Adiabatic Motion Research Articles

Quantifying adiabatic motion in the outer radiation belt and ring current with invariant matching

Adiabatic motion is a fundamental reversible process for geomagnetically trapped particle populations, including particles comprising the ring current and radiation belts. During adiabatic motion, a particle’s trajectory in configuration space responds to sufficiently slow changes in the magnetospheric magnetic field. Previous research has highlighted expected patterns in adiabatic motion, such as radial motion or the Dst effect. In this work, we introduce a method we call Invariant Matching for quantifying adiabatic motion between a pair of magnetospheres. This method can be applied to both simulation and semi-empirical magnetic field models, is computationally efficient, and in particular does not require tracing the particle trajectories. In this work, we use the Tsyganenko et al., Journal of Geophysical Research: Space Physics, 2005, 110 (TS05) magnetic field model, and present adiabatic motion between a storm commencement, the time of the storm’s Dst minimum, and a nominal recovery time. We also analyze adiabatic motion which occurs in response to enhancements of individual major current systems (including the ring current, Chapman-Ferraro current, Birkeland current, and tail current). Our methodology yields vector fields quantifying the displacement of mirror points throughout the magnetosphere, prepared in a way appropriate for application to both outer radiation belt and ring current populations.

Study of the Method of Photon Neutralization of Powerful Beams of Negative Ions at the Budker Institute of Nuclear Physics

A short review of the studies carried out at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences (BINP SB RAS) on the photon neutralization of the beams of negative ions is presented. The principal distinctive feature of the presented approach consists in the nonresonant accumulation of photons in a limited space. Their confinement is based on the adiabatic motion of photons in a system of concave mirrors, which is insensitive to the quality of the injected radiation. An analysis is carried out of the possibility of using the neutralizer based on such a nonresonant photon trap in large-scale installations such as ITER and TRT, and a future experiment is described on the photon neutralization using a beam of negative hydrogen ions with energy up to 130 keV and a current of about 10 mA.

Evaluation of weak discontinuity in rotating medium with magnetic field, characteristic shock and weak discontinuity interaction

Abstract In this article we investigated the characteristic shock and weak discontinuity wave in a rotating medium of perfect gas in the case of one-dimensional (1-D) adiabatic motion under an axial magnetic field governed by the system of PDEs (partial differential equations). We have obtained some classes of analytical solutions of the system of PDEs that demonstrates the time-space dependency. With change in the values of rotational parameter, adiabatic index and the ratio of initial magnetic pressure to dynamic pressure, effect on the acceleration wave’s amplitude and jump in the flow variables across the characteristic shock is analyzed in detail. We have obtained an expression for the jump in shock acceleration, the amplitudes of transmitted and reflected waves caused by the incident wave on the characteristic shock after the interaction of a weak discontinuity. It is investigated that the jump function across the characteristic shock decay effect, and goes to 0 as time t → ∞, whereas a weak discontinuity wave may culminate into a shock wave, depending on the initial amplitude value. It is also found that the shock formation time reduces due to the consideration of magnetic field or rotating medium.

On the pattern of interannual polar vortex–ozone co-variability during northern hemispheric winter

