spatio temporal variability in suspended particulate matter concentration and the role of aggregation on size distribution in a coral reef lagoon this paper presents the concentration and size distribution of suspended particles in the south west coral reef lagoon of the island of new caledonia data are provided by filtration techniques optical backscattering obs measurements and in situ laser diffraction particle sizing the concentration of suspended particles increased from reef to land a bottom nepheloid layer occurred over the entire lagoon and was more distinct on the nearshore area small particles were more abundant in the bottom nepheloid layer than in the overlying water column the concentration of suspended particles showed more variability over space than over time conversely the particle size distribution of suspended particles showed more variability at a given location over a month time variability than at a given moment over the lagoon space variability analysis showed that aggregates represented a large fraction of suspended particles microscope visualization and chemical analysis of a sample suggest the inclusion of a transparent exopolymeric matrix the relative abundance of aggregates over suspended particle volume concentration was found to increase as the quantity of suspended particle decreased the spatial distribution of the relative abundance of aggregates suggests more aggregates proximal to coral reefs the high concentration of aggregates at low turbidity and the spatial distribution of the relative abundance infer that aggregation is induced by the presence of organic ligands unlike optical backscattering and light attenuation measurements that are size sensitive measurements of suspended particle concentration in situ laser diffraction particle sizing provides a relevant optical measurement of suspended particulate matter in such an aggregate dominated system

unexpected characteristics of the 150 km echoes observed over gadanki and their implications recent discovery of two distinct types of 150 km echoes namely type a and type b and subsequent progress in the large scale kinetic simulation of photoelectron induced plasma waves have begun a new era in resolving the five decades long 150 km echoing riddle in this paper we present hitherto unrevealed three important and unexpected findings on the two distinct types of 150 km echoes based on gadanki radar observations our observations show unexpected predominance of type a echoes strong seasonal dependence of both type a and type b echoes and a surprising connection of the type b echoes to the unusually deep solar minimum of 2008 2009 we discuss how these results provide important new clues in tethering the competing processes involved in the daytime 150 km echoes and have significance in the recently proposed photoelectron induced plasma fluctuations as a potential mechanism for the 150 km echoes

daytime zonal drifts in the ionospheric 150 km and e regions estimated using ear observations multi beam observations of the 150 km echoes made using the equatorial atmosphere radar ear located at kototabang indonesia provide unique opportunity to study both vertical and zonal exb plasma drifts in the equatorial ionosphere in this paper we focus on estimating daytime zonal drifts at the 150 km 140 160 km and e 100 110 km regions using multi beam observations of 150 km and e region echoes made using the ear and study the daytime zonal drifts covering all seasons not studied before from kototabang zonal drifts in the 150 km and e regions are found to be westward and mostly below 80 m s 1 and 60 m s 1 respectively while the zonal drifts in the 150 km and e regions do not go hand in hand on a case by case basis the seasonal mean drifts in the two height regions are found to be in good agreement with each other zonal drifts at the 150 km region show seasonal variations with three maxima peaking around may september and january the zonal drifts at the 150 km region are found to be smaller than the f region drifts obtained from cindi onboard c nofs by about 25 m s 1 consistent with the height variations of f region zonal drifts observed by the jicamarca radar these results constitute the first comprehensive study of zonal drifts at the 150 km and e regions from kototabang indonesia and the results are discussed in the light of current understanding on the low latitude electrodynamics and coupling

a comparative study of equatorial daytime vertical e b drift in the indian and indonesian sectors based on 150 km echoes 1 in this paper we study for the first time the daytime vertical e bdrift velocities from gadanki and kototabang using the doppler shifts of the 150 km echoes observed during 2008 2010 a period of low solar activity drift velocities are mostly positive and confined to 35 m s 1 at both the locations except for gadanki where on a few occasions negative drift velocities have been observed in the afternoon hours drift velocities generally show a decreasing trend with local time and the largest drift is generally observed in the forenoon hours consistent with extensively reported observations and models of e bdrift drift velocities from gadanki and kototabang compared exceeding well on some days and differed remarkably on many days despite the fact that they are longitudinally separated by only 20 the day to day variation in the drift velocity could be as high as 15 m s 1 at gadanki and 7 m s 1at kototabang seasonal mean drifts over gadanki are found to be generally larger than those of kototabang the observations have been compared in detail with those reported earlier based on ground and satellite based observations and also with the scherliess fejer model the observed differences in the drifts at the two locations including the downward drifts have been discussed in the light of current understanding of the longitudinal variability ofe b drift

observation of coherent echoes with narrow spectra near 150 km altitude during daytime away from the dip equator 1 we present the rare observation of backscatter echoes perpendicular to the geomagnetic field from the 150 km altitude vicinity over a region situated away from the dip equator namely at gadanki 13 5 n 79 2 e 6 4 dip latitude a layer of weak echoes having signal to noise ratio snr of the order of 12 to 3 db was seen drifting downward from 157 km at 0930 lt to about 148 km at 1028 lt on july 12 1997 the doppler velocity as well as doppler width was in the range 10 20 ms 1 while there was no quasi periodicity as such in terms of echo occurrence the echo properties were in other respects very similar to 150 km echoes seen in equatorial regions this included the descending phase with time during the morning hours these constitute the first observations of daytime 150 km echoes away from the dip equator and only add to the mystery regarding the origin of these structures

hainan coherent scatter phased array radar hcopar system design and ionospheric irregularity observations the hainan coherent scatter phased array radar hcopar is one of the most important radio systems of the chinese meridian space weather monitoring project meridian project the radar is located at fuke station 19 5 n 109 1 e dip latitude 8 1 n hainan island china to observe the field aligned irregularities in ionospheric e and f regions it is operated with a peak power of 54 kw and uses the barker codes for good sensitivity its antenna array is composed of 18 times 4 five element yagi antennas and is used for both transmitting and receiving the yagi antennas are arranged in a rectangular grid 100 m long and 20 m wide covering an area of 2000 m2 this antenna arrangement forms seven radar beams from 22 5 to 22 5 in azimuth with an angle step of 7 5 the central beam points to due geographic north a brief description of the radar system data processing and signal characteristics is also provided the intensity doppler velocities and spectral widths of the quasi periodic echoes measured in the nighttime of june 23 2013 are presented as typical data of type ii irregularities in the e region the data recorded by the hcopar in the fan beam mode on september 15 2013 are displayed as the typical f region plasma bubbles

