Double Cusp Research Articles

Complex dayside particle precipitation observed during the passage of a solar wind rotational discontinuity

The dayside particle precipitation during the passage of a solar wind rotational discontinuity (RD) event on 10 April 2015 is examined and reviewed. The RD leads to complex structures at the magnetopause, boundary layer, mantle, and cusp even though the geomagnetic activity level remains low. Particle precipitation data from DMSP F17 reveal the formation of an unusual boundary layer where the low energy (cold) ions exhibit energy-latitude dispersion that is usually associated with mantle while the high energy (hot) ions look like typical magnetospheric ions. DMSP F17 and F19 observe a double cusp that is a signature of magnetic reconnection occurring at both high- and low-latitudes due to the dominant IMF By. A global MHD simulation of the event supports the existence of the simultaneous reconnections at high- and low-latitude magnetopause that are consistent with the anti-parallel and component merging models, respectively. Finally, Cluster C2, located at high-latitude and high-altitude in the southern hemisphere, observes velocity fluctuations and reversals with peak-to-peak amplitudes >800 km·s–1 as it crosses the magnetopause. Guided by the MHD simulation, the Cluster observation can be interpreted as the spacecraft crossing reconnection outflows while moving from one side of the X-line to the other.

Multispacecraft Observations of the Simultaneous Occurrence of Magnetic Reconnection at High and Low Latitudes During the Passage of a Solar Wind Rotational Discontinuity Embedded in the April 9‐11, 2015 ICME

AbstractNumerous questions remain about how solar wind directional discontinuities, for example, rotational discontinuities (RDs), affect energy and transport processes at the magnetopause. The impact on the dayside magnetosphere of a solar wind RD is studied. The study shows that the RD leads to complex structures at the magnetopause, boundary layer, mantle, and cusp even though the geomagnetic activity level remains low. At low altitudes, the Defense Meteorological Satellite Program spacecraft observe a double cusp that is a signature of magnetic reconnection occurring at both high and low latitudes due to the dominant IMF By, while Cluster C2, located at high‐latitude and high‐altitude in the southern hemisphere, observes velocity fluctuations and reversals with peak‐to‐peak amplitudes >800 km s−1 as it crosses the magnetopause. A global MHD simulation of the event shows that the C2 observations are consistent with the spacecraft crossing reconnection outflows while moving from one side of the X‐line to the other.

Minimizing plasma temperature for antimatter mixing experiments

The ASACUSA collaboration produces a beam of antihydrogen atoms by mixing pure positron and antiproton plasmas in a strong magnetic field with a double cusp geometry. The positrons cool via cyclotron radiation inside the cryogenic trap. Low positron temperature is essential for increasing the fraction of antihydrogen atoms which reach the ground state prior to exiting the trap. Many experimental groups observe that such plasmas reach equilibrium at a temperature well above the temperature of the surrounding electrodes. This problem is typically attributed to electronic noise and plasma expansion, which heat the plasma. The present work reports anomalous heating far beyond what can be attributed to those two sources. The heating seems to be a result of the axially open trap geometry, which couples the plasma to the external (300 K) environment via microwave radiation.

Sporadic E Layer with a Structure of Double Cusp in the Vertical Sounding Ionogram

In this study, we analyzed a large number of vertical sounding ionograms, obtained by the mid-latitude Cyclone ionosonde (55.85° N; 48.8° E) of Kazan (Volga Region) Federal University, which operates in a rapid-run mode of ionograms (1 ionogram per minute). Ionograms with a sporadic E layer type c, which have an unusual double cusp on the trace from the sporadic layer, were found among them. We attempted to simulate this unusual double cusp trace shape. Model calculations were performed to clarify the reasons for the appearance of the double cusp and to determine the shape of the lower part of the E and Es layers. The simulation was performed by fitting the profile of the electron densities of the E and Es layers, calculating the virtual reflection heights based on the refractive index using the Appleton-Hartree formula, and comparing them with the virtual heights of the layers on the ionogram. An estimate of the half-thickness of the lower part of the Es-layer was obtained. The possible reasons for the appearance of a trace with a double cusp of the Es layer are discussed. We assumed that the possible reasons for this phenomenon were the stratification of the E layer, and the interaction between the E and F layers in the form of descending or intermediate layers and atmospheric wave propagation. As an illustration of these phenomena, examples of an intermediate (descending) sporadic E layer and stratification of the E region and the Es layer are given according to observations of the lower ionosphere. These examples were obtained through the resonant scattering of probe radio waves by artificial periodic irregularities (API technique) of the ionospheric plasma, performed on the SURA mid-latitude heating facility (56.1° N; 46.1° E). The scattering of probe radio waves on the APIs generated by the heating facility made it possible to study various phenomena in the Earth’s ionosphere.