Abstract. Stratospheric ozone is important for both stratospheric and surface climate. In the lower stratosphere during winter, its variability is governed primarily by transport dynamics induced by wave–mean flow interactions. In this work, we analyze interannual co-variations between the distribution of zonal-mean ozone and the strength of the polar vortex as a measure of dynamical activity during northern hemispheric winter. Specifically, we study co-variability between the seasonal means of the ozone field from modern reanalyses and polar-cap-averaged temperature at 100 hPa, which represents a robust and well-defined index for polar vortex strength. We focus on the vertically resolved structure of the associated extratropical ozone anomalies relative to the winter climatology and shed light on the transport mechanisms that are responsible for this response pattern. In particular, regression analysis in pressure coordinates shows that anomalously weak polar vortex years are associated with three pronounced local ozone maxima just above the polar tropopause, in the lower to mid-stratosphere and near the stratopause. In contrast, in isentropic coordinates, using ERA-Interim reanalysis data, only the mid- to lower stratosphere shows increased ozone, while a small negative ozone anomaly appears in the lowermost stratosphere. These differences are related to contributions due to anomalous adiabatic vertical motion, which are implicit in potential temperature coordinates. Our analyses of the ozone budget in the extratropical middle stratosphere show that the polar ozone response maximum around 600 K and the negative anomalies around 450 K beneath both reflect the combined effects of anomalous diabatic downwelling and quasi-isentropic eddy mixing, which are associated with consecutive counteracting anomalous ozone tendencies on daily timescales. We find that approx. 71 % of the total variability in polar column ozone in the stratosphere is associated with year-by-year variations in polar vortex strength based on ERA5 reanalyses for the winter seasons 1980–2022. MLS observations for 2005–2020 show that around 86 % can be explained by these co-variations with the polar vortex.

Fast-forward adiabatic quantum dynamics of XY spin model on three spin system

We discussed a method to accelerate an adiabatic quantum dynamics of XY spin model by using the fast-forward method proposed by Masuda and Nakamura. The Accelerated scheme is constructed by adding the driving Hamiltonian to the original Hamiltonian and speeding it up with a large time-scaling factor and an adiabatic parameter that realizes adiabatic quantum dynamics in a shortened time. Accelerated adiabatic dynamics start by assuming the candidate of driving Hamiltonian consists of the pair-wise exchange interaction and magnetic field. The driving Hamiltonian terms multiplied by the velocity function together with the original Hamiltonian give fast-forward driving for adiabatic states. We apply our method to XY spin model by considering three spin systems on the Kagome lattice. In this model, we obtained the XY pair-wise exchange interaction of nearest neighbors and next-nearest neighbors should be added to the original Hamiltonian as a driving interaction to accelerate the adiabatic motion. This pair-wise driving interaction in the fast-forward scheme guarantees the complete fidelity of accelerated states.

Regimes of ion dynamics in current sheets: The machine learning approach.

Current sheets are spatially localized almost-one-dimensional (1D) structures with intense plasma currents. They play a key role in storing the magnetic field energy and they separate different plasma populations in planetary magnetospheres, the solar wind, and the solar corona. Current sheets are primary regions for the magnetic field line reconnection responsible for plasma heating and charged particle acceleration. One of the most interesting and widely observed types of 1D current sheets is the rotational discontinuity, which can be force-free or include plasma compression. Theoretical models of such 1D current sheets are based on the assumption of adiabatic motion of ions, i.e., ion adiabatic invariants are conserved. We focus on three current sheet configurations, widely observed in the Earth magnetopause and magnetotail and in the near-Earth solar wind. The magnetic field in such current sheets is supported by currents carried by transient ions, which exist only when there is a sufficient number of invariants. In this paper, we apply a machine learning approach, AI Poincaré, to determine parametrical domains where adiabatic invariants are conserved. For all three current sheet configurations, these domains are quite narrow and do not cover the entire parametrical range of observed current sheets. We discuss possible interpretation of obtained results indicating that 1D current sheets are dynamical rather than static plasma equilibria.

Dynamics of a charged Thomas oscillator in an external magnetic field

In this letter, we provide a detailed numerical examination of the dynamics of a charged Thomas oscillator in an external magnetic field. We do so by adopting and then modifying the cyclically symmetric Thomas oscillator to study the dynamics of a charged particle in an external magnetic field. These dynamical behaviours for weak and strong field strength parameters fall under two categories; conservative and dissipative. The system shows a complex quasi-periodic attractor whose topology depends on initial conditions for high field strengths in the conservative regime. There is a transition from adiabatic motion to chaos on decreasing the field strength parameter. In the dissipative regime, the system is chaotic for weak field strength and weak damping but shows a limit cycle for high field strengths. Such behaviour is due to an additional negative feedback loop that comes into action at high field strengths and forces the system dynamics to be stable in periodic oscillations. For weak damping and weak field strength, the system dynamics mimic Brownian motion via chaotic walks. We claim that the modified Thomas oscillator is a prototypical model to understand the dynamics of an active particle.

