peculiar features of the low latitude and midlatitude ionospheric response to the st patrick s day geomagnetic storm of 17 march 2015 the current study aims at investigating and identifying the ionospheric effects of the geomagnetic storm that occurred during 17 19 march 2015 incidentally with sym h hitting a minimum of 232 nt this was the strongest storm of the current solar cycle 24 the study investigates how the storm has affected the equatorial low latitude and midlatitude ionosphere in the american and the european sectors using available ground based ionosonde and gps tec total electron content data the possible effects of prompt electric field penetration is observed in both sectors during the main phase of the storm in the american sector the coexistence of both positive and negative ionospheric storm phases are observed at low latitudes and midlatitudes to high latitudes respectively the positive storm phase is mainly due to the prompt penetration electric fields the negative storm phase in the midlatitude region is a combined effect of disturbance dynamo electric fields the equatorward shift of the midlatitude density trough and the equatorward compression of the plasmapause in combination with chemical compositional changes strong negative ionospheric storm phase is observed in both ionosonde and tec observations during the recovery phase which also shows a strong hemispherical asymmetry additionally the variation of equatorial ionization anomaly as seen through the swarm constellation plasma measurements across different longitudes has been discussed we also take a look at the performance of the iri real time assimilative mapping during this storm as an ionospheric space weather tool

the heat burst of 29 may 1976 abstract an unusual phenomenon occurred in central oklahoma in the late evening and early morning hours of 29 30 may 1976 surface temperatures suddenly rose as much as 6 c the sudden large temperature rise and humidity fall which sometimes accompanies nocturnal thunderstorms defines the heat burst the origin of a heat burst may be adiabatic subsidence near dissipating or rear edges or storms in addition to increasing temperature and falling relative humidity the hear burst is characterized by the erosion of clouds and radar echoes and gusty winds this paper documents the mesoscale events associated with this phenomenon

prompt penetration electric fields ppefs and their ionospheric effects during the great magnetic storm of 30 31 october 2003 1 we explore the ionospheric effects of prompt penetration electric fields ppefs for a variety of interplanetary magnetic field directions we use the great magnetic storm of 30 31 october as an example of ppef effects for intense southward interplanetary magnetic fields imfs inward plasma sheet convection occurs with the result of magnetospheric ring current formation and an intense magnetic storm concurrent with the above positive phase ionospheric storms occur in the dayside and negative phase ionospheric storms occur on the nightside the topics of this paper the dayside ionospheric storms due to ppefs are characterized by transport of near equatorial plasma to higher altitudes and latitudes forming a giant plasma fountain these features are part of what is called the dayside ionospheric superfountain dis for these southward imfs dusk and dawn plasma are predicted to be transported toward the dayside for northward imfs negative phase ionospheric storms are expected on the dayside if the ppefs indeed reach that region of space imf by components are expected to have weak or neglible ionospheric effects on the basis of ppef arguments intervals of imf by should not be related to geomagnetic storms they are not imf by intervals should however cause a shearing of the magnetotail a feature that has been previously reported in the literature

review of magnetic and electric field effects near active faults and volcanoes in the u s a abstract synchronized measurements of geomagnetic field have been recorded along 800 km of the san andreas fault and in the long valley caldera since 1974 and during eruptions on mount st helens since 1980 for shorter periods of time continuous measurements of geoelectric field measurements have been made on mount st helens and near the san andreas fault where moderate seismicity and fault slip frequently occurs significant tectonic and volcanic events for which nearby magnetic and electric field data have been obtained include 1 two moderate earthquakes m l 5 8 for which magnetometers were close enough to expect observable signals about three source lengths 2 one moderate earthquake m s 7 3 for which magnetometers were installed as massive fluid outflow occurred during the post seismic phase 3 numerous fault creep events and moderate seismicity 4 a major explosive volcanic eruption and numerous minor extrusive eruptions and 5 an episode of aseismic uplift for one of the two earthquakes with m l 5 8 seismomagnetic effects of 1 3 and 0 3 nt were observed for this event magnetometers were optimally located near the epicenter and the observations obtained are consistent with simple seismomagnetic models of the event similar models for the other event indicate that the expected seismomagnetic effects are below the signal resolution of the nearest magnetometer precursive tectonomagnetic effects were recorded on two independent instruments at distances of 30 and 50 km from a m l 5 2 earthquake longer term changes were recorded in one region in southern california where a moderate m l 5 9 earthquake has since occurred surface observations of fault creep events have no associated magnetic or electrical signature above the present measurement precision 0 25 nt and 0 01 respectively and are consistent with near surface fault failure models of these events longer term creep is sometimes associated with corresponding longer term magnetic field perturbations correlated changes in gravity magnetic field areal strain and uplift occurred during episodes of aseismic deformation in southern california primarily between 1979 and 1983 because the relationships between these parameters agrees with those calculated from simple deformation and tectonomagnetic models the preferred explanation appeals to short term strain episodes independently detected in each data set an unknown source of meteorologically generated noise in the strain gravity and uplift data and an unknown but correlated disturbance in the absolute magnetic data might also explain the data no clear observations of seismoelectric or tectonoelectric effects have yet been reported the eruption of mount st helens generated large oscillatory fields and 9 2 nt offset on the only surviving magnetometer a large scale traveling magnetic disturbance passed through the san andreas array from 1 to 2 h after the eruption subsequent extrusive eruptions generated small precursory magnetic changes in some cases these data are consistent with a simple volcanomagnetic model magneto gas dynamic effects and a blast excited traveling ionospheric disturbance traveling ionospheric disturbances tids also generated by earthquake related atmospheric pressure waves may explain many electromagnetic disturbances apparently associated with earthquakes local near fault magnetic field transients rarely exceed a few nt at periods of a few minutes and longer

the life cycle of thunderstorm gust fronts as viewed with doppler radar and rawinsonde data abstract this paper presents the time dependent analysis of the thunderstorm gust front with the use of project nimrod data rhi cross sections of reflectivity and doppler velocity are constructed to determine the entire vertical structure the life cycle of the gust front is divided into four stages 1 the formative stage 2 the early mature stage 3 the late mature stage and 4 the dissipation stage a new finding is a horizontal roll detected in the reflectivity pattern resulting from airflow that is deflected upward by the ground while carrying some of the smaller precipitation ahead of the main echo core of the squall line this feature is called a precipitation roll as determined from rawinsonde data the cold air behind the gust front accounts for the observed surface pressure rise calculations confirm that the collision of two fluids produce a nonhydrostatic pressure at the leading edge of the outflow the equation governing the propagation speed of a density current accurately predicts t

on the ulf magnetic ratio increase before the 2008 iwate miyagi nairiku earthquake by hirano and hattori 2011 abstract hirano and hattori 2011 hereafter cited as h h report the observation of anomalous increases in the ulf geomagnetic field spectral density ratio which the authors claim to be possible precursors of the 2008 iwate miyagi nairiku earthquake here the results of h h are reviewed taking into account the global geomagnetic activity level by means of k p index this paper cast serious doubts on the seismogenic origin of the magnetic signatures documented by h h showing that the anomalous signals are normal ulf magnetic variations induced by solar terrestrial interaction in summary h h s claims that magnetic field disturbances about a month before the mw 6 9 iwate miyagi nairiku earthquake on june 13 2008 are precursors to the earthquake are unlikely to be correct

further investigations of geomagnetic diurnal variations associated with the 2011 off the pacific coast of tohoku earthquake mw 9 0 abstract as one of the most promising candidates for short term earthquake forecasting the seismo electromagnetic phenomena have been intensively studied for several decades recently xu et al 2013 have reported unusual behaviors of geomagnetic diurnal variations in the vertical component prior to the 2011 off the pacific coast of tohoku earthquake mw 9 0 to validate this result further investigations have been applied in this study geomagnetic data of 16 years long term observation have been analyzed using the same method in xu et al 2013 ratios of diurnal variation range between the target station esashi esa which is about 130 km from the epicenter and the remote reference station kakioka kak about 300 km distant to the epicenter have been computed after removing seasonal variations revealed by wavelet transform analysis the 15 day mean values of the ratios in the vertical component shows a clear anomaly exceeding the statistical threshold about 2 months before the mega event this anomaly is unique over a 16 year long background and further discussions indicate that this anomaly is unlikely caused by strong geomagnetic storms or a statistical fluke therefore this study has provided a strong support to the previous results in xu et al 2013

evidence of electro seismic phenomena abstract ground based observations of electromagnetic precursors to large earthquakes have been reported in japan iran chile greece and the soviet union ionospheric disturbances measured by soviet satellites have been claimed to be seismic precursors in addition observations of very low frequency anomalies measured by geos satellites have been reported by french researchers to confirm reports of electromagnetic precursors to earthquakes a series of low frequency broadband radio frequency receivers were deployed along the san andreas fault system this system of monitors has recorded electromagnetic anomalies occurring just before earthquakes between 1983 and 1986 these anomalies are of two types and are presumably caused by separate effects both of which may be related to stress induced changes in the crust just before fault rupture the first of these types of anomalies appears to be an interruption in the propagation of radio waves radio depressions lasting for many hours before an earthquake the second type is similar to those in previously published reports and consists of short duration broadband radio emissions given the results reported by other researchers and the results from our own experiments we believe that electromagnetic data may be useful as a tool for predicting earthquakes

