Field-aligned currents, convection electric fields, and ULF-ELF waves in the cusp

NASA Technical Reports Server (NTRS)

Saflekos, N. A.; Potemra, T. A.; Kintner, P. M., Jr.; Green, J. L.

1979-01-01

Nearly simultaneous observations from the Triad and Hawkeye satellites over the Southern Hemisphere, at low altitudes near the noon meridian and close to the usual polar cusp latitudes, show that in and near the polar cusp there exist several relationships between field-aligned currents (FACs), convection electric fields, ULF-ELF magnetic noise, broadband electrostatic noise and interplanetary magnetic fields. The most important findings are (1) the FACs directed into the ionosphere in the noon-to-dusk local time sector and directed away from the ionosphere in the noon-to-dawn local time sector and identified as region-1 permanent FACs (Iijima and Potemra, 1976a) and are located equatorward of the regions of antisunward (westward) convection; (2) the observations are consistent with a two-cell convection pattern symmetric in one case (throat positioned at noon) and asymmetric in another (throat located in a sector on the forenoon side in juxtaposition to the region of strong convection on the afternoon side); and (3) fine-structure FACs are responsible for the generation of ULF-ELF noise in the polar cusp.

A super-cusp divertor configuration for tokamaks

NASA Astrophysics Data System (ADS)

Ryutov, D. D.

2015-10-01

> This study demonstrates a remarkable flexibility of advanced divertor configurations created with the remote poloidal field coils. The emphasis here is on the configurations with three poloidal field nulls in the divertor area. We are seeking the structures where all three nulls lie on the same separatrix, thereby creating two zones of a very strong flux expansion, as envisaged in the concept of Takase's cusp divertor. It turns out that the set of remote coils can indeed produce a cusp divertor, with additional advantages of: (i) a large stand-off distance between the divertor and the coils and (ii) a thorough control that these coils exert over the fine features of the configuration. In reference to these additional favourable properties acquired by the cusp divertor, the resulting configuration could be called `a super-cusp'. General geometrical features of the three-null configurations produced by remote coils are described. Issues on the way to practical applications include the need for a more sophisticated control system and possible constraints related to excessively high currents in the divertor coils.

Long-term Variability of Beach Cusps

NASA Astrophysics Data System (ADS)

Pianca, C.; Holman, R. A.; Siegle, E.

2016-02-01

The most curious morphological features observed on beaches are the cusps. Due to their rhythmic spacing, beach cusps have attracted many observers and many, often contradictory, theories as to their form. Moreover, most of the research about beach cusps has focused on their formation. Few had available long time series to study such things as the variability of alongshore and cross-shore position and spacing on the cusp field, the presence, longevity and interactions between higher and lower sets of cusps, and the processes by which cusp fields extend, shrink or change length scale. The purpose of this work is to use long-term data sets of video images from two study sites, an intermediate (Duck, USA, 26 years) and a reflective beach (Massaguaçu, Brazil, 3 years), to investigate the temporal and spatial changes of cusps conditions. Time-evolving shoreline data were first extracted using an algorithm called ASLIM (Pianca et al 2015). Cusps were then identified based on the band-passed variability of time exposure image data about this shoreline as a function of elevation relative to MSL. The identified beaches cusps will be analyzed for cusp spacing, positions (upper or lower cusps), alongshore variability, merging events, percentage of cusp events, patterns of the events and time scales of variability. Finally, the relationship of these characteristics to environmental conditions (wave, tides, beach conditions) will be studied.

Particle Detectors and Data Analysis for Cusp Transient Features Campaign

NASA Technical Reports Server (NTRS)

Sharber, James R.

1998-01-01

On December 3, 1997, a rocket payload (36.152) was launched from Ny Alesund into the dark cusp at 0906:00 U (1206:00 LT) during an interval of southward B(sub Z), and positive B(sub y). Launch occurred during a time interval of northeastward moving auroral forms observed between 0845 and 0945 UT by ground-based meridian scanning photometers. Ground photometric measurements during the flight show that the payload passed over the poleward portion of the most intense 6300 A emissions of the dayside cusp/cleft region. Electrons of energy up to a few hundred eV were detected immediately upon instrument turn-on at an altitude of 205 km and throughout the flight until the payload reached an altitude of approximately 197 km on the downleg. Electron spectra were either quasithermal with peak energies approximately 100 eV or showed evidence of acceleration along the magnetic field line by potentials of 100-200 V. Precipitating ions were observed throughout much of the flight. Their spectra were broadly peaked in energy with the peak energy decreasing from approximately 500 eV to approximately 250 eV as the payload flew approximately westward over the dayside precipitationregion. Structure(spatial or temporal intensity variation) was observed between T + 180 s and T + approximately 400 s. At the rocket altitudes(less than 450km) the ions were observed to be precipitating. During the flight, the DMSPF-13 satellite passed through the all-sky imager field-of-view just poleward of the brightest dayside emissions enabling the identification of plasma sheet and boundary layer regions along the orbit. We thus conclude that particle fluxes detected by the rocket flight were either cusp plasma or boundary layer/mantle plasmajust poleward of the dayside cusp/cleft. Further investigation of the particle characteristics and their relationship to ionospheric convection patterns is continuing.

Magnetic-cusp, cathodic-arc source

DOEpatents

Falabella, S.

1995-11-21

A magnetic-cusp for a cathodic-arc source wherein the arc is confined to the desired cathode surface, provides a current path for electrons from the cathode to the anode, and utilizes electric and magnetic fields to guide ions from the cathode to a point of use, such as substrates to be coated. The magnetic-cusp insures arc stability by an easy magnetic path from anode to cathode, while the straight-through arrangement leads to high ion transmission. 3 figs.

A super-cusp divertor configuration for tokamaks

DOE PAGES

Ryutov, D. D.

2015-08-26

Our study demonstrates a remarkable flexibility of advanced divertor configurations created with the remote poloidal field coils. The emphasis here is on the configurations with three poloidal field nulls in the divertor area. We are seeking the structures where all three nulls lie on the same separatrix, thereby creating two zones of a very strong flux expansion, as envisaged in the concept of Takase’s cusp divertor. It turns out that the set of remote coils can produce a cusp divertor, with additional advantages of: (i) a large stand-off distance between the divertor and the coils and (ii) a thorough controlmore » that these coils exert over the fine features of the configuration. In reference to these additional favourable properties acquired by the cusp divertor, the resulting configuration could be called ‘a super-cusp’. General geometrical features of the three-null configurations produced by remote coils are described. Furthermore, issues on the way to practical applications include the need for a more sophisticated control system and possible constraints related to excessively high currents in the divertor coils.« less

Climatology of the relationship of cusp-related density anomaly with zonal wind and large-scale FAC based on CHAMP observations: IMF By and solar cycle dependence

NASA Astrophysics Data System (ADS)