Significant enhancements of the mesospheric Na layer bottom below 75 km observed by a full-diurnal-cycle lidar at Beijing (40.41° N, 116.01° E), China

Abstract. Based on the full-diurnal-cycle sodium (Na) lidar observations at Beijing (40.41∘ N, 116.01∘ E), we report pronounced downward extensions of the Na layer bottomside to below 75 km near mid-December 2014. Considerable Na atoms were observed even as low as ∼ 72 km, where Na atoms are short-lived. More interestingly, an unprecedented Na density of ∼ 2500 atoms cm−3 around 75 km was observed on 17 December 2014. Such high Na atoms concentration was 2 orders of magnitude larger than that normally observed at the similar altitude region. The variations of Na density on the layer bottom were found to be accompanied by warming temperature anomalies and considerable perturbations of minor chemical species (H, O, O3) in the upper mesosphere. Different from the previous reported metal layer bottom enhancements mainly contributed by photolysis after sunrise, these observational results suggest more critical contributions were made by the Na neutral chemical reactions to the Na layer bottom extensions reported here. The time–longitudinal variations of background atmospheric parameters in the upper mesosphere and stratosphere from global satellite observations and ERA reanalysis data indicated that the anomalous structures observed near the lidar site in mid-December 2014 were associated with planetary wave (PW) activities. The anomalies of temperature and O3 perturbation showed opposite phase in the altitude range of 70–75 and 35–45 km. This implied that the vertical coupling between the mesosphere and stratosphere, possibly driven by the interactions of PW activities with background atmosphere and modulation of gravity wave (GW) filtering by stratospheric wind, contributed to the perturbations of background atmosphere. Furthermore, the bottom enhancement on 17 December 2014 was also accompanied by clear wavy signatures in the main layer. The strong downwelling regions are likely due to the superposition of tide and GW, suggesting the wave-induced adiabatic vertical motion of the air parcel contributed greatly to the formation of the much stronger Na layer bottom enhancement on 17 December 2014. These results provide a clear observational evidence for the Na layer bottom response to the planetary-scale atmospheric perturbations in addition to tide and GW through affecting the chemical balance. The results of this paper also have implications for the response of the metal layer to vertical coupling between the lower atmosphere and the mesosphere.

Voltage-driven exchange resonance achieving 100% mechanical efficiency

Magnetic resonances driven by current-induced torques are crucial tools to study magnetic materials but are very limited in frequency and mechanical efficiency. We propose an alternative mechanism, voltage-induced torque, to realize high efficiency in generating high-frequency magnetization dynamics. When a ferromagnet--topological insulator--ferromagnet trilayer heterostructure is operated as an adiabatic quantum motor, voltage-induced torque arises from the adiabatic motion of gapped topological electrons on the two interfaces and act oppositely on the two ferromagnetic layers, which can excite the exchange mode where the two ferromagnetic layers precess with a $\ensuremath{\pi}$-phase difference. The exchange mode resonance, bearing a much higher frequency than the ferromagnetic resonance, is accompanied by topological charge pumping, leading to a sharp peak in electrical admittance at the resonance point. Because the output current is purely adiabatic while dissipative current vanishes identically, the proposed voltage-driven exchange resonance entails a remarkably high mechanical efficiency close to unity, which is impossible in any current-driven systems.

Effect of electronic concentration on the self-trapping transition of polaron for the weakly correlated system in the adiabatic limit

The self-trapping transition of the polaron is investigated for the two-dimensional extended Holstein-Hubbard model. A series of canonical transformations are performed on the Hamiltonian followed by a many phonon averaging, to eliminate the phonon degrees of freedom from the system. The mean field Hartree-Fock calculation has been done to solve the effective electronic Hamiltonian and the ground state energy is obtained variationally. The effect of electronic concentration on the polaronic hopping parameter is studied with respect to the electron–phonon interaction strengths in the weak Coulomb correlation limit. The transition from a delocalized mobile polaron to a localized self-trapped polaron has been found to be discontinuous for the adiabatic motion of the polaron and the self-trapping transition needs stronger electron–phonon interaction strength as the electronic concentration minimizes.