a total electron content space weather study of the nighttime weddell sea anomaly of 1996 1997 southern summer with topex poseidon radar altimetry this paper reports on a total electron content space weather study of the nighttime weddell sea anomaly overlooked by previously published topex poseidon climate studies and of the nighttime ionosphere during the 1996 1997 southern summer to ascertain the morphology of spatial tec distribution over the oceans in terms of hourly geomagnetic longitudinal and summer winter variations the topex tec magnetic and published neutral wind velocity data are utilized to understand the underlying physical processes the tec results are combined with inclination and declination data plus global magnetic field line maps to investigate spatial and temporal tec variations geographic magnetic latitudes and local times are computed as results show the nighttime weddell sea anomaly is a large 1 600 2 22 million km2 estimated for a steady ionosphere space weather feature extending between 200 e and 300 e geographic it is an ionization enhancement peaking at 50 s 60 s 250 e 270 e and continuing beyond 66 s it develops where the spacing between the magnetic field lines is wide medium easterly declination is large medium 20 50 and inclination is optimum 55 s its development and hourly variations are closely correlated with wind speed variations there is a noticeable 43 reduction in its average area during the high magnetic activity period investigated southern summer nighttime tecs follow closely the variations of declination and field line configuration and therefore introduce a longitudinal division of four indian western eastern pacific atlantic northern winter nighttime tecs measured over a limited area are rather uniform longitudinally because of the small declination variation topex maps depict the expected strong asymmetry in tec distribution about the magnetic dip equator

large scale traveling ionospheric disturbances impacting equatorial ionization anomaly development in the local morning hours of the halloween superstorms on 29 30 october 2003 this study investigates the development of eia like features during the halloween superstorms these features are similar to a well developed equatorial ionospheric anomaly eia and therefore suggest superfountain effects we tracked eia like features in the early morning sector of 29 30 october 2003 and at around midday on 30 october their plasma environment was studied with field aligned plasma density vertical plasma drift electron temperature and vertical plasma flow profiles coupled thermosphere ionosphere plasmasphere ctip simulations reproduced storm generated equatorward wind surges when these eia like features appeared early morning on 29 30 october there was no forward fountain circulation only large scale traveling ionospheric disturbances tids and strong equatorward winds were present these provide observational evidence that large scale tids created large plasma depletions over the dip equator and with the aid of equatorward winds some large enhancements at 30 n geomagnetic resulting in the development of early morning eia like features we identified tid signatures in the equatorial and midlatitude ionosonde and magnetometer data and studied eia like features at around midday on 30 october utilizing non field aligned topex tec 2000 ut and published champ tec 2030 ut 2200 ut line plots according to our analysis the eia like features seen in the tec data were created by large scale tids at 2000 and 2030 ut and by the combined effects of large scale tids and forward superfountain at 2200 ut ctip simulations demonstrate the crucial role of the neutral winds mechanical or direct effects in the development of high plasma densities at low midlatitudes

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

gust front characteristics and the kinematics associated with interacting thunderstorm outflows abstract the morphology kinematic and thermodynamic characteristics of 30 gust fronts were examined with single and dual doppler radar and surface mesonet data collected in eastern colorado during the summers of 1982 and 1984 the majority of gust fronts examined exhibited the general shape of laboratory produced gravity currents including the elevated head body and turbulent wake region the average head depth was 1 3 km only 0 1 km above the average body depth small scale features in the vertical and horizontal vorticity fields were also observed the passage of the fronts was marked in order of event by a pressure rise wind direction and velocity change and temperature drop at the surface the average propagation speed and maximum surface wind within the outflows were 8 6 and 14 5 m s 1 respectively the average maximum temperature drop at the surface was 3 5 c and the average hydrostatic pressure rise was 0 06 kpa dual doppler analyses of colliding gust fronts revealed strong circulations a

circulations associated with a mature to decaying midlatitude mesoscale convective system part i surface features heat bursts and mesolow development abstract this study examines surface features associated with a mature to dissipating midlatitude mesoscale convective system that occurred on 23 24 june 1985 during the oklahoma kansas preliminary regional experiment for storm central the primary data sources include a 400 500 km surface mesonetwork on a 50 km grid rawinsonde observations from 12 supplementary sites in kansas and oklahoma and radar measurements from conventional as well as dual doppler networks the mesoscale convective system under investigation developed in an environment with weak vertical shear and had a lifetime of 9 12 h it consisted in its mature stage of a southward moving arc shaped line of deep convective cells with a trailing stratiform precipitation region to the north thirty three percent of the surface rain in the portion of the mesonetwork experiencing storm passage was from the stratiform region an intense mesoscale downdraft developed beneath the stratiform cloud with a strong mesohigh at the surface a wake low w

electromagnetic emissions during dilating fracture of a rock abstract a lot of experiments on electromagnetic emissions emes have been reported under axial compressive fracture shear fracture indentation fracture and stick slip friction in lab and blasting in situ but there are rare reports on the in lab experimental work on emes during dilating fracture of a rock which is helpful in studying and understanding emes related to slow earthquakes and the earthquakes due to volcanic activities and water level changes of reservoirs therefore in the present paper in order to check whether there are detectable emes during dilating fracture of a rock in lab dilating fracture experiments were conducted the dry cuboid specimens of initially intact granodiorite and limestone were tested inside magnetic field free space mffs at room temperature we arranged evenly 20 eme antennas whose resonance frequencies range from 2 5 khz to 540 khz close to rock specimens our experimental results strongly indicate that detectable emes could generate during dilating fracture of a rock they were recorded only associated with some but not all phases of fracture their waveforms often took on the trend that a peak arrived at first and then attenuated sharply and followed by a series of low amplitude oscillations the electromagnetic em signals after eliminating the effects of eme antennae via deconvolution had the maximum peak to peak amplitudes of about 80 0 mv and 40 5 mv for granodiorite and limestone respectively their main spectral components often concentrated in the band of several khz to 60 khz and of several khz to 280 khz the emission of electrons and charged particles from fracture surfaces and or micro fracture electrification could be possible mechanisms for our experimental results

multiple seismo anomalies associated with the m6 1 ludian earthquake on august 3 2014 abstract multiple geophysical parameters including groundwater level water temperature water radon crustal deformation electromagnetic waves and total electron contents tec in the ionosphere are examined together to investigate pre earthquake anomalous phenomena associated with the mw6 1 ludian earthquake on august 3 2014 cross parameter comparison eliminates anomalies that are detected in one parameter only and examine earthquake related phenomena in various fields simultaneously retrieved anomalies show that abnormal decreases of water temperature and radon concentration related to anomalous uplift of groundwater levels appeared about 1 8 days before the earthquake even without contributions from rain significant step like changes are observed from data recorded by strainmeters on july 31 and are consistent with water related anomalies in timing no significant anomalies can be found from electromagnetic data through the preliminary observation in contrast tec appeared positive anomalies 1 3 days before the ludian earthquake although causal mechanisms of the tec anomalies from stressed rocks are not fully understood multiple parameter examination can increase credibility of determination regarding pre earthquake phenomena

the initiation and organization of convective cells atop a cold air outflow boundary abstract on 13 july 1986 a cold air outflow from thunderstorms over illinois and missouri propagated through the mist microburst and severe thunderstorm network over northern alabama the study of this outflow is important since the gust front was solely responsible for the initiation of numerous convective cells previous studies have documented the initiation of convection due to colliding gust fronts in addition there was a pronounced mesoscale organization of the cells atop the outflow boundary this was most likely due to a combination of kelvin helmholtz k h and internal gravity ig wave activity in contrast to previous cases the k h wave crests were oriented nearly perpendicular to the gust front within the analysis area the resulting intersections between the circulations associated with the k h waves and the gust front produced favorable locations for the initiation of convection subsequently the convective cells remained along the updraft side of the k h wave circulations as they pro

magnetic field observations in the near field the 28 june 1992 mw 7 3 landers california earthquake recent reports suggest that large magnetic field changes occur prior to and during large earthquakes two continuously operating proton magne tometers lsbm and ochm at distances of 17 3 and 24 2 km respectively from the epicenter of the 28 june 1992 mw 7 3 landers earthquake recorded data through the earthquake and its aftershocks these two stations are part of a differentially connected array of proton magnetometers that has been operated along the san andreas fault since 1976 the instruments have a sensitivity of 0 25 nt or better and transmit data every 10 min through the goes satellite to the usgs headquarters in menlo park california seismomagnetic offsets of 1 2 0 6 and 0 7 0 7 nt were observed at these sites in comparison offsets of 0 3 0 2 and 1 3 0 2 nt were observed during the 8 july 1986 mt 5 9 north palm springs earthquake which occurred directly beneath the ochm magnetometer site the observations are generally consistent with seismomagnetic models of the earthquake in which fault geometry and slip have the same form as that determined by either inversion of the seismic data or inversion of geodetically determined ground displacements produced by the earthquake in these models right lateral rupture occurs on connected fault seg ments in a homogeneous medium with average magnetization of 2 a m the fault slip distribution has roughly the same form as the observed surface rupture and the total moment release is 1 1 1020 nm there is no indication of dif fusion like character to the magnetic field offsets that might indicate these ef fects result from fluid flow phenomena it thus seems unlikely that these earth quake generated offsets and those produced by the north palm springs earthquake were generated by electrokinetic effects also there are no indications of en hanced low frequency magnetic noise before the earthquake at frequencies be low 0 001 hz