Kervalishvili, Guram; Lühr, Hermann

2014-05-01

We present climatology of the relationship of cusp-related density enhancement with the neutral zonal wind velocity, large-scale field-aligned current (FAC), small-scale FAC, and electron temperature using the superposed epoch analysis (SEA) method. The dependence of these variables on the interplanetary magnetic field (IMF) By component orientation and solar cycle are of particular interest. In addition, the obtained results of relative density enhancement (ρrel), zonal wind, electron temperature and FAC are subdivided into three local seasons of 130 days each: local winter (1 January ±65 days), combined equinoxes (1 April ±32 days and 1 October ±32 days), and local summer (1 July ±65 days). Our investigation is based on CHAMP satellite observations and NASA/GSFC's OMNI online data set for solar maximum (Mar/2002-2007) and minimum (Mar/2004-2009) conditions in the Northern Hemisphere. The SEA technique uses the time and location of the thermospheric mass density anomaly peaks as reference parameters. The relative amplitude of cusp-related density enhancement does on average not depend on the IMF By orientation, solar cycle phase, and local season. Also, it is apparent that the IMF By amplitude does not have a big influence on the relative amplitude of the density anomaly. Conversely, there exists a good correlation between ρrel and the negative amplitude of IMF Bz prevailing about half an hour earlier. In the cusp region, both large-scale FAC distribution and thermospheric zonal wind velocity exhibit a clear dependence on the IMF By orientation. In the case of positive (negative) IMF By there is a systematic imbalance between downward (upward) and upward (downward) FACs peaks equatorward and poleward of the reference point, respectively. The zonal wind velocity is directed towards west i.e. towards dawn in a geomagnetic latitude-magnetic local time (MLat-MLT) frame. This is true for all local seasons and solar conditions. The thermospheric density

The effects of relative food item size on optimal tooth cusp sharpness during brittle food item processing

PubMed Central

Berthaume, Michael A.; Dumont, Elizabeth R.; Godfrey, Laurie R.; Grosse, Ian R.

2014-01-01

Teeth are often assumed to be optimal for their function, which allows researchers to derive dietary signatures from tooth shape. Most tooth shape analyses normalize for tooth size, potentially masking the relationship between relative food item size and tooth shape. Here, we model how relative food item size may affect optimal tooth cusp radius of curvature (RoC) during the fracture of brittle food items using a parametric finite-element (FE) model of a four-cusped molar. Morphospaces were created for four different food item sizes by altering cusp RoCs to determine whether optimal tooth shape changed as food item size changed. The morphospaces were also used to investigate whether variation in efficiency metrics (i.e. stresses, energy and optimality) changed as food item size changed. We found that optimal tooth shape changed as food item size changed, but that all optimal morphologies were similar, with one dull cusp that promoted high stresses in the food item and three cusps that acted to stabilize the food item. There were also positive relationships between food item size and the coefficients of variation for stresses in food item and optimality, and negative relationships between food item size and the coefficients of variation for stresses in the enamel and strain energy absorbed by the food item. These results suggest that relative food item size may play a role in selecting for optimal tooth shape, and the magnitude of these selective forces may change depending on food item size and which efficiency metric is being selected. PMID:25320068

The influence of anode position and structure on cusped field thruster

NASA Astrophysics Data System (ADS)

Niu, Xiang; Liu, Hui; Yang, Chiyu; Jiang, Wenjia; Yu, Daren; Ning, Zhongxi

2018-04-01

A cusped field thruster is a kind of electric propulsion device using multi-stage cusped fields to realize plasma discharges and produce thrust. A previous study showed that plasma discharges in this thruster are non-uniform. In this work, a multi-annulus anode is used to measure the radial distribution of anode current density at different anode positions. The experimental results reveal that some electrons may reach the anode along the axis after they accelerate from the final cusp regardless of the anode positions. To further validate this idea and find out the mechanism of this central path along the axis, the central part of the anode is replaced with ceramics. This results in an increase in the total current with larger contributions at larger radii. The current oscillations also get larger. This brief letter is helpful to further understand the movement of electrons in cusped field thrusters and provide guidance on reducing the non-uniform degree of current density.

On the Relation Between Soft Electron Precipitations in the Cusp Region and Solar Wind Coupling Functions

NASA Astrophysics Data System (ADS)

Dang, Tong; Zhang, Binzheng; Wiltberge, Michael; Wang, Wenbin; Varney, Roger; Dou, Xiankang; Wan, Weixing; Lei, Jiuhou

2018-01-01

In this study, the correlations between the fluxes of precipitating soft electrons in the cusp region and solar wind coupling functions are investigated utilizing the Lyon-Fedder-Mobarry global magnetosphere model simulations. We conduct two simulation runs during periods from 20 March 2008 to 16 April 2008 and from 15 to 24 December 2014, which are referred as "Equinox Case" and "Solstice Case," respectively. The simulation results of Equinox Case show that the plasma number density in the high-latitude cusp region scales well with the solar wind number density (ncusp/nsw=0.78), which agrees well with the statistical results from the Polar spacecraft measurements. For the Solstice Case, the plasma number density of high-latitude cusp in both hemispheres increases approximately linearly with upstream solar wind number density with prominent hemispheric asymmetry. Due to the dipole tilt effect, the average number density ratio ncusp/nsw in the Southern (summer) Hemisphere is nearly 3 times that in the Northern (winter) Hemisphere. In addition to the solar wind number density, 20 solar wind coupling functions are tested for the linear correlation with the fluxes of precipitating cusp soft electrons. The statistical results indicate that the solar wind dynamic pressure p exhibits the highest linear correlation with the cusp electron fluxes for both equinox and solstice conditions, with correlation coefficients greater than 0.75. The linear regression relations for equinox and solstice cases may provide an empirical calculation for the fluxes of cusp soft electron precipitation based on the upstream solar wind driving conditions.

On the evolutionary advantage of multi-cusped teeth

PubMed Central

Bush, Mark B.; Barani, Amir; Lawn, Brian R.

2016-01-01

A hallmark of mammalian evolution is a progressive complexity in postcanine tooth morphology. However, the driving force for this complexity remains unclear: whether to expand the versatility in diet source, or to bolster tooth structural integrity. In this study, we take a quantitative approach to this question by examining the roles of number, position and height of multiple cusps in determining sustainable bite forces. Our approach is to use an extended finite-element methodology with due provision for step-by-step growth of an embedded crack to determine how fracture progresses with increasing occlusal load. We argue that multi-cusp postcanine teeth are well configured to withstand high bite forces provided that multiple cusps are contacted simultaneously to share the load. However, contact on a single near-wall cusp diminishes the strength. Location of the load points and cusp height, rather than cusp number or radius, are principal governing factors. Given these findings, we conclude that while complex tooth structures can enhance durability, increases in cusp number are more likely to be driven by the demands of food manipulation. Structural integrity of complex teeth is maintained when individual cusps remain sufficiently distant from the side walls and do not become excessively tall relative to tooth width. PMID:27558851

Particle orbits in model current sheet with a nonzero B(y) component

NASA Technical Reports Server (NTRS)

Zhu, Zhongwei; Parks, George

1993-01-01

The problem of charged particle motions in magnetotaillike model current sheets is revisited with the inclusion of a nonzero dawn-dusk magnetic field component. Three cases are examined considering both trapped and escaped orbits. The results show that a nonzero B(y) component disturbs the particle orbits by destroying orbit symmetry in the phase space about the z = 0 plane. It also changes the bounce frequency of particle orbits. The presence of B(y) thus modifies the Speiser orbits, particularly near the ejection phase. The process of ejected particle such as ejection direction, ejection velocity, and pitch angles are shown to depend on the sign of the charge.