The “striated delta” signature of gravity waves generated near the jet stream during rapid extratropical cyclogenesis

AbstractDistinctive, triangular‐shaped “striated delta” clouds provide a novel framework for better understanding large‐amplitude gravity wave generation near upper‐tropospheric jets and fronts during rapid extratropical cyclogenesis, as the transverse cloud‐top banding is thought to be the imprint of gravity waves. For 28 striated deltas in the Australian region between May and September 2009, cloud formations have a mean length of 1,034 km, width of 537 km, lifetime of 7 hr and striation wavelength of 74 km. Composite analysis in ECMWF operational analysis data shows that deltas typically occur within the poleward jet exit during baroclinic evolution, located near the axis of inflection between an upstream upper trough and downstream ridge. Candidate gravity wave generation mechanisms in the vicinity of the upper jet coinciding with striated delta development are examined, including large parcel accelerations, nonlinear imbalance within the broadscale flow and deep moist convection. The striated delta shape is partly explained by a triangular pattern of Q‐vector convergence and quasi‐geostrophic adiabatic vertical motion forcing within the poleward jet exit, although the pattern is displaced a few hundred kilometres upstream.

Adiabaticity parameters for the categorization of light-matter interaction: From weak to strong driving

We investigate theoretically and numerically the light-matter interaction in a two-band system (TBS) as a model system for excitation in a solid-state band structure. We identify five clearly distinct excitation regimes, categorized with well-known adiabaticity parameters: (1) the perturbative multiphoton absorption regime for small driving field strengths, and four light-field-driven regimes, where intraband motion becomes important (2) the impulsive Landau-Zener (LZ) regime, (3) the nonimpulsive LZ regime, (4) the adiabatic regime, and (5) the adiabatic-impulsive regime for large electric field strengths. This categorization is tremendously helpful to understand the highly complex excitation dynamics in solids, in particular, when the driving field strength varies, and this categorization naturally connects Rabi physics with Landau-Zener physics. In addition, we find an insightful analytical expression for the photon orders connecting the perturbative multiphoton regime with the light-field-driven regimes. Moreover, in the adiabatic-impulsive regime, adiabatic motion and impulsive LZ transitions are equally important, leading to a broken symmetry of the TBS and a residual current when applying few-cycle laser pulses of broken temporal symmetry. This categorization allows a deep understanding of strong-field excitation in solids, including current and high-harmonic generation in a large variety of settings, and will help to find optimal driving parameters for a given purpose.

Self-Consistent Adiabatic Inspiral and Transition Motion.

The transition motion of a point particle around the last stable orbit of Kerr is described at leading order in the transition-timescale expansion. Taking systematically into account all self-force effects, we prove that the transition motion is still described by the Painlevé transcendent equation of the first kind. Using an asymptotically matched expansions scheme, we consistently match the quasicircular adiabatic inspiral with the transition motion. The matching requires us to take into account the secular change of angular velocity due to radiation reaction during the adiabatic inspiral, which consistently leads to a leading-order radial self-force in the slow timescale expansion.

Observations and Simulations of Dropout Events and Flux Decays in October 2013: Comparing MEO Equatorial With LEO Polar Orbit