the generation and propagation of a nocturnal squall line part i observations and implications for mesoscale predictability abstract the initiation and forcing of a squall line on 26 27 may 1985 near wichita kansas is examined the squall line is secondary convection in the sense that it is preceded in the diurnal cycle by other mesoscale convective systems the squall fine develops in synoptic conditions frequently associated with convective weather in the central united states this includes moderate shear moderate to high convective available potential energy a quasi stationary dryline a low level southerly jet and an 85 kpa moist tongue the initiation of free convection is specifically attributed to a gust front that propagates into a low level jet with attendant horizontal vorticity convergence and moisture the gust front initially propagates as a gravity current and subsequently as an internal undular bore observations of gravity currents gravity waves and the collision of radar echo boundaries provide valuable clues for short period forecasting they establish the presence of potential triggering mechanism

super plasma fountain and equatorial ionization anomaly during penetration electric field 1 relative importance of diffusion electric field and neutral wind on equatorial plasma fountain and equatorial ionization anomaly eia during a strong daytime eastward prompt penetration electric field ppef event are evaluated using the sheffield university plasmasphere ionosphere model and the recorded ppef during the super geomagnetic storm of 9 november 2004 the fountain rapidly develops into a super fountain during the ppef event the super fountain becomes strong with less poleward turning of the velocity vectors in the presence of an equatorward wind that reduces or stops the downward velocity component due to diffusion and raises the ionosphere to high altitudes of reduced chemical loss the eia crests in peak electron density and total electron content shift rapidly to higher than normal latitudes during the ppef event however the crests become stronger than normal only in the presence of an equatorward wind the results suggest that the presence of an equatorward neutral wind is required to produce a strong positive ionospheric storm during a daytime eastward ppef event the equatorward neutral wind need not be a storm time wind though stronger wind can lead to stronger ionospheric storms

experimental measurement of electromagnetic emissions possibly related to earthquakes in japan recent observations in the ussr appear to suggest that wide band electromagnetic radiation occurs just prior to earthquakes to apply this phenomenon to earthquake prediction measurements have been carried out at the sugadaira space radiowave observatory in japan under the ussr japan cooperation program in 1980 the recorded noise level at 81 khz is comparatively quiet throughout the day and night however about one half hour before the main shock of a magnitude 7 earthquake at 0733 ut on march 31 1980 the instrument recorded an anomalous amplitude increase to 15 db higher than the normal level vlf data recorded synoptically at sugadaira suggest that unusual impulsive radiation at frequencies below 1 5 khz also occurred shortly before the earthquake similar 81 khz emissions were observed prior to magnitude 5 and 6 earthquakes on september 25 1980 and january 28 1981

application of pattern recognition techniques to earthquake catalogs generated by model of segmented fault systems in three dimensional elastic solids techniques and seismicity parameters described by eneva and ben zion 1997 are used to examine synthetic earthquake catalogs generated by ben zion 1996 for precursory patterns of large model events different model realizations represent various levels of fault zone disorder these include models with uniform properties u a parkfield type asperity a fractal brittle properties f and multi size scale heterogeneities m the seismicity parameters used are based on information contained in typical earthquake catalogs reflecting earthquake distribution in space time and size the analysis highlights the complexity of the information content of the synthetic earthquake catalogs simple repetitive precursory signals have not been found however local extrema in the examined parameters are found to have significant association in time with large events thus our techniques and parameters may be useful for intermediate term earthquake prediction especially when parameters are used in combinations some analysis results are the same for all model realizations and some depend on the model features characterizing all catalogs are as follows 1 large model events are statistically predictable on the basis of patterns in the distribution of smaller events 2 for a given parameter the type of precursory extrema maxima or minima is the same for all models 3 the interparameter correlation for any parameter pair has the same sign positive or negative in all models 4 the large events are neither slip nor time predictable based on previous large events results that differ from model to model include the following 1 the degree of predictability of large events correlates with the degree of regularity in the assumed fault properties following the order u f a and m 2 there is no one to one correlation between type of precursory extrema maxima or minima and type of precursory trends increase or decrease this produces great variations in observable trends for any given parameter both from model to model and for different events in the same model 3 the interparameter correlations vary among models with the highest correlations in model f most discussed patterns are in agreement with observations from seismically active zones laboratory models and mining induced seismicity

natural time analysis on the ultra low frequency magnetic field variations prior to the 2016 kumamoto japan earthquakes abstract on 15 april 2016 a very strong and shallow earthquake eq m w 7 0 depth 10 km occurred in southwest japan under the city of kumamoto while two very strong foreshocks m w 6 2 and m w 6 0 preceded by about one day the kumamoto eqs being very catastrophic have already attracted much attention among the scientific community in a quest for understanding the generation mechanism as well as for reporting any preseismic anomalies in various observables and assessing the effectivity of the current early warning systems in the present article we report precursory behavior of the ground based observed ultra low frequency ulf magnetic field variations before the kumamoto eqs by analyzing specific ulf magnetic field characteristics in terms of the recently introduced natural time nt analysis method we identified that ulf magnetic field variations presented critical features from 2 weeks up to 1 month before the kumamoto eqs specifically the ulf magnetic field characteristics f h f z d h and d e p were analyzed the first two represent variations of the horizontal and vertical components of the geomagnetic field the third and fourth characteristics correspond to the depression decrease and a relative depression of the horizontal magnetic field variations respectively the latter depends on the degree of ionospheric disturbance all of them were found to reach criticality before the kumamoto eqs however in different time periods for each characteristic

pre seismic geomagnetic anomaly and earthquake location article i nfo many researchers studied the relationships between appearances of geomagnetic anomalies and their distances to earthquake epicenters or faults yet occasionally some magnetometer stations located nearby earthquake epicenters and or faults do not observe geomagnetic anomalies in this paper a new hybrid system which simultaneously takes the hypocenter and fault plane solution into account is constructed to examine 38 earthquakes interpreted to be associated with geomagnetic anomalies during the period 1988 2001 in taiwan the surface magnetic anomaly reference tip smart of the new system is used instead of the epicenter or the fault to investigate statistically the distance relationship between the anomalies and the earthquake parameters results show that the anomalies gather along the fault and in the belt zone to the smart possible mechanisms causing the anomalies in the two zones are proposed and discussed characteristics of the anomaly might shed some light on locations of faults before earthquake occurrences

some simple simulations of thunderstorm outflows three idealized simulations of thunderstorm outflows are presented each outflow is a response to an instantaneous low level cooling the vertical structures of the coolings differ as do the environments in which the outflows form and consequently the dynamics of the outflows differ one outflow is a gravity current another is a gravity wave and the third comprises both a gravity current and a gravity wave the horizontal transport of mass is important for the advance of the gravity current outflow but not for the gravity wave outflow and it is suggested that this is the defining dynamical distinction between the two outflows the simulations are compared to observations and it is suggested that some outflows previously characterized as gravity currents may better fit the gravity wave or gravity current wave archetypes it is also noted that the gravity wave component of an outflow may be generated directly by low level cooling in addition to the commonly suggested mechanism of the interaction of a gravity current with a stable layer

three dimensional numerical modeling of convection produced by interacting thunderstorm outflows part i control simulation and low level moisture variations abstract the klemp wilhelmson three dimensional numerical cloud model is used to investigate cloud development along intersecting thunderstorm outflow boundaries the model initial environment is characterized by a temperature and moisture profile typically found in strong convective situations and the initial wind field is prescribed by a constant unidirectional shear 2 9 m s 1 km 1 from 0 8 to 8 9 km with a constant wind everywhere else the wind shear vector is perpendicular to the line containing the two initial outflow producing clouds which are spaced 16 km apart and are triggered by thermal impulses centered at the top of the boundary layer the dynamics of the outflow collision are documented using time dependent kinematic air parcel trajectories and thermodynamic data we find that ambient air in the outflow collision region is literally squeezed out of the way as the two outflows collide some of this air is lifted to saturation triggering two convective clouds the upshear member of the

