relative contribution of ionospheric conductivity and electric field to the auroral electrojets data from continuous scans of the chatanika radar beam along the magnetic meridian plane are used to determine the latitudinal profile of height integrated ionospheric conductivities and horizontal electric fields from which the latitudinal distribution of ionospheric currents is deduced the observations cover invariant latitudes between 62 and 68 where the ims alaska meridian chain of magnetometers was also in operation although the conductivities and the electric fields are interrelated the relative importance of the two in driving the eastward and westward auroral electrojet currents can be assessed it is found that for moderate and large current densities i e 0 2 a m the northward electric field strength increases as the magnitude of the eastward electrojet in the evening sector increases the height integrated hall conductivity stays generally at the level of 10 mhos even when the current density becomes as large as 1 a m however when the eastward electrojet is small substantial electric fields of 10 20 mv m may still exist as if the magnetosphere has a persistent voltage source there appear to be two distinct components to the westward electrojet in the midnight and early morning sestors 0300 mlt is dominated by a strong southward electric field

key points model for polar region currents 1 the equivalent ionospheric electric currents in the polar region mainly consist of the dp1 and dp2 systems the former involves a westward electrojet around midnight while the later involves a two cell system with foci on the morningside and eveningside respectively in space weather prediction and nowcasting sophisticated models of the polar currents are needed but concise and convenient models are also useful to predict or nowcast the principal characteristics of the current systems such as intensity and position in this paper we propose a key points model for outlining the basic features of the polar region current system for different disturbance levels the key points model or kp model includes six key points of the current system the centers of two dp2 cells the maximum densities of the eastward and westward electrojets and the maximum densities of the northward and southward currents each of six key points is described by three parameters intensity local time and latitude the ae dependences of the 18 parameters are deduced from the equivalent current systems for every 5 min during a 2 d period 18 19 march 1978 the kp model reveals systematic variations of the current systems when ae increases the currents and the current densities are simultaneously enhanced linearly and most of the key points concentrate towards midnight in addition when ae increases the key points k2 and k4 for the evening current cell move equatorward while the key points k1 and k3 for morning cell move poleward

an active deep marine strike slip basin along the north anatolian fault in turkey the tekirdag depression within the marmara sea in the mediterranean region is an active rhomb shaped strike slip basin along the north anatolian fault with a basin floor at a water depth of 1150 m new multichannel seismic reflection data and on land geological studies indicate that the basin is forming along a releasing bend of the strike slip fault and is filled with syntransform sediments of pliocene quaternary age the basin is bounded on one side by the north anatolian fault and on the other side by a subparallel normal fault which forms the steep submarine slope in cross section the basin is strongly asymmetric with the thickness of the syntransform strata increasing from a few tens of meters on the submarine slope to over 2 5 km adjacent to the north anatolian fault seismic sections also show that the slope forming normal fault connects at depth to the north anatolian fault implying that the basin is completely detached from its substratum the whole structure can be envisaged as a huge rather flat negative flower structure the releasing bend of the north anatolian fault responsible for the formation of the basin is flanked by a constraining bend along the constraining bend the syntransform strata are being underthrust implying a recent change in the direction of the regional displacement vector this thrusting is responsible for the uplift of the submarine slope to a height of 924 m possibly by a mechanism of elastic rebound regional geology suggests that most of the syntransform strata are lacustrine with only the topmost few hundred meters consisting of deep marine clays the anomalous present depth of the tekirdag depression is due to reduced quaternary sedimentation coupled with high rates of displacement along the north anatolian fault which amounts to 20 mm yr in the marmara sea region

modeling substorm current systems using conductivity distributions inferred from de auroral images images of auroral emissions observed with dynamics explorer 1 de 1 are used to calculate ionospheric conductivities over the polar region the combination of ground based magnetometer data and the inferred conductivities enables us to estimate on a global scale the distributions of ionospheric electric fields and currents and field aligned currents as well as the joule heating production rate with a time resolution of 12 min although our inference of the conductivity distribution requires further improvements the following conclusions may be drawn from this work 1 the westward electrojet is in general collocated with the region of high auroral luminosity while the region of relatively low luminosity in the evening sector is collocated with the eastward electrojet 2 the upward field aligned currents exist in the brightest auroral region on the poleward side of the evening auroral oval and on the equatorward side of the morning oval however the magnitudes of these upward currents are not in proportion to the auroral luminosities suggesting that the characteristic energies of precipitating electrons carrying the upward currents and generating the auroral luminosities may be different 3 a significant amount of ionospheric currents can flow in regions where there are no bright auroral emissions an example of this effect is found over the poleward half of the westward electrojet in the morning sector where the electric field is the main contributor to the ionospheric currents 4 the distribution of calculated field aligned currents displays many localized structures which characterize the development of the substorm current system previous satellite observations may represent gross time averages of such complicated distributions

a missing link in the tectonic configuration of the almacik block along the north anatolian fault zone nw turkey active faulting in the bolu plain based on seismic reflection studies

inversion of field data in fault tectonics to obtain the regional stress iii a new rapid direct inversion method by analytical means summary a new method for determining the reduced stress tensor with four degrees of freedom the orientations of the three principal stress axes as well as the ratio of principal stress differences using fault slip data or focal mechanisms of earthquakes is presented from a computational point of view the inversion of fault slip data is made in a direct way by purely analytical means as a result the determination process is extremely fast and adaptable on small microcomputers from a physical point of view the method aims at simultaneously i minimizing the angles between theoretical shear stress and actual slip vector and ii having relative magnitudes of shear stress large enough to induce slip despite rock cohesion and friction examples of application to actual fault slip data sets with good or poor variety of fault slip orientations are shown the double significance of the basic criterion adopted results in a more realistic solution of the inverse problem than the single minimization of the shear stria angle

