Showing papers on "Standing wave published in 2005"
TL;DR: It is demonstrated that the lowest threshold of spin-wave excitation in an in-plane magnetized magnetic nanocontact driven by spin-polarized current is achieved for a nonlinear self-localizedspin-wave mode-standing spin- wave bullet--stabilized by current-induced nonlinear dissipation.
Abstract: We demonstrate that the lowest threshold of spin-wave excitation in an in-plane magnetized magnetic nanocontact driven by spin-polarized current is achieved for a nonlinear self-localized spin-wave mode-standing spin-wave bullet--stabilized by current-induced nonlinear dissipation. This nonlinear mode has a nonpropagating evanescent character, is localized in the region comparable with the contact radius, and has a frequency that is lower than the frequency of the linear ferromagnetic resonance. The threshold current and generated frequency at the threshold theoretically calculated for this mode are in quantitative agreement with experiment.
228 citations
TL;DR: In this article, an optical conveyor belt is used to trap and deliver submicron particles over a distance of hundreds of micrometers using a standing wave (SW) created from two counter-propagating non-fracting beams where the phase of one of the beams can be changed.
Abstract: We demonstrate an optical conveyor belt that provides trapping and subsequent precise delivery of several submicron particles over a distance of hundreds of micrometers. This tool is based on a standing wave (SW) created from two counter-propagating nondiffracting beams where the phase of one of the beams can be changed. Therefore, the whole structure of SW nodes and antinodes moves delivering confined micro-objects to specific regions in space. Based on the theoretical calculations, we confirm experimentally that certain sizes of polystyrene particles jump more easily between neighboring axial traps and the influence of the SW is much weaker for certain sizes of trapped object. Moreover, the measured ratios of longitudinal and lateral optical trap stiffnesses are generally an order of magnitude higher compared to the classical single beam optical trap.
222 citations
TL;DR: An electromagnetically induced absorption grating is formed in a three-level atomic vapor under the condition of electromagnetsically induced transparency in which the strong coupling beam is replaced by a standing wave.
Abstract: An electromagnetically induced absorption grating is formed in a three-level atomic vapor under the condition of electromagnetically induced transparency in which the strong coupling beam is replaced by a standing wave The transmission and reflection behaviors of the weak probe beam are greatly modified at certain frequencies near the two-photon resonance An all-optical two-port signal router–all-optical switch is demonstrated
209 citations
TL;DR: In this paper, the standing wave difference method (SWDM) is applied to several configurations of pipe systems with different leak locations and sizes to identify the leak frequencies and estimate the approximate location.
Abstract: The current paper focuses on leakage detection in pipe systems by means of the standing wave difference method (SWDM) used for cable fault location in electrical engineering. This method is based on the generation of a steady-oscillatory flow in a pipe system, by the sinusoidal maneuver of a valve, and the analysis of the frequency response of the system for a certain range of oscillatory frequencies. The SWDM is applied to several configurations of pipe systems with different leak locations and sizes. A leak creates a resonance effect in the pressure signal with a secondary superimposed standing wave. The pressure measurement and the spectral analysis of the maximum pressure amplitude at the excitation site enable the identification of the leak frequencies and, consequently, the estimation of the leak approximate location. Practical difficulties of implementation of this technique in real life systems are discussed.
182 citations
TL;DR: In this paper, a scheme for sub-half-wavelength localization of an atom conditioned upon the absorption of a weak probe field at a particular frequency was proposed, where one of the drive fields is a standing-wave field of a cavity.
Abstract: We propose a scheme for subwavelength localization of an atom conditioned upon the absorption of a weak probe field at a particular frequency. Manipulating atom-field interaction on a certain transition by applying drive fields on nearby coupled transitions leads to interesting effects in the absorption spectrum of the weak probe field. We exploit this fact and employ a four-level system with three driving fields and a weak probe field, where one of the drive fields is a standing-wave field of a cavity. We show that the position of an atom along this standing wave is determined when probe-field absorption is measured. We find that absorption of the weak probe field at a certain frequency leads to subwavelength localization of the atom in either of the two half-wavelength regions of the cavity field by appropriate choice of the system parameters. We term this result as sub-half-wavelength localization to contrast it with the usual atom localization result of four peaks spread over one wavelength of the standing wave. We observe two localization peaks in either of the two half-wavelength regions along the cavity axis.