geological features controlling factors and potential prospects of the gas hydrate occurrence in the east part of the pearl river mouth basin south china sea abstract logging while drilling lwd and wireline log cwl data were acquired during china s second gas hydrate drilling expedition gmgs 2 in the east of pearl river mouth basin south china sea disseminated and massive gas hydrates deposits were found at different sites gas hydrate bearing lithologies identified from the sample coring included the fine grained sediments and coarse grained sediments lwd logs from site gmgs2 08 indicate significant gas hydrate in clay bearing sediments including two layers with massive gas hydrate with a bulk density near to 1 08 g cm3 high electrical resistivities with a range of 2 5 2000 0 m and high p wave velocities are simultaneously observed in the hydrate bearing sediments the average gas hydrate saturation estimated from the pore water freshing analysis ranges from 45 to 55 of the pore space buried carbonate layers above the massive gas hydrate deposit discovered at sites gmgs2 08 indicate that the formations are likely to have formed initially at the surface and then were buried significant high amplitude seismic anomalies discontinuous bottom simulating reflection bsr and blanking zone are detected in the drilling zone the hydrate bearing sediments predominantly consist of silty clay and limestone grains in which the gas hydrates are deposited primarily in the form of laminated massive veins or nodule the gas hydrates occurrences are subjected to the sediment lithology new tectonic activities migration of fluid and gas and also the factors such as heat flow salinity and time which affect the nucleation of gas hydrates its natural morphologies present massive laminated nodular nugget and disseminated of which the former four often formed in shallow fault inter layer s weak cementation zone and on the seabed the buried gas hydrates with high saturation are good zones for gas hydrate exploitation

f3 layer during penetration electric field 1 the occurrence of an additional layer called f3 layer in the equatorial ionosphere at american indian and australian longitudes during the super double geomagnetic storm of 7 11 november 2004 is presented using observations and modeling the observations show the occurrence reoccurrence and quick ascent to the topside ionosphere of unusually strong f3 layer in australian longitude during the first super storm 8 november and in indian longitude during the second super storm 10 november all with large reductions in peak electron density nmax and total electron content gps tec the unusual f3 layers can arise mainly from unusually strong fluctuations in the daytime vertical e b drift as indicated by the observations and modeling in american longitude the strongest upward e b drift or eastward prompt penetration electric field ppef ever recorded at jicamarca produces unusually strong f3 layer in the afternoon hours 1400 1600 lt of ppef with large reductions in nmax and tec the layer also reappears in the following evening 1700 1800 lt owing to an unusually large downward drift at night when the drift is unusually upward and strong the f region splits into two layers

electric field patterns as seismic precursors in this paper we report the results of two and a half years of measurements of the ground electric field at the pacific coast of mexico the analysis of the voltage itself does not show any distinguishable feature that could be correlated to earthquakes fourier analysis however gives clear patterns of the electric field prior to the four ms w 6 earthquakes that occurred in the zone during the time interval considered

response of seismicity to coulomb stress triggers and shadows of the 1999 mw 7 6 chi chi taiwan earthquake 1 the correlation between static coulomb stress increases and aftershocks has thus far provided the strongest evidence that stress changes promote seismicity a correlation that the chi chi earthquake well exhibits several studies have deepened the argument by resolving stress changes on aftershock focal mechanisms which removes the assumption that the aftershocks are optimally oriented for failure here one compares the percentage of planes on which failure is promoted after the main shock relative to the percentage beforehand for chi chi we find a 28 increase for thrust and an 18 increase for strike slip mechanisms commensurate with increases reported for other large main shocks however perhaps the chief criticism of static stress triggering is the difficulty in observing predicted seismicity rate decreases in the stress shadows or sites of coulomb stress decrease detection of sustained drops in seismicity rate demands a long catalog with a low magnitude of completeness and a high seismicity rate conditions that are met at chi chi we find four lobes with statistically significant seismicity rate declines of 40 90 for 50 months and they coincide with the stress shadows calculated for strike slip faults the dominant faulting mechanism the rate drops are evident in uniform cell calculations 100 month time series and by visual inspection of the m 3 seismicity an additional reason why detection of such declines has proven so rare emerges from this study there is a widespread increase in seismicity rate during the first 3 months after chi chi and perhaps many other main shocks that might be associated with a different mechanism

the role of convectively generated gravity waves on convective initiation a case study abstracta case study of a convection initiation ci event involving a mesoscale gravity wave is presented this severe convection event occurred in east china on 5 june 2009 high frequency automatic weather station aws data visible satellite data and doppler radar data were combined to depict the features of the gravity wave and the development of several convection centers the gravity wave was manifested by a surface pressure dip and surface wind shift propagating westward away from the early convection the pressure dip propagated at a speed of 30 m s 1 which is comparable with that in previous observational studies of convectively generated gravity waves a special focus is on the initiation of a deep convection cell in anhui province which resulted in 25 deaths surface observations showed two precursors before ci including a convergence line and wind shift at the eastern end of the convergence line high resolution numerical simulations with the weather research and forecasting wrf model

phenomenology of sahelian convection observed in niamey during the early monsoon thisstudyaimstoachieveabetterunderstandingoftheinitiationofdeepconvection in the sahel by using the african monsoon multidisciplinary analyses amma dataset based on the massachusetts institute of technology mit radar wind profiler satellitedata surfacefluxandmeteorologicalstations wehavecharacterised the atmospheric convection which occurred over niamey during the onset period of the monsoon from 6 to 31 july radar reflectivity fields combined with brightness temperatures were used to classify the type of convection observed each day within a 50km radius of the mit radar location four types of convection have been identified fair weather fw with a clear sky throughout the entire day shallow convection sh afternoon locally initiated deep convection lc and propagating deep convection pc subsequently the mechanisms responsible for the initiation of local deep convection were investigated neither early morning convective available potential energy nor the convective triggering potential allowed the onset of local deep convection to be predicted correctly in effect they were both favourable to deep convection most of the time while convective inhibition was typically quite large our results show that the daytime growth of the atmospheric boundary layer needed to be sufficient for local deep convection to occur during that period convergence lines which grew within the morning clear air roll organisation were found to be precursors of local deep convection classes fw sh and lc ultimately behaved quite similarly with notable convergence in the lower troposphere but fw showed smaller boundarylayer growth and fw and sh classes revealed a significant divergence above the boundary layer most cases of lc generated a circular gust front these density currents almost always generated new convective cells copyright c 2013 royal

signals recorded by demeter satellite over active volcanoes during the period 2004 august 2007 december more than 1500 volcanoes can potentially enter into eruption but only some tens of them are equipped with monitoring networks most of volcanic eruptions can be predicted by the integration of continuous real time observations data processing and analysing in the electromagnetic field em a long history of ground observations shows that electric magnetic and electromagnetic signals may precede and accompany volcanic eruptions the possibility that volcanic eruptions may also be preceded by transient electromagnetic anomalies in the ionosphere can be analysed on the basis of demeter mission this microsatellite launched by cnes in 2004 covers 14 orbits per day over seismic and volcanic regions of the earth two complementary and systematic studies are presented over the time period 2004 august 2007 december the first study shows that three types of electric and or magnetic anomalies can be observed in the time window of 30 d preceding an eruption and 15 d after on the 74 eruptions occurring on 50 volcanoes under consideration 48 anomalies are recognised along 30 eruptions 41 per cent of the eruptions were accompanied by em signals on board of the satellite 81 per cent of the anomalies are observed before the eruptions for the period 30 d 15 d and 69 per cent for the period 15 d 15 d in the second study the anomalies above three nearby volcanoes lopevi ambrym and aoba are systematically looked for all orbits between 2004 august and 2006 december anomalies are only observed during periods of larger activity on each of them taking into account that no anomaly is observed a long time before an eruption on can allocate the anomalies to each volcano although the database is still limited the study shows that volcanic activity may be preceded by em perturbations of the ionosphere

ionospheric electron content within the equatorial f 2 layer anomaly belt this paper describes some new results on the day to day behavior of the location of the equatorial anomaly in the columnar electron content the measurements were made from a unique network of stations covering dip latitudes from 0 n to 25 n during the period in 1975 1976 near sunspot minimum when the ats 6 satellite was visible from india the latitudinal distribution of the total electron content on a particular day was found to depend only on the strength of the electrojet current as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and another outside the equatorial electrojet rather than on the horizontal magnetic field measured only at the equatorial station during magnetically disturbed periods the presence or absence of the anomaly was also found to depend only upon the strength of the electrojet current the varying electrojet current that is the equatorial electric field is very effective in moving the ionization to the anomaly latitudes of 15 20 but the columnar electron content over the magnetic equator remains relatively constant

potential relationships between seismo deformation and seismo conductivity anomalies abstract this study examines the relationships between seismo deformation and seismo conductivity anomalies during two m6 earthquakes that occurred on march 27th and june 2nd 2013 in taiwan the hilbert huang transform is applied on surface displacement data to remove the effects of noise semi annual and annual cycles and the long term plate movements the residual displacements have similar orientations when earthquake related stress accumulates in the crust once the accumulated stress approaches the threshold for fault rupture the orientations of the residual displacements generally become random except in a small region near the epicenter interestingly high conductivity anomalies which can be detected from the 3 component magnetic data via the magnetic transfer function exist in places very close to this small region near the epicenter spatial and temporal correlations between the high conductivity anomalies and the small region of seismo deformation anomalies suggest that electric charges may migrate and become trapped in the region during seismogenic processes due to differential stress accumulation these electric charges form a high conductivity material that affects the parkinson vector of the geomagnetic field