swarm satellite and eiscat radar observations of a plasma flow channel in the auroral oval near magnetic midnight we present swarm satellite and eiscat radar observations of electrodynamical parameters in the midnight sector at high latitudes the most striking feature is a plasma flow channel located equatorw

two component auroral electrojet importance for substorm studies this paper attempts to synthesize the diverse number of observations of electric fields and currents in the high latitude ionosphere during substorms by demonstrating that there are often spatial shifts among regions of high ionospheric conductivity large electric fields and intense currents in the auroral electrojet it is shown that substorm time variations of the current patterns over the entire polar region consist of two basic components the first is related to the two cell convection pattern and the second to the westward electrojet in the dark sector which is in turn related to the three dimensional wedge current system these two components result from the relative strength of electric fields and conductivities in the intensification of the auroral electrojet and are identified as the signatures for directly driven and the unloading components in solar wind magnetosphere interactions we contend that disturbed intervals do not necessitate the presence of substorm expansion phase activity and that the vast number of earlier complex results concerning the auroral electrojet can be ascertained from the high degree of variability of the two components depending on substorm events substorm phases and their own spatial temporal scale sizes it is demonstrated that several major issues that have remained controversial are now accounted for reasonably well in terms of this two component electrojet model we also predict specific features of the substorm auroral electrojet that have not yet been observed

tectonic evolution of the marmara sea and its surroundings abstract the basins in the marmara sea are the products of a superimposed evolutionary history defined by two different aged fault systems the early miocene early pliocene thrace eskisehir fault zone and its branches and the late pliocene recent north anatolian fault and its branches the thrace eskisehir fault and its westward branching secondary fault systems define the early neotectonic signature in the region the late neotectonic period started at the end of the early pliocene when the north anatolian fault divided the thrace eskisehir fault into four parts during the late neotectonic period the north anatolian fault extended westward as a number of splays by joining with the ganos bandirma behramkale and manyas edremit fault zones the branches of the north anatolian fault zone nafz caused the evolution of a number of basins which differ in character depending on the trend and past characteristics of the older branches that became connected since the northern branch of the north anatolian fault is connected to the n80 e trending ganos fault zone gfz in the west a single buried fault has developed in the marmara sea causing the well known troughs and ridges superimposed onto the negative flower structure formed by the gfz in the early neotectonic period the middle strand which extends from iznik lake to bandirma is oriented east west up to the n60 e trending bandirma behramkale fault zone then turns southward in the vicinity of bandirma forming a region dominated by compressional tectonics this bending caused n30 e trending tension in addition to the strike slip motion between the eastern part of gemlik bay and bandirma bay the southern branch of the nafz on the other hand produced three pull apart basins with different characteristics along the yenisehir bursa and manyas segments the southern branch of the nafz connected to the manyas edremit fault zone which is oriented n45 e to the south of manyas and the associated bending and rotation caused a n15 e trending extension in addition to the strike slip regime between manyas and uluabat the branches of north anatolian fault cut through the thrace eskisehir fault at three places the east marmara sea region in gemlik bay and to the east of bursa giving lateral offsets of 58 59 7 8 and 10 11 km respectively the cumulative motion is 75 78 km corresponding to the total lateral offset of the north anatolian fault in the region the correlation of these offsets with global positioning system slip vectors and with stratigraphic results implies that the north anatolian fault reached into the marmara sea region about 3 5 million yr ago tectonic processes forming the marmara sea and its environs were initiated by the thrace eskisehir fault and its splays have been most recently controlled by the north anatolian fault and its splays during the last 3 5 million yr

north marmara trough architecture of basin infill basement and faults from psdm reflection and obs refraction seismics abstract the reflection and refraction seismic data collected during the seismarmara leg 1 survey in the sea of marmara provide detailed imaging of sedimentary record and fault activity with deep penetration into its basement first a detailed analysis of pre stack depth migrated seismic lines crossing the central basin enable us to discuss the space and time relations of the large and smaller nested basins of the inner depression as well as the diversity of style and rate of activity of motion at the diverse basin border faults second forward modeling of obs refraction arrival times reveals the effect of compaction on the sedimentary pile whereas its layering imaged by mcs as seismic reflectors rather recorded the tectonic evolution another major result of the refraction modeling is the identification of the crystalline basement the latter is imaged about 1 or 2 km deeper than the base of the layered sedimentary sequence imaged on the coincident mcs profiles this basement exhibits sharp topography across the central high the kumburgaz basin and the eastern tip of the cinarcik north imrali basin in an unexpected way with respect to the sea bottom depressions we furthermore imaged several large tilted basement blocks which separate the deep basins as between the cinarcik and imrali basins despite the varying width of the nmt and the sizes of the tilted blocks we propose that the imaged finite deformation results from a similar process of partitioning deformation over more than one or even two faults across the nmt that may have changed activity with time and space

