Energy Fluctuations Research Articles

Anisotropy of free-surface wave turbulence induced by a horizontal magnetic (electric) field

This work investigates the effects of anisotropy of free-surface wave turbulence under the influence of an external horizontal magnetic (electric) field based on direct numerical simulation technique. As the field increases, the surface wave system passes into the magnetohydrodynamic (MHD) turbulence regime with the formation of anisotropic condensate of capillary waves slowly propagating perpendicular to the external field. In the high field regime, the effect of the formation of discrete levels of frequency broadening in the space–time spectrum of capillary waves is reported for the first time. The performed correlation analysis showed that the resonance curve of the three-wave interaction is compressed with increasing field. This process leads to a non-local energy transfer from large-scale MHD waves to the small-scale capillary waves. Thus, discrete frequency levels in the spectrum of capillary waves arise as a result of the resonant decay of a MHD wave into secondary harmonics. Despite the anisotropy, the angle-averaged spectrum of surface elevations agrees well with the analytical estimate obtained under the assumption of isotropic wave propagation. We explain this contradiction by the fact that magnetic energy fluctuations on the liquid surface are distributed quasi-isotropically, and the anisotropic coherent condensate of capillary waves has a weak effect on the turbulence spectrum.

Measurements of turbulence characteristics in a warped transition

Transitions are needed to connect open-channel sections of different shapes and sizes that commonly exist in water supply channels, hydropower channels, irrigation canals and so on. A warped transition (WT) smoothly connects a rectangular with a trapezoidal channel-section and is considered the most efficient transition type with the least flow separation. This paper aims to experimentally investigate the turbulence characteristics in the WT. It reports acoustic Doppler velocimetry measurements of fluctuations in turbulence intensity, kinetic energy and shear stress, as well as of the stationary flow field. The fluctuations are significant and entirely result from the influence of the transition. In the transition, the turbulence features a small jet-like core and reversed flows along one sidewall outside this core; even laterally-averaged velocities have complicated vertical structures. This paper contributes to new benchmark turbulence conditions, useful for assessing the effectiveness of turbulence control devices and validating numerical models of turbulent flow.

Residual Energy and Broken Symmetry in Reduced Magnetohydrodynamics

Alfvénic interactions that transfer energy from large to small spatial scales lie at the heart of magnetohydrodynamic turbulence. An important feature of the turbulence is the generation of negative residual energy—excess energy in magnetic fluctuations compared to velocity fluctuations. By contrast, an MHD Alfvén wave has equal amounts of energy in fluctuations of each type. Alfvénic quasi-modes that do not satisfy the Alfvén wave dispersion relation and exist only in the presence of a nonlinear term can contain either positive or negative residual energy, but until now, an intuitive physical explanation for why negative residual energy is preferred has remained elusive. This paper shows that the equations of reduced MHD are symmetric in that they have no intrinsic preference for one sign of the residual energy over the other. An initial state that is not an exact solution to the equations can break this symmetry in a way that leads to net-negative residual energy generation. Such a state leads to a solution with three distinct parts: nonresonant Alfvénic quasi-modes, normal modes produced to satisfy initial conditions, and resonant normal modes that grow in time. The latter two parts strongly depend on initial conditions; the resulting symmetry breaking leads to net-negative residual energy both in Alfvénic quasi-modes and ω = k ∥ V A = 0 modes. These modes have net-positive residual energy in the equivalent boundary value problem, suggesting that the initial value setup is a better match for solar wind turbulence.