AbstractWe compare ESA PROBA‐V observations of electron flux at LEO with those from the NASA Van Allen Probes mostly at MEO for October 2013. Dropouts are visible at all energy during four storms from both satellites. Equatorially trapped electron fluxes are higher than at LEO by 102 (<1 MeV) to 105 (>2.5 MeV). We observe a quite isotropic structure of the outer belt during quiet times, contrary to the inner belt, and pitch angle dependence of high energy injection. We find a very good overlap of the outer belt at MEO and LEO at ∼0.5 MeV. We use test‐particle simulations of the energetic electrons trapped in the terrestrial magnetic field to study the outer radiation belt electron flux changes during geomagnetic storms. We show that the Dst (Disturbance storm time) effect during the main phase of a geomagnetic storm results in a betatron mechanism causing outward radial drift and a deceleration of the electrons. This outward drift motion is energy independent, pitch angle‐dependent, and represents a significant distance (∼1 L‐shell at L = 5 for moderate storms). At fixed L‐shell, this causes a decay of the LEO precipitating flux (adiabatic outward motion), followed by a return to the normal state (adiabatic inward motion) during main and recovery phases. Dst effect, associated with magnetopause shadowing and radial diffusion can explain the main characteristics of outer radiation belt electron dropouts in October 2013. We also use Fokker‐Planck simulations with event‐driven diffusion coefficients at high temporal resolution, to distinguish instantaneous loss from the gradual scattering that depopulates the slot region and the outer belt after storms. Simulations reproduce the slot formation and the gradual loss in the outer belt. The typical energy dependence of these losses leads to the absence of scattering for relativistic and ultra‐relativistic electrons in the outer belt, oppositely to dropouts.

Dynamics of East Asian Spring Rainband and Spring–Autumn Contrast: Environmental Forcings of Large-Scale Circulation

AbstractDynamics of the East Asian spring rainband are investigated with a reanalysis dataset and station observations. Here, it is revealed that the rainband is anchored by external forcings. The midtropospheric jet core stays quasi-stationary around Japan. It has two branches in its entry region, which originate from the south and north flanks of the Tibetan Plateau and then run northeastward and southeastward, respectively. The southern branch advects warm air from the Tibetan–Hengduan Plateau northeastward, forming a rainband over southern China through causing adiabatic ascent motion and triggering diabatic feedback. The rainband is much stronger in spring than in autumn due to the stronger diabatic heating over the Tibetan–Hengduan Plateau, a more southward-displaced midtropospheric jet, and the resulting stronger warm advection over southern China. The northern jet branch forms a zonally elongated cold advection belt, which reaches a maximum around northern China, and then weakens and extends eastward to east of Japan. The westerly jet also steers strong disturbance activities roughly collocated with the cold advection belt via baroclinic instability. The high disturbance activities belt causes large cumulative warm advection (CWA) through drastically increasing extremely warm advection days on its eastern and south flanks, where weak cold advection prevails. CWA is more essential for monthly/seasonally rainfall than conventionally used time-average temperature advection because it is shown that strengthened warm advection can increase rainfall through positive diabatic feedback, while cold advection cannot cause negative rainfall. Thus, the rainband is collocated with the large CWA belt instead of the warm advection south of it. This rainband is jointed to the rainband over southern China, forming the long southwest–northeast-oriented East Asian spring rainband. Increasing moisture slightly displaces the rainband southeastward.

Berry phase for a Bose gas on a one-dimensional ring

We study a system of strongly interacting one-dimensional (1D) bosons on a ring pierced by a synthetic magnetic flux tube. By the Fermi-Bose mapping, this system is related to the system of spin-polarized non-interacting electrons confined on a ring and pierced by a solenoid (magnetic flux tube). On the ring there is an external localized delta-function potential barrier $V(\phi)=g \delta(\phi-\phi_0)$. We study the Berry phase associated to the adiabatic motion of delta-function barrier around the ring as a function of the strength of the potential $g$ and the number of particles $N$. The behavior of the Berry phase can be explained via quantum mechanical reflection and tunneling through the moving barrier which pushes the particles around the ring. The barrier produces a cusp in the density to which one can associate a missing charge $\Delta q$ (missing density) for the case of electrons (bosons, respectively). We show that the Berry phase (i.e., the Aharonov-Bohm phase) cannot be identified with the quantity $\Delta q/\hbar \oint \mathbf{A}\cdot d\mathbf{l}$. This means that the missing charge cannot be identified as a (quasi)hole. We point out to the connection of this result and recent studies of synthetic anyons in noninteracting systems. In addition, for bosons we study the weakly-interacting regime, which is related to the strongly interacting electrons via Fermi-Bose duality in 1D systems.