auroral electrojet al index and polar magnetic disturbances in two hemispheres 1 earlier we found that the auroral electrojet al index indicating substorm activity in the northern hemisphere in local summer months correlates much better with geomagnetic activity not in the nearby polar cap but in the opposite polar cap we explained this effect as a result of interhemispheric field aligned currents which suppress substorm field aligned currents in the summer hemisphere but increase these currents in the winter hemisphere in the present paper we took into account this effect and examined a method for reliably monitoring the substorm auroral electrojet measured with the auroral electrojet al index by using hourly averages of geomagnetic field from two polar observatories thule and vostok in two hemispheres we tested this method for 3 years the correlation between the predicted and actual al indices for these years was stable and very high and it showed no significant dependence on season and a relatively weak ut variation the correlation coefficient between the predicted and actual al indices for these three years was about 0 89 the proposed method based on using magnetic field data from two polar geomagnetic observatories in two hemispheres not only significantly improves the reliability of monitoring the westward auroral electrojet in the northern hemisphere but it may also be used for monitoring the westward auroral electrojet in the southern hemisphere where no al index is available because a significant portion of the southern auroral zone is located over the oceans the results of this paper show that measurements of geomagnetic field in two hemispheres are of high importance for reliably monitoring the geomagnetic activity and related events in each hemisphere

characteristic features of the north anatolian fault in the eastern marmara region and its tectonic evolution shallow seismic profiles are used to image the tectonic and stratigraphic setting in izmit bay eastern marmara sea four seismic units were detected in the sediments of izmit bay which carry the effects of the tectonic uplift and global sea level variations the area appears to be a negative flower structure controlled by the northern branch of the north anatolian fault in the late pliocene the north anatolian fault reached marmara sea as a master fault smallscale faults were evolved around the master fault under a regime of dextral shear the northward bending of the master fault gave rise to en echelon faults opening the sub basins in izmit bay as releasing bends the secondary faults which developed as low angle oblique to the master fault are also the products of dextral shear to the south short dextral ene wsw trending faults are interpreted as p shears while to the north dextral wnw ese trending faults represents r shears these faults absorbed the deformation at the western end of the ruptured zone during the

ground based studies of ionospheric convection associated with substorm expansion the instantaneous patterns of electric fields and currents in the high latitude ionosphere are deduced by combining satellite and radar measurements of the ionospheric drift velocity along with ground based magnetometer observations for october 25 1981 for this purpose an updated version of the assimilative mapping of ionospheric electrodynamics technique has been used these global patterns are unobtainable from any single data set the period under study was characterized by a relatively stable southward interplanetary magnetic field imf so that the obtained electric field patterns do reflect in general the state of sustained and enhanced plasma convection in the magnetosphere during one of the satellite passes however an intense westward electrojet caused by a substorm intruded into the satellite de 2 and radar chatanika alaska field of view in the premidnight sector providing a unique opportunity to differentiate the enhanced convection and substorm expansion fields the distributions of the calculated electric potential for the expansion and maximum phases of the substorm show the first clear evidence of the coexistence of two physically different systems in the global convection pattern the changes in the convection pattern during the substorm indicate that the large scale potential distributions are indeed of general two cell patterns representing themore southward imf status but the night morning cell has two positive peaks one in the midnight sector and the other in the late morning hours corresponding to the substorm expansion and the convection enhancement respectively 40 refs 12 figs 1 tab less

electrodynamics of the westward traveling surge it is shown that the global convection pattern the ionospheric current and the field aligned current associated with the westward traveling surge in the asymptotic state can be modeled quantitatively as consequences of a blockage of the hall current from closure in the magnetosphere via field aligned currents the conductivity is allowed to increase self consistently with increasing upward field aligned current in the model this inclusion of the self consistent enhanced ionospheric conductivity due to discrete auroral precipitations is found to generate a localized intense westward electrojet on the poleward side of the harang discontinuity the westward electrojet is also found to rotate counterclockwise merging into the eastward electrojet around the leading edge of the surge thus the major features of the westward traveling surge can be reproduced reasonably well in our model

sequential rotation of stretching axes and block rotations a structural and paleomagnetic study along the north anatolian fault abstract fault kinematics of the western part of the north anatolian fault an active transcurrent fault were investigated consistent successive counterclockwise rotation of incremental stretching directions was derived from the seven areas investigated we assumed that the changes in stretching directions correlate to the consistent rotation of one or several blocks caused by interaction of major fault segments in order to test this hypothesis we compared magnetic remanence directions measured within tertiary calc alkaline volcanic rocks with the changes in stretching direction in spite of the successive changes in stretching systematic changes in remanence directions were not observed most of the latter show no or low angular distances to the reference direction of d 335 i 50 both positive and negative signs are inferred for movements about subhorizontal and subvertical axes where magnetic remanence directions suggest rotation we conclude that changes in the overall deformation explain the systematic changes in incremental directions better than consistent external rotation a deformation path is proposed that includes ne sw and n s shortening during the paleogene and possibly lower miocene nw se shortening and penecontemporaneous local n s extension for the miocene and nw se to e w shortening and sw ne to n s extension for the pliocene until the present

insight into the crustal structure of the eastern marmara region nw turkey in order to investigate crustal structure beneath the eastern marmara region a seismic refraction survey was conducted across the north anatolian fault naf zone in north west turkey two reversed profiles across two strands of the naf zone were recorded in the armutlu highland where a tectonically active region was formed by different continents we used land explosions in boreholes and quarry blasts as seismic sources a reliable crustal velocity and depth model is obtained from the inversion of first arrival travel times the velocity depth model will improve the positioning of the earthquake activities in this active portion of the naf a high velocity anomaly 5 6 5 8 km s 1 in the central highland of armutlu block and the low velocity 4 90 km s 1 pattern north of iznik lake are the two dominant features the crustal thickness is about 26 2 km in the north and increases to about 32 2 km beneath the central armutlu block in the south p wave velocities are about 3 95 km s 1 to 4 70 km s 1 for the depth range between about 1 km and 5 km in the upper crust the eastern marmara region has different units of upper crust with velocities varying with depth to almost 8 km the high upper crust velocities are associated with armutlu metamorphic rocks while the low velocity anomalies are due to unconsolidated sedimentary sequences the western side of armutlu block has complex tectonics and is well known for geothermal sources if these sources are continuous throughout the portions of the crust it may be associated with a granitic intrusion and deformation along the naf zone that is the geothermal sources associated with the low velocity may be due to the occurrence of widespread shear heating even shear melting the presence of shear melting may indicate the presence of crustal fluid imposed by two blocks of the naf system