hydrodynamic influences on acoustical and optical backscatter in a fringing reef environment observations of hydrodynamics along with optical and acoustical water characteristics in a tropical fringing reef environment reveal a distinct signature associated with flow characteristics and tidal conditions flow conditions are dominated by tidal forcing with an offshore component from the reef flat during ebb measurements span variable wave conditions enabling identification of wave effects on optical and acoustical water properties high frequency acoustic backscatter 6 mhz is strongly correlated with tidal forcing increasing with offshore directed flow and modulated by wave height indicating dominant hydrodynamic influence backscatter at 300 and 1200 khz is predominantly diurnal suggesting a biological component optical backscatter is closely correlated with high frequency acoustic backscatter across the range of study conditions acoustic backscatter frequency dependence is used along with changes in optical properties to interpret particle size variations changes across wave heights suggest shifts in particle size distributions with increases in relative concentrations of smaller particles for larger wave conditions establishing a connection between the physical processes of a fringing tropical reef and the resulting acoustical and optical signals allows for interpretation and forecasting of the remote sensing response of these phenomena over larger scales

descending ion layer property in the gadanki radar observations of 150 km echoes and its implication to the echoing phenomenon 1 gadanki radar observations of the daytime 150 km echoes displaying descending features resembling the descending ion layer behavior are presented the descending pattern is intriguing since it indicates the possible role of density gradient associated with the ion layer in generating the irregularities responsible for 150 km radar echoes not envisioned before unusually strong snr and narrow spectral features of these echoes clearly indicate the role of sharp density gradients in the echoing process given the fact that gadanki is located at magnetically low latitude it is argued that these descending echoing layers are produced by interchange instability on the gradient of daytime descending ion layer formed by meridional wind shear associated with tidal gravity waves quite similar to that observed during nighttime the observations reported here are first of its kind illustrating the role of density gradient layers and are important in furthering our understanding on the puzzling 150 km echoing phenomenon

biofouling control for optical backscatter suspended sediment sensors abstract the use of optical backscatter instruments for measuring water turbidity for extended periods has been very limited due to the debilitating effect of biological fouling this is particularly the case in tropical coastal waters we describe a simple wiping mechanism attached to a logging nephelometer which can usually control fouling for up to a month even under conditions most favourable for fouling without a wiper deployment periods can be limited to only a few days scratching of the nephelometer by the wiper is not a major contributor to nephelometer error

channel adjustments to reservoir construction and gravel extraction along stony creek california stony creek drainage area 1920 km2 a tributary to the sacramento river 200 km north of san francisco has experienced channel adjustments to both dam construction and instream gravel extraction black butte dam constructed in 1963 reduced flood peaks and trapped the annual 100 000 m3 of bedload sediment formerly delivered from the upper watershed the reach below the dam changed from an active braided channel to an incised single thread channel shortly after dam construction about 25 km downstream of the dam large instream gravel mines annually extract 230 000 580 000 m su3 and have induced channel incision of over 5 m necessitating bridge repairs costing us 1 4 million

environmental effects of river sand mining a case from the river catchments of vembanad lake southwest coast of india rivers in the southwest coast of india are under immense pressure due to various kinds of human activities among which indiscriminate extraction of construction grade sand is the most disastrous one the situation is rather alarming in the rivers draining the vembanad lake catchments as the area hosts one of the fast developing urban cum industrial centre the kochi city otherwise called the queen of arabian sea the vembanad lake catchments are drained by seven rivers whose length varies between 78 and 244 km and catchment area between 847 and 5 398 km2 on an average 11 73 million ty 1 of sand and gravel are being extracted from the active channels and 0 414 million ty 1 of sand from the river floodplains the quantity of instream mining is about 40 times the higher than the sand input estimated in the gauging stations as a result of indiscriminate sand mining the riverbed in the storage zone is getting lowered at a rate of 7 15 cm y 1 over the past two decades this in turn imposes severe damages to the physical and biological environments of these river systems the present paper deals with the environmental effects of indiscriminate sand mining from the small catchment rivers in the southwest coast of india taking the case of the rivers draining the vembanad lake catchments as an example

high resolution observations of 150 km echoes at jicamarca high resolution soundings of equatorial upper e region echoes at jicamarca exhibit gravity wave modulated signal intensity distributions and doppler velocities corresponding to vertical plasma drifts a gravity wave wind driven interchange instability is suggested as a possible generation mechanism of the field aligned plasma irregularities responsible for the echoes the echoes may be utilized in gravity wave studies and in zonal electric field measurements by radars with modest sensitivities

fluidization of mud in estuaries the south alligator river located in the northern territory australia is a macrotidal estuary with suspended sediment concentration values reaching 10 g 1 1 in september 1986 in the dry season the estuary was well mixed in temperature and salinity while the vertical gradients in suspended sediment concentration were small at flood tides for most of the ebb tide duration a lutocline separated a clear upper layer from an extremely turbid bottom layer both layers being of comparable thickness the tidal evolution of the suspended sediment concentration is consistent with that computed by a numerical model based on the equation of conservation of mass of suspended sediment in this model sediment is entrained from the bottom and mixed vertically upward by eddy diffusion but through a richardson number dependence sediment induced buoyancy effects inhibit vertical mixing the final depth of the turbid layer can be readily estimated analytically as a result of a balance between the rate of kinetic energy input and the buoyancy flux determined by the particle fall velocity the presence of a lutocline helps form mud banks on the inner side of a meander

julia radar studies of equatorial spread f this paper presents coherent scatter radar observations of plasma irregularities in the equatorial f region ionosphere made with the julia jicamarca unattended long term studies of the ionosphere and atmosphere radar and discusses model equations and simulations pertinent to their interpretation the data set shows that bottom type and bottomside scattering layers are prevalent throughout solar minimum equinox bottom type layers are undifferentiated and relatively weak layers confined to a narrow range of altitudes falling within regions of the ionosphere driven by the e region dynamo these layers are often precursors to large scale radar plumes as well as to bottomside layers which are broader more structured and more intense layers than the bottom type variety bottomside layers are the source of intermediate scale plasma depletions that can ascend and penetrate through to the topside fluid simulations of the collisional interchange instability suggest that dynamo theory explains why one kind of layer emerges at a given time and altitude