Born-Oppenheimer and non-Born-Oppenheimer contributions to time-dependent electron momenta.

Using a model system for a coupled electron-nuclear motion, we calculate time-dependent expectation values of the electronic momentum operator. Whereas, within the velocity form, this quantity vanishes if the Born-Oppenheimer (BO) approximation is applied, it differs from zero if the calculation employs the length form of the expectation value. Using the adiabatic expansion of the total wave function, it is analyzed which terms contribute to the mean electronic momentum. For an adiabatic motion, where the BO approximation holds, it is shown that in the length form, the BO wave function yields an excellent estimate of the momentum. On the other hand, in the velocity form, it is necessary to include non-BO terms to calculate its value. This illustrates the different convergence behavior of the matrix elements in the two formulations. In the diabatic limit where the electron density does only marginally change upon the nuclear motion, both approaches converge to a vanishing mean electronic momentum.

Long range frequency chirping of Alfvén eigenmodes

A theoretical framework has been developed for an NBI scenario to model the hard non-linear evolution of global Alfvén eigenmodes (GAEs) where the adiabatic motion of phase-space structures (holes and clumps), associated with frequency chirping, occurs in generalised phase-space of slowing down energetic particles. The radial profile of the GAE is expanded using finite elements which allows update of the mode structure as the mode frequency chirps. Constants of motion are introduced to track the dynamics of energetic particles during frequency chirping by implementing proper action-angle variables and canonical transformations which reduce the dynamics essentially to 1D. Consequently, we specify whether the particles are drifting inward/outward as the frequency deviates from the initial MHD eigenfrequency. Using the principle of least action, we have derived the non-linear equation describing the evolution of the radial profile by varying the total Lagrangian of the system with respect to the weights of the finite elements. For the choice of parameters in this work, it is shown that the peak of the radial profile is shifted and also broadens due to frequency chirping. The time rate of frequency change is also calculated using the energy balance and we show that the adiabatic condition remains valid once it is satisfied. This model clearly illustrates the theoretical treatment to study the long range adiabatic frequency sweeping events observed for Alfvén gap modes in real experiments.

Regimes of Motion of Water–Air Flow in a Short Vertical Tube with the Underfeed of Phases

Results of experimental investigation of adiabatic motion of a water–air flow in a short vertical tube with the underfeed of phases and the injection feed of water have been presented. It has been shown that the size of the gap between the bottom edge of the tube and the level of liquid in the apparatus casing has a decisive influence on the regime of flow. Conditions for the occurrence of characteristic hydrodynamic regimes, and also the heat loss in the active zone of a contact-apparatus model have been determined.

Excitation transport in molecular aggregates with thermal motion.

Molecular aggregates can under certain conditions transport electronic excitation energy over large distances due to dipole-dipole interactions. Here, we explore to what extent thermal motion of entire monomers can guide or enhance this excitation transport. The motion induces changes of aggregate geometry and hence modifies exciton states. Under certain conditions, excitation energy can thus be transported by the aggregate adiabatically, following a certain exciton eigenstate. While such transport is always slower than direct migration through dipole-dipole interactions, we show that transport through motion can yield higher transport efficiencies in the presence of on-site energy disorder than the static counterpart. For this we consider two simple models of molecular motion: (i) longitudinal vibrations of the monomers along the aggregation direction within their inter-molecular binding potential and (ii) torsional motion of planar monomers in a plane orthogonal to the aggregation direction. The parameters and potential shapes used are relevant to dye-molecule aggregates. We employ a quantum-classical method, in which molecules move through simplified classical molecular dynamics, while the excitation transport is treated quantum mechanically using Schrödinger's equation. For both models we find parameter regimes in which the motion enhances excitation transport, however these are more realistic for the torsional scenario, due to the limited motional range in a typical Morse type inter-molecular potential. We finally show that the transport enhancement can be linked to adiabatic quantum dynamics. This transport enhancement through adiabatic motion appears a useful resource to combat exciton trapping by disorder.