reply to kamide and richmond detailed empirical models of the ionospheric convection electric field and auroral latitude conductance are used to show that at 04 magnetic local time mlt the electric field magnitude peaks at least 5 poleward of the hall conductance and is the stronger contributor to the poleward half of the westward electrojet current in the morning sector at 20 mlt the eastward electrojet current is centered on the electric field and conductance profiles which have a similar peak latitude and extent

the north anatolian fault a new look dedicated to the memory of three pioneers ihsan ketin sirri erinc and melih tokay and a recent student aykut barka who burnt himself out in pursuit of the mysteries of the north anatolian fault abstract the north anatolian fault naf is a 1200 km long dextral strike slip fault zone that formed by progressive strain localization in a generally westerly widening right lateral keirogen in northern turkey mostly along an interface juxtaposing subduction accretion material to its south and older and stiffer continental basements to its north the naf formed approximately 13 to 11 ma ago in the east and propagated westward it reached the sea of marmara no earlier than 200 ka ago although shear related deformation in a broad zone there had already commenced in the late miocene the fault zone has a very distinct morphological expression and is seismically active since the seventeenth century it has shown cyclical seismic behavior with century long cycles beginning in the east and progressing westwa

aurora and electrojet configuration in the early morning sector nearly simultaneous data from the chatanika radar the triad satellite and the ims alaska meridian chain of magnetic and auroral observatories are utilized to examine the spatial relationship among auroras field aligned currents ionospheric electric fields and conductivities in the westward electrojet in early morning hours the westward electrojet is found to be dominated by one of two different quantities depending on latitudinal locations in this local time sector the poleward half of the electrojet is governed by a relatively intense southward electric field on the other hand the hall conductivity is the dominant factor in controlling the electrojet current in the equatorward half the electrojet center appears to be located within the region of the upward field aligned current major auroral activity is present only in the equatorward half of the electrojet in which the upward field aligned current prevails although it appears that the latitudinal variations of the conductivity and current intensity are not well related within that region

the large scale current system during auroral substorms we present an empirical model of the equivalent current system in the ionosphere during the peak of a classical bulge type auroral substorm this model is derived from measurements made by 110 ground magnetometer stations during 116 substorms the data are temporally and spatially organized using global auroral images obtained by the polar visible imaging system earth camera the empirical equivalent current system displays three key features a poleward shift of the westward electrojet connecting the postmidnight and premidnight components a polar cap swirl and significantly different magnitudes of the postmidnight and premidnight westward electrojets this leads us to propose a two wedge current system linking the ionosphere to the magnetosphere the bulge current wedge is located in the premidnight region just equatorward of the open closed field line boundary while another three dimensional current system is located in the postmidnight region well within the auroral oval we use biot and savart calculations and tsyganenko mapping and show that this new model is a likely solution for the large scale current system

asymmetric slip partitioning in the sea of marmara pull apart a clue to propagation processes of the north anatolian fault between 1939 and 1999 the north anatolian fault naf experienced a westward progression of eight large earthquakes over 800 km of its morphological trace the 2000 km long north anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale 10 myr the sea of marmara is a large pull apart that appears to have been a geometrical mechanical obstacle encountered by the naf during its propagation the present paper focuses on new high resolution data on the submarine fault system that forms a smaller pull apart beneath the northern sea of marmara between two well known strike slip faults on land izmit and ganos faults the outstandingly clear submarine morphology reveals a segmented fault system including pull apart features at a range of scales which indicate a dominant transtensional tectonic regime there is no evidence for a single continuous purely strike slip fault this result is critical to understanding of the seismic behaviour of this region of the naf close to istanbul additionally morphological and geological evidence is found for a stable kinematics consistent both with the long term displacement field determined for the past 5 myr and with present day anatolia eurasia motion determined with gps however within the sea of marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull apart the loading associated with the westward propagation process of the naf may have provided a favourable initial geometry for such a slip separation

estimation of the long term slip surface uplift and block rotation along the northern strand of the north anatolian fault zone inferences from geomorphology of the almacik block abstract the almacik block is one of the key morphotectonic units in the eastern marmara region associated with the long term slip partitioning within the north anatolian fault zone nafz in this study we provide new geomorphic reconstructions of offset drainage basins morphometric analysis of topography and longitudinal profiles of the rivers crossing different flanks of the almacik block our geomorphic reconstructions of offset drainage basins along the hendek and karadere faults imply mean offsets of 2 3 0 4 km and 8 4 0 7 km respectively during the quaternary our dataset also imply that slip partitioning occurs in a broader zone than previously proposed and that the total 10 7 0 6 km offset along the hendek and karadere faults of the northern strand must be taken into account for long term slip partitioning in the eastern marmara region together with previously suggested 10 km offset along the southern strand yaltirak 2002 16 1 0 km offset along the middle strand ozalp et al 2013 and the 52 1 0 km offset along the mudurnu segment of the northern strand akbayram et al 2016 our newly proposed geomorphic markers raise the cumulative offset in the eastern marmara region associated with the naf to 89 1 0 km since the latest pliocene quaternary in addition to these lateral displacements our morphometric analysis and longitudinal profiles of the rivers imply up to 1130 130 m surface uplift of the almacik block as a combined result of vertical displacement within the deformation zone of the northern strand of the nafz finally by assuming that river basins act as passive deformation markers our basin azimuth analyses imply 20 2 clockwise rotation of the almacik block associated with the nafz