evaluation of the topex poseidon dual frequency ionosphere correction the nasa altimeter on board topex poseidon exploits the difference in the delays of the ku and c band radar pulses to estimate an ionosphere correction to the range measurement the dependence of the ionosphere correction on ocean and satellite parameters is less than 1 cm the standard deviation of the 1 s averaged ionosphere correction depends on the height of the ocean waves and ranges from 5 to 14 mm the accuracy of the ionosphere correction is better than 1 cm at the 1 confidence level the ionosphere correction should be averaged over 140 km 20 s along track in order to minimize its noise without sacrificing its accuracy ionosphere models must achieve an independent sample spacing of 900 km or less in order to allow a single frequency altimeter to have an ionosphere correction comparable in accuracy to that of the nasa dual frequency altimeter

statistical analysis of ulf seismomagnetic phenomena at kakioka japan during 2001 2010 to clarify and verify the ultralow frequency ulf seismomagnetic phenomena we have performed statistical studies on the geomagnetic data observed at the kakioka kak station japan during 2001 2010 we investigated the energy of ulf geomagnetic signals of the frequency around 0 01 hz using wavelet transform analysis to minimize the influences of artificial noises and global geomagnetic perturbations we used only the geomagnetic data observed at nighttime lt 2 30 a m to 4 00 a m and utilized observations from a remote station kanoya as a reference statistical results of superposed epoch analysis have indicated that ulf magnetic anomalies are more likely to appear before sizable earthquake events es 108 rather than after them especially 6 15 days before the events further statistical investigations show clearly that the ulf geomagnetic anomalies at kak station are more sensitive to larger and closer events finally we have evaluated the precursory information of ulf geomagnetic signals for local sizable earthquakes using molchan s error diagram the probability gain is around 1 6 against a poisson model the above results have indicated that the ulf seismomagnetic phenomena at kak clearly contain precursory information and have a possibility of improving the forecasting of large earthquakes

shear wave polarizations and subsurface stress directions at lost hills field 2 2 s wave data matrix accomplished by computationally rotating sources and receivers although polarization directions obtained by assuming a homogeneous subsurface were moderately consistent with depth considerable improvement in consistency resulted from analytically stripping off a thin near surface layer whose fast s wave polarization direction was about n 6 e s wave birefringence for vertical travel averaged 3 percent in two zones 200 700 ft and 1200 2100 ft 60 210 m and 370 640 m which had closely similar s wave polarizations between those zones the polarization direction changed and the birefringence magnitude was not well defined s wave polarizations from two concentric rings of offset vsps were consistent in azimuth with one another and with polarizations of the near offset vsp this consistency argues strongly for the robustness of the s wave polarization technique as applied in this area the s wave polarization pattern in offset data fits a model of vertical cracks striking n 55 e

dynamics of a thunderstorm outflow abstract the kinematic and thermodynamic structures of a thunderstorm outflow are examined by means of dual doppler radar analysis mesonet lower and sounding data the data were collected in the denver colorado area during june 1984 the dual doppler analysis shows that the cold outflow is ducted beneath the pbl inversion along the gust front there is a narrow quasi two dimensional updraft kelvin helmholtz instability khi developed along the top of the gust front head near the surface front and propagated backwards dissipating in the wake of the head region an isothermal layer aloft appears to have limited billow amplification to the quasi neutral layer below the gust front s leading edge had numerous inflections which are believed to result from barotrophic instabilities small vortices develop at some of the inflection points detailed analysis of one such circulation shows evidence of the formation of two enhanced updrafts separated by an occlusion downdraft these observations are the firs

an inversion of geomagnetic deep sounding data using simulated annealing abstract a maiden attempt on the use of the global optimization technique of simulated annealing s a inversion to model the conductivity structure derived from the geomagnetic deep sounding data of nw india is reported here the location of the proposed model is now in agreement with the theory since the conductive bodies are centered exactly below the center of the response function which was not feasible by the earlier linearized inversion the central body is located at a depth of 19 km from the surface suggesting thickness of 15 km and resistivity of 14 m the resistivity contrast of this ensemble of conductive bodies with the background is varying by a factor of 100 to 385 existence of mid crustal conductor the conductivity estimate is marginally different is clearly indicated which was also not detected in the earlier study a likely explanation could be due to the presence of graphitic carbon at lower crustal depths however the role of electrolytic fluid present in the interconnected pore spaces of rocks may be another explanation

surface rupture of 1999 chi chi earthquake yields insights on active tectonics of central taiwan the 1999 chi chi earthquake was caused by rupture of the chelungpu fault one of the most prominent active thrust faults of taiwan this largest of taiwan s historical fault ruptures broke the surface for over 90 km at the western base of the rugged mountain range a short right lateral tear extended southwestward from the southern end of the chelungpu fault and a complex assemblage of shallow folds and faults ran northeastward from the northern end vertical offsets averaged about 2 m along the southern half of the chelungpu fault and about 4 m along the northern half and offsets of 5 to 7 m were typical along the northern part of the major thrust the sinuous nature of the surface trace is consistent with seismographic data that indicate a dip of about 30 the 1999 rupture draws attention to the fact that this active fault system is highly segmented and that this segmentation influences the characteristics of seismic ruptures active faults to the south north and west of the chelungpu fault have distinctly different characteristics faults to the south and north broke the surface during earthquakes in 1906 and 1935 the active changhua fault to the west a blind thrust similar in length to the chelungpu has not ruptured in the historical period and should be considered a prime candidate for generating a future earthquake manuscript received 4 october 2000

anomalous behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 there have been many reports on ultra low frequency ulf electromagnetic phenomena associated with earthquakes in a very wide frequency range in this study unusual behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 have been reported ratios of diurnal variation range between the target station esashi esa which is about 135 km from the epicenter and the remote reference station kakioka kak about 302 km distant to the epicenter have been computed the results of 10 day running mean of the ratios showed a clear anomaly exceeding the statistical threshold in the vertical component about 2 months before the mega event this anomaly is unique over a 3 year background and the further stochastic test indicates that this anomaly is unlikely a random anomaly which is highly suggestive of correlation with the mega event the original records of geomagnetic fields of the esa station also exhibit continuous anomalous behaviors for about 10 days in the vertical component approximate 2 months prior to the mw9 0 earthquake

a dayside ionospheric positive storm phase driven by neutral winds 1 this paper presents observations and numerical simulations of ionospheric and thermospheric disturbances associated with a moderate geomagnetic storm on 10 september 2005 during the event the incoherent radars located in millstone hill and arecibo observed a dayside positive storm phase as manifested by the enhanced electron density in the f region the universal time ut altitude profile of electron density measured by both radars displayed a structure that closely resembles the greek letter a similar structure is also reproduced by the thermosphere ionosphere electrodynamics general circulation model tiegcm this peculiar electron density distribution is found to be associated with vertical ion drift which initially was upward and then became downward using realistic time dependent ionospheric convection and auroral precipitation as inputs the tiegcm reveals that the primary cause of the positive storm response was the enhanced meridional neutral wind rather than the penetration magnetospheric electric field this study reiterates the importance of neutral wind effects on ionospheric disturbance

initiation of convective storms at radar observed boundary layer convergence lines abstract the origin of 653 convective storms occurring over a 5000 km2 area immediately east of the colorado rocky mountains from 18 may to 15 august 1984 was examined seventy nine percent of the 418 storms that initiated within the study area occurred in close proximity to radar observed boundary layer convergence lines this percentage increased to 95 when only the more intense storms 60 dbze were considered colliding convergence lines initiated new storms or intensified existing storms in 71 of the cases a new storm took a median time of 24 min to grow to 30 dbz following line collision the convergence lines ranged in length between ten and several hundred kilometers both radar and mesonet stations indicated that the primary convergence was concentrated in a zone 0 5 to 5 km in width these lines were characterized on doppler radar as thin lines of enhanced reflectivity between 0 and 20 dbze and as a line of strong radial or azimuthal gradient in doppler velocity these lines were observed ev

elf vlf recordings during the 11 march 2011 japanese tohoku earthquake 1 broadband elf vlf radio recordings 0 2 40 khz were made at a site in onagawa japan located 102 km from the epicenter of the m9 0 11 march 2011 earthquake the fifth most powerful earthquake in recorded history the receiver operated for about two minutes after the start of the earthquake after which the receiver lost power examination of the vlf data shows no radio emissions preceding or coincident with the onset of the earthquake however once the secondary seismic waves reached the receiver a number of impulses and diffuse noise bands arose which may result from the entire power grid shaking or from radio emissions from compressing rocks examination of the elf data 0 2 1 khz show no precursor effect in the hours preceding the earthquake examination of vlf data from narrowband transmitters shows no anomalous activity in the days or weeks preceding the earthquake our instrument low frequency cut off is 200 hz and thus we cannot comment on emissions in the ulf range 10 hz