in situ high frequency long term measurements of suspended sediment concentration in turbid estuarine system seine estuary france optical turbidity sensors response to suspended sediment characteristics abstract the aim of this study is to investigate the complex response of optical turbidity sensors side and back scattering sensors to suspended particle matter spm characteristics and the consequences when investigating spm dynamics from long term high frequency monitoring networks our investigation is based on the analysis of a unique dataset of monthly 12 h cycle measurements of spm characteristics such as turbidity concentration floc size distribution floc density and organic matter content in the macrotidal seine estuary france between february 2015 and june 2016 results reveal that despite calibration to a formazin standard turbidity sensor response to spm concentrations in the range of 7 7000 mg l 1 are strongly variable from the tidal scale to the annual scale and in different compartments of the seine estuary the variability in the calibration relationships is related to changes in the sensor sensitivity according to i the sensor intern technology mainly due to optical geometry and ii the variability in inherent optical properties iop of spm side scattering optical instruments measuring scattering at 90 provide at the annual scale a more stable optical response than backscattering sensor measuring scattering at angles larger than 100 for a wide variety of floc size and density in the estuarine environment while at the tidal scale the backscatter sensors are the most accurate sensor sensitivity is strongly affected by floc characteristics i e their median size d50 dry density and the scattering efficiency qb results highlight that the median particle diameter contribute to modify the scattering efficiency qb as well as the dry density qb increases with increasing floc size and for a given floc size qb increases with floc density in this study the results are next applied to turbidity data from the long term automated monitoring network in order to estimate spm concentrations and estimate the related uncertainties

in situ video and diffraction analysis of marine particles a design for a new underwater video system to detect and observe suspended particles is presented particles are collected and isolated in a rectangular box where they are highly illuminated by a white light plane the total field of view is determined the camera equipped with a remote controlled zoom can resolve particles sizes ranging from 25 m to several millimetres real time image analyses are therefore performed particle counts and size spectra are calculated and displayed total light intensity scattered by the illuminated particles is closely related to the back scattering values determined by an optical back scatter sensor a particle size analyser using diffraction analysis is associated to this video system on a custom profiler hydrological parameters are measured by a standard ctd probe associated to a chlorophyll sensor results are acquired and graphically presented in real time this custom profiler presents numerous advantages in oceanographic research two examples of its use in different coastal areas are presented in an estuary temporal evolution of particle characteristics was described in relation to the tide cycle while the video system allows direct visualization and characterization of the largest particles the particle size analyser performs precise quantification of the finest ones it was shown that the two methods were in accordance for quantification of large aggregates which were observed around slack tide when salinity decreased video analyses cannot be performed above 25 mg l 1 dry weight equivalent the system reliability resolution and limits were also demonstrated during a cruise in the gulf of finland a typical profile is presented here showing different layers one characterized by the association of heterotrophic flagellates and detritals and another dominated by zooplankton the surface layer being characterized by cyanobacterial colonies video associated to diffraction analyses allows the study of flocculation processes in estuaries and a detailed description of thin layers

the calibration of optical backscatter sensors for suspended sediment of varying darkness levels a series of calibration experiments were run in order to determine the effect of the colour of suspended sediment on the response of optical backscatter sensors obs munsell notation describes the properties of soil and sediment colour using the three parameters hue chroma and value which represent respectively the spectral position lightness level and amount of pure chromatic colour present the exposure of the obs to munsell soil chart patches revealed that the obs is sensitive to variations in munsell value and not munsell hue or chroma since obs output decreased with darkness level and increased with lightness level and munsell value it is suggested that the level of blackness of particles acts to absorb the near infrared ir signal of the obs modifying its output a strong correlation r2 0 984 was found between the observed and predicted obs outputs of varying concentrations and ratios of black and white suspended sediment the obs output was predicted using a linear mixture model incorporating end member calibrations of black and white sediment similar to green and boon green m o boon j d iii 1993 the measurement of constituent concentrations in nonhomogeneous sediment suspensions using optical backscatter sensors marine geology 110 pp 73 81 a strong correlation r2 0 907 was also observed between luminance factor and ir reflectance for various minerals suggesting a link between munsell notation and obs output formulae were developed to predict the ir reflectance of sediment of known munsell value concentration and size models predicting sediment transport should consider the effect of the level of blackness of particles on the obs response

the equatorial electrojet an integrated treatment of observations and models of the undisturbed equatorial electrojet is presented previous reviews have concentrated on particular aspects of the electrojet phenomenon such as ground magnetic variations the counterelectrojet or e region electron density irregularities and associated plasma instabilities here accomplishments during the past 15 years involving all aspects of the phenomenon are covered and where possible interrelated observational and theoretical studies during recent years have emphasized the local time longitude vertical and latitudinal structure of electric fields and currents in the electrojet this review similarly places its emphasis along these lines and by necessity involves a detailed examination of electrodynamic coupling with the neutral atmosphere tidal oscillations in temperature composition and winds the review concludes with an assessment of current knowledge concerning the equatorial electrojet and suggestions for the future direction of observational and theoretical research on electrodynamical processes in the equatorial ionosphere

a laboratory evaluation of optical backscatterance suspended solids sensors exposed to sand mud mixtures abstract optical suspended solids sensors were studied in the laboratory in order to obtain calibration factors and evaluate the general behavior of the instrument when exposed to suspensions of mud and sand the sensors were found to be capable of measuring the time averaged concentration of either suspended sand or suspended mud but the relative sensitivity of the sensor to these two different types of sediment varied by approximately an order of magnitude in mixtures with a constant or known mud concentration the instrument response to the mud may be treated as an offset and gains appropriate to sand may be used to estimate the suspended sand concentrations semi quantitative observations of the effects of flow direction relative to sensor orientation indicate that significant concern is warranted

evaluation of infilling and replenishment of river sand mining pits rivers are one of the main sources to supply sand and gravel for construction projects depending on river morphology and hydraulic characteristics its sediment transport capacity and mining operation method the extraction of river bed materials may affect its ecosystem through bank and bed erosion to advance the mechanisms of river pit infilling the effects of various parameters i e the distance between pits the pit plan shape the pit depth sediment size and approaching flow velocity on pit infilling volume are investigated in this research the results of this research show that infilling volume of upstream pit is insignificantly affected by the distance between the pits and it is completely refilled for different distances however the infilling volume of downstream pit decreases by increasing the distance between the pits in addition by reducing the ratio of pit length to its width pit shape extension in spanwise direction the pits can be excavated in a shorter distance from each other when this ratio decreases by 15 the infilling volume increases up to 30 subsequently as a cost effective option the pit distance can be reduced up to 50 in these conditions according to the obtained results although the sediment size has negligible effect on infilling volume in the studied range the infilling volume increases up to 20 by an increase of 8 in the approaching flow velocity increasing the ratio of pit length to its width pit shape extension in streamwise direction highlights the effectiveness of smaller depths so that the infilling volume increases up to 20 by a decrease of 20 in the pit depth in this regard it is recommended that the pit depth be restricted to 70 of the channel flow depth to have a complete pit refilling

sand and gravel mining impact on the surface water quality a case study from the city of tirebolu giresun province ne turkey the water resources in turkey are under immense pressure due to various kinds of anthropogenic activities among which sand and gravel mining is the most disastrous one due to its adverse environmental impacts in this study impacts of the sand and gravel mining activities in the city of tirebolu giresun province on the water quality of the stream harsit which courses in the eastern black sea basin of turkey are investigated in terms of ten water quality indicators namely turbidity t electrical conductivity ec dissolved oxygen do ph suspended sediment concentration ssc water hardness wh aluminum ion al3 manganese ion mn2 total chromium and total iron based on the average annual values of the studied water quality indicators it was concluded that the stream water quality was not impacted with regard to ec do ph wh and al3 despite the seventeen sand and gravel pits operated in the stream harsit due to the fact that sand and gravel mining has used the stream harsit surface water for material washing an increase of 125 in t 134 in ssc 63 in mn2 98 in total chromium and 111 in total iron has been determined respectively and so the stream water quality has been deteriorated it is thought that this deterioration may affect the groundwater quality of the stream harsit aquifer from there a groundwater of two and a half million cubic meters per year of which has been drawn for domestic water demand of the people in the city of tirebolu

