

a genetic story of olivine crystallisation in the mark kimberlite canada revealed by zoning and melt inclusions abstract elucidating the composition of primary kimberlite melts is essential to understanding the nature of their source petrogenesis rheology transport and ultimately the origin of diamonds kimberlite rocks are typically comprised of abundant olivine 25 60 vol which occurs as individual grains of variable size and morphology and includes xenocrysts and zoned phenocrysts zoning patterns and inclusions in olivine can be used to decipher the petrogenetic history of kimberlites starting from their generation in the mantle through to emplacement in the crust this study examines well preserved euhedral zoned olivine crystals from the mark kimberlite lac de gras canada olivine typically consists of xenocrystic cores which are homogeneous in composition but vary widely between grains fo88 1 93 6 these cores are in turn surrounded by in order of crystallisation magmatic rims and mg rich rinds fo95 3 98 1 in addition we document a new type of olivine zone outmost rind that overgrows mg rich rinds crystal and melt fluid inclusions are abundant in olivine and preserve a record of kimberlite melt evolution for the first time in the studies of kimberlite olivine we report primary melt inclusions hosted in mg rich olivine rinds in addition we observe that pseudosecondary melt fluid inclusions are restricted to interior olivine zones cores rims and are considered to have formed prior to rind formation pseudosecondary melt fluid inclusions are inferred to have been entrapped at depth as evidenced by measured densities in thermometric experiments of co2 and decrepitation haloes indicating a minimum entrapment pressure of 200 450 mpa or 6 15 km both primary and pseudosecondary melt inclusions in olivine have daughter minerals dominated by ca mg and k na ba sr bearing carbonates k na chlorides along with subordinate silicates e g phlogopite monticellite fe mg al ti spinel perovskite phosphates and sulphates sulphides and periclase in addition to phases reported in primary melt inclusions pseudosecondary melt inclusions contain more diverse and exotic daughter mineral assemblages where they contain phases such as tetraferriphlogopite ba or k sulphates kalsilite and na phosphates the daughter mineral assemblages are consistent with a silica poor alkali dolomitic carbonatite melt we demonstrate that the different types of inclusions in olivine can assist in constraining the timing of multi stage olivine growth and the composition of the crystallising melt the large variance in olivine zoning patterns morphologies and ni distribution i e both coupling with and decoupling from fo indicates that olivine in the studied mark kimberlite samples represent an accumulation of olivine where olivine was derived from successive stages of the ascending magma and or from multiple but related pulses of magma primary and pseudosecondary melt fluid inclusions in olivine indicate that a variably differentiated silica poor halogen bearing alkali dolomitic melt crystallised and transported olivine in the mark kimberlite

a model study of the effects of winds on concentric rings of gravity waves from a convective plume near fort collins on 11 may 2004 1 using a convective plume model and a ray trace model we investigate the effects of winds on concentric rings of gravity waves gws excited from a convective plume on 11 may 2004 near fort collins colorado we find that winds can shift the apparent center of the concentric rings at z 87 km from the plume location we also find that critical level filtering for gws with small phase speeds propagating in the same direction as the wind and wave reflection for high frequency gws with small horizontal wavelengths propagating in the opposite direction to the wind prevent many gws from reaching the oh airglow layer additionally we find that strong winds disrupt the concentric ring patterns causing distorted squashed ring and arc like patterns instead using a zero wind profile and a representative april mean zonal wind profile we compare our model results with observations of concentric rings at the yucca ridge field station 40 7n 104 9w we find that the model horizontal wavelengths and periods agree reasonably well with the observed data we also compare the model temperature perturbations with the temperature perturbations calculated from the intensity perturbations because the observations show less critical level filtering than from the april wind profile and more critical level filtering than from the zero wind profile we conclude that the winds on 11 may were likely somewhat smaller than the april zonal wind profile assumed here