Density Variations in the Earth's Magnetospheric Cusps

NASA Technical Reports Server (NTRS)

Walsh, B. M.; Niehof, J.; Collier, M. R.; Welling, D. T.; Sibeck, D. G.; Mozer, F. S.; Fritz, T. A.; Kuntz, K. D.

2016-01-01

Seven years of measurements from the Polar spacecraft are surveyed to monitor the variations of plasma density within the magnetospheric cusps. The spacecraft's orbital precession from 1998 through 2005 allows for coverage of both the northern and southern cusps from low altitude out to the magnetopause. In the mid- and high- altitude cusps, plasma density scales well with the solar wind density (n(sub cusp)/n(sub sw) approximately 0.8). This trend is fairly steady for radial distances greater then 4 R(sub E). At low altitudes (r less than 4R(sub E)) the density increases with decreasing altitude and even exceeds the solar wind density due to contributions from the ionosphere. The density of high charge state oxygen (O(greater +2) also displays a positive trend with solar wind density within the cusp. A multifluid simulation with the Block-Adaptive-Tree Solar Wind Roe-Type Upwind Scheme MHD model was run to monitor the relative contributions of the ionosphere and solar wind plasma within the cusp. The simulation provides similar results to the statistical measurements from Polar and confirms the presence of ionospheric plasma at low altitudes.

Cusped magnetic field mercury ion thruster. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Beattie, J. R.

1976-01-01

The importance of a uniform current density profile in the exhaust beam of an electrostatic ion thruster is discussed in terms of thrust level and accelerator system lifetime. A residence time approach is used to explain the nonuniform beam current density profile of the divergent magnetic field thruster. Mathematical expressions are derived which relate the thruster discharge power loss, propellant utilization, and double to single ion density ratio to the geometry and plasma properties of the discharge chamber. These relationships are applied to a cylindrical discharge chamber model of the thruster. Experimental results are presented for a wide range of the discharge chamber length. The thruster designed for this investigation was operated with a cusped magnetic field as well as a divergent field geometry, and the cusped field geometry is shown to be superior from the standpoint of beam profile uniformity, performance, and double ion population.

High-Energy Electron Confinement in a Magnetic Cusp Configuration

NASA Astrophysics Data System (ADS)

Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni

2015-04-01

We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure) is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad's work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β . This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

Analytic relations for magnifications and time delays in gravitational lenses with fold and cusp configurations

NASA Astrophysics Data System (ADS)

Congdon, Arthur B.; Keeton, Charles R.; Nordgren, C. Erik

2008-09-01

Gravitational lensing provides a unique and powerful probe of the mass distributions of distant galaxies. Four-image lens systems with fold and cusp configurations have two or three bright images near a critical point. Within the framework of singularity theory, we derive analytic relations that are satisfied for a light source that lies a small but finite distance from the astroid caustic of a four-image lens. Using a perturbative expansion of the image positions, we show that the time delay between the close pair of images in a fold lens scales with the cube of the image separation, with a constant of proportionality that depends on a particular third derivative of the lens potential. We also apply our formalism to cusp lenses, where we develop perturbative expressions for the image positions, magnifications and time delays of the images in a cusp triplet. Some of these results were derived previously for a source asymptotically close to a cusp point, but using a simplified form of the lens equation whose validity may be in doubt for sources that lie at astrophysically relevant distances from the caustic. Along with the work of Keeton, Gaudi & Petters, this paper demonstrates that perturbation theory plays an important role in theoretical lensing studies.

Associations between Carabelli trait and cusp areas in human permanent maxillary first molars.

PubMed

Kondo, Shintaro; Townsend, Grant C

2006-02-01

Few dental anthropological studies have investigated the associations between tooth crown size and crown traits in humans using quantitative methods. We tested several hypotheses about overall crown size, individual cusp areas, and expression of Carabelli cusps in human permanent first molars by obtaining data from standardized occlusal photographs of 308 Australians of European descent (171 males and 137 females). Specifically, we aimed to calculate the areas of the four main molar cusps, and also Carabelli cusp, and to compare the relative variability of cusp areas in relation to timing of development. We also aimed to compare cusp areas between males and females and to describe how Carabelli cusp interacted with other molar cusps. Measurements included maximum crown diameters (mesiodistal and buccolingual crown diameters), the areas of the four main cusps, and the area of Carabelli cusp. The pattern of relative variability in absolute areas of molar cusps corresponded with their order of formation, the first-forming paracone displaying the least variation, and the last-forming Carabelli cusp showing the greatest. Overall crown size and areas of individual cusps all showed sexual dimorphism, with values in males exceeding those in females. Sexual dimorphism was smallest for paracone area and greatest for Carabelli cusp area. Overall crown size and cusp areas were larger in individuals displaying a Carabelli cusp, especially the hypocone area. Although the combined area of the protocone and a Carabelli cusp was greater in cuspal forms than noncuspal forms, protocone area alone was significantly smaller in the former. Our findings lead us to propose that, in individuals with the genotype for Carabelli trait expression, larger molar crowns are more likely to display Carabelli cusps, whereas molars with smaller crowns are more likely to display reduced forms of expression of the trait. We suggest that the pattern of folding of the internal enamel epithelium in

Beach Cusps: Spatial distribution and time evolution at Massaguaçú beach (SP), Brazil

NASA Astrophysics Data System (ADS)

dos Santos, H. H.; Siegle, E.; Sousa, P. H.