171 citations
TL;DR: In this paper, a density wave in quark matter is discussed at finite temperature, which occurs along with the chiral condensation, and is described by a dual standing wave in scalar and pseudoscalar condensates on the Chiral circle.
Abstract: A density wave in quark matter is discussed at finite temperature, which occurs along with the chiral condensation, and is described by a dual standing wave in scalar and pseudoscalar condensates on the chiral circle. The mechanism is quite similar to that for the spin density wave suggested by Overhauser and entirely reflects many-body effects. It is found within a mean-field approximation for the Nambu--Jona-Lasinio model that the chiral-condensed phase with the density wave develops at a high-density region just outside the usual chiral-transition line in phase diagram. A magnetic property of the density wave is also elucidated.
152 citations
TL;DR: A flexible and parallel procedure to generate large-area, free-standing films of subwavelength hole arrays has been demonstrated, and multilayered films of different materials were constructed.
Abstract: A flexible and parallel procedure to generate large-area, free-standing films of subwavelength hole arrays has been demonstrated. This method is materials-general, and multilayered films of different materials were constructed. The optical quality of these films was tested using a near-field scanning optical microscope, which revealed the formation of surface plasmon standing wave patterns that were consistent with numerical simulations. Because the properties of the holes and the film materials can be easily tailored, new types of plasmonic and photonic devices can be envisioned and tested.
114 citations
TL;DR: A new simple procedure for microwave-assisted organic synthesis under continuous flow processing has been developed for use in a monomodal microwave synthesizer with direct temperature control using the instrument's in-built IR sensor.
Abstract: A new simple procedure for microwave-assisted organic synthesis under continuous flow processing has been developed for use in a monomodal microwave synthesizer with direct temperature control using the instrument's in-built IR sensor. This design makes optimum use of the standing wave cavity to improve the energy efficiency of microwave-assisted flow reactions.
113 citations
TL;DR: It was shown that the hydrodynamic stress imposed on cells by acoustic streaming is less than that imposed by gentle preparative centrifugation procedures, and it was concluded that the standing wave trap operates only to concentrate cells locally, as in tissue, and does not modify the in vitro expression of surface receptor interactions.
Abstract: 2-D mammalian cell aggregates can be formed and levitated in a 1.5 MHz single half wavelength ultrasound standing wave trap. The physical environment of cells in such a trap has been examined. Attention was paid to parameters such as temperature, acoustic streaming, cavitation and intercellular forces. The extent to which these factors might be intrusive to a neural cell aggregate levitated in the trap was evaluated. Neural cells were exposed to ultrasound at a pressure amplitude of 0.54 MPa for 30 s; a small aggregate had been formed at the center of the trap. The pressure amplitude was then decreased to 0.27 MPa for 2 min, at which level the aggregation process continued at a slower rate. The pressure amplitude was then decreased to 0.06 MPa for 1 h. Temperature measurements that were conducted in situ with a 200 μm thermocouple over a 30 min period showed that the maximum temperature rise was less than 0.5 K. Acoustic streaming was measured by the particle image velocimetry method (PIV). It was shown that the hydrodynamic stress imposed on cells by acoustic streaming is less than that imposed by gentle preparative centrifugation procedures. Acoustic spectrum analysis showed that cavitation activity does not occur in the cell suspensions sonicated at the above pressures. White noise was detected only at a pressure amplitude of 1.96 MPa. Finally, it was shown that the attractive acoustic force between ultrasonically agglomerated cells is small compared with the normal attractive van der Waals force that operates at close cell surface separations. It is concluded that the standing wave trap operates only to concentrate cells locally, as in tissue, and does not modify the in vitro expression of surface receptor interactions. E-mail. coakley@cf.ac.uk
108 citations
TL;DR: In this paper, the authors developed a theoretical and experimental methodology to obtain localized stationary wave fields (with high transverse localization) whose longitudinal intensity pattern can approximately assume any desired shape within a chosen interval 0�z⩽L of the propagation axis z.