The 40S ribosomal subunit recycling complex modulates mitochondrial dynamics and endoplasmic reticulum - mitochondria tethering at mitochondrial fission/fusion hotspots

The 40S ribosomal subunit recycling pathway is an integral link in the cellular quality control network, occurring after translational errors have been corrected by the ribosome-associated quality control (RQC) machinery. Despite our understanding of its role, the impact of translation quality control on cellular metabolism remains poorly understood. Here, we reveal a conserved role of the 40S ribosomal subunit recycling (USP10-G3BP1) complex in regulating mitochondrial dynamics and function. The complex binds to fission-fusion proteins located at mitochondrial hotspots, regulating the functional assembly of endoplasmic reticulum-mitochondria contact sites (ERMCSs). Furthermore, it alters the activity of mTORC1/2 pathways, suggesting a link between quality control and energy fluctuations. Effective communication is essential for resolving proteostasis-related stresses. Our study illustrates that the USP10-G3BP1 complex acts as a hub that interacts with various pathways to adapt to environmental stimuli promptly. It advances our molecular understanding of RQC regulation and helps explain the pathogenesis of human proteostasis and mitochondrial dysfunction diseases.

Deep Reinforcement Learning Based Optimal Operation of Low-Carbon Island Microgrid with High Renewables and Hybrid Hydrogen–Energy Storage System

Hybrid hydrogen–energy storage systems play a significant role in the operation of islands microgrid with high renewable energy penetration: maintaining balance between the power supply and load demand. However, improper operation leads to undesirable costs and increases risks to voltage stability. Here, multi-time-scale scheduling is developed to reduce power costs and improve the operation performance of an island microgrid by integrating deep reinforcement learning with discrete wavelet transform to decompose and mitigate power fluctuations. Specifically, in the day-ahead stage, hydrogen production and the hydrogen blending ratio in gas turbines are optimized to minimize operational costs while satisfying the load demands of the island. In the first intraday stage, rolling adjustments are implemented to smooth renewable energy fluctuations and increase system stability by adjusting lithium battery and hydrogen production equipment operations. In the second intraday stage, real-time adjustments are applied to refine the first-stage plan and to compensate for real-time power imbalances. To verify the proposed multi-stage scheduling framework, real-world island data from Shanghai, China, are utilized in the case studies. The numerical simulation results demonstrate that the proposed innovative optimal operation strategy can simultaneously reduce both the costs and emissions of island microgrids.

Energy exchange statistics and fluctuation theorem for nonthermal asymptotic states

Energy exchange statistics and fluctuation theorem for nonthermal asymptotic states

Dual Actuator Control Strategy for Temperature Stability in High Temperature Solar Receivers

Abstract Fluctuations in incoming solar energy adversely affect the temperature stability within solar receivers, leading to a decrease in thermal efficiency. Therefore, it is essential to design a control system with the capability to maintain quasi-steady temperatures inside the reactor consistently throughout the day. This study introduces a dual actuator control technology to regulate the temperature within a high–temperature cylindrical cavity type gas receiver. The actuating system comprises two primary components. The first component involves a variable aperture mechanism, executed through a rotary mechanism made of stainless steel. This mechanism features seven holes of fixed diameters arranged in a half-circle configuration. The rotary mechanism is powered by a stepper motor regulated by a feedback control system. The second actuator is a Mass Flow Controller (MFC) responsible for meticulous adjustment of the inlet gas flow directed towards the solar receiver. The Direct Normal Irradiance (DNI) is simulated using a 10 kW High Flux Solar Simulator (HFSS) with a variable power supply ranging from 80 to 200 A. This setup enables the simulation of different operational conditions. The dual actuator method concurrently adjusts both gas flowrate and aperture size. While utilizing each of these methods individually can achieve reasonable temperature control performance, the hybrid approach leverages the strengths of both control methods, resulting in a significant improvement in the temperature regulation performance of the solar receiver. Two control strategies, namely Proportional Integral (PI) and Model Predictive Controller (MPC), were implemented to regulate the temperature inside a cavity type gas receiver. Experimental tests indicate that the incorporating the dual actuators controller is a promising technique, and its application can be extended to include additional parameters for utilization in a multi–input multi-output (MIMO) control system.

The tunable electronic band structure of a AlP3/Cs3Bi2I6Cl3 van der Waals heterostructure induced by an electric field: a first-principles study.