2013-05-01

Beach cusps are crescentic morphological structures observed on the foreshore of beaches characterized by steep seaward protruding extensions, called cusp horns, and gently sloped landward extensions, called cusp embayments. Their formation depends on the grain size, beach slope, tidal range and incoming waves. Cusps are best developed on gravel or shingle beaches, small tidal range with a large slope for incoming waves generate a well-developed swash excursion. These structures are quickly responding to wave climate and tidal range, changing the position of the rhythmic features on the beach face. Beach cusps are favored by normal incoming waves, while oblique waves tend to wash these features out. This study aims to analyze the spatial distribution and temporal evolution of rhythmic features such as beach cusps in Massaguaçú embayment (Caraguatatuba, northern coast of São Paulo, Brazil). This embayment has an extension of 7.5 km with reflective beaches cusped mainly in its more exposed central portion. The data set for this study consists of a series of video images (Argus system), covering a stretch of the beach. Visible beach cusps were digitalized from these rectified images. Results obtained from the images were related to the wave climate, water level and the storm surges. Results show that the cusps on the upper portion of the foreshore were more regular and present than the cusps on the lower portion of the foreshore due to the tidal modulation of wave action. The cusp spacing on the upper portion of the foreshore is of about 38 m and the lower portion of the foreshore is of about 28 m and their presence was correlated with the wave direction and water elevation. As expected, waves approaching with shore-normal angles (southeast direction) were favorable to the formation of beach cusps while the waves from the southwest, south, east and northeast generated a longshore current that reduced or destroyed any rhythmic feature. Other important forcing was

Experimental investigation of plasma sheaths in magnetic mirror and cusp configurations

NASA Astrophysics Data System (ADS)

Jiang, Zhengqi; Wei, Zi-an; Ma, J. X.

2017-11-01

Sheath structures near a metal plate in a magnetized plasma were experimentally investigated in magnetic mirror and cusp configurations. Plasma parameters and the sheath potential distributions were probed by a planar and an emissive probe, respectively. The measured sheath profiles in the mirror configuration show that the sheath thickness first decreases and then increases when the magnetic strength is raised. A magnetic flux-tube model was used to explain this result. In the cusp configuration, the measured sheath thickness decreases with the increase of the coil current creating the magnetic cusp. However, when normalized by the electron Debye length, the dependence of the sheath thickness on the coil current is reversed.

Localized Models of Charged Particle Motion in Martian Crustal Magnetic Cusps

NASA Astrophysics Data System (ADS)

Brain, D. A.; Poppe, A. R.; Jarvinen, R.; Dong, Y.; Egan, H. L.; Fang, X.

2017-12-01

The induced magnetosphere of Mars is punctuated by localized but strong crustal magnetic fields that are observed to play host to a variety of phenomena typically associated with global magnetic fields, such as auroral processes and particle precipitation, field-aligned current systems, and ion outflow. Each of these phenomena occur on the night side, in small-scale magnetic `cusp' regions of vertically aligned field. Cusp regions are not yet capable of being spatially resolved in global scale models that include the ion kinetics necessary for simulating charged particle transport along cusps. Local models are therefore necessary if we are to understand how cusp processes operate at Mars. Here we present the first results of an effort to model the kinetic particle motion and electric fields in Martian cusps. We are adapting both a 1.5D Particle-in-Cell (PIC) model for lunar magnetic cusps regions to the Martian case and a hybrid model framework (used previously for the global Martian plasma interaction and for lunar magnetic anomaly regions) to cusps in 2D. By comparing the models we can asses the importance of electron kinetics in particle transport along cusp field lines. In this first stage of our study we model a moderately strong nightside cusp, with incident hot hydrogen plasma from above, and cold planetary (oxygen) plasma entering the simulation from below. We report on the spatial and temporal distribution of plasma along cusp field lines for this initial case.

Feedbacks of Composition and Neutral Density Changes on the Structure of the Cusp Density Anomaly

NASA Astrophysics Data System (ADS)

Brinkman, D. G.; Walterscheid, R. L.; Clemmons, J. H.

2015-12-01

The Earth's magnetospheric cusp provides direct access of energetic particles to the thermosphere. These particles produce ionization and kinetic (particle) heating of the atmosphere. The increased ionization coupled with enhanced electric fields in the cusp produces increased Joule heating and ion drag forcing. These energy inputs cause large wind and temperature changes in the cusp region. Measurements by the CHAMP satellite (460-390- km altitude) have shown strongly enhanced density in the cusp region. The Streak mission (325-123 km), on the other hand, showed a relative depletion. The atmospheric response in the cusp can be sensitive to composition and neutral density changes. In response to heating in the cusp, air of heavier mean molecular weight is brought up from lower altitudes significantly affecting pressure gradients. This opposes the effects of temperature change due to heating and in-turn affects the density and winds produced in the cusp. Also changes in neutral density change the interaction between precipitating particles and the atmosphere and thus change heating rates and ionization in the region affected by cusp precipitation. In this study we assess the sensitivity of the wind and neutral density structure in the cusp region to changes in the mean molecular weight induced by neutral dynamics, and the changes in particle heating rates and ionization which result from changes in neutral density. We use a high resolution two-dimensional time-dependent nonhydrostatic nonlinear dynamical model where inputs can be systematically altered. The resolution of the model allows us to examine the complete range of cusp widths. We compare the current simulations to observations by CHAMP and Streak. Acknowledgements: This research was supported by The Aerospace Corporation's Technical Investment program

Penetration of the Interplanetary Magnetic Field B(sub y) into Earth's Plasma Sheet

NASA Technical Reports Server (NTRS)

Hau, L.-N.; Erickson, G. M.

1995-01-01

There has been considerable recent interest in the relationship between the cross-tail magnetic field component B(sub y) and tail dynamics. The purpose of this paper is to give an overall description of the penetration of the interplanetary magnetic field (IMF) B(sub y) into the near-Earth plasma sheet. We show that plasma sheet B(sub y) may be generated by the differential shear motion of field lines and enhanced by flux tube compression. The latter mechanism leads to a B(sub y) analogue of the pressure-balance inconsistency as flux tubes move from the far tail toward the Earth. The growth of B(sub y), however, may be limited by the dawn-dusk asymmetry in the shear velocity as a result of plasma sheet tilting. B(sub y) penetration into the plasma sheet implies field-aligned currents flowing between hemispheres. These currents together with the IMF B(sub y) related mantle field-aligned currents effectively shield the lobe from the IMF B(sub y).

Features of polar cusp electron precipitation associated with a large magnetic storm

NASA Technical Reports Server (NTRS)

Berko, F. W.

1974-01-01

Measurements of precipitating electrons made by the OGO-4 satellite reveal several interesting phenomena in the polar cusp. Extremely high fluxes of 0.7 keV electrons were observed in the polar cusp ninety minutes following the sudden commencement of a very large magnetic storm. Structured, fairly high fluxes of 7.3 keV electrons were also observed in the cusp region, accompanied by very strong search coil magnetometer fluctuations, indicative of strong field-aligned currents. The observations confirm previously reported latitudinal shifts in the location of the polar cusp in response to southward interplanetary magnetic fields.