some statistical results on very low frequency radiowave emissions in the upper ionosphere over earthquake zones abstract an anomalous increase in the intensity of low frequency 0 1 16 khz radiowave emissions was detected using intercosmos 19 data when the satellite was nearly over the epicentre of an earthquake zone ample statistical data are the basis for a determination of the probable spatial temporal dimensions of the region of the upper ionosphere in justify which elf vlf emissions were detected the reliability of the detected phenomenon is 0 8 0 9 the ionospheric regions with the low frequency emissions observed by intercosmos 19 have been found to be formations noise belts extended along 60 of geographic longitude and 2 of geographic latitude the spectral characteristics of elf vlf emissions near seismic areas are specified the earthquake depth and location under a continent or under an ocean has an effect on the results of the satellite observations of earthquakes possible mechanisms of the phenomenon are discussed

formation and evolution of the ionospheric plasma density shoulder and its relationship to the superfountain effects investigated during the 6 november 2001 great storm this study investigates the 6 november 2001 great storm s impact on the topside ionosphere utilizing data from the onboard topex poseidon nasa altimeter defense meteorological satellite program special sensor ions electrons and scintillation instruments and ace interplanetary observatory a set of field aligned profiles demonstrate the storm evolution caused by the precursor and promptly penetrating interplanetary eastward electric e fields and strong equatorward winds reducing chemical loss during the long duration negative bz events at daytime evening the forward fountain experienced repeated strengthening as the net eastward e field suddenly increased the resultant symmetrical equatorial anomaly exhibited a continuous increase while the energy inputs at both auroral regions were similar in both hemispheres by progressing poleward a midlatitude shoulder exhibiting increased plasma densities a plasma density dropoff steep gradient and a plasma depletion appeared these features were maintained while the reverse fountain operated at the dropoff elevated temperatures indicated the plasmapause consequently the plasma depletion was the signature of plasmaspheric erosion in each hemisphere an isolated plasma flow supplying the minimum plasma was detected at the shoulder plasmaspheric compression due to the enhanced e fields could trigger this plasma flow exhibiting strong longitudinal variation at evening nighttime the shoulder increased 306 over the southeastern pacific where the nighttime weddell sea anomaly wsa appeared before the storm there the shoulder indicated the storm enhanced equatorward section of the quiet time wsa owing to the substantial equatorward plasmapause movement a larger poleward section of the quiet time wsa eroded away leaving a large depletion behind this study reports first these northern southern plasma flows and dramatic storm effects on a nighttime wsa

equatorial plasma fountain and its effects over three locations evidence for an additional layer the f 3 layer the equatorial plasma fountain and equatorial anomaly in the ionospheres over jicamarca 77 w trivandrum 77 e and fortaleza 38 w are presented using the sheffield university plasmasphere ionosphere model under magnetically quiet equinoctial conditions at high solar activity the daytime plasma fountain and its effects in the regions outside the fountain lead to the formation of an additional layer the f3 layer at latitudes within about plus or minus 10 of the magnetic equator in each ionosphere the maximum plasma concentration of the f3 layer which occurs at about 550 km altitude becomes greater than that of the f2 layer for a short period of time before noon when the vertical e b drift is large within the f3 layer the plasma temperature decreases by as much as 100 k the ionograms recorded at fortaleza on january 15 1995 provide observational evidence for the development and decay of an f3 layer before noon the neutral wind which causes large north south asymmetries in the plasma fountain in each ionosphere during both daytime and nighttime becomes least effective during the prereversal strengthening of the upward drift during this time the plasma fountain is symmetrical with respect to the magnetic equator and rises to over 1200 km altitude at the equator with accompanying plasma density depletions in the bottomside of the underlying f region the north south asymmetries of the equatorial plasma fountain and equatorial anomaly are more strongly dependent upon the displacement of the geomagnetic and geographic equators jicamarca and trivandrum than on the magnetic declination angle fortaleza

laboratory measurements anomalous 0 1 0 5 hz streaming potential under geochemical changes implications for electrotelluric precursors to earthquakes streaming potentials resulting from flow of various salt solutions in rock were measured on saturated sediments fontainebleau sandstones the streaming potential v was found to be proportional to the driving pore pressure p pulses of amplitude 15 40 mv in the frequency range of 0 1 to 0 5 hz were observed when the conductivity of the injected water was decreased and the fluid flow rate was relatively low corresponding to a darcian velocity of 17 to 30 cm h the amplitudes of these pulses are 47 to 133 of the corresponding steady components of the v values such geochemically induced effects may possibly be responsible for the frequency signals from 0 1 to 0 5 hz that were sometimes observed before an earthquake

storm enhanced plasma density sed features auroral and polar plasma enhancements and rising topside bubbles of the 31 march 2001 superstorm 1 this study focuses on the 31 march 2001 superstorm s evening and nighttime sectors we specified forward fountain circulation and equatorial ionization anomaly eia storm enhanced density sed plume plasma flows auroral zones polar cap regions and traveling ionospheric disturbances tids these permitted analyzing low latitude plasma structures and middle and high latitude plasma buildups results reveal significant low latitude plasma structuring around ancon due to topside rising bubbles during the initial phase under disturbance conditions the deep equatorial plasma depletion appearing over the pacific during the main phase is an eia trough bubble structure topside bubbles and tid related drift perturbations structured sed plume plasma plasma distribution maximized when tids were in phase with fountain circulation and sed plume plasma flows and equatorward wind surges maintained high plasma densities plasma density and plasma flow measurements demonstrate the sed plume plasma s poleward migration through the auroral zone into the polar region and the maintenance and increase of auroral and polar enhancements forming a polar tongue of ionization toi our results contradict previous studies on this superstorm reporting the suppression of bubble formation over ancon and the absence of toi and explaining the development of equatorial depletion with no e b drift action our results oppose the current hypothesis that plasma enhancements are transported over many hours into the polar region indeed sed plume plasma produced by plasmaspheric detachment processes creates multiple downward plasma flows stretching from the midlatitude trough s equatorward edge to the polar cap region that in turn create plasma buildups at various latitudes where flow stagnates

the frontal hydraulic head a micro α scale 1 km triggering mechanism for mesoconvective weather systems abstract measurements from the noaa boulder atmospheric observatory bao 300 m tower the national center for atmospheric research ncar sabreliner aircraft and the noaa goes 5 satellite give evidence for the cross front scale collapse of nonprecipitating surface cold frontal zones to horizontal distances of 1 km or less the leading edges of these frosts possess the characteristic structure of density current flows an elevated hydraulic head followed by a turbulent wake vertical motions at the frontal heads exceed 5 m s 1 at 300 m agl the ascent at the frontal head may act as a 1 km scale triggering mechanism for the release of potential instability and the formation of intense squall line mesoconvection

tropical island convection in the absence of significant topography part ii nowcasting storm evolution abstract this paper examines influences on the short range prediction of organized convection under conditions of strong diurnal forcing the analyses are based on data provided by the maritime continent thunderstorm experiment which was conducted in 1995 over the tiwi islands 11 s 50 100 km north of the australian continent organized convection over the tiwi islands is often dubbed hector by residents and researchers alike the authors purpose is to utilize results from these analyses to improve convective storm nowcast systems and their associated forecast and warning products the environmental near surface wind direction is shown to be singularly influential in statistically predicting the location of convection and its time of occurrence over the tiwi islands this finding is robust despite the fact that mean wind speeds were merely 1 4 m s 1 the island boundary layer water vapor mixing ratio derived from a morning sounding and inland surface stations is shown to be correlated with measu

boundary layer development over a tropical island during the maritime continent thunderstorm experiment abstract data collected during the maritime continent thunderstorm experiment mctex 10 november 10 december 1995 have been used to analyze boundary layer development and circulations over two almost flat tropical islands the two adjacent islands have a combined length of about 170 km from east to west and 70 km from north to south intense thunderstorms formed over these islands every day of the field campaign the boundary layer depth temperature and circulation over the island have been measured over the full diurnal cycle using a multiple radar analysis combined with surface and radiosonde measurements on average the island boundary layer depth reaches 1 5 km by early to midafternoon coinciding with the development of the deep convection thus the island boundary layer is significantly deeper than the typical tropical oceanic boundary layer in the midafternoon thunderstorm outflows and their associated cold pool stabilize the lower boundary layer suppressing late convection this is follo