Abstract: In this work, starting by suitable superpositions of equal-frequency Bessel beams, we develop a theoretical and experimental methodology to obtain localized stationary wave fields (with high transverse localization) whose longitudinal intensity pattern can approximately assume any desired shape within a chosen interval 0⩽z⩽L of the propagation axis z. Their intensity envelope remains static, i.e., with velocity v=0, so we have named “frozen waves” (FWs) these new solutions to the wave equations (and, in particular, to the Maxwell equation). Inside the envelope of a FW, only the carrier wave propagates. The longitudinal shape, within the interval 0⩽z⩽L, can be chosen in such a way that no nonnegligible field exists outside the predetermined region (consisting, e.g., in one or more high-intensity peaks). Our solutions are notable also for the different and interesting applications they can have—especially in electromagnetism and acoustics—such as optical tweezers, atom guides, optical or acoustic bistouries, and various important medical apparatuses.
105 citations
Journal Article•
TL;DR: In this article, a standing wave oscillator (SWO) utilizing standing-wave-adaptive tapered transmission lines is proposed. But the SWO is not suitable for the position-dependent amplitudes of standing waves.
Abstract: In this paper, we introduce a novel standing wave oscillator (SWO) utilizing standing-wave-adaptive tapered transmission lines. This structure enhances Q and lowers phase noise through loss-reducing shaping of the transmission line, such that it is adapted to the position-dependent amplitudes of standing waves. Measurements validate the advantages of the proposed technique. The phase noise of a MOS SWO with the tapered line is 5-10 dB less than that of a uniform-line MOS SWO over a wide range of offset frequencies, centered about 15 GHz. Demonstrating a valuable exploitation of standing wave properties, the novel design concept boosts the potential for the emergence of standing wave oscillators as a useful alternative to the traditional lumped LC oscillator.
TL;DR: In this article, the uniformity of the ion energy across large-area electrodes (40cm2) was also studied in conditions under which the standing wave effect is important, i.e., conditions such that the rf voltage and the ion flux are strongly nonuniform.
Abstract: Ion energy distribution functions and ion fluxes in low-pressure, high-frequency (13.56–80MHz) capacitive discharges were investigated both theoretically and experimentally. In most of the conditions explored, the ion energy distribution function was a single peak centered at the time-averaged plasma potential. Lower energy ions with higher fluxes are obtained as the frequency increases. The uniformity of the ion energy across large-area electrodes (40cm2) was also studied in conditions under which the standing wave effect is important, i.e., conditions such that the rf voltage and the ion flux are strongly nonuniform. Unlike the latter quantities, the ion energy was uniform across the reactor at all frequencies, due to dc current flowing radially in the plasma and in the electrodes.
TL;DR: In this paper, the authors consider slow magnetosonic standing waves that are impulsively excited in a solar coronal loop and evaluate the excitation and damping times of a standing wave in hot coronal loops based on a parametric study.
Abstract: We consider slow magnetosonic standing waves that are impulsively excited in a solar coronal loop. The one-dimensional numerical model we implement includes the effects of nonlinearity, optionally thermal conduction, heating, and cooling of the solar plasma. We numerically evaluate excitation and damping times of a standing wave in hot coronal loops on the basis of a parametric study. Results of the numerical simulations reveal that initially launched impulses mainly trigger the fundamental mode and its first harmonic, depending on the location of these pulses in space. Parametric study shows that these standing waves are excited in a dozen or so wave periods corresponding roughly to 13 min and that they are strongly damped over a similar time-scale.