an assessment of changes in properties of steppe kurgan paleosoils in relation to prevailing climates over recent millennia comparative analysis of morphological and chemical properties of the soil chronosequence on kastanozems soils in the steppe zone of the russian plain which included paleosoils buried beneath kurgans erected ca 2000 bc ad 50 ad 200 and ad 1250 was performed to reconstruct the paleoenvironmental conditions in this archeologically important region paleoenvironmental dynamics were traced using the state of microbial communities of paleo and modern soils including the dynamics of total and glucose reactive biomass and the abundance of microorganisms grown on selected media we demonstrate that the share of the glucose reactive microorganisms in the microbial community the ecological trophic structure and oligotrophicity index might serve as indicators of the state of microbial communities and be used for paleoenvironmental reconstructions the morphological chemical and microbial properties confirm an arid period ca 2000 bc slightly wetter conditions ca ad 50 and more humid conditions ca ad 1250

monitoring the earthquake source process in north america with the implementation of the usgs national earthquake information center prompt assessment of global earthquakes for response system pager rapid determination of earthquake moment magnitude is essential especially for earthquakes that are felt within the contiguous united states we report an implementation of moment tensor processing for application to broad seismically active areas of north america this effort focuses on the selection of regional crustal velocity models codification of data quality tests and the development of procedures for rapid computation of the seismic moment tensor we systematically apply these techniques to earthquakes with reported magnitude greater than 3 5 in continental north america that are not associated with a tectonic plate boundary using the 0 02 0 10 hz passband we can usually determine with few exceptions moment tensor solutions for earthquakes with m w as small as 3 7 the threshold is significantly influenced by the density of stations the location of the earthquake relative to the seismic stations and of course the signal to noise ratio with the existing permanent broadband stations in north america operated for rapid earthquake response the seismic moment tensor of most earthquakes that are m w 4 or larger can be routinely computed as expected the nonuniform spatial pattern of these solutions reflects the seismicity pattern however the orientation of the direction of maximum compressive stress and the predominant style of faulting is spatially coherent across large regions of the continent

characteristics of eastward drifting omega bands in the morning sector of the auroral oval the stare radars and the scandinavian networks of magnetometers all sky cameras and riometers recorded during the night of october 21 22 1979 the occurrence of a fairly regular sequence of auroral omega bands and associated magnetic and electric field variations the combined two dimensional data are used to derive a realistic model for the three dimensional current flow associated with the auroral forms in the model calculations the observed structure in the particle precipitation is accounted for by an inhomogeneous ionospheric conductivity distribution the main resulting feature of the model current system is a sequence of east west orientated pairs of upward and downward directed field aligned currents associated with the bright and dark areas of the visual aurora respectively the major source of magnetic disturbances on the ground is a meandering ionospheric hall current composed of a westward background electrojet and circular hall current vortices around the locations of the localized field aligned currents the total magnetic disturbance observed on the ground during different events appears however to be strongly dependent on the hall to pedersen conductivity ratio and the degree of inhomogeneity in the conductivity distribution the three dimensional current system associated with the auroral omega bands drifts eastward with a velocity comparable to an e b drift within the general southward directed electric background field however complete agreement was not found at all times

substorm and convection bay compared auroral and magnetotail dynamics during convection bay using observations from eight spacecraft and a ground network we study two subsequent bay like disturbances on december 10 1996 initiated by southward interplanetary magnetic field intervals one being a classic substorm and another one a convection bay both events showed enhanced convection and dst decreases as well as pi2 pulsations in the auroral zone contrasting to the well defined substorm signatures of the first event poleward auroral expansion substorm current wedge strong particle injection to 6 6 r e resulting from energy loading unloading and near earth reconnection in the tail these signatures were virtually absent during the convection bay cb distinctive features of the cb event were the same as those during the steady magnetospheric convection intervals 1 wide double oval at the nightside 2 thick plasma sheet relaxed lobe field and enhanced magnetic flux closure large b z and multiple bursty earthward flows bbfs in the midtail 3 sporadic narrow soft injections to 6 6 r e 4 auroral streamers associated with both bbfs and narrow injections we emphasize the development of multiple and sporadic auroral streamers which start at the poleward oval boundary propagate equatorward in 3 8 min and end with a long duration bright spot in the equatorward oval we conclude that the plasma sheet and auroral dynamics during the convection bay was formed by sporadic narrow a few r e wide plasma streams plasma bubbles which transported the plasma sheet material from the distant magnetotail reconnection regions to the inner magnetosphere and may significantly contribute to the magnetospheric circulation on the nightside we modeled the nightside tail configuration using magnetotail magnetic observations and low altitude particle boundaries to show that at the beginning of the convection bay the increase of magnetic flux tube volume with distance was small in the midtail therefore the pressure crisis in the tail was significantly reduced during the convection bay and the efficient earthward transport by sporadic narrow plasma streams was probably able to balance the magnetospheric circulation to avoid the large scale instability of the magnetotail