Constructing van der Waals heterostructures (vdWHs) has emerged as an attractive strategy to combine and enhance the optoelectronic properties of stacked materials. Herein, by means of first-principles calculations, we investigate the geometric and electronic structures of the AlP3/Cs3Bi2I6Cl3 vdWH as well as its tunable band structure via an external electric field. The AlP3/Cs3Bi2I6Cl3 vdWH is structurally and thermodynamically stable due to the low binding energy and the small energy fluctuation at room temperature. Our band structure calculations demonstrate that the AlP3/Cs3Bi2I6Cl3 vdWH possesses an indirect bandgap and a type-I band alignment with the band edges both dominated by an AlP3 layer. Notably, the band alignment of heterostructures can be flexibly tuned between type-I and type-II by employing an external electric field. Besides, an indirect-to-direct bandgap transition can be observed by increasing the intensity of negative electric field. These results reveal the potential of the AlP3/Cs3Bi2I6Cl3 vdWH as a novel candidate material for the experimental designs of multi-functional devices.

Co-Optimization Operation of Distribution Network-Containing Shared Energy Storage Multi-Microgrids Based on Multi-Body Game.

Under the carbon peaking and carbon neutrality target background, efficient collaborative scheduling between distribution networks and multi-microgrids is of great significance for enhancing renewable energy accommodation and ensuring stable system operation. Therefore, this paper proposes a collaborative optimization method for the operation of distribution networks and multi-microgrids with shared energy storage based on a multi-body game. The method is modeled and solved in two stages. In the first stage, a multi-objective optimization configuration model for shared energy storage among multi-microgrids is established, with optimization objectives balancing the randomness of renewable energy fluctuations and the economics of each microgrid undertaking shared energy storage. The charging and discharging interactive power of energy storage and each microgrid at various time periods are obtained and passed to the second stage. In the second stage, with the distribution network as the leader and shared energy storage and multi-microgrids as followers, a game optimization model with one leader and 2 followers is established. The model is solved based on an outer-layer genetic algorithm nested with an inner-layer solver to determine the electricity purchase and sale prices among the distribution network, multi-microgrids, and shared energy storage at various time periods, thereby minimizing operational costs. Finally, based on the power interaction of microgrids to measure their contributions, an improved Shapley value cost allocation method is proposed, effectively achieving a balanced distribution of benefits among the distribution network, shared energy storage, and multi-microgrids, thereby improving overall operational revenue. Meanwhile, a new method for calculating the shared energy storage capacity and the upper limit of charging and discharging power based on a game framework was proposed, which can save 37.23% of the power upper limit and 44.89% of the capacity upper limit, effectively saving the power upper limit and capacity upper limit.

RED-E-Function-Based Equilibrium Parameter Finder: Finding the Best Restraint Parameters in Absolute Binding Free Energy Calculations.

Free energy perturbation (FEP)-based absolute binding free energy (ABFE) calculations have emerged as a powerful tool for the accurate prediction of ligand-protein binding affinities in drug discovery. The restraint addition is crucial in FEP-ABFE calculations; however, due to the non-orthogonal couplings between the restrained degrees of freedom, it typically requires numerous λ windows to ensure the phase-space overlap during restraint addition. This study introduces the RED-E-function-based equilibrium parameter finder (REPF), a novel method that relies on harmonic restraints to optimize the equilibrium values in restraints, enhancing phase-space overlap and improving the convergence of the restraint addition. REPF was applied to 44 protein-ligand complexes across 5 targets and compared to restraint schemes reported in the literature. We found that REPF-optimized restraints achieve an accuracy comparable to that of the 12λ approach while using only 2λ simulations, resulting in a significant reduction in computational costs. Extensive tests confirmed the improved convergence behavior and reduced energy fluctuations of REPF-optimized restraints.

Suppressing Friction-Induced Stick-Slip Vibration and Noise of Zinc-Coated Steel through Temper Rolling.