CUSP9* treatment protocol for recurrent glioblastoma: aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, ritonavir, sertraline augmenting continuous low dose temozolomide

PubMed Central

Kast, Richard E.; Karpel-Massler, Georg; Halatsch, Marc-Eric

2014-01-01

CUSP9 treatment protocol for recurrent glioblastoma was published one year ago. We now present a slight modification, designated CUSP9*. CUSP9* drugs- aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, sertraline, ritonavir, are all widely approved by regulatory authorities, marketed for non-cancer indications. Each drug inhibits one or more important growth-enhancing pathways used by glioblastoma. By blocking survival paths, the aim is to render temozolomide, the current standard cytotoxic drug used in primary glioblastoma treatment, more effective. Although esthetically unpleasing to use so many drugs at once, the closely similar drugs of the original CUSP9 used together have been well-tolerated when given on a compassionate-use basis in the cases that have come to our attention so far. We expect similarly good tolerability for CUSP9*. The combined action of this suite of drugs blocks signaling at, or the activity of, AKT phosphorylation, aldehyde dehydrogenase, angiotensin converting enzyme, carbonic anhydrase -2,- 9, -12, cyclooxygenase-1 and -2, cathepsin B, Hedgehog, interleukin-6, 5-lipoxygenase, matrix metalloproteinase -2 and -9, mammalian target of rapamycin, neurokinin-1, p-gp efflux pump, thioredoxin reductase, tissue factor, 20 kDa translationally controlled tumor protein, and vascular endothelial growth factor. We believe that given the current prognosis after a glioblastoma has recurred, a trial of CUSP9* is warranted. PMID:25211298

CUSP9* treatment protocol for recurrent glioblastoma: aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, ritonavir, sertraline augmenting continuous low dose temozolomide.

PubMed

Kast, Richard E; Karpel-Massler, Georg; Halatsch, Marc-Eric

2014-09-30

CUSP9 treatment protocol for recurrent glioblastoma was published one year ago. We now present a slight modification, designated CUSP9*. CUSP9* drugs--aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, sertraline, ritonavir, are all widely approved by regulatory authorities, marketed for non-cancer indications. Each drug inhibits one or more important growth-enhancing pathways used by glioblastoma. By blocking survival paths, the aim is to render temozolomide, the current standard cytotoxic drug used in primary glioblastoma treatment, more effective. Although esthetically unpleasing to use so many drugs at once, the closely similar drugs of the original CUSP9 used together have been well-tolerated when given on a compassionate-use basis in the cases that have come to our attention so far. We expect similarly good tolerability for CUSP9*. The combined action of this suite of drugs blocks signaling at, or the activity of, AKT phosphorylation, aldehyde dehydrogenase, angiotensin converting enzyme, carbonic anhydrase -2,- 9, -12, cyclooxygenase-1 and -2, cathepsin B, Hedgehog, interleukin-6, 5-lipoxygenase, matrix metalloproteinase -2 and -9, mammalian target of rapamycin, neurokinin-1, p-gp efflux pump, thioredoxin reductase, tissue factor, 20 kDa translationally controlled tumor protein, and vascular endothelial growth factor. We believe that given the current prognosis after a glioblastoma has recurred, a trial of CUSP9* is warranted.

Feedbacks of Composition and Neutral Density Changes on the Structure of the Cusp Density Anomaly

NASA Astrophysics Data System (ADS)

Brinkman, D. G.; Walterscheid, R. L.; Clemmons, J. H.

2016-12-01

The Earth's magnetospheric cusp provides direct access of energetic particles to the thermosphere. These particles produce ionization and kinetic (particle) heating of the atmosphere. The increased ionization coupled with enhanced electric fields in the cusp produces increased Joule heating and ion drag forcing. These energy inputs cause large wind and temperature changes in the cusp region. Measurements by the CHAMP satellite (460-390- km altitude) have shown strongly enhanced density in the cusp region. The Streak mission (325-123 km), on the other hand, showed a relative depletion. The atmospheric response in the cusp can be sensitive to composition and neutral density changes. In response to heating in the cusp, air of heavier mean molecular weight is brought up from lower altitudes significantly affecting pressure gradients. This opposes the effects of temperature change due to heating and in-turn affects the density and winds produced in the cusp. Also changes in neutral density change the interaction between precipitating particles and the atmosphere and thus change heating rates and ionization in the region affected by cusp precipitation. In this study we assess the sensitivity of the wind and neutral density structure in the cusp region to changes in the mean molecular weight induced by neutral dynamics via advection, and the changes in particle heating rates and ionization which result from changes in neutral density. We use a high resolution two-dimensional time-dependent nonhydrostatic nonlinear dynamical model where inputs can be systematically altered. The resolution of the model allows us to examine the complete range of cusp widths. We compare the current simulations to observations by CHAMP and Streak. Acknowledgements: This material is based upon work supported by the National Aeronautics and Space Administration under Grant: NNX16AH46G issues through the Heliophysics Supporting Research Program. This research was also supported by The Aerospace

ULF Narrowband Emissions Analysis in the Terrestrial Polar Cusps

NASA Astrophysics Data System (ADS)

Grison, B.; Pisa, D.

2013-05-01

Polar cusps are known to be a key region for transfer of mass and momentum between the adjacent magnetosheath and the magnetosphere. The 4 spacecraft of the Cluster ESA mission crossed the polar cusps in their most distant part to the Earth in the early years of the mission (2000-2004) because of their highly eccentric orbit. The ULF wave activity in the cusp region has been linked with the magnetosheath plasma penetration since HEOS observations (D'Angelo et al., 1974). Wave and particle interaction play an important role in this colisionless plasma. The observed wave activity certainly results from both distant and local generation mechanisms. From Cluster case studies we propose to focus on one aspect for each of this place of generation. Concerning the distant generation, the possibility of a wave generation at the magnetopause itself is investigated. For this purpose we compare the propagation of the emissions on each side of the magnetopasue, i.e. in the cusp and in the magnetosheath. Concerning the local generation, the presence of locally generated waves above the local proton gyrofrequency that display a left hand polarization has been reported in Polar and Cluster studies (Le et al., 2001; Nykyri et al., 2003 ). The Doppler shift was not large enough to explain the observed frequency. We propose here to combine various techniques (k-filtering analysis, WHAMP simulations) to achieve a precise wave vector estimation and to explain these observations. References: D'Angelo, N., A. Bahnsen, and H. Rosenbauer (1974), Wave and particle measurements at the polar cusp, J. Geophys. Res., 79( 22), 3129-3134, doi:10.1029/JA079i022p03129. Le, G., X. Blanco-Cano, C. T. Russell, X.-W. Zhou, F. Mozer, K. J. Trattner, S. A. Fuselier, and B. J. Anderson (2001), Electromagnetic ion cyclotron waves in the high-altitude cusp: Polar observations, J. Geophys. Res., 106(A9), 19067-19079, doi:10.1029/2000JA900163. Nykyri, K., P. J. Cargill, E. A. Lucek, T. S. Horbury, A. Balogh

Performance characteristics of ring-cusp thrusters with xenon propellant

NASA Technical Reports Server (NTRS)

Patterson, M. J.