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

new instrumentation for the investigation of sediment suspension processes in the shallow marine environment abstract an instrumentation system has been developed that continuously measures flow velocity water depth and suspended sediment concentration profiles in the nearshore zone the system consists of four components 1 an array of electronic sensors including an electromagnetic current meter a surface piercing resistance wave gauge and a five element array of optical back scatterance sensors 2 a signal processing electronics unit 3 a guyed mast support structure and 4 a data acquisition system the small size of the sensors and their response characteristics make the array suitable for monitoring sediment transport to within a few centimeters of the bed under moderately large breaking waves 2 m results from an experiment on an exposed ocean beach on the coast of washington u s a indicate that sand suspension events of long duration 15 40 sec relative to the period of incident waves contribute a significant quantity of sand to the total littoral drift work is now in progress to modify the system for self contained operation on the continental shelf field investigations with the modified system will focus on the acquisition of a data set to test the validity of the suspended sediment distribution equation

aggregate resources production and environmental constraints aggregates are produced from sand and gravel deposits or from bedrock sources production sites are numerous to minimize transport and are more and more in a competing land use position urbanization while creating a market also sterilizes deposits and pressures producers to relocate further from populated areas regulating and permitting quarries is an issue in regions with growing populations this regulatory environment may cause exploitation schemes to evolve towards greater recycling importing and marine production for example these changes may be entirely attributable to increased environmental constraints on producing operations and not on conventional mining constraints such as overburden ore grade and costs of operation

on a summer maximum in the occurrence frequency of 150 km f1 radar echoes over pohnpei 1 using three and a half years of 50 mhz radar data collected from pohnpei federated states of micronesia 6 96 n 158 19 e geographic 0 3 magnetic dip latitude we show for the first time that the occurrence frequency of 150 km or f1 echoes has a broad but conspicuous maximum during northern summer in this longitude sector with minimal activity in other months given a seasonal similarity to sporadic e es we suggest that an es layer instability cosgrove and tsunoda 2002 generates a polarization electric field which maps along geomagnetic field lines to the f1 region there forms thin plasma sheets that provide gradients to excite 3 m scale plasma waves via an interchange process

first vhf radar observations of tropical latitude e region field aligned irregularities indian mst radar at gadanki 13 5 n 79 2 e 12 5 dip was operated during july august 1994 to observe the 3 m scale size field aligned irregularities associated with the lower e region irregularity structure was studied by using height time variation of the echo intensity and weighted mean doppler velocity in this paper results of three diurnal cycles of observation are presented field perpendicular echoes were observed both during daytime and nighttime a layered irregularity structure extending down to altitude below 86 km was seen during the nighttime the daytime structure showed a narrow echoing region with significant downward slope doppler velocity was in the range of 20 50 ms 1 both during day and night and was in general consistent with the slope of scattering structure observed in the height time intensity plots

equatorial ionospheric electric fields during the november 2004 magnetic storm 1 we use radar measurements from the jicamarca radio observatory magnetometer observations from the pacific sector and ionosonde data from brazil to study equatorial ionospheric electric fields during the november 2004 geomagnetic storm our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour indicative of undershielding and overshielding prompt penetration electric fields in the pacific equatorial region during the november 7 main phase of the storm when the southward imf the solar wind and reconnection electric fields and the polar cap potential drops had very large and nearly steady values this result is inconsistent with the recent suggestion that solar wind electric fields penetrate without attenuation into the equatorial ionosphere for several hours during storm main phase the largest daytime prompt penetration electric fields about 3 mv m ever observed over jicamarca occurred during the november 9 storm main phase when large equatorial electrojet current and drift perturbations were also present in the pacific and brazilian equatorial regions the rise and decay times of these equatorial electric fields were about 20 min longer than of the corresponding solar wind electric fields the ratios of prompt penetration electric fields and corresponding solar wind electric field changes were highly variable even during the day and had largest values near dawn also the prompt penetration electric fields did not show polar cap potential drop saturation effects our results clearly highlight that the relationships of prompt penetration and solar wind electric fields and polar cap potentials are far more complex than implied by simple proportionality factors

laboratory apparatus for calibrating optical suspended solids sensors abstract an apparatus for testing and calibrating miniature to medium sized optical suspended solids sensors is described stable suspensions of sedimentary particles ranging in size from 10 6 to 4 10 3 m can be produced in water with concentrations exceeding 100 g 1 1 flow velocities in the test volume can be varied continuously from 0 1 to 1 5 m s 1 and samples of suspensions can be withdrawn directly with a peristaltic pump for gravimetric and particle size analyses the apparatus has been used to evaluate the effects of particle size flow speed and air bubbles on the performance of optical backscatterance sensors and transmissometers

further investigations on 150 km echoing riddle using simultaneous observations of 150 km and e region echoes from off electrojet location gadanki 1 in this paper we present a detailed study of the off electrojet daytime 150 km echoes based on simultaneous observations of daytime 150 km and e region echoes made on a few days per month during july 2005 to august 2006 using the gadanki radar daytime 150 km echoes are found to occur in all seasons over gadanki although echo occurrence is found to be maximum in equinoxes and minimum in summer no clear seasonal preference over gadanki has been observed in contrast e region echo occurrence made simultaneously shows a strong seasonal dependence with remarkably low occurrence in winter as compared to other seasons interestingly the 150 km echoes show a distinctly different morphology in winter as compared to other seasons echoes are observed in two distinct height regions in winter as compared to one broad region in other seasons also the strongest echo and the lowest altitude of echo occurrence are found to be associated with winter further a significant share of doppler velocities is found to be downward in winter as compared to predominantly upward velocities observed in other seasons no seasonal dependence in the spectral width of 150 km echoes however has been observed seasonally averaged doppler velocities are quite similar to those of the f region drifts reported from jicamarca again seasonally averaged drifts are found to be downward in winter afternoon as compared to upward velocities observed in other seasons notwithstanding the seasonal differences observed in the 150 km echoes echo occurrence is found to have a common feature of strong forenoon afternoon asymmetry with forenoon occurrence being greater these observations are discussed in the light of present understanding on the daytime 150 km echoing phenomenon