the convection electric field in auroral substorms dynamics explorer 2 de 2 electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge type auroral substorms thirty one individual de 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained by de 1 the selected passes which occurred during substorm expansion phase maximum or early recovery phase cover the entire nighttime substorm the organization of the data used the method developed by fujii et al 1994 which divided the data into six local time sectors covering the nighttime substorm region following the procedures employed in the paper by gjerloev and hoffman 2000b the latitudinal width and location of each auroral oval crossing was then adjusted to fit the sector average in addition to the detailed study of the characteristics of the field within each sector this database enabled us to compile a model of the ionospheric convection electric field the characteristics of the premidnight convection reversal show a pronounced local time dependency far west of the surge it is a fairly well defined point reversal or convection shear approaching the surge and within the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields therefore we adopt the term harang region rather than the harang discontinuity for the premidnight convection reversal a relatively narrow convection channel is coincident with the highest conductances located just poleward of the harang region this channel drives the substorm current wedge component of the westward electrojet in the surge and middle surge sectors it is present in all premidnight passes and consequently is an integral part of the three dimensional substorm current wedge system

palaeomagnetic evidence for substantial rotation of the almacik flake within the north anatolian fault zone nw turkey summary palaeomagnetic data on eocene rocks from within the almacik flake bounded by two strands of the north anatolian right lateral fault indicate that the flake has undergone an apparent counterclockwise rotation of about 148 on average we interpret this as a real 212 clockwise rotation because the almacik flake is entirely delimited by the right lateral north anatolian fault strands the only dominant post eocene structure in the area and because areas surrounding the flake do not show the same rotation this rotation must have occurred since the north anatolian fault originated in the late medial miocene late serravallian 11 5 ma and if so may imply either a larger total slip along it than hitherto estimated or that the almacik flake is the surface expression of a flower structure rotating above a shear zone narrower than the present width of the flake

structures and kinematics of the north anatolian fault zone adapazari bolu region northwest turkey abstract this study presents new detailed maps of the fault patterns earthquake ruptures geology and morphology along the north anatolian fault and models of structures at single bends of strike slip faults the active north anatolian fault forms extensional bends and oversteps in the study area the blocks on both sides of the main fault follow the changing directions and adapt their margins to the deflected course the block margins remain in contact with the receding fault line close up to it by fault normal extension on faults parallel to the principal strike slip fault and by acute angled synthetic strike slip faults extension caused by oversteps or bends can be transmitted from the immediate course of a main fault deeper into the interior of blocks by the closing up process in this way pull apart basins can extend normal to the principal fault or can be displaced away from the fault rotation of the whole block can prevent extension the total displacement of the north anatolian fault in the study area is estimated using the closing up structures to be 21 km shortening axes from fault plane analyses and stress axes from earthquakes which have occurred in the study area are comparable with the computed stress pattern of oversteps published by guiraud and seguret

auroral arc and oval electrodynamics in the harang region 1 auroral arcs are typically described in terms of an upward field aligned current fac sheet above the arc connected by ionospheric pedersen current to a downward fac sheet near the arc on the basis of data measured by the fast spacecraft conjugate with ground optical observations we present first a wide and stable winter evening arc where this standard model does not apply the arc is observed in the harang region during the growth phase of a modest substorm poleward of the convection reversal cr boundary although the magnetic field data suggest the typical configuration the two fac sheets appear to be decoupled near the satellite footprint the upward fac is fed by the westward electrojet wej while the downward fac feeds the eastward electrojet eej the examination of the arc by the newly developed aladyn technique confirms this peculiar current topology for comparison we apply aladyn also to a second evening arc located within the harang region equatorward from the cr the arc is confirmed to have the standard configuration consistent with a former study but substantial fac ej coupling is inferred in the auroral oval both poleward and equatorward of the arc a key element for the topology of the current closure is the westward component of the electric field which influences the relative location of the cr with respect to the large scale fac reversal fr boundary as proved by tests on synthetic data a westward component of the electric field pushes the cr toward the fr preventing thus the standard fac closure while the conductance and fac pattern shape the cr profile since a westward electric field is often measured in the harang region the fac ej coupling is expected to be an essential ingredient there this has important implications for the current closure in the equatorial magnetosphere and for the auroral current circuit in the wej region closely related to the substorm process

triggering of expansive phase intensifications of magnetospheric substorms by northward turnings of the interplanetary magnetic field over the past decade evidence has arisen suggesting that northward turnings of the interplanetary magnetic field after an interval of sustained southward imf can trigger the onset of major substorm expansive phase effects however there has been some question in the past as to just how many substorms are triggered and whether indeed the correlation of substorm onsets and northward turnings was just a matter of chance one reason for doubt was that the examples presented in the literature appeared during disturbed periods where the ims was fluctuating significantly on a time scale of less than one hour and many substorm expansive phase intensifications were observable in the time frame where the correlation between the imf and ground data was reported the purpose of this paper is to present three clear cut examples of isolated substorms where the reader may be able to convince himself of the validity of the reported triggering effect for these events it will be clear that the substorm current wedge triggered by the northward turning of the imf carries substantially larger currents than the driven system associated with the overall substorm event the role of the imf in externally triggering episodes of joule heating and particle precipitation within the substorm process will be discussed