1986-01-01

The performance characteristics and operating envelope of several 30-cm ring-cusp ion thrusters with xenon propellant were investigated. Results indicate a strong performance dependence on the discharge chamber boundary magnetic fields and resultant distribution of electron currents. Significant improvements in discharge performance over J-series divergent-field thrusters were achieved for large throttling ranges, which translate into reduced cathode emission currents and reduced power dissipation which should be of significant benefit for operation at thruster power levels in excess of 10 kW. Mass spectrometry of the ion beam was documented for both the ring-cusp and J-series thrusters with xenon propellant for determination of overall thruster efficiency, and lifetime. Based on the lower centerline values of doubly charged ions in the ion beam and the lower operating discharge voltage, the screen grid erosion rate of the ring-cusp thruster is expected to be lower than the divergent-field J-series thruster by a factor of 2.

Performance characteristics of ring-cusp thrusters with xenon propellant

NASA Technical Reports Server (NTRS)

Patterson, M. J.

1986-01-01

The performance characteristics and operating envelope of several 30-cm ring-cusp ion thrusters with xenon propellant were investigated. Results indicate a strong performance dependence on the discharge chamber boundary magnetic fields and resultant distribution of electron currents. Significant improvements in discharge performance over J-series divergent-field thrusters were achieved for large throttling ranges, which translate into reduced cathode emission currents and reduced power dissipation which should be of significant benefit for operation at thruster power levels in excess of 10 kW. Mass spectrometer of the ion beam was documented for both the ring-cusp and J-series thrusters with xenon propellant for determination of overall thruster efficiency, and lifetime. Based on the lower centerline values of doubly charged ions in the ion beam and the lower operating discharge voltage, the screen grid erosion rate of the ring-cusp thruster is expected to be lower than the divergent-field J-series thruster by a factor of 2.

Enhanced Discharge Performance in a Ring Cusp Plasma Source

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.

2000-01-01

There is a need for a lightweight, low power ion thruster for space science missions. Such an ion thruster is under development at NASA Glenn Research Center. In an effort to better understand the discharge performance of this thruster, a thruster discharge chamber with an anode containing electrically isolated electrodes at the cusps was fabricated and tested. Characteristics of this ring cusp ion discharge were measured without ion beam extraction. Discharge current was measured at collection electrodes located at the magnetic cusps and at the anode body itself. Discharge performance and plasma properties were measured as a function of power, which was varied between 20 and 50 W. It was found that ion production costs decreased by as much as 20 percent when the two most downstream cusp electrodes were allowed to float. Floating the electrodes did not give rise to a significant increase in discharge power even though the plasma density increased markedly. The improved performance is attributed to enhanced electron containment.

The polar cusp: Cluster observations and simulations

NASA Astrophysics Data System (ADS)

Escoubet, C. Philippe; Berchem, Jean; Pitout, Frederic; Richard, Robert; Trattner, Karlheinz; Grison, Benjamin; Taylor, Matthew; Laakso, Harri; Masson, Arnaud; Dunlop, Malcolm; Dandouras, Iannis; Reme, Henri; Fazakerley, Andrew N.

The polar cusp, together with the magnetopause, are the magnetospheric regions in direct contact with the shocked solar wind flowing continuously from the Sun. Therefore any changes in the solar wind plasma reaching the magnetopause induce changes in the polar cusp with a delay of a few minutes to a few tens of minutes. For instance a change of the interplanetary magnetic field (IMF) direction from South to North will displace the polar cusp poleward and at the same time will change the injection of ions from the subsolar magnetopause to the magnetotail lobes. In the mid and low-altitude cusp a spacecraft will then observe a reversal of the dispersion in energy of the ions. We will use Cluster string of pearl configuration in the mid-altitude polar cusp to investigate the temporal variations of ion injections in the polar cusp. In the period from July to September, the Cluster spacecraft follow each other in the mid-altitude cusp with a delay of few minutes up to one hour. A few examples of cusp crossings will be presented to illustrate the influence of solar wind changes in the polar cusp. We will show that a sudden change in the IMF direction from South to North produces a double cusp crossing. By opposition, a change of the IMF from North to South produces a temporal injection on the equatorward side of the cusp and an erosion of the magnetosphere. Finally, we will show that when the interplanetary conditions are stable with the IMF pointing Northward or Southward for more than 10 min the polar cusp ion dispersion stays constant. MHD and large-scale particle simulations will also be used to complement the Cluster data.

Cusp and LLBL as Sources of the Isolated Dayside Auroral Feature During Northward IMF

NASA Technical Reports Server (NTRS)

Chang, S.; Gallagher, D. L.; Spann, J. F., Jr.; Mende, S.; Greenwald, R.; Newell, P. T.

2004-01-01

An intense dayside proton aurora was observed by IMAGE FUV for an extensive period of northward interplanetary magnetic field (IMF) on 17 and 18 September, 2000. This aurora partially coincided with the auroral oval and intruded farther poleward into the polar cap, and it showed longitudinal motions in response to IMF $B-y$ variation. Intense magnetosheath-like electron and ion precipitations have been simultaneously detected by DMSP above the poleward portion of the high-latitude dayside aurora. They resemble the typical plasmas observed in the low-altitude cusp. However, less intense electrons and more intense energetic ions were detected over the equatorward part of the aurora. These plasmas are closer to the low-latitude boundary layer (LLBL) plasmas. Under strongly northward IMF, global ionospheric convection derived from SuperDARN radar measurements showed a 4-cell pattern with sunward convection in the middle of the dayside polar cap and the dayside aurora corresponded to two different convection cells. This result further supports two source regions for the aurora. The cusp proton aurora is on open magnetic field lines convecting sunward whereas the LLBL proton aurora is on closed field lines convecting antisunward. These IMAGE, DMSP and SuperDARN observations reveal the structure and dynamics of the aurora and provide strong evidence for magnetic merging occurring at the high-latitude magnetopause poleward from the cusp. This merging process was very likely quasi-stationary.

How wide in magnetic local time is the cusp? An event study

NASA Astrophysics Data System (ADS)

Maynard, N. C.; Weber, E. J.; Weimer, D. R.; Moen, J.; Onsager, T.; Heelis, R. A.; Egeland, A.

1997-03-01

A unique pass of the DMSP F11 satellite, longitudinally cutting through the cusp and mantle, combined with simultaneous optical measurements of the dayside cusp from Svalbard has been used to determine the width in local time of the cusp. We have shown from this event study that the cusp was at least 3.7 hours wide in magnetic local time. These measurements provide a lower limit for the cusp width. The observed cusp optical emissions are relatively constant, considering the processes which lead to the 630.0 nm emissions, and require precipitating electron flux to be added each minute during the DMSP pass throughout the local time extent observed by the imaging photometer and probably over the whole extent of the cusp defined by DMSP data. We conclude that the electron fluxes which produce the cusp aurora are from a process which must have been operable sometime during each minute but could have had both temporal and spatial variations. The measured width along with models of cusp precipitation provide the rationale to conclude that the region of flux tube opening in the dayside merging process involves the whole frontside magnetopause and can extend beyond the dawn-dusk terminator. The merging process for this event was found to be continuous, although spatially and temporally variable.