TL;DR: In this article, the authors proposed two techniques that improve the convergence and accuracy properties of SWAN in the prediction of stationary wave conditions in the nearshore zone, by making the extent of updates during the iteration process, which underlies a route to steady state, is made proportional to wave frequency.
TL;DR: In this article, the authors report on a pronounced redistribution of the local electronic density of states at the graphite surface, which is induced by the presence of low energy hydrogen-ion induced point defects.
Abstract: We report on a pronounced redistribution of the local electronic density of states at the graphite surface, which is induced by the presence of low energy hydrogen-ion induced point defects. Scanning tunneling microscopy reveals standing waves in the local density of states, which are due to backscattering of electron wave functions at individual point defects. The superstructure thereby formed is directly related to the pointlike structure of the Fermi surface of graphite. For high defect density interference patterns are observed which sensitively change structure on the relative positions of the defects. These patterns could be reproduced by tight binding simulations of various defect distributions.
TL;DR: It is shown that drifting small particles concentrate in either the nodes or antinodes of a standing wave, depending on whether they are hydrophilic or hydrophobic, as a result of a surface-tension effect that violates Archimedes' law of buoyancy.
Abstract: Capillarity effects drive hydrophilic or hydrophobic particles to congregate at specific points on a wave.
TL;DR: In this paper, a new theoretical model for the study of slow standing sausage mode oscillations in hot (T > 6 MK) active region coronal loops is presented, which contains the transition region and the upper chromosphere which enables the entire process of hot loop oscillations -from the impulsive footpoint excitation phase to the rapid damping phase.
Abstract: A new theoretical model for the study of slow standing sausage mode oscillations in hot (T > 6 MK) active region coronal loops is presented. These oscillations are observed by the SUMER spectrometer on board the SoHO satellite. The model contains the transition region and the upper chromosphere which enables us to study the entire process of hot loop oscillations -from the impulsive footpoint excitation phase to the rapid damping phase. It is shown that standing acoustic waves can be excited by an impulsive heat deposition at the chromospheric footpoint of a loop if the duration of the pulse matches the fundamental mode period. The pulse is immediately followed by a standing wave consistent with the SUMER observations in hot loops. The amount of released energy determines the oscillation amplitude. The combined effects of thermal conduction and radiation on the behaviour of the standing acoustic waves in hot gravitationally stratified loops are investigated. In addition to damping, these effects lead to downflows which are superimposed on the oscillations. The implications of the results in coronal seismology are discussed.
TL;DR: In this article, a 700:1 high aspect ratio probe shank is fabricated with a 7μm diameter, and attached at one end to an oscillator, which produces a standing wave in the oscillating probe.
Abstract: Nondestructive measurement of microscale features remains a challenging metrology problem. For example, to assess a high aspect ratio small hole it is currently common to cut a cross section and measure the features of interest using an atomic force microscope, scanning probe microscope, or scanning electron microscope. Typically, these metrology tools may be suitable for surface finish measurement but often lack the capability for dimensional metrology. The aim of this article is to discuss the development of a high aspect-ratio microscale probe for measurement of microscale features. A 700:1 high aspect ratio probe shank is fabricated with a 7μm diameter, and attached at one end to an oscillator. The oscillator produces a standing wave in the oscillating probe shank as opposed to conventional probes that use a microscale sphere on the end of a comparatively rigid shank. As a result of the standing wave formed in steady state vibration, the free end of the shank generates an amplitude of oscillation grea...
Patent•
23 Sep 2005
TL;DR: In this article, a method and a device for separating particles using ultrasonic standing waves which are switched between two different frequencies was proposed, where a second order harmonic standing wave is used together with the fundamental standing wave.
Abstract: The invention relates to a method and a device for separating particles using ultrasonic standing waves which are switched between two different frequencies. A second order harmonic standing wave is used together with the fundamental standing wave. If the particles are exposed to the fundamental standing wave, the forces act to collect particles at the centre. If the particles are exposed to the second order harmonic standing wave, the forces act to collect particles at the two pressure nodes at the sides. By switching the frequency between the second order harmonic standing wave and the fundamental standing wave, particles with different properties will be exposed to different accelerations and are separated into two streams.