statistical nature of geomagnetic storms on the basis of geomagnetic activity indices and solar wind parameters a superposed epoch analysis has been conducted for more than 300 geomagnetic storms the intensity of magnetic storms is found to depend on the duration of the main phase larger storms have longer timescales for intense storms however not only the duration of energy injection into the ring current but also the strength of injection is important in determining their size it is confirmed that the southward component of the interplanetary magnetic field plays a crucial role both in triggering the storm main phase and in determining the magnitude of magnetic storms it is also found that the time profile of the energy injection rate during the main phase tends to have two peaks this is particularly the case for intense magnetic storms where the second peak is more intense than the first implications of our findings are discussed in terms of the existing concept of geomagnetic storms and recent observations of ring current particles and of interplanetary disturbances

network analysis of geomagnetic substorms using the supermag database of ground based magnetometer stations the overall morphology and dynamics of magnetospheric substorms is well established in terms of the observed qualitative auroral features seen in ground based magnetometers this paper focuses on the quantitative characterization of substorm dynamics captured by ground based magnetometer stations we present the first analysis of substorms using dynamical networks obtained from the full available set of ground based magnetometer observations in the northern hemisphere the stations are connected in the network when the correlation between the vector magnetometer time series from pairs of stations within a running time window exceeds a threshold dimensionless parameters can then be obtained that characterize the network and by extension the spatiotemporal dynamics of the substorm under observation we analyze four isolated substorm test cases as well as a steady magnetic convection smc event and a day in which no substorms occur these test case substorms are found to give a consistent characteristic network response at onset in terms of their spatial correlation such responses are differentiable from responses to the smc event and nonsubstorm times we present a method to optimize network parametrization with respect to the different individual station responses the spatial inhomogeneity of stations in the northern hemisphere and the choice of correlation window sizes our results suggest that dynamical network analysis has potential to quantitatively categorize substorms dimensionless parameters can then be obtained that characterise the network and by extension the spatio temporal dynamics of the substorm un der observation we analyse four isolated substorm test cases as well as a steady magnetic convection smc event and a day in which no substorms occur these test case substorms are found to give a consistent characteristic net work response at onset in terms of their spatial correlation such responses are differentiable from responses to the smc event and non substorm times we present a method to optimise network parametrisation with respect to the different individual station responses the spatial inhomogeneity of stations in the northern hemisphere and the choice of correlation window sizes our results suggest that dynamical network analysis has potential to quantitatively categorise substorms

substorm convection patterns observed by the super dual auroral radar network a study of convection patterns during substorms observed by the super dual auroral radar network superdarn radar network is presented specific attention is given to the growth phase and the time immediately following expansion onset it is found that the growth phase is characterized by the enhancement of the velocity shear near midnight and its extension to low latitudes and to local times across the midnight meridian the velocity shear was observed to diminish at expansion onset in addition the ionospheric flow velocity magnitude was observed to be enhanced for some period of time prior to expansion onset and to decrease at expansion onset possible explanations for the establishment of the midnight velocity shear during growth phase and its subsequent disappearance at expansion onset are presented also arguments are presented regarding the decrease of ionospheric flow velocity at expansion onset

the two component auroral electrojet by using the al index for one year as well as some of the ims meridian chain records the longitudinal center of the substorm westward electrojet is examined although on the average al is most often dominated by stations located near 0300 mlt the westward electrojet during the expansion and maximum phase of substorms tends to be centered in the premidnight to early morning sector and during the recovery phase it is most intense in morning hours it is suggested that the substorm associated westward electrojet consists of two components which have different characteristic times one produced mainly by hall conductivity enhancements which dominate in the midnight sector and the other one by southward electric fields in the morning sector

reconstructing the deformation of the north anatolian fault zone through restoring the oligo miocene exhumation pattern of the almacik block northwestern turkey based on the apatite u th he ages the almacik block is an approximately 73 km long and 21 km wide tectonic sliver formed by the north anatolian fault zone in northwestern turkey morphologically it is one of the most pronounced st

storm time field aligned currents on the nightside inferred from ground based magnetic data at midlatitudes relationships with the interplanetary magnetic field and substorms 1 on the basis of analysis of east west geomagnetic disturbance fields at midlatitudes we investigated the characteristics of temporal variations of field aligned currents on the nightside during geomagnetic storms the results indicate that upward field aligned currents develop on the nightside especially in the postmidnight when the interplanetary magnetic field imf is directed southward this suggests that the upward field aligned currents are principally associated with the convection electric field it is also found that the upward field aligned currents in the postmidnight can be intensified at substorm expansion while they principally depend on the southward component of the imf the intensification of the upward currents is regarded as a different physical process from the formation of a substorm current wedge at a substorm expansion we discuss some possible effects of the imf and substorms on the generation of the upward currents on the nightside especially in the postmidnight

middle pleistocene extinction process of pull apart basins along the north anatolian fault zone abstract numerous basins that present in northern turkey formed in plio quaternary period by the strike slip tectonics of the north anatolian fault zone these pull apart basins isolated from their surrounding topographies by major scarps of faults along their margins that mapped as active faults but the mapped recent traces in the pull apart basins are in disagreement about these marginal faults and commonly characterized by the faults that pass through basin floors in the cases of surface rupturings in great earthquakes during the last century these faults have migrated from the basin rims to the center of the basins in agreement with the extinction model of pull apart basins here we review observations about numerous basins along the north anatolian fault zone to show that the migration of these faults in middle pleistocene related with the maturity of basins through their evolution