observational evidence of wave ducting and evanescence in the mesosphere a collaborative radar and imaging study of gravity waves over the hawaiian islands was performed during october 1993 as part of the airborne lidar and observations of hawaiian airglow 1993 coupling and dynamics of regions equatorial aloha 93 cadre campaign to investigate the propagation characteristics of short period 1 hour waves at nightglow altitudes the horizontal wavelengths and apparent phase speeds of quasi monochromatic wave events were measured in four separate nightglow emissions using data obtained by a high resolution ccd imager this information was correlated with simultaneous mf radar wind measurements over the same height interval 80 100 km to infer intrinsic wave parameters in each case correlating the two data sets allowed the determination of the local vertical wavenumber for each event in particular whether it be real indicative of freely propagating waves or imaginary indicative of ducted or evanescent waves the results of this study indicate a preponderance of ducted or evanescent waves at 80 100 km during the time of the observations with up to 75 of the events recorded exhibiting ducted or evanescent behavior also noted was a tendency for ducted behavior to be more prevalent among waves with shorter horizontal wavelengths in agreement with doppler ducting theory these results suggest that ducted waves are relatively common in the upper mesosphere and lower thermosphere region at least over the mid pacific ocean as small scale waves which are ducted have the potential to travel much longer horizontal distances than freely propagating waves the frequency of their occurrence should be taken into account in efforts to quantify gravity wave effects at these altitudes

mesospheric concentric gravity waves generated by multiple convective storms over the north american great plain 1 we report on six continuous hours of oh airglow imager observations at z 87 km of convectively generated gravity waves gws near fort collins colorado on the evening of 08 september 2005 these gws appeared as nearly concentric rings and had epicenters near the locations of deep convection in three thunderstorms in colorado nebraska and south dakota using goes satellite and weather radar observations we show that the gws closely follow the thunderstorms using the background wind from a nearby radar the intrinsic wave parameters and vertical wavelengths are calculated the temperature perturbations are estimated to be t t 1 3 for gws with horizontal wavelengths h 20 40 km and horizontal phase speeds 40 60 m s the horizontal wavelengths of gws from a convective cluster decreased in time from 30 to 15 km we employ convective plume and ray trace models to simulate the gw induced oh intensity perturbations from convective plumes clusters and complexes we find that the results using the background model wind radiosonde time gcm agree well with the late time observations when the images are dominated by southwestward short wavelength high frequency gws these late time gws propagate against the background wind and have h 30 40 km and periods of 20 30 min the oh intensity perturbations are enhanced because the vertical wavelengths z increased t t increased and the vertical velocity perturbations w decreased because the gws were near their reflection levels we also find that these short wavelength gws were created 5 h earlier by an extremely energetic deep convective plume in south dakota thereby showing that small scale convective gws directly link the troposphere and mesopause region

concentric gravity waves in the mesosphere generated by deep convective plumes in the lower atmosphere near fort collins colorado 1 gravity waves in the mesopause region 80 105 km may induce perturbations in oh meinal band emissions at 87 km these perturbations can be observed by ground based oh airglow imagers in this paper we present observations of concentric gravity waves cgw by the all sky oh imager at yucca ridge field station 40 7 n 104 9 w near fort collins colorado we find that expanding rings of concentric gravity waves were observed on 9 out of 723 clear nights from 2003 to 2008 in particular on 11 may 2004 concentric rings were observed for 1 5 h with nearly perfect circular rings entirely in the field of view during the first 30 min the centers of the concentric rings occurred at the geographic locations of two strong convective plumes which were active in the troposphere 1 h earlier we measured the horizontal wavelengths and periods of these gravity waves as functions of both radius and time these results agreed reasonably well with the internal boussinesq gravity wave dispersion relation with an assumed zero background wind similarly for the other 8 cases strong convective plumes occurred prior to the cgw observations near the apparent center of each of the arcs or rings for the 7 out of the 9 cases radiosonde data were available up to z 30 35 km these data showed that the wind speeds from the tropopause to 30 35 km were smaller than 20 30 m s because 8 of the 9 cases occurred when the total horizontal mean winds were weak and because the horizontal winds below 87 km were less than 20 m s on 11 may 2004 according to radiosonde and time gcm model data we postulate that weak background horizontal winds are likely a necessary condition for gravity waves excited from convective overshooting to be observed as concentric arcs or rings in the oh layer