TL;DR: The observed Lagrangian streaming velocities are consistent with Rott's theory, indicating that the dependence of viscosity on temperature is important, and are seen to be contaminated by significant errors due to the LDA/BSA system.
Abstract: Laser Doppler anemometry (LDA) with burst spectrum analysis (BSA) is used to study the acoustic streaming generated in a cylindrical standing-wave resonator filled with air. The air column is driven sinusoidally at a frequency of approximately 310 Hz and the resultant acoustic-velocity amplitudes are less than 1.3 m/s at the velocity antinodes. The axial component of fluid velocity is measured along the resonator axis, across the diameter, and as a function of acoustic amplitude. The velocity signals are postprocessed using the Fourier averaging method [Sonnenberger et al., Exp. Fluids 28, 217–224 (2000)]. Equations are derived for determining the uncertainties in the resultant Fourier coefficients. The time-averaged velocity-signal components are seen to be contaminated by significant errors due to the LDA/BSA system. In order to avoid these errors, the Lagrangian streaming velocities are determined using the time-harmonic signal components and the arrival times of the velocity samples. The observed Lagrangian streaming velocities are consistent with Rott’s theory [N. Rott, Z. Angew. Math. Phys. 25, 417–421 (1974)], indicating that the dependence of viscosity on temperature is important. The onset of streaming is observed to occur within approximately 5 s after switching on the acoustic field.
TL;DR: In this paper, a simple one-dimensional fluid model of a Hall thruster discharge in which cold ions are accelerated between two electrodes within a quasineutral plasma was investigated with a shortwave asymptotics applied to linearized equations.
Abstract: Longitudinal waves characterized by a phase velocity of the order of the velocity of ions have been recurrently observed in Hall thruster experiments and simulations. The origin of this so-called ion transit-time instability is investigated with a simple one-dimensional fluid model of a Hall thruster discharge in which cold ions are accelerated between two electrodes within a quasineutral plasma. A short-wave asymptotics applied to linearized equations shows that plasma perturbations in such a device consist of quasineutral ion acoustic waves superimposed on a background standing wave generated by discharge current oscillations. Under adequate circumstances and, in particular, at high ionization levels, acoustic waves are amplified as they propagate, inducing strong perturbation of the ion density and velocity. Responding to the subsequent perturbation of the column resistivity, the discharge current generates a standing wave, the reflection of which sustains the generation of acoustic waves at the inlet boundary. A calculation of the frequency and growth rate of this resonance mechanism for a supersonic ion flow is proposed, which illustrates the influence of the ionization degree on their onset and the approximate scaling of the frequency with the ion transit time. Consistent with experimental reports, the traveling wave can be observed on plasma density and velocity perturbations, while the plasma potential ostensibly oscillates in phase along the discharge.
TL;DR: In this article, the authors reported properties of substorm-related, globally excited Alfven waves on a temporal scale of 6 to 300 s (3.3 to 167 mHz) at geocentric distances between 5 and 6 RE.