A Hecke-equivariant decomposition of spaces of Drinfeld cusp forms via representation theory, and an investigation of its subfactors

There are various reasons why a naive analog of the Maeda conjecture has to fail for Drinfeld cusp forms. Focussing on double cusp forms and using the link found by Teitelbaum between Drinfeld cusp forms and certain harmonic cochains, we observed a while ago that all obvious counterexamples disappear for certain Hecke-invariant subquotients of spaces of Drinfeld cusp forms of fixed weight, which can be defined naturally via representation theory. The present work extends Teitelbaum’s isomorphism to an adelic setting and to arbitrary levels, it makes precise the impact of representation theory, it relates certain intertwining maps to hyperderivatives of Bosser-Pellarin, and it begins an investigation into dimension formulas for the subquotients mentioned above. We end with some numerical data for A={mathbb {F}}_3[t] that displays a new obstruction to an analog of a Maeda conjecture by discovering a conjecturally infinite supply of {mathbb {F}}_3(t)-rational eigenforms with combinatorially given (conjectural) Hecke eigenvalues at the prime t.

Accessory cusp expression at the enamel-dentine junction of hominin mandibular molars.

Studies of hominin dental morphology frequently consider accessory cusps on the lower molars, in particular those on the distal margin of the tooth (C6 or distal accessory cusp) and the lingual margin of the tooth (C7 or lingual accessory cusp). They are often utilized in studies of hominin systematics, where their presence or absence is assessed at the outer enamel surface (OES). However, studies of the enamel-dentine junction (EDJ) suggest these traits may be more variable in development, morphology and position than previously thought. Building on these studies, we outline a scoring procedure for the EDJ expression of these accessory cusps that considers the relationship between these accessory cusps and the surrounding primary cusps. We apply this scoring system to a sample of Plio-Pleistocene hominin mandibular molars of Paranthropus robustus, Paranthropus boisei, Australopithecus afarensis, Australopithecus africanus, Homo sp., Homo habilis and Homo erectus from Africa and Asia (n = 132). We find that there are taxon-specific patterns in accessory cusp expression at the EDJ that are consistent with previous findings at the OES. For example, P. robustus M1s and M2s very often have a distal accessory cusp but no lingual accessory cusp, while H. habilis M1s and M2s show the opposite pattern. The EDJ also reveals a number of complicating factors; some apparent accessory cusps at the enamel surface are represented at the EDJ only by shouldering on the ridges associated with the main cusps, while other accessory cusps appear to have little or no EDJ expression at all. We also discuss the presence of double and triple accessory cusps, including the presence of a double lingual accessory cusp on the distal ridge of the metaconid in the type specimen of H. habilis (OH 7–M1) that is not clear at the OES due to occlusal wear. Overall, our observations, as well as our understanding of the developmental underpinnings of cusp patterning, suggest that we should be cautious in our comparisons of accessory cusps for taxonomic interpretations.

Evolution processes of coupled thermal qubits

We investigate the quantum speed limit time (QSLT) of quantum evolution before thermal equilibrium of two coupled qubits each of which is coupled to a separate thermal bath at the same temperature within the Born-Markov approximation. The evolution process in one particular initial state can change between speed-up and speed-down two times before reaching equilibrium. We call this double cusp behaviour. This behaviour is an anomalous phenomenon in evolution processes in the weak-coupling Markovian regime. We study QSLT corresponding to all pure initial energy eigenstates and categorise them. In addition, we also display the conditions for double cusp behaviour in terms of temperature, qubit interaction and frequency.

Antiproton beams with low energy spread for antihydrogen production

A low energy antiproton transport from the ASACUSA's antiproton accumulation trap (MUSASHI trap) to the antihydrogen production trap (double cusp trap) is developed. The longitudinal antiproton energy spread after the transport line is 0.23±0.02 eV, compared with 15 eV with a previous method used in 2012. This reduction is achieved by an adiabatic transport beamline with several pulse-driven coaxial coils. Antihydrogen atoms are synthesized by directly injecting the antiprotons into a positron plasma, resulting in the higher production rate.

Hylleraas-configuration interaction study of the ground state of the negative Li ion

In a previous work Sims and Hagstrom (2014 J. Chem. Phys. 140 224312) reported Hylleraas-configuration interaction (Hy-CI) method variational calculations for the neutral atom and positive ion ground states of the beryllium isoelectronic sequence. The Li− ion, nominally the first member of this series, has a decidedly different electronic structure. This paper reports the results of a large, comparable calculation for the Li− ground state to explore how well the Hy-CI method can represent the more diffuse L shell of Li− which is representative of the Be(2sns) excited states as well. The best non-relativistic energy obtained was −7.500 776 596 hartree, indicating that 10–20 nh accuracy is attainable in Hy-CI and that convergence of the double cusp is fast and that this correlation type can be accurately represented within the Hy-CI model.