enhanced velocities and a shear in daytime esq over kwajalein and their relationship to 150 km echoes over the dip equator we present the first evidence of enhanced irregularity drift velocities and a velocity shear in the daytime e region at 4 3 n dip latitude these features found in radar measurements from kwajalein during q type sporadic e esq events are interpreted in terms of a polarization electric field that develops in response to the presence of latitudinal gradients in field line integrated conductivity caused by sporadic e layers because the e region over kwajalein connects directly to 150 km altitude over the magnetic dip equator we suggest that a similar polarization process is responsible for the so called 150 km echoes that have been observed routinely by the jicamarca radar

in situ particle size spectra and density of particle aggregates in a dredging plume abstract an in situ laser particle sizer the lisst 100 was used to describe the spatial variation of beam attenuation coefficient in situ particle size spectra and aggregate densities in a dredging plume in the sound oresund between denmark and sweden the results proved that the above mentioned parameters varied significantly within the investigated length of the plume approximately 2 km it is shown how the small single primary particles aggregate and change the in situ particle size spectra into a slightly better sorted and coarser size distribution and at the same time how the mean density of particles aggregates decreases significantly this shift in the state in which the particles exist in the water effectively changes the optical response of the mass of particles suspended in the water it is shown that adequate correlations between mass concentrations and beam attenuation coefficients can only be obtained if parameters describing the in situ quality and state of the mass of particles e g standard deviation of the size spectra and volume concentration is included in the regression from the spatial variation in mean density and in situ particle size it was possible to calculate the spatial difference in settling velocity it was found that the difference in settling velocity was only about a factor of 1 7 because increasing in situ particle size was counter balanced by decreasing mean density furthermore the time scale of flocculation within the plume was found to be in the order of 50 min

flood disturbance recovery and inter flood incision on a large sand bed river abstract the lower 800 km of the missouri river has been incising for decades however the 2011 flood scoured more sediment than the previous 12 yr combined the river rebounded in the following two years re depositing over 70 of the sediment scoured during the 2011 flood historic evidence suggests that past missouri river floods may have followed similar scour rebound patterns this paper analyzes 16 channel surveys from 1987 to 2014 including 50 723 total cross sections to document the morphological history of the lower 800 km of the missouri river over the last thirty years including flood disturbance and long term trends the last thirty years on the missouri river included two basic morphologic regimes steady incision during low to moderate flow periods and rapid scour rebound responses to floods surveys collected during the 2011 flood demonstrate that the river scoured throughout the flood including the falling limb and did not begin a rebound phase until after the flood the analysis also identifies sediment sinks associated with each of these scour regimes flood scour and incision between floods that exceed the total volume eroded from the bed during those periods results suggest that floodplain deposition may induce the supply limitation that drives flood scour on this large sand bed river additionally aggregate mining removes substantially more sediment than the total river incision between floods and the reaches with maximum scour during the 1993 and 2011 floods correspond to the zones of aggregate mining

radar observations of daytime 150 km echoes from outside the equatorial electrojet belt over gadanki 1 we present systematic observations of daytime 150 km echoes from gadanki 13 5 n 79 2 e 6 3 dip latitude the echoing region is confined to 142 162 km altitude and show forenoon descent and afternoon ascent displaying a necklace shape quite similar to that of the equatorial 150 km echoes signal to noise ratio velocity and spectral width are as high as 13 db above noise 5 to 35 m s 1 and 2 to15 m s 1 respectively the observed necklace shape is first of its kind from gadanki and the present observations have almost all characteristics of equatorial daytime 150 km echoes the gadanki radar observations hence provide first experimental evidence on the occurrence of daytime 150 km echoes outside the equatorial electrojet belt

role of imf b y in the prompt electric field disturbances over equatorial ionosphere during a space weather event on 7 january 2005 a p 40 prompt penetration electric field perturbations of opposite polarities were observed over thumba and jicamarca on a few occasions during 13 45 16 30 ut however the electric field was found to be eastward during 14 45 15 30 ut over both thumba and jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points on closer scrutiny three important observational features are noticed during 14 10 15 15 ut first during 14 10 14 45 ut despite increasing southward interplanetary magnetic field imf b z condition the already westward electric field over thumba weakened less westward while the eastward electric field over jicamarca intensified more eastward second the electric field not only became anomalously eastward over thumba but also got intensified further during 14 45 15 00 ut similar to jicamarca third during 15 00 15 15 ut despite imf b z remaining steadily southward the eastward electric field continued to intensify over thumba but weakened over jicamarca it is suggested that the changes in imf b y component under southward imf b z condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that thumba came into the same dp2 cell as that of jicamarca leading to anomalous electric field variations magnetic field measurements along the indian and jicamarca longitude sectors and changes in high latitude ionospheric convection patterns provide credence to this proposition thus the present investigation shows that the variations in imf b y are fundamentally important to understand the prompt penetration effects over low latitudes

julia radar studies of electric fields in the equatorial electrojet first results from the julia radar at jicamarca are presented these include coherent scatter observations of the equatorial electrojet and of 150 km echoes interferometry is used to measure the zonal drift rate of kilometer scale waves in the electrojet as functions of altitude a technique for estimating the background zonal electric field from the interferometry data is described the electric field estimates can be calibrated against the doppler speed of the 150 km echoes when the latter are present the kilometer scale wave drifts sometimes exhibit large amplitude periodic height variations with vertical wavelengths of about 10 km these signatures are reminiscent of the wind profiles measured with chemical release techniques in the lower thermosphere during the guara campaign

equatorial 150 km irregularities observed at pohnpei first observations of meter scale equatorial 150 km plasma irregularities outside the american longitude sector are reported the observations conducted at pohnpei western pacific with a wind profiling st radar demonstrate the feasibility of making ionospheric electric field measurements with low cost instruments and also reveal a potentially important anisotropy in the angular distribution of 150 km vhf radar echoes