Abstract: [1] We report properties of substorm-related, globally excited Alfven waves on a temporal scale of 6 to 300 s (3.3 to 167 mHz) at geocentric distances between 5 and 6 RE. The waves were observed in the tail lobes and the plasma sheet boundary layer (PSBL) by the Polar satellite. In each region we made the following observations: (1) The tail lobe Alfven waves started at substorm onset as determined from ground magnetometer data. Hence these ULF lobe waves can possibly be used as a new substorm indicator. Although on open field lines, they often showed local standing wave signatures with a large perpendicular scale size and a near-zero net Poynting flux. We do not classify those waves as FLR but interpret them as the superposition of incident and reflected waves. The same oscillations were simultaneously recorded in ground magnetometer data. Immediately poleward of the PSBL, the lobe Alfven waves traveled earthward (no reflection), suggesting their dissipation in the ionosphere. The lobe waves were superimposed on the signature of a field-aligned current (FAC). The onset of this FAC was simultaneous to the onset of the magnetic substorm bay. (2) The substorm-related PSBL Alfven waves carried two to three orders of magnitude larger Poynting flux (∼1 erg cm−2 s−1) than the lobe Alfven waves. These PSBL waves were a mixture of standing and traveling Alfven waves for different frequency ranges. Most Poynting flux was carried in large-scale earthward traveling waves (40–300 s). For one event, we also measured large standing wave components (>0.5 erg cm−2 s−1), but such events are rare. In the intermediate range (40–67 s), which overlaps with the Pi2 range, some waves showed clear standing wave signatures. At smaller periods (6–24 s), noninterfering earthward and tailward traveling waves were present with small Poynting fluxes (<0.05 erg cm−2 s−1). A trend for increasing E to B ratios with increasing wave frequency was observed. The PSBL waves were left-hand elliptically polarized. The wave vector was within 35° of the background magnetic field direction, suggesting that the waves were phase-mixed. The large-amplitude, substorm-related PSBL Alfven wave events (∼1 erg cm−2 s−1) were found in regions of upward currents.
TL;DR: Results show how the damping due to absorption, the change of the interior fluid inside the shells' hollow regions, and the exterior fluid surrounding their structures, affect the acoustic radiation force.
TL;DR: In this paper, the authors investigate how observation of upper state atomic populations localizes atomic position distributions for three-level atoms within a classical standing wave light field and explore the dependence of localization on the parameters of the field-atom interaction.
Abstract: We investigate how observation of upper state atomic populations localize atomic position distributions for three-level atoms within a classical standing wave light field. We consider a three-level atom, with the standing wave near-resonantly coupling one transition and a probe laser field near-resonantly coupling the second transition. Two different cases of localization are identified and we explore the dependence of localization on the parameters of the field–atom interaction.
TL;DR: In this paper, a large negative lateral shift of a light beam reflected from the so-called Kretschmann-Raether configuration containing left-handed material is predicted due to the formation of the unusual standing wave.
Abstract: A large negative lateral shift of a light beam reflected from the so-called Kretschmann–Raether configuration containing left-handed material is predicted due to the formation of the unusual standing wave. An analytical resonant condition is given when there is a large negative lateral shift.
TL;DR: The resulting chirp images demonstrate remarkable reduction of the standing wave artifact compared to the "fixed frequency" VA images.
Abstract: Vibro-acoustography (VA) is an imaging technique that uses the dynamic (oscillatory) radiation force of two continuous-wave (CW) ultrasound to image objects at low frequency (within the kHz range). In this technique, the dynamic radiation force is created by means of a confocused transducer emitting two ultrasound beams at slightly-shifted frequencies f/sub 1/ and f/sub 2/=f/sub 1/+/spl Delta/f. It has been demonstrated previously that high-resolution images of various types of inclusions and tissues can be obtained using this technique. However, if the targeted object reflects ultrasound directly back to the transducer, standing waves are produced that result in an artifact in the VA image. The goal of this study is to remove the standing wave artifact and improve VA images by means of a new process called chirp imaging. The procedure consists of sweeping the frequencies of the primary ultrasound beams in a selected bandwidth while keeping /spl Delta/f constant during the sweep. The chirp image is produced by averaging the amplitude of the acoustic emission produced during the sweep. Vibro-acoustography chirp imaging experiments are performed on a stainless-steel sphere attached to a latex sheet in a tank of degassed water. The resulting chirp images demonstrate remarkable reduction of the standing wave artifact compared to the "fixed frequency" VA images.
TL;DR: A significant correlation is observed between the temperature gradient and the behavior of the streaming: as the magnitude of theTemperature gradient increases, the magnitudeof the streaming decreases and the shape of the Streaming cell becomes increasingly distorted.