low frequency magnetic field measurements near the epicenter of the ms 7 1 loma prieta earthquake the authors report the results of measurements of low frequency magnetic noise by two independent monitoring systems prior to the occurrence of the m sub s 7 1 loma prieta earthquake of 17 october 1989 their measurements cover 25 narrow frequency bands in the more than six decade frequency range 0 01 hz 32 khz with a time resolution varying from a half hour in the ulf range 0 01 10 hz to one second in the elf vlf range 10 hz 32 khz the ulf system is located near corralitos about 7 km from the epicenter the elf vlf system is located on the stanford campus about 52 km from the epicenter analysis of the elf vlf system is located on the stanford campus about 52 km from the epicenter analysis of the elf vlf data has revealed no precursor activity that they can identify at this time however the ulf data have some distinctive and anomalous features first a narrow band signal appeared in the range 0 05 0 2 hz around september 12 and persisted until the appearance of the second anomalous feature which consisted of a substantial increase in the noise background starting on 5 october and covering almost the entire frequency range of the ulf system third there was an anomalousmore dip in the noise background in the range 0 2 5 hz starting one day ahead of the earthquake finally and perhaps most compelling there was an increase to an exceptionally high level of activity in the range 0 01 0 5 hz starting approximately three hours before the earthquake there do not appear to have been any magnetic field fluctuations originating in the upper atmosphere that can account for this increase further while the systems are sensitive to motion seismic measurements indicate that there were no significant shocks preceding the quake thus the various anomalous features in the data and in particular the large amplitude increase in activity starting three hours before the quake may have been magnetic precursors less

a study of anomalous underground electric field variations associated with a volcanic eruption continuous measurements of vertical subsurface geoelectric fields in the frequency range dc 0 6 hz and 1 3 khz vlf are reported anomalous field variations of the ulf band are observed a few days prior to and a month after a minor volcanic eruption of mt mihara the variations displayed essentially distorted pulses rising sharply initially gradually decreasing and then suddenly falling off the electric field variations also seem to extend to the vlf band it is felt that the anomalous electric field variations were caused by electrokinetic phenomena induced by variations of hydrothermal circulation around the crater or by variations of crack density due to volcanic activity

a successfully stress forecast earthquake summary a m 5 earthquake in iceland has been successfully stress forecast by using variations in time delays of seismic shear wave splitting to assess the time and magnitude at which stress modified microcracking reaches fracture criticality within the stressed volume where strain is released local investigations suggested the approximate location of the forecast earthquake we report the criteria on which this stress forecast was based

temporal changes in shear wave splitting during an earthquake swarm in arkansas shear wave splitting has been observed in seismograms of two aftershock and one foreshock sequence recorded over 12 days by a local network of nine three component digital seismometers during the 1982 enola arkansas earthquake swarm polarizations of the faster split shear wave show alignments within the shear wave window which correlate with the regional stress field the time delay between split shear waves appears to increase before and to decrease at or after the time of each main shock this behavior is similar to observations before and after a m 6 0 event near the anza seismic gap southern california and may correspond to variations in crack geometry caused by changes in the stress field before and after the earthquakes there are indications that the decrease in delay may occur a few hours before the main shock and could be a possible precursor for earthquake prediction

an observational and modeling study of the processes leading to deep moist convection in complex terrain abstracta case study of orographic convection initiation ci that occurred along the eastern slopes of the vosges mountains in france on 6 august 2007 during the convective and orographically induced precipitation study cops is presented global positioning system gps receivers and two doppler on wheels dow mobile radars sampled the preconvective and storm environments and were respectively used to retrieve three dimensional tomographic water vapor and wind fields these retrieved data were supplemented with temperature moisture and winds from radiosondes from a site in the eastern rhine valley high resolution numerical simulations with the weather research and forecasting wrf model were used to further investigate the physical processes leading to convective precipitation this unique time varying combination of derived water vapor and winds from observations illustrated an increase in low level moisture and convergence between upslope easterlies and downslope westerlies along the eastern slo

storm enhanced plasma density features investigated during the bastille day superstorm field aligned passes track true profiles such defense meteorological satellite program passes permitted investigating storm enhanced plasma density sed feature development during the bastille day superstorm in a comprehensive way we tracked equatorial ionization anomaly eia and sed features and their underlying forward fountain circulation and downward sed plume plasma flows respectively northward subauroral polarization stream e fields detaching plasma and producing sed plumes were also detected we assessed the effects of south atlantic magnetic anomaly and summer towinter interhemispheric plasma flows on the eia and found a southward dipping gradient in drift flow when no storm evening related fountain strengthening occurred we investigated the relative importance of different plasma sources in sed development an extremely large plasma enhancement seen over florida at 2200 ut on 15 july 2000 was a sed feature that was tracked by many gps total electron content tec maps as a 200 tec unit tecu enhancement we tracked its equally large conjugate pair over trelew argentine patagonia and unraveled their development their underlying sed plume supplied most of the plasma appearing between these two sed features a small and highly asymmetrical eia offered on each side a low baseline upon which the downward streaming sed plume plasma piled up contradicting a currently accepted explanation there was no enhanced fountain action detected to contribute 150 tecu to the 200 tecu later 2400 ut there was enhanced fountain action but sed plume contribution still dominated proven by observational evidence sed development is a complex process of sed plume plasma flows and equatorward wind effects that cannot be described by one single explanation

spatiotemporal characteristics of the geomagnetic diurnal variation anomalies prior to the 2011 tohoku earthquake mw 9 0 and the possible coupling of multiple pre earthquake phenomena abstract xu et al 2013 and han et al 2015 have reported unusual behaviors of geomagnetic diurnal variation gdv in the vertical component prior to the 2011 off the pacific coast of tohoku earthquake mw 9 0 to make a better understanding of this phenomenon temporal spatial analyses of gdv have been applied in this study geomagnetic data of long term observations at 17 stations in japan have been analyzed using the same method in han et al 2015 ratios of diurnal variation range between the reference station kak and the target stations have been computed after removing seasonal variations the 15 day backward running mean values of the ratios in the vertical component shows a clear anomaly exceeding the statistical threshold about 2 months before the mega event at both esa and miz stations in the tohoku region locations of anomalies in spatial distribution show a good correlation with the epicenter of the mw 9 0 earthquake these spatiotemporal results are consistent with those obtained from other independent observations such as groundwater level and gps displacements the coupling of multiple pre earthquake phenomena may help to understand the preparation process of a mega earthquake in the subduction zone

physical mechanism and statistics of occurrence of an additional layer in the equatorial ionosphere a physical mechanism and the location and latitudinal extent of an additional layer called the f3 layer that exists in the equatorial ionosphere are presented a statistical analysis of the occurrence of the layer recorded at the equatorial station fortaleza 4 s 38 w dip 9 s in brazil is also presented the f3 layer forms during the morning noon period in that equatorial region where the combined effect of the upward e b drift and neutral wind provides a vertically upward plasma drift velocity at altitudes near and above the f2 peak this velocity causes the f2 peak to drift upward and form the f3 layer while the normal f2 layer develops at lower altitudes through the usual photochemical and dynamical effects of the equatorial region the peak electron density of the f3 layer can exceed that of the f2 layer the f3 layer is predicted to be distinct on the summer side of the geomagnetic equator during periods of low solar activity and to become less distinct as the solar activity increases ionograms recorded at fortaleza in 1995 show the existence of an f3 layer on 49 of the days with the occurrence being most frequent 75 and distinct in summer as expected during summer the layer occurs earlier and lasts longer compared to the other seasons on the average the layer occurs at around 0930 lt and lasts for about 3 hours the altitude of the layer is also high in summer with the mean peak virtual height being about 570 km however the critical frequency of the layer f0f3 exceeds that of the f2 layer f0f2 by the largest amounts in winter and equinox f0f3 exceeds f0f2 by a yearly average of about 1 3 mhz

two dimensional convection in non constant shear a model of mid latitude squall lines numerical simulations of two dimensional deep convection are analysed using analytical models extended to include shallow downdraughts and non constant shear the cumulonimbus are initiated by low level convergence created by a finite amplitude downdraught these experiments have constant low level shear and differ only in the profile of mid and upper level winds quasi steady convenction is produced if the mid and upper level flow has small shear and the low level shear is large the surface precipitation ismaximized for no intial relative relative flow aloft if stationary this storm p o can give prodigious locilized rainfall p o is the two dimentisonal equivalent of the supercell these results are placed in context with previous two dimensional simulations attention is drawn to the similiarity with previous two dimensional simulations attention is drawn to the similarity with squall lines in central and eastern u s a storm p o is analysed by construction of time averaged fields of streamfunction vorticity teperature and height deviation the smoothness of these fields suggests a conceptual model of the storm dynamics which involves cooperation between distinct charcteristic flows an overturning updraught a jump type updraught a shallow downdraught a low level rotor and a boundary layer an idealized analytical model is described by solution of the equations for steady convection these solutions for the remote flow are derived from energy conversation mass continuity and a momentum budget and they give relationships between the non dimensional parameteres of the problem it is apparent that the convection is a high froude or low richardson number flow demanding the existence of a cross storm pressure gradient inherent in this idealized model is a vortex sheet between updraught and down draught and it is considered that the dynamical instability of this sheet is related to complexities in the numerical simulation furthermore these results show that in two dimensions both non constant shear and a shallow downdraught are necessary to maintain steady convection

physical properties of the variations of the electric field of the earth preceding earthquakes i abstract in an earlier paper we described the physical properties of the preseismic transient variations in the electrotelluric field the present letter clarifies a few points that were not properly emphasized in our previous publications furthermore recent results like that of the destructive kalamata earthquake on september 13 1986 indicate that the duration of a preseismic electric signal may reach considerably high values lasting up to several hours