characteristics of 150 km echoes linked with solar eclipse and their implications to the echoing phenomenon 1 this paper presents a study based on gadanki radar observations of 150 km echoes made during the solar eclipse of 15 january 2010 that occurred during 1122 1515 ist radar echoes were observed only during 1150 1215 ist and 1344 1356 ist linked with the entry and recovery phases of the eclipse respectively the most striking observation found is the unusual ascending and descending features of the echoing regions observed during these two time periods although these echoes occurred at higher altitudes than those of control days snr and spectral width of these echoes are similar to those of the lower echoing region observed on the control days further doppler velocities suggest the presence of westward electric field unlike those of the control days concurrent ionosonde observations showed ascent and descent of the f1 layer very similar to those observed in the 150 km echoes these observations and related analysis suggest that the observed echoes were due to the combined action of the electron density gradients and the reduced recombination rate linked with the solar eclipse effect these observations are first of its kind and elucidate the role of density gradient and recombination rate in the 150 km echoing process

geochemistry of cu co ni zn cd and cr in the surficial sediments of a tropical estuary southwest coast of india a granulometric approach geochemical characteristics of six trace metals cu co ni zn cd and cr in the bulk sediment and sand silt and clay fractions of a tropical estuary on the southwest coast of india have been studied and discussed in bulk sediment the trace metal concentration is controlled mainly by the textural composition of the sample mud sandy mud and sandy silt register higher concentrations of trace metals than that in sand dominant sediments the granulometric partitioning studies also re affirmed the role of particle size in enriching the trace metals the silt and clay fractions exhibit 7 8 times the enrichment of cu and cd compared to that in sand the enrichment factors of zn cr ni and co in the silt and clay fractions compared to that in sand are 5 6 4 5 2 5 and 2 3 times respectively the trace metals in the sand fraction particularly ni and cr exhibit strong positive correlation with the heavy mineral content of the samples it clearly indicates a heavy mineral pathway to the trace metals in the sand fraction cu and co in silt and clay fractions exhibit a marked decrease towards the high saline zones of the estuary this is attributed to the desorption of cu and co from particulate phases during estuarine mixing contrary to cu and co the content of zn in the clay fraction shows a marginal increase towards the estuarine mouth this could be explained by the influx of zn rich contaminant discharges from zn smelting industries located slightly north of the estuarine mouth the released zn will effectively be held in the lattices of the clay mineral montmorillonite which also exhibits a marked increase towards the estuarine mouth the anomalously high values of cd in some places of the central vembanad estuary is attributed to the local pollution

kilometric irregularities in the e and f regions of the daytime equatorial ionosphere observed by a high resolution hf radar during the international equatorial electrojet year high resolution vertical hf coherent radar experiments were performed in the ivory coast 9 24 62 n 5 37 38 w at frequencies in the range 1 8 mhz kilometric scale irregularities were observed in the e and f regions of the daytime equatorial ionosphere these irregularities constitute a large sporadic e layer within the altitude range 100 to 150 km larger than the width of the equatorial electrojet the higher part of this irregular region is detached in the morning and evening forming an intermediate region at 150 160 km these 150 km echoes overtakes the e region electrojet echoes at 100 120 km at noon the echolocation shows that the reflections arise from the vertical direction up to 150 km with a significant contribution of reflections from east west directions above 110 km the f1 region irregularities are characterized by time and height scales significantly larger than the e region irregularities scales as in the e region the f1 region reflections arise from the vertical and from east west directions when the reflection distance increases the variations of the doppler frequency versus the observation distance at several sounding frequencies are well explained by a horizontal motion of the irregular plasma flow both in the e and f regions with velocities of 100 m s and 130 m s respectively

on the linkage of daytime 150 km echoes and abnormal intermediate layer traces over sanya 1 the daytime 150 km echoes which are associated with the upper e region field aligned irregularities have been observed around the equatorial electrojet region but never before at magnetic latitudes near the northern anomaly crest region we present first results of daytime 150 km echo over sanya china a station located far away from the dip equator in the northern hemisphere a layer of weak radar echoes with spectral width less than 10 m s 1 was seen in the height range from 145 km at 12 15 lt to 152 km at 13 45 lt on 21 july 2010 the interesting aspect is that the rare observation of daytime 150 km echoes with the small sanya vhf radar was preceded by the occurrence of an unusual intermediate layer which is identified as abnormal traces at the upper e region in corresponding ionograms the abnormal intermediate layer associated with possible gravity wave activity that implicates the presence of upper e region density gradients could make a significant contribution to the growth of irregularities responsible for the rarely detected daytime 150 km echoes over sanya

suspended sediment transport and the role of infragravity waves in a barred surf zone abstract collocated optical backscatterance suspended solids sensors and electromagnetic flowmeters were deployed at stanhope lane beach p e i canada to assess the contributions of wind waves infragravity waves and mean currents to the cross shore flux of suspended sediment across a barred surf zone the local net transport of suspended sediment magnitude and direction was highly variable both spatially and temporally with respect to the relative magnitudes of the suspended sediment transport 1 that induced by quasi steady mean currents and oscillatory currents at both incident and infragravity frequencies were almost equal in magnitude when the total surf zone was averaged over the storm event 2 waves in the near infragravity band were quantitatively more important during the waning of the storm especially where when surf persisted well after the initial decay of the offshore wave field 3 incident waves were important where when the waves were not saturated i e during the early stages of the storm at all locations and persistently throughout the storm on the seaward slope of the bar where wave saturation was limited to a very short period with respect to the direction of net sediment transport 1 that attributable to mean currents was directed offshore in the inner surf zone probably reflecting the presence of an undertow while further seaward an onshore transport occurred probably resulting from mass transport induced by surf bores or drift velocities induced by the infragravity wave boundary layer 2 that induced by oscillatory currents at incident wave frequencies was generally onshore at any one location throughout the storm event in contrast oscillatory transport at low frequencies changed direction and also varied in magnitude at any given location in part these changes reflect the existence of significant oscillatory sediment transport at discrete infragravity frequencies the standing infragravity waves consistently transported suspended sediment towards antinodes in the water surface elevation

on the sheet like nature of 150 km f1 radar echoes 1 the so called 150 km or f1 echoes are shown to arise from field aligned irregularities fai that are embedded in a sheet like region using a 49 92 mhz radar on christmas island which has an antenna beam directed toward geographic east at a zenith angle of 29 5 high resolution doppler velocity variations within the radar scattering volume are used to infer that the sheet like region could have both tilt and curvature this finding is used to infer that plasma density n must be enhanced within the sheet like region and that fai could be generated by an interchange instability driven by a vertical electric field or a zonal neutral wind that acts on the horizontal component of the gradient in n how tilted sheet like structures could form in the f1 region is discussed