Abstract: Following the experimental method of Thompson and Atchley [J. Acoust. Soc. Am. 117, 1828-1838 (2005)] laser Doppler anemometry (LDA) is used to investigate the influences of a thermoacoustically induced axial temperature gradient and of fluid inertia on the acoustic streaming generated in a cylindrical standing-wave resonator filled with air driven sinusoidally at a frequency of 308 Hz. The axial component of Lagrangian streaming velocity is measured along the resonator axis and across the diameter at acoustic-velocity amplitudes of 2.7, 4.3, 6.1, and 8.6 m/s at the velocity antinodes. The magnitude of the axial temperature gradient along the resonator wall is varied between approximately 0 and 8 K/m by repeating measurements with the resonator either surrounded by a water jacket, suspended within an air-filled tank, or wrapped in foam insulation. A significant correlation is observed between the temperature gradient and the behavior of the streaming: as the magnitude of the temperature gradient increases, the magnitude of the streaming decreases and the shape of the streaming cell becomes increasingly distorted. The observed steady-state streaming velocities are not in agreement with any available theory.
Journal Article•
TL;DR: In this paper, the authors reported properties of substorm-related, globally excited Alfven waves on a temporal scale of 6 to 300 s (3.3 to 167 mHz) at geocentric distances between 5 and 6 R E.
Abstract: We report properties of substorm-related, globally excited Alfven waves on a temporal scale of 6 to 300 s (3.3 to 167 mHz) at geocentric distances between 5 and 6 R E . The waves were observed in the tail lobes and the plasma sheet boundary layer (PSBL) by the Polar satellite. In each region we made the following observations: (1) The tail lobe Alfven waves started at substorm onset as determined from ground magnetometer data. Hence these ULF lobe waves can possibly be used as a new substorm indicator. Although on open field lines, they often showed local standing wave signatures with a large perpendicular scale size and a near-zero net Poynting flux. We do not classify those waves as FLR but interpret them as the superposition of incident and reflected waves. The same oscillations were simultaneously recorded in ground magnetometer data. Immediately poleward of the PSBL, the lobe Alfven waves traveled earthward (no reflection), suggesting their dissipation in the ionosphere. The lobe waves were superimposed on the signature of a field-aligned current (FAC). The onset of this FAC was simultaneous to the onset of the magnetic substorm bay. (2) The substorm-related PSBL Alfven waves carried two to three orders of magnitude larger Poynting flux (∼1 erg cm -2 s -1 ) than the lobe Alfven waves. These PSBL waves were a mixture of standing and traveling Alfven waves for different frequency ranges. Most Poynting flux was carried in large-scale earthward traveling waves (40-300 s). For one event, we also measured large standing wave components (>0.5 erg cm -2 s -1 ), but such events are rare. In the intermediate range (40-67 s), which overlaps with the Pi2 range, some waves showed clear standing wave signatures. At smaller periods (6-24 s), noninterfering earthward and tailward traveling waves were present with small Poynting fluxes (<0.05 erg cm -2 s -1 ). A trend for increasing E to B ratios with increasing wave frequency was observed. The PSBL waves were left-hand elliptically polarized. The wave vector was within 35° of the background magnetic field direction, suggesting that the waves were phase-mixed. The large-amplitude, substorm-related PSBL Alfven wave events (∼1 erg cm -2 s -1 ) were found in regions of upward currents.
TL;DR: This work optically detects the positions of single neutral cesium atoms stored in a standing wave dipole trap with a subwavelength resolution of 143 nm rms and places single atoms at a predetermined position along the trap axis to within 300 nm rMS.
Abstract: We optically detect the positions of single neutral cesium atoms stored in a standing wave dipole trap with a subwavelength resolution of 143 nm rms. The distance between two simultaneously trapped atoms is measured with an even higher precision of 36 nm rms. We resolve the discreteness of the interatomic distances due to the 532 nm spatial period of the standing wave potential and infer the exact number of trapping potential wells separating the atoms. Finally, combining an initial position detection with a controlled transport, we place single atoms at a predetermined position along the trap axis to within 300 nm rms.