Double-cusp simulation during northward IMF using 3D PIC global code

The cusp has important effects on the transportation of particles and their energy from the solar wind to the magnetosphere, and ionosphere, and high-altitude atmosphere. The cusp can be considered to be a part of the magnetospheric boundary layer with weaker magnetic fields. It has been studied since 1971 by different satellite observations. Despite many years of investigation, some problems, such as the boundaries, shapes, and method of construction, remain to be solved. The double cusp was first reported by Wing using the observation of the DMSP satellite. He also compared the results of observations with the results of a 2D MHD simulation. In this study, by performing simulations and analyzing the results, we report the observation of a V-shaped double-cusp structure under the northward Interplanetary Magnetic Field (IMF). In our simulation, the double cusp was seen only for electrons, although a weak double cusp was observed for ions as well. We showed that this double cusp occurred because of electron precipitation from different sources of solar wind and magnetosphere with different magnetic field strengths. In previous studies of the double cusp, there were debates on its spatial structure or on its temporal behavior due to the cusp movement caused by the sharp solar wind effects on the magnetosphere shape. Here we report the spatial detection of the double cusp similar to the one observed by the DMSP satellite, but for the northward IMF case. Also, we investigate the asymmetry along the dawn-dusk side of the magnetosphere using our 3D PIC simulation code.

Cassini observations of Saturn's southern polar cusp

AbstractThe magnetospheric cusps are important sites of the coupling of a magnetosphere with the solar wind. The combination of both ground‐ and space‐based observations at Earth has enabled considerable progress to be made in understanding the terrestrial cusp and its role in the coupling of the magnetosphere to the solar wind via the polar magnetosphere. Voyager 2 fully explored Neptune's cusp in 1989, but highly inclined orbits of the Cassini spacecraft at Saturn present the most recent opportunity to repeatedly study the polar magnetosphere of a rapidly rotating planet. In this paper we discuss observations made by Cassini during two passes through Saturn's southern polar magnetosphere. Our main findings are that (i) Cassini directly encounters the southern polar cusp with evidence for the entry of magnetosheath plasma into the cusp via magnetopause reconnection, (ii) magnetopause reconnection and entry of plasma into the cusp can occur over a range of solar wind conditions, and (iii) double cusp morphologies are consistent with the position of the cusp oscillating in phase with Saturn's global magnetospheric periodicities.

The development of the superconducting double cusp magnet for intense antihydrogen beams

SynopsisWe have developed a superconducing double cusp magnet for the production of polarized intense antihydrogen atomic beams which are used to make microwave spectroscopy of a ground state hyperfine transition to test the CPT symmetry. The detail of specification and the focusing performance of the magnet will be presented.

Review of Solar Wind Entry into and Transport Within the Plasma Sheet

The plasma sheet is populated in part by the solar wind plasma. Four solar entry mechanisms are examined: (1) double cusp or double lobe reconnection, (2) Kelvin-Helmholtz Instability (KHI), (3) Kinetic Alfven waves (KAW), and (4) Impulsive Penetration. These mechanisms can efficiently fill the plasma sheet with cold dense ions during northward interplanetary magnetic field (IMF). The solar wind ions appear to have been heated upon entry along the plasma sheet dawn flank. The cold-component (solar wind origin) ion density is higher on the dawn flank than the dusk flank. The asymmetric evolution of the KAW and magnetic reconnection in association with the KHI at the dawn and dusk flank magnetopause may partly produce the dawn-dusk temperature and density asymmetries. Solar wind that crosses the magnetopause lowers the specific entropy (s=p/ρ γ ) of the plasma sheet along the flanks. Subsequent transport of the cold ions from the flanks to the midnight meridian increases s by a factor of 5. T i , T e , s i , and s e increase when the solar wind particles are transported across the magnetopause, but T i /T e is roughly conserved. Within the magnetotail, E×B and curvature and gradient drifts play important roles in the plasma transport and can explain the large features seen in the plasma sheet. Turbulence can also play a significant role, particularly in the cold plasma transport from the flanks to the midnight meridian. Total entropy (S=pV γ ) conservation provides important constraints on the plasma sheet transport, e.g., fast flows.