vertical exb drifts from radar and c nofs observations in the indian and indonesian sectors consistency of observations and model in this paper we analyze vertical exb drifts obtained from the doppler shifts of the daytime 150 km radar echoes from two radar stations located off the magnetic equator namely gadanki in india and kototabang in indonesia and compare those with corresponding coupled ion neutral dynamics investigation cindi observations onboard the c nofs satellite and the scherliess fejer model in an effort to understand to what extent the low latitude vertical exb drifts of the 150 km region represent the f region vertical exb drifts the radar observations were made during 9 16 lt in january june july and december 2009 a detailed comparison reveals that vertical exb drifts observed by the radars at both locations agree well with those of cindi and differ remarkably from those of the model importantly the model and observed drifts show large disagreement when the observed drifts are either large or downward further while the cindi as well as the radar observations from the two longitudes are found to agree with each other on the average they differ remarkably on several occasions when compared on a one to one basis the observed difference in detail is due to measurements made in different volumes linked with latitudinal and or longitudinal differences and underlines the role of neutral dynamics linked with tides and gravity waves in the two longitude sectors on the respective vertical exb drifts the results presented here are the first of their kind and are expected to have wider applications in furthering our understanding on fine scale longitudinal variabilities in the ionosphere in general and ionospheric electrodynamics in the indian and indonesian sectors in particular

first results on low latitude e and f region irregularities obtained using the gadanki ionospheric radar interferometer a 30 mhz radar has recently been established at gadanki 13 5 n 79 2 e 6 5 n magnetic latitude to make unattended observations of the ionospheric field aligned irregularities fai this radar called the gadanki ionospheric radar interferometer giri has been designed to have scanning capability of 100 in the east west plane perpendicular to earth s magnetic field and interferometry imaging system to study drifts and spatial distribution of plasma irregularities at both large and small scales in this paper we present the first results on the e and f region fai made using the scanning capability of the giri daytime observations of e region fai show type 2 echoes with velocities predominantly upward northward downward southward at altitudes 100 km 100 km and westward eastward in the forenoon afternoon with signature of tidal wind field f region irregularities show bottom type bottomside and plume structures with close resemblance to those observed over the magnetic equator observations made with the east west scanning capability have been used to study the origin evolution and drift of the fai for the first time from gadanki eastward drifts are estimated to be 90 210 m s 1 during 20 24 lt upward velocity as large as 500 m s 1 has been observed in the initial phase of the plume structures intriguingly downward velocity as large as 60 m s 1 has also been observed in the plumes displaying descending pattern observed in the early evening hours these results are presented and discussed in the light of current understanding of low latitude plasma irregularities and future prospects of giri are outlined

characteristics of the equatorial plasma drifts as obtained by using canadian doppler ionosonde over southern tip of india we present here characteristics of the doppler drift measurements over tirunelveli 8 73 n 77 70 e dip 0 5 n an equatorial site over southern india using doppler interferometry technique of canadian ionosonde three dimensional bulk motions of the scatterers as reflected from the ionosphere are derived by using doppler interferometry technique at selected frequencies using spaced receivers arranged in magnetic e w and n s directions after having compared with lowell s digisonde drifts at trivandrum we studied the temporal and seasonal variabilities of quiet time drifts for the year 2012 the observations showed higher vertical drifts during post sunset in the equinox followed by winter and summer seasons the comparison of doppler vertical drifts with the drifts obtained from a virtual height and b fejer drift model suggests that doppler vertical drifts are relatively higher as compared to the drifts obtained from model and virtual height methods further it is seen that vertical drifts exhibited equinoctial asymmetry in prereversal enhancement quite similar to such asymmetry observed in the spread f in the ionograms and gps l band scintillations the zonal drifts on the other hand showed westward during daytime with mean drifts of 150 200 m s and correlated well with equatorial electrojet strength indicating the role of e region dynamo during daytime while they are eastward during nighttime with mean drifts of 100 m s resembling f region dynamo process also zonal drifts showed large westward prior to the spread f onset during autumn equinox than vernal equinox suggesting strong zonal shears which might cause equinoctial asymmetry in spread f

shoreline variations and coastal dynamics a space time data analysis of the jonian littoral italy abstract morphological variations of coastlines are caused by several key processes that are influenced by climate conditions sea level variations wave energy tectonics and human induced phenomena these processes affect the dynamics of catchment basins and the coastal environment since the second half of the 20th century the jonian coast of the basilicata region italy has witnessed a widespread retreating phenomenon predominantly due to anthropogenic causes affecting transport processes along the riverbeds and causing reductions in the sediment supply to the coast the disturbance in the balance between sediment transport carried out by the sea and the sediment supply performed by rivers has led to a deficit in the sediment budget to understand the morphological dynamics of the littoral environment and quantify the amount of coastal erosion an analysis of coastline change has been carried out using various data sources historical cartography aerial photographs and gps surveys between 1870 and 1954 the 32 km long jonian littoral under examination showed an accretion trend while the loss in beach surface steadily increased between 1954 and 2005 the average change in beach surface has been calculated as about 55 000 m 2 yr accretion between 1870 and 1954 and 16 500 m 2 yr erosion between 1954 and 2005 overall 640 000 m 2 of sandy beaches were lost along the entire jonian coast of the basilicata region between 1954 and 2005 comparing the shoreline between 1870 and 1954 the average net shoreline movement nsm is 110 m vs 30 m between 1954 and 2005 this analysis approach has proven to be effective in quantifying the erosion phenomenon and its effects despite the lack of homogeneous data series and the variety of spatial and temporal scales over which coastal evolution occurs the study represents an important step in understanding coastal dynamics in this region as coastal areas are being affected by an increasing number of population and socio economic activities identification of shoreline changes and forecasts of coastline evolution represent key information for coastal scientists engineers decision makers and stakeholders for both the management of and development of future plans for coastal environments and for reducing exposure risk to coastal erosion

daytime 150 km echoes observed with the equatorial atmosphere radar in indonesia first results 1 results of the daytime 150 km echoes from 10 36 s magnetic latitude observed using the equatorial atmosphere radar ear which are first of its kind from magnetic southern hemisphere are presented the echoing region of 145 165 km shows forenoon descent and afternoon ascent with signal intensity modulation with time resembling a necklace and the doppler spectra are narrow which are quite similar to those reported earlier from other locations westward and upward southward irregularity drifts are found to be consistent with daytime background electric fields providing a tool to investigate low latitude daytime electrodynamics detectability of these echoes suggests the absence of strong latitudinal dependence in contrast to the earlier belief suggesting a possibility of their detection at mid latitudes also the echoes show zonal anisotropy that is opposite to that observed over pohnpei the implications of these observations are discussed in the light of present understanding of 150 km echoing phenomenon