a statistical study on elf whistlers emissions and m 5 0 earthquakes in taiwan 1 in this paper we conduct statistical approaches to study the potential relation between elf whistlers emissions below 100 hz and 20 m 5 0 earthquakes occurred in taiwan in the period from 26 august 2003 to 13 july 2004 occurrence ratios of the elf whistler and elf emission of the entire study period are computed as the reference backgrounds our study shows that the elf whistlers and elf emissions during the earthquake period appear less and more frequently than their associated backgrounds respectively for the elf emission the larger earthquakes generally yield the higher occurrence ratios the statistical analyses confirm that the occurrence ratios of the elf emission significantly enhance 5 7 days before the earthquakes and are proportional to the earthquake magnitude but inversely to the distance from the observatory to the epicenter

vlf emissions associated with earthquakes and observed in the ionosphere and the magnetosphere abstract several electromagnetic phenomena recorded at the time of earthquakes were recorded independently by the geostationary satellite geos 2 above africa longitude 37 e and the polar orbiting satellite aureol 3 apogee 2012 km perigee 408 km inclination 82 5 period 109 5 min the observations were made with magnetic and electric antennae in the frequency range 10 hz 15 khz characteristics of the emissions and differences between low and high altitude observations are presented some geos 2 very low frequency data can be correlated with ionospheric measurements made on ground at the djibouti station latitude 11 n longitude 42 e where increases of the critical frequency f 0 e s of the sporadic e s layer are observed when earthquakes occur nearby time differences between disturbance at ionospheric level and at the height of geos 2 seem to indicate that earthquakes cause two distinct types of electromagnetic disturbance an electromagnetic wave in the ionosphere and a density increase of the e s layer

2 d inversion of geomagnetic deep sounding data near ujjain guna india summary the inductive response of a hypothesized conductor located between ujjain and guna india has been modelled in the absence of a satisfactory fit from forward numerical modelling 2 d inversion of the anomaly profile of z h ratio has revealed the main conductor to be situated below ujjain guna with an offset and another secondary conductor in the form of a jointed body the main conductor is at a depth of 23 km from the surface thickness being 20 km and the resistivity 3 m the jointed secondary conductors are at depths of 31 km and 28 km with thicknesses of 14 km and 21 km and resistivities 3 m and 5 m respectively the resistivity contrast with the background is a factor of 1600 or even slightly more the possibility of mineralization on the flanks of the subsurface granitic intrusion cannot be ruled out however partial melting of the subsurface granites seems to be another plausible explanation for the high conductivity contrast

convection waves observations of gravity wave systems over convectively active boundary layers widespread gravity wave systems have been found to exist over convectively active boundary layers cbls in the presence of vertical wind shear in contrast to mountain waves these convection waves occur over flat terrain and are ubiquitous over fields of shallow fair weather cumuli or clear air thermals they extend vertically to at least 9km a m s l probably to the tropopause first discovered by glider pilots as thermal waves they have now been systematically investigated by research aircraft during the ncar convection wave project which also incorporates an effort in numerical simulation the flight results are reported in this paper while the numerical simulations are described in a companion paper typical wavelengths of convection waves were found to range from 5 to 15 km average 9 km and typical vertical motion amplitudes from 1 to 3 m s 1 in all cases vertical wind shear exceeded 3 10 3s 1 under these conditions cloud tops were measured to move with relative velocities of 8 to 10 m s 1 against their environment hence they present an obstacle to the surrounding airflow the analogy to mountainous obstacles launching gravity waves into the atmosphere is suggestive and borne out by the aforementioned numerical simulations which describe this process step by step the interaction between the cbl and the overlying stable layers is studied by spectral and cross spectral analysis of aircraft data including coherence and phase relations between wave motions and cloud population underneath consideration is given to other potential sources of the observed gravity waves at this stage the conclusions of our pilot study may be considered tentative some implications for further research are also discussed

precursory analysis of gps time series for seismic hazard assessment we discuss the use of fractal analysis of geophysical big data as a precursory method for the estimation of current seismic hazard we begin by analyzing gps time series of land surface displacements recorded in various regions of the planet exhibiting different degrees of seismic activity we show how the quantitative measure of chaoticity based on a modified detrended fluctuation analysis dfa method can be used to distinguish critical and noncritical regimes of evolution of the earth s crust having established the reference values for the measure of chaoticity we then choose california as the case study region and apply modified dfa to over 1200 time series for determining local areas currently exposed to higher seismic hazard we comprehensively analyze the results obtained and compare them with those produced by conventional risk assessment methods we demonstrate consistency of our results and yet discover that the suggested approach allows us to quantify two qualitatively different mechanisms involved in the growth of seismic hazards we propose a hypothesis which relates these mechanisms to the known mechanisms of earthquake generation that evince a growth of collective behavior in the earth s crust on the eve of an earthquake in order to verify the hypothesis we analyze the same gps data by an independent statistical method canonical coherence analysis cca which permits us to quantify the degree of synchronized behavior of constituents of the earth s crust the cca method confirms our previously obtained estimates thus supporting fractal analysis of gps time series as a suitable precursory method for current seismic hazard assessment

thermodynamic and vertical velocity structure of two gust fronts observed with a wind profiler rass during mctex high time resolution wind profiler rass observations are used to describe the vertical velocity temperature and reflectivity fields of two gust fronts in detail the first was a freely propagating gust front and the second interacted with a rain cell near the profiler site the first of these shows a large updraft confined to the warm air ahead of the front this updraft coincided with the nonhydrostatic pressure jump the vertical motions within the gust front were an order of magnitude smaller the updraft impinging on the top of the boundary layer excited a clear gravity wave signature in the free troposphere the interaction of the vertical circulation and the weakly precipitating cloud in the second case coincided with explosive growth of the cell with reflectivities increasing from 30 dbz to 50 dbz in 6 min a descending reflectivity core was observed at this time precipitation loading played a significant role in a downdraft behind the gust front head leading to adiabatic warming as no evidence of evaporative cooling in the downdraft was seen a distinct clear air peak was visible in the profiler doppler spectra even during the heavy rain

an intense quasi steady thunderstorm over mountainous terrain part ii doppler radar observations of the storm morphological structure abstract an analysis of an intense quasi steady thunderstorm which developed over mountainous terrain is presented this storm extensively analyzed using multiple doppler radar and surface mesonet data formed within an environment having strong low level wind shear the evolution and characteristics of the mesoscale systems prior to storm formation are presented in part i cotton et al 1982 such an environment was responsible for several unique storm features including a quasi steady primary updraft circulation and movement 50 to the left of the cloud layer 2 8 km agl environmental winds several interactions were observed or inferred near and within the storm vertical transport of northerly low level momentum within the updraft imparted a significant blocking on mid level flow having southerly momentum such a blocking affected the movement and characteristics of adjacent less organized storms additional storm environment interactions produced an organized recirculation of precipitation par

the fracture criticality of crustal rocks summary the shear wave splitting observed along almost all shear wave ray paths in the earth s crust is interpreted as the effects of stress aligned fluid filled cracks microcracks and preferentially oriented pore space once away from the free surface where open joints and fractures may lead to strong anisotropy of 10 per cent or greater intact ostensibly unfractured crustal rock exhibits a limited range of shear wave splitting from about 1 5 to 4 5 per cent differential shear wave velocity anisotropy interpreting this velocity anisotropy as normalized crack densities a factor of less than two in crack radius covers the range from the minimum 1 5 per cent anisotropy observed in intact rock to the 10 per cent observed in heavily cracked almost disaggregated near surface rocks this narrow range of crack dimensions and the pronounced effect on rock cohesion suggests that there is a state of fracture criticality at some level of anisotropy between 4 5 and 10 per cent marking the boundary between essentially intact and heavily fractured rock when the level of fracture criticality is exceeded cracking is so severe that there is a breakdown in shear strength the likelihood of progressive fracturing and the dispersal of pore fluids through enhanced permeability the range of normalized crack dimensions below fracture criticality is so small in intact rock that any modification to the crack geometry by even minor changes of conditions or minor deformation particularly in the presence of high pore fluid pressures may change rock from being essentially intact below fracture criticality to heavily fractured above fracture criticality this recognition of the essential compliance of most crustal rocks and its effect on shear wave splitting has implications for monitoring changes in any conditions affecting the rock mass these include monitoring changes in reservoir evolution during hydrocarbon production and enhanced oil recovery and in monitoring changes before and after earthquakes amongst others

observation of a cold front with rope cloud abstract observations are presented of a cold front which passed over the florida peninsula and produced a rope cloud visible on satellite imagery the low level structure of the leading edge of the front is revealed with data from the 150 m tower at cape canaveral air force station it is shown that the leading edge of the front is very similar to thunderstorm gust fronts and the speed is predicted well by the gust front speed equation this indicates that the rope cloud is directly analogous to the arc cloud sometimes observed along thunderstorm gust fronts further the rope cloud appears to be a less intense manifestation of the forced convection that produces the narrow cold frontal rainbands observed in some other cold front studies