perturbations to the lower ionosphere by tropical cyclone evan in the south pacific region very low frequency vlf electromagnetic signals from navigational transmitters propagate worldwide in the earth ionosphere waveguide formed by the earth and the electrically conducting lower ionosphere changes in the signal properties are signatures of variations in the conductivity of the reflecting boundary of the lower ionosphere which is located in the mesosphere and lower thermosphere and their analysis is therefore a way to study processes in these remote regions here we present a study on amplitude perturbations of local origin on the vlf transmitter signals npm nlk naa and jji observed during tropical cyclone tc evan 9 16 december 2012 when tc was in the proximity of the transmitter receiver links we observed a maximum amplitude perturbation of 5 7db on jji transmitter during 16 december event from long wave propagation capability model applied to three selected events we estimate a maximum decrease in the nighttime d region reference height h by 5 2 km 13 december npm and maximum increase in the daytime d region h by 6 1 km and 7 5 km 14 16 december jji the results suggest that the tc caused the neutral densities of the mesosphere and lower thermosphere to lift and sink bringing the lower ionosphere with it an effect that may be mediated by gravity waves generated by the tc the perturbations were observed before the storm was classified as a tc at a time when it was a tropical depression suggesting the broader conclusion that severe convective storms in general perturb the mesosphere and the stratosphere through which the perturbations propagate

duration and periodicity of kimberlite volcanic activity in the lac de gras kimberlite field canada and some recommendations for kimberlite geochronology abstract establishing the emplacement ages and distribution pattern of central slave kimberlites has played a key role in diamond exploration within the lac de gras kimberlite field nonetheless emplacement age information is lacking for approximately 80 of the known kimberlites in this field making the assessment of emplacement age patterns difficult this study expands the number and geographic coverage of kimberlite emplacement ages within the lac de gras field to re assess the absolute timing duration and possible number of pulses of kimberlite eruption u pb perovskite ages for eight previously undated kimberlites and an additional thirteen kimberlites which were previously dated by either the rb sr or u pb methods fall within the age range of 75 45 ma as previously suggested for kimberlite magmatism in this area we report the first carboniferous age kimberlite in the central lac de gras field the eddie kimberlite with a u pb perovskite age of 321 0 3 0 ma a compilation of 57 kimberlite emplacement ages from the central lac de gras field was evaluated using probability density and mixture modeling methods five short duration 4 5 ma periods of kimberlite magmatism are recognized at 48 54 61 66 and 72 ma the three younger pulses have been previously recognized and remain relatively unchanged the 54 ma pulse represents the major kimberlite eruption event containing 40 of the currently dated kimberlites in lac de gras field a detailed evaluation of the temporal spatial evolution of lac de gras kimberlites reveals that the oldest diamond poor kimberlites 75 60 ma were emplaced in the northern and eastern parts of the field whereas the younger 55 48 ma economic kimberlites are concentrated in the center of the field

ionospheric disturbances induced by a missile launched from north korea on 12 december 2012 1 ionospheric disturbances caused by a missile launched from north korea on 12 december 2012 were investigated by using the gps total electron content tec the spatial characteristic of the front edge of v shaped disturbances produced by missiles and rockets was first determined considering the launch direction and the height of estimated ionospheric points at which gps radio signal pierces the ionosphere the missile passed through the ionosphere at heights of 391 425 and 435 km at 0056 30 0057 00 and 0057 30 ut respectively the observed velocities of the missile were 2 8 and 3 2 km s at that time which was estimated from the traveling speed of the front edge of v shaped disturbances westward and eastward v shaped disturbances propagated at 1 8 2 6 km s the phase velocities of the westward and eastward v shaped disturbances were much faster than the speed of acoustic waves reported in previous studies suggesting that sources other than acoustic waves may have played an important role furthermore the plasma density depletion that is often observed following missile and rocket launches was not found this suggests that the depletion resulting from the missile s exhaust was not strong enough to be observed in the tec distribution in the topside ionosphere