Observed destruction of a beach cusp system in presence of a double-coupled cusp system: the example of Grand Popo, Benin

Senechal, N., Laibi, R.A., Almar, R., Castelle, B., Biausque, M., Lefebvre, E. J. Anthony, J.-P., Dorel, M., Chuchla, R., Hounkonnou, M.H., Du Penhoat, Y., 2014. Observed destruction of a beach cusp system in presence of a double-coupled cusp system: the example of Grand Popo, Benin. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 669–674, ISSN 0749-0208.Beach cusps are common features of steep reflective and intermediate beaches. However, very few observations have reported double coupled cusp systems. Here, we present a dataset of observations of a beach exhibiting two sets of beach cusps. Data were collected at Grand Popo Beach (Benin, West Africa) in February 2013. Daily topographic surveys along a 380 m long stretch of shore allowed observation of the dynamics of the two sets of beach cusps. At the beginning of the field survey, we clearly observe two sets of cusps; the upper beach cusps system is relatively asymmetric with a typical wavelength of about 45 m, while the lower beach cusps system is relatively symmetric with a typical wave length slightly shorter (about 35 m). After two days, we measured the total destruction of the lower set of beach cusps while the upper set of beach cusps was only partially destroyed. The data suggest that destruction of the lower beach cusp system may be related to persistent accretionary conditions and/or calm conditions but probably also to the transition from wave-driven circulation (dominated by weak alongshore currents with flash and swash rips), to a second period characterized by dominant longshore currents further increasing in speed (with rare swash rips). Conversely, the disappearance of the western upper beach cusp may be related to an accretionary pattern and to the coalescence of two individual features. Our observations, consistent with previous works, suggest that beach cusps certainly arise as a result of some combination of erosion and accretion.

Double cusp encounter by Cluster: double cusp or motion of the cusp?

Abstract. Modelling plasma entry in the polar cusp has been successful in reproducing ion dispersions observed in the cusp at low and mid-altitudes. The use of a realistic convection pattern, when the IMF-By is large and stable, allowed Wing et al. (2001) to predict double cusp signatures that were subsequently observed by the DMSP spacecraft. In this paper we present a cusp crossing where two cusp populations are observed, separated by a gap around 1° Invariant Latitude (ILAT) wide. Cluster 1 (C1) and Cluster 2 (C2) observed these two cusp populations with a time delay of 3 min, and about 15 and 42 min later Cluster 4 (C4) and Cluster 3 (C3) observed, respectively, a single cusp population. A peculiarity of this event is the fact that the second cusp population seen on C1 and C2 was observed at the same time as the first cusp population on C4. This would tend to suggest that the two cusp populations had spatial features similar to the double cusp. Due to the nested crossing of C1 and C2 through the gap between the two cusp populations, C2 being first to leave the cusp and last to re-enter it, these observations are difficult to be explained by two distinct cusps with a gap in between. However, since we observe the cusp in a narrow area of local time post-noon, a second cusp may have been present in the pre-noon sector but could not be observed. On the other hand, these observations are in agreement with a motion of the cusp first dawnward and then back duskward due to the effect of the IMF-By component.

Transient overshoot extensional rheology of long-chain branched polyethylenes: Experimental and numerical comparisons between filament stretching and cross-slot flow

This work analyses the high-strain extensional behavior of long-chain branched polyethylenes, employing two novel extensional rheometer devices, the filament stretching rheometer and the cross-slot extensional rheometer. The filament stretching rheometer uses an active feedback loop to control the imposed strain rate on a filament, allowing Hencky strains of around 7 to be reached. The cross-slot extensional rheometer uses optical birefringence patterns to determine the steady-state extensional viscosity from planar stagnation point flow. The two methods probe different strain-rate regimes and in this paper we demonstrate the agreement when the operating regimes overlap and explore the steady-state extensional viscosity in the full strain-rate regime that these two complimentary techniques offer. For long-chain branched materials, the cross-slot birefringence images show a double cusp pattern around the outflow centre line (named W-cusps). Using constitutive modeling of the observed transient overshoot in extension seen in the filament stretching rheometer and using finite element simulations we show that the overshoot explains the W-cusps seen in the cross-slot extensional rheometer, further confirming the agreement between the two experimental techniques.