paleomagnetic evidence of complex tectonic rotation pattern in the nw anatolian region implications for the tectonic history since the middle eocene abstract the kinematic evolution of the almacik block and the armutlu region which are surrounded by the branches of the north anatolian fault is not completely understood because of incompatible paleomagnetic data a previous paleomagnetic study in the almacik block indicated that there have been large rotations associated with the rotation as a whole coherent block and another study postulated a more complex tectonic evolution the aim of this study was to obtain paleomagnetic directions on middle eocene volcanic volcanoclastic rocks at 25 sites in nw anatolia and to determine the tectonic deformation process along the north anatolian fault zone after rock magnetic measurements and stepwise thermal and alternating field demagnetisation most of the samples taken were characterised by one component of magnetisation after the removal of viscous magnetisation a characteristic remanent magnetisation was obtained at 500 580 c showing evidence of magnetite and titanomagnetite with a small amount of ti however in some cases a high temperature component was isolated between 600 and 650 c indicating a titanohematite composition the mean direction obtained from the istanbul zone d 191 5 i 47 1 95 7 1 indicated no tectonic rotation relative to the reference direction of the stable eurasian plate d 191 0 i 53 2 95 5 0 besse and courtillot 2002 torsvik et al 2008 in the middle eocene the paleomagnetic directions in the almacik block and the armutlu region suggest counterclockwise rotations of 22 3 7 8 and 17 7 14 6 respectively relative to the istanbul zone when integrated together with previous studies our paleomagnetic results indicate that both the armutlu region and the almacik block were emplaced in the same area during the middle eocene the deformation of the northern branch of the north anatolian fault resulted in a bend and an overstep fault offset of 25 km between lake sapanca and lake abant during this process both the almacik block and the armutlu region were separated distinctly from each other with a counter clockwise rotation with respect to the istanbul zone in addition within some parts of the almacik block an internal deformation with large declination anomalies ranging from 160 to 250 was observed in this study and in previous studies these different declinations could be the result of chemical remagnetisation of hydrothermal events stress related magnetisation or small block rotations

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

nightside ionospheric electrodynamics associated with substorms pfisr and themis asi observations 1 observations from the newly available poker flat incoherent scatter radar have been used to study the ionospheric electrodynamics during the substorm expansion phase substorm events selected have been divided into three categories based on onset location relative to the radar and repeatable features have been identified west of onset westward flows increased in response to the passage of the westward traveling surge wts poleward of them the enhanced flows occurred within the sub auroral polarization streams region of downward region 2 currents which extend equatorward from near the equatorward boundary of electron precipitation strong e region ionization increase associated with the wts occurred poleward of the enhanced westward flows suggesting that poleward pedersen currents fed by the downward region 2 field aligned current fac further equatorward contribute at least partially to closure of the upward fac of the wts an enhanced eastward flow channel developed east of onset e region ionization decreased poleward of this flow peak implying formation of downward fac and further increased equatorward of the flow peak suggesting strengthening of preexisting region 2 upward fac these observations indicate that the downward fac formed at onset at least partially closes via the upward region 2 currents the enhanced eastward flows decreased after passage of the auroral bulge and the reduced e region ionization increased again when onset occurred within the radar fov the thin breakup arc of onset occurred at the center of the harang reversal while if the optical onset was poleward of the radar fov the harang reversal was observed after the onset a 2 d picture of the evolution of ionospheric electrodynamics was generated by synthesizing observations from the three categories which provides a schematic description of the relationship between region 2 and substorm expansion electrodynamics

currents in auroral substorms 1 we present a model of the three dimensional current system in the nighttime sector during the expansion phase through early recovery phase for bulge type aurora substorms the height integrated horizontal ionospheric currents are calculated from models of the height integrated conductivity and convection electric field previously published gjerloev and hoffman 2000a 2000b 2001 that were based on a set of data from the dynamics explorer 2 satellite while the field aligned currents are deduced from the divergence of the horizontal currents these model derived field aligned currents are then compared with the field aligned currents determined from magnetometer data from the same data set used to develop the conductance and electric field models the comparison shows good agreement thereby serving as an independent verification of the entire self consistent substorm model we find that the feeding as well as the drainage of the substorm current wedge component of the westward electrojet is principally due to an imbalance of the downward region 0 and upward region 1 current sheets under which the electrojet is flowing we do not find evidence of a simple downward current postmidnight and upward current premidnight the eastward electrojet which almost entirely originates on the dayside is partly drained by a poleward current flowing across the harang region into the westward electrojet at 19 21 magnetic local time mlt and partly by net upward field aligned currents located just prior to midnight

time constants of earth s magnetotail for responding to a southward excursion of imf the super high pressure magnetotail event of 10 december 1996 1 geomagnetic and plasma conditions in the nightside magnetosphere and the northern polar region are examined in detail for the first 6 hours of 10 december 1996 in association with a southward turning of the interplanetary magnetic field the polar cap potential drop began to increase and maximized within several minutes after the peak of the energy inflow from the solar wind into the magnetosphere the total pressure observed by geotail in the midmagnetotail however continued increasing for 50 min after the peak of the polar cap potential drop resulting in an exceptionally high total pressure in the midmagnetotail auroral images from polar and magnetograms from ground stations show that there was no major breakup of substorms during the period concerned this unique event provides us with an opportunity to study the solar wind magnetosphere coupling without any intense disturbances associated with major substorms using an equivalent circuit model it is attempted to reproduce variations in the polar cap potential drop and the midtail total pressure the time lag between them is particularly focused on in this study it is found that the characteristic time constants of the equivalent circuit model for this event are significantly longer than those estimated in previous papers