Cusp observations with Cluster and THEMIS in preparation for the SMILE mission

NASA Astrophysics Data System (ADS)

Escoubet, C.-Philippe

2017-04-01

Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a novel self-standing mission, being designed in collaboration between ESA and the Chinese Academy of Science. Its objective is to observe solar wind-magnetosphere coupling via simultaneous in situ solar wind/magnetosheath plasma and magnetic field measurements, soft X-Ray images of the magnetosheath and polar cusps, and UV images of global auroral distributions. The observations of the cusps and magnetosheath with the X-ray imager are possible thanks to the relatively recent discovery of solar wind charge exchange (SWCX) X-ray emissions, first at comets and subsequently in the vicinity of the Earth's magnetosphere. To prepare for the mission, we must determine the cusp's expected morphology, motion, and in situ properties (density, velocity, temperature). We have selected a series of Cluster cusp crossings that define these properties and can therefore be used to estimate X-ray emissions across the width of the cusp for different IMF orientations. We will show that the peak soft X-ray emissions occur near the centre of the cusp where ion densities maximize. We then show that the integral lines of sight emissions through the cusp are a factor of 2.4 times larger for IMF-Bz northward than for IMF-Bz southward. The mid-altitude cusp is a factor of 7 brighter than the exterior cusp.

Electric currents and voltage drops along auroral field lines

NASA Technical Reports Server (NTRS)

Stern, D. P.

1983-01-01

An assessment is presented of the current state of knowledge concerning Birkeland currents and the parallel electric field, with discussions focusing on the Birkeland primary region 1 sheets, the region 2 sheets which parallel them and appear to close in the partial ring current, the cusp currents (which may be correlated with the interplanetary B(y) component), and the Harang filament. The energy required by the parallel electric field and the associated particle acceleration processes appears to be derived from the Birkeland currents, for which evidence is adduced from particles, inverted V spectra, rising ion beams and expanded loss cones. Conics may on the other hand signify acceleration by electrostatic ion cyclotron waves associated with beams accelerated by the parallel electric field.

WOOLLY CUSPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nauenberg, M.; Pais, A.

1962-04-01

A study is made of the elastic scattering 1 + 2 yields 1 + 2 in the energy region where the inelastic process 1 + 2 yields 3 + 4 sets in, for the case that particle 3 is unstable. By woolly cusp'' is meant the phenomenon that corresponds to the sharp cusp in the stable case. The procedure followed is to consider the inelastic channel to be of the three-body type, where the three- body states are parametrized by a Breit-Wigner formula around a mean mass m of particle 3. The connection between a woolly and a sharp cuspmore » is made evident. The problem is studied in terms of a twochannel S-wave K matrix. In the two- channel approximation the woolly cusp necessarily shows a decrease in the elastic cross section sigma above a characteristic energy. As a function of energy, sigma must either show a maximum or an inflection point. In either case, the energy at which this happens may lie above or below the inelastic threshold for the fictitious case that particle 3 has a sharp mass m. The sign and magnitude of the elastic scattering phase shift at this m point'' approximately determines which case is actually realized. (auth)« less

The concave cusp as a determiner of figure-ground.

PubMed

Stevens, K A; Brookes, A

1988-01-01

The tendency to interpret as figure, relative to background, those regions that are lighter, smaller, and, especially, more convex is well known. Wherever convex opaque objects abut or partially occlude one another in an image, the points of contact between the silhouettes form concave cusps, each indicating the local assignment of figure versus ground across the contour segments. It is proposed that this local geometric feature is a preattentive determiner of figure-ground perception and that it contributes to the previously observed tendency for convexity preference. Evidence is presented that figure-ground assignment can be determined solely on the basis of the concave cusp feature, and that the salience of the cusp derives from local geometry and not from adjacent contour convexity.

How does relativity affect magnetically induced currents?

PubMed

Berger, R J F; Repisky, M; Komorovsky, S

2015-09-21

Magnetically induced probability currents in molecules are studied in relativistic theory. Spin-orbit coupling (SOC) enhances the curvature and gives rise to a previously unobserved current cusp in AuH or small bulge-like distortions in HgH2 at the proton positions. The origin of this curvature is magnetically induced spin-density arising from SOC in the relativistic description.

Tordo 1 polar cusp barium plasma injection experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wescott, E.M.; Stenbaek-Nielsen, H.C.; Davis, T.N.

1978-04-01

In January 1975, two barium plasma injection experiments were carried out with rockets launched from Cape Parry, Northwest Territories, Canada, into the upper atmosphere where field lines from the dayside cusp region intersect the ionosphere. One experiment, Tordo 1, took place near the beginning of a worldwide magnetic storm. It became a polar cap experiment almost immediately as convection perpendicular to B moved the fluorescent plasma jet away from the cusp across the polar cap in an antisunward direction. Convection across the polar cap with an average velocity of more than 1 km/s was observed for nearly 40 min untilmore » the barium flux tubes encountered large E fields associated with a poleward bulge of the auroral oval near Greenland. Prior to the encounter with the aurora near Greenland there is evidence of upward acceleration of the barium ions while they were in the polar cap. The three-dimensional observations of the plasma orientation and motion give an insight into convection from the cusp region across the polar cap, the orientation of the polar cap magnetic field lines out to several earth radii, the causes of polar cap magnetic perturbations, and parallel acceleration processes.« less

Statistical Study in the mid-altitude cusp region: wave and particle data comparison using a normalized cusp crossing duration

NASA Astrophysics Data System (ADS)

Grison, B.; Escoubet, C. P.; Pitout, F.; Cornilleau-Wehrlin, N.; Dandouras, I.; Lucek, E.

2009-04-01

In the mid altitude cusp region the DC magnetic field presents a diamagnetic cavity due to intense ion earthward flux coming from the magnetosheath. A strong ultra low frequency (ULF) magnetic activity is also commonly observed in this region. Most of the mid altitude cusp statistical studies have focused on the location of the cusp and its dependence and response to solar wind, interplanetary magnetic field, dipole tilt angle parameters. In our study we use the database build by Pitout et al. (2006) in order to study the link of wave power in the ULF range (0.35-10Hz) measured by STAFF SC instrument with the ion plasma properties as measured by CIS (and CODIF) instrument as well as the diamagnetic cavity in the mid-altitude cusp region with FGM data. To compare the different crossings we don`t use the cusp position and dynamics but we use a normalized cusp crossing duration that permits to easily average the properties over a large number of crossings. As usual in the cusp, it is particularly relevant to sort the crossings by the corresponding interplanetary magnetic field (IMF) orientation in order to analyse the results. In particular we try to find out what is the most relevant parameter to link the strong wave activity with. The global statistic confirms previous single case observations that have noticed a simultaneity between ion injections and wave activity enhancements. We will also present results concerning other ion parameters and the diamagnetic cavity observed in the mid altitude cusp region.