The Ground State and the Long-Time Evolution in the CMC Einstein Flow

Let (g,K)(k) be a CMC (vacuum) Einstein flow over a compact three-manifold M with non-positive Yamabe invariant (Y(M)). As noted by Fischer and Moncrief, the reduced volume V(k)=(-k/3)^{3}Vol_{g(k)}(M) is monotonically decreasing in the expanding direction and bounded below by V_{\inf}=(-1/6)Y(M))^{3/2}. Inspired by this fact we define the ground state of the manifold M as "the limit" of any sequence of CMC states {(g_{i},K_{i})} satisfying: i. k_{i}=-3, ii. V_{i} --> V_{inf}, iii. Q_{0}((g_{i},K_{i}))< L where Q_{0} is the Bel-Robinson energy and L is any arbitrary positive constant. We prove that (as a geometric state) the ground state is equivalent to the Thurston geometrization of M. Ground states classify naturally into three types. We provide examples for each class, including a new ground state (the Double Cusp) that we analyze in detail. Finally consider a long time and cosmologically normalized flow (\g,\K)(s)=((-k/3)^{2}g,(-k/3))K) where s=-ln(-k) is in [a,\infty). We prove that if E_{1}=E_{1}((\g,\K))< L (where E_{1}=Q_{0}+Q_{1}, is the sum of the zero and first order Bel-Robinson energies) the flow (\g,\K)(s) persistently geometrizes the three-manifold M and the geometrization is the ground state if V --> V_{inf}.

Percutaneous management of chronic deep venous reflux: review of experimental work and early clinical experience with bioprosthetic valve

Lower extremity chronic deep venous insufficiency (CDVI) is common and remains a major health problem worldwide. Selected patients benefited from direct deep vein valve surgical repair or valve transplantation. A major limitation of this approach is that most of the patients are not candidates for these procedures due to obstructions or residual thrombus throughout the vein. The past 15 years have witnessed experimental efforts at catheter-based management of CDVI. This review describes the initial designs and experimental evolution of a mechanical and bioprosthetic venous valve that can be implanted by using a transcatheter technique. These valves consisted of single, double, or triple cusp leaflets made of synthetic or biological materials attached to a carrier or frame. All described devices for percutaneous transcatheter valve placement rely on some form of a vascular stent for valve attachment.

Frequency and variability of the dental morphology in African-Colombian children of a school institution of Puerto Tejada, Cauca, Colombia.

Objectives: To assess the frequency and variability of eleven non-metric dental crown traits (winging, shovel-shape, double shovel shape, Carabelli trait, deflecting wrinkle, protostylid, groove pattern, cusp number, sixth and seventh cusps) in permanent (UI1/UI2/UM1/LM1) teeth, in order to understanding the ethnic influence and the biological distance of the sample in study. Materials and methods: In this descriptive and quantitative study, frequency and variability of twelve non-metric dental crown traits were analyzed, through the ASUDAS System, in dental casts from 84 African-Colombian children of both sexes (42 females and 42 males), in mixed-dentition from Puerto Tejada, Cauca (Colombia) inhabitants. Results: High frequencies of Carabelli trait in grade 5; and +5 y +6 groove patterns, suggests Western dental complex influence. High frequencies of protostylid (P point or foramen secum) and deflecting wrinkle that suggest Mongoloid influence from the miscegenation with regional indigenous groups were observed. Winging, shovel-shape, double shovel, cusp number and cusp 6 showed low frequencies. Bilateral symmetry and absence of sexual dimorphism were demonstrated (except winging, shovel-shape and protostylid).

Two sources of magnetosheath ions observed by Cluster in the mid-altitude polar cusp

Double cusps have been observed on a few occasions by polar orbiting spacecraft and ground-based observatories. The four Cluster spacecraft observed two distinct regions, showing characteristics of a double cusp, during a mid-altitude cusp pass on 7 August 2004. The Wind spacecraft detected a southward turning of the Interplanetary Magnetic Field (IMF) at the beginning of the cusp crossings and IMF–Bz stayed negative throughout. Cluster 4 observed a high energy step in the ion precipitation around 1 keV on the equatorward side of the cusp and a dense ion population in the cusp centre. Cluster 1, entering the cusp around 1 min later, observed only a partial ion dispersion with a low energy cutoff reaching 100 eV, together with the dense ion population in the cusp centre. About 9 min later, Cluster 3 entered the cusp and observed full ion dispersion from a few keV down to around 50 eV, together with the dense ion population in the centre of the cusp. The ion flow was directed poleward and eastward in the step/dispersion, whereas in the centre of the cusp the flow was directed poleward and westward. In addition the altitude of the source region of ion injection in the step/dispersion was found 50% larger than in the cusp centre. This event could be explained by the onset of dayside reconnection when the IMF turned southward. The step would be the first signature of component reconnection near the subsolar point, and the injection in the centre of the cusp a result of anti-parallel reconnection in the northern dusk side of the cusp. A three-dimensional magnetohydrodynamic (MHD) simulation is used to display the topology of the magnetic field and locate the sources of the ions during the event.