drift and aspect sensitivity of scattering irregularities in the upper equatorial e region recent observations at jicamarca peru of vhf radio signals coherently scattered from the upper equatorial e region during midday hours show that the corresponding irregularities in the electron density distribution are aligned along the earth s magnetic field vertical electron drift velocities in the altitude region between 120 km and 170 km show spatial and temporal variations of as much as 30 these variations are attributed to small scale varying electric fields which are generated by the dynamo action of gravity waves in the neutral atmosphere

the effect of flocs on optical backscattering measurements of suspended material concentration abstract optical backscattering measurements were made using coagulated kaolin and estuary sediments at various concentrations and subjected to two flow conditions these measurements showed that the size of the flocs can give the same effect as changing the concentration by up to 2 5 times in using optical measurements as indicators of suspended sediment concentration care must be used to evaluate the in situ floc size in estuarine and coastal studies

impact of seasonal vertical stratification on the dispersion patterns of dredging plumes off the south coast of korea abstract simultaneous satellite and ship borne surveys have been conducted to investigate the dispersion patterns of dredging plumes off the south coast of korea in two contrasting seasons spring and autumn the distribution of total suspended solid tss derived from sequential satellite imagery showed that the dredging plumes in spring developed over longer distances along the surface current than those in autumn in spring the deep and strong stratified condition in the water column contributed to the increase in radius of plume dispersion along the water surface in autumn the shallow and vertically well mixed or un stratified condition in the water column enhanced sinking of suspended dredged materials this difference is due to the brunt vaisala frequency being higher in spring 0 0183 s 1 than in autumn 0 0123 s 1 although the sediment laden overflow significantly increased tss near the surface during the dredging period the tss contribution to water column stratification was only 2 3 5 6 of the thermohaline contribution therefore the seasonal variation of thermohaline density is the main factor determining the dispersion patterns of dredging plumes in the study area

an integrated optic and acoustic ioa approach for measuring suspended sediment concentration in highly turbid environments abstracts accurate measurement of suspended sediment concentration ssc in highly turbid environments has been a problem due to optical or acoustic signal saturation and attenuation the saturation returns a limited measurement range and the attenuation raises an ambiguity problem that a low optical or acoustic output could mean a low or a high ssc in this study an integrated optic and acoustic ioa approach is proposed to i overcome the ambiguity problem ii increase the measurement range to high ssc values and iii obtain high resolution ssc profiles the ioa approach is a combination of argus suspension meter asm optical backscatter sensor obs and acoustic doppler velocimeter adv in this approach the asm derived ssc is preferred because of its lowest relative error followed by obs and adv the asm can produce high resolution 1 cm interval ssc profiles when it is not saturated usually ssc

ionospheric electric field estimates from radar observations of the equatorial electrojet estimates of the zonal ionospheric electric field have been made on the basis of julia radar observations of the equatorial electrojet at jicamarca two observing techniques were used and their merits compared one technique here referred to as the oblique technique made use of a new small antenna array with a broad beam in the equatorial plane electric fields were estimated from the doppler shifts of type ii radar echoes at low elevation angles as a function of range in the manner of balsley 1969a for the other technique the main jicamarca antenna array was used and interferometry was employed to measure altitude profiles of the phase speeds of intermediate scale primary gradient drift waves in the electrojet directly overhead electric fields were inferred from these profiles following a modeling approach similar to the one described by murthy and ravindran 1994 zonal ionospheric electric field measurements comparable to seasonal average incoherent scatter radar measurements were obtained using both methods however the interferometric observations reveal the presence of intense waves and jets in the zonal neutral wind similar to what has been seen in recent chemical release sounding rocket experiments zonal winds mainly control the zonal phase speeds of the primary gradient drift waves in the late afternoon and evening although the prereversal enhancement of the zonal electric field is evident in data from the oblique technique there is no evidence of it in measurements derived from the interferometric technique

geomorphic response to riverine land cover dynamics in a quarried alluvial river kangsabati south bengal india this paper deals with impact of geomorphic responses such as thalweg shifting sandbar instability pool riffle alteration river bank erosion channel incision river bed lowering and river bank erosion on riverine land cover dynamics arises by instream and floodplain sand mining in an alluvial reach as kangsabati river from mukutmonipur dam to rajnagar confluence 193 km during 2002 2016 four segments i e lalgarh mohanpur kapastikri and rajnagar share as 554 656 m ton year sand from 141 mining sites whereas others segment as khatra raipur dherua and panskura share only 33 497 m ton year sand from 50 mining sites in the entire channel several maps were prepared to identify consequences of morphological responses with the help of field study and gis technique friend and sinha s method geol soc lond 75 1 105 111 1993 was used to detect planform change with geomorphic responses throughout the course pearson correlation matrix is used to establish the relation between geomorphic responses and land cover dynamics incorporates with mining intensity the result shows that higher value of geomorphic responses decrease sandchar riparian area but increases channel mining pits and clay cover in mining prone segments as lalgarh mohanpur kapastikri and rajnagar the lower value of geomorphic responses increase sandchar riparian area but decreases channel mining pit sites and clay cover in sandchar segments as khatra raipur dherua and panskura respectively therefore sand mining greatly impact on riverine land covers dynamic following instable geomorphic responses moreover this study reveals that sustainable sand mining incorporates with stable geomorphic responses maintain fluvial dynamics controlling of erosion and deposition process

a quiet time empirical model of equatorial vertical plasma drift in the peruvian sector based on 150 km echoes 1 equatorial vertical plasma drift is an important consequence of the e and f region dynamos understanding the climatology of vertical drift can provide significant insight into many ionospheric phenomena in this study we present the first empirical model of vertical plasma drifts at 150 km altitude observed by the jicamarca unattended long term studies of the ionosphere and atmosphere julia coherent scatter radar located in peru the model called julia vertical drift model jvdm describes the local time seasonal and solar flux behavior of the equatorial vertical drifts in the peruvian sector the model is valid from 0800 through 1600 local time which is typically when julia makes vertical drift measurements during very high solar flux conditions however the model is unreliable before 1000 local time owing to a lack of julia data the model includes a climatology of the 150 km equatorial vertical drifts as well as an estimate of the day to day variability which can be significant the daytime drifts typically peak between 1000 and 1200 lt and have amplitudes of 25 30 m s 10 m s the model has been validated against the global empirical model of scherliess and fejer with a total rms difference of under 4 m s for 1000 to 1600 lt this model will allow researchers to study daily variations in the equatorial electric field by subtracting the climatological mean model coefficients and software are available online at http geomag org models and http www earthref org

solar flare effects on 150 km echoes observed over jicamarca waccm x simulations submitted manuscript accepted for publication in geophysical research letters https doi org 10 1029 2019gl084790 copyright 2019 american geophysical union further reproduction or electronic distribution is not permitted