Study on field-aligned electrons with Cluster observation in the Earth's cusp

NASA Astrophysics Data System (ADS)

Shi, Jiankui; Torkar, Klaus; Cheng, Zhengwei

2017-04-01

Cusp region is very important to the solar wind-magnetosphere coupling. The solar wind particles, through the cusp, can directly entry into the magnetosphere and ionosphere, and transport the mass, momentum and energy. The gyrating charged particles with field-aligned velocity are significant to perform the transportation. In this study, data from Cluster observation are used to study the characteristics of field-aligned electrons (FAE's) including the downward and the upward FAEs in the cusp. We select FAE event to do analysis. The durations of the FAE event covered a wide range from 6 to 475 seconds. The FAE's were found to occur very commonly in a circumpolar zone in the polar region and the MLT and ILAT distributions showed that most of the FAE events were observed around the cusp (70-80°ILAT, 0900-1500MLT). With the FAE flux the contribution of the electrons to the Field-Aligned Current (FAC) is estimated and the result shows that the FAE was the main carrier to the FAC in the cusp. The physical mechanisms of the FAE are analyzed, namely that the downward electrons were mainly from the solar wind and the upward electrons may originated from accelerated ionospheric up-flowing electrons or mirrored solar wind electrons. The energy transportation into the magnetosphere by the solar wind electrons through the cusp is also investigated.

Detecting Inter-Cusp and Inter-Tooth Wear Patterns in Rhinocerotids

PubMed Central

Taylor, Lucy A.; Kaiser, Thomas M.; Schwitzer, Christoph; Müller, Dennis W. H.; Codron, Daryl; Clauss, Marcus; Schulz, Ellen

2013-01-01

Extant rhinos are the largest extant herbivores exhibiting dietary specialisations for both browse and grass. However, the adaptive value of the wear-induced tooth morphology in rhinos has not been widely studied, and data on individual cusp and tooth positions have rarely been published. We evaluated upper cheek dentition of browsing Diceros bicornis and Rhinoceros sondaicus, mixed-feeding R. unicornis and grazing Ceratotherium simum using an extended mesowear method adapted for rhinos. We included single cusp scoring (EM(R)-S) to investigate inter-cusp and inter-tooth wear patterns. In accordance with previous reports, general mesowear patterns in D. bicornis and R. sondaicus were attrition-dominated and C. simum abrasion-dominated, reflecting their respective diets. Mesowear patterns for R. unicornis were more attrition-dominated than anticipated by the grass-dominated diet, which may indicate a low intake of environmental abrasives. EM(R)-S increased differentiation power compared to classical mesowear, with significant inter-cusp and inter-tooth differences detected. In D. bicornis, the anterior cusp was consistently more abrasion-dominated than the posterior. Wear differences in cusp position may relate to morphological adaptations to dietary regimes. Heterogeneous occlusal surfaces may facilitate the comminution of heterogeneous browse, whereas uniform, broad grinding surfaces may enhance the comminution of physically more homogeneous grass. A negative tooth wear gradient was found in D. bicornis, R. sondaicus and R. unicornis, with wear patterns becoming less abrasion-dominated from premolars to molars. No such gradients were evident in C. simum which displayed a uniform wear pattern. In browsers, premolars may be exposed to higher relative grit loads, which may result in the development of wear gradients. The second premolar may also have a role in food cropping. In grazers, high absolute amounts of ingested abrasives may override other signals, leading to

Detecting inter-cusp and inter-tooth wear patterns in rhinocerotids.

PubMed

Taylor, Lucy A; Kaiser, Thomas M; Schwitzer, Christoph; Müller, Dennis W H; Codron, Daryl; Clauss, Marcus; Schulz, Ellen

2013-01-01

Extant rhinos are the largest extant herbivores exhibiting dietary specialisations for both browse and grass. However, the adaptive value of the wear-induced tooth morphology in rhinos has not been widely studied, and data on individual cusp and tooth positions have rarely been published. We evaluated upper cheek dentition of browsing Diceros bicornis and Rhinoceros sondaicus, mixed-feeding R. unicornis and grazing Ceratotherium simum using an extended mesowear method adapted for rhinos. We included single cusp scoring (EM(R)-S) to investigate inter-cusp and inter-tooth wear patterns. In accordance with previous reports, general mesowear patterns in D. bicornis and R. sondaicus were attrition-dominated and C. simum abrasion-dominated, reflecting their respective diets. Mesowear patterns for R. unicornis were more attrition-dominated than anticipated by the grass-dominated diet, which may indicate a low intake of environmental abrasives. EM(R)-S increased differentiation power compared to classical mesowear, with significant inter-cusp and inter-tooth differences detected. In D. bicornis, the anterior cusp was consistently more abrasion-dominated than the posterior. Wear differences in cusp position may relate to morphological adaptations to dietary regimes. Heterogeneous occlusal surfaces may facilitate the comminution of heterogeneous browse, whereas uniform, broad grinding surfaces may enhance the comminution of physically more homogeneous grass. A negative tooth wear gradient was found in D. bicornis, R. sondaicus and R. unicornis, with wear patterns becoming less abrasion-dominated from premolars to molars. No such gradients were evident in C. simum which displayed a uniform wear pattern. In browsers, premolars may be exposed to higher relative grit loads, which may result in the development of wear gradients. The second premolar may also have a role in food cropping. In grazers, high absolute amounts of ingested abrasives may override other signals, leading to

Solar wind controls on Mercury's magnetospheric cusp

NASA Astrophysics Data System (ADS)

He, Maosheng; Vogt, Joachim; Heyner, Daniel; Zhong, Jun

2017-06-01

This study assesses the response of the cusp to solar wind changes comprehensively, using 2848 orbits of MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) observation. The assessment entails four steps: (1) propose and validate an approach to estimate the solar wind magnetic field (interplanetary magnetic field (IMF)) for MESSENGER's cusp transit; (2) define an index σ measuring the intensity of the magnetic disturbance which significantly peaks within the cusp and serves as an indicator of the cusp activity level; (3) construct an empirical model of σ as a function of IMF and Mercury's heliocentric distance rsun, through linear regression; and (4) use the model to estimate and compare the polar distribution of the disturbance σ under different conditions for a systematic comparison. The comparison illustrates that the disturbance peak over the cusp is strongest and widest extending in local time for negative IMF Bx and negative IMF Bz, and when Mercury is around the perihelion. Azimuthal shifts are associated with both IMF By and rsun: the cusp moves toward dawn when IMF By or rsun decrease. These dependences are explained in terms of the IMF Bx-controlled dayside magnetospheric topology, the component reconnection model applied to IMF By and Bz, and the variability of solar wind ram pressure associated with heliocentric distance rsun. The applicability of the component reconnection model on IMF By indicates that at Mercury reconnection occurs at lower shear angles than at Earth.