The stick-slip phenomenon as a prevalent friction instability poses significant challenges to industry, including frictional vibration, reduced precision, and noise generation. The interfacial interactions between asperities on the surface of materials are critical in influencing stick-slip behavior. This study focused on modifying the asperities on the surface of zinc-coated steel through temper rolling as a new approach to suppress friction-induced stick-slip vibration and noise. It was revealed that temper rolling effectively suppressed the stick-slip behavior when the deformation of zinc-coated steel exceeded 2.3%. The proposed mechanism suggested that the temper rolling reduced surface asperity density, resulting in diminished potential energy fluctuations and a subsequent decrease in the stick-slip amplitude (the difference between the static and kinetic friction coefficients). In situ observation using the digital image correlation (DIC) technique demonstrated that the decrease in the stick-slip amplitude affected the motion state of the friction pair, effectively suppressing the stick-slip vibration and noise generation. These findings highlight the potential of temper rolling as an effective strategy for tailoring the surface topography to suppress the stick-slip phenomenon along with its related vibration and noise.

A Brayton Pumped Thermal Energy Storage System Based on Supercritical Carbon Dioxide Recompression Reheating Discharge Cycle

Abstract In recent years, renewable energy such as solar energy and large-scale energy storage, which is a very important technology to compensate for solar energy's fluctuation due to weather issues, have been extensively investigated. In this paper, a Pumped Thermal Energy Storage (PTES) cycle based on a supercritical carbon dioxide (sCO2) Recompression Reheating cycle and energy pump with a recuperator has been proposed and analyzed. Molten salt with varying temperatures of 565 °C to 730 °C has been used for energy storage. The pressure ratios have been fixed in the discharge cycle as 2.5, and in the charging cycle, it varies in order to find the optimum operation condition. Parametric studies have been made to determine the best performance of the new system. Molten salt temperature, split ratio, pressure ratio, and intermediate pressure have been varied in the calculation. Exergy analysis has been developed in order to determine exergy destruction in all components. Roundtrip efficiencies have been calculated over a wide range of operating conditions. Different working fluids such as argon, carbon dioxide, and nitrogen were used in both cycles. Performance was determined for different combinations of working fluids. It is concluded that for best performance working fluid for energy pump (charging) should be argon and carbon dioxide should be the working fluid for discharging cycle. For this combination operating at optimum molten salt temperature, intermediate pressure and split ratio in the discharging cycle, the roundtrip efficiency is 66%, which is the maximum.

Fracture propagation characteristics and energy evolution law of deep coal seam containing gangue based on discrete lattice method

Hydraulic fracturing is a key technology for the development of deep coal-rock reservoirs. Gangue, a common rock type within coal-bearing strata, significantly influences fracture morphology after fracturing. Understanding fracture propagation in coal-rock containing gangue and effectively controlling artificial fractures remain critical challenges in fracturing operations. To address this, the study investigates the coal-bearing strata of the Benxi Formation in the Daning-Jixian area of the Ordos Basin, characterized by the presence of gangue. A three-dimensional discrete lattice model was developed to analyze the effects of gangue-related factors, including the number, thickness, dip angle, and type, on hydraulic fracturing. The fracture propagation patterns and stimulation effects under these factors were systematically compared. Using node path tracking and post-processing techniques, the study identified the fracturing characteristics and fracture propagation modes at different stages. The findings indicate that gangue characteristics significantly impact fracture morphology and propagation paths. Specifically, an increase in the number of gangue layers enhances fracture complexity but reduces the effective stimulation ratio. Gangue thickness positively correlates with fracture tortuosity and inversely correlates with the effective stimulation ratio. The dip angle of gangue determines the direction of fracture propagation but has minimal influence on the stimulation area. The gangue type also affects fracture morphology; for instance, sandstone gangue leads to narrower fractures and more interface fractures at the sandstone–coal boundary compared to mudstone gangue. Fracture propagation, characterized by energy changes, can be divided into four distinct stages: Stage I (initial injection phase), Stage II (onset of fracture propagation), Stage III (fluid energy storage within gangue), and Stage IV (fracture penetration through gangue). These stages are marked by variations in fluid injection energy, fluctuation energy, surface energy, and strain energy as the fracture penetrates the layer, deflects, and forms horizontal fractures. The simulation of fracture network evolution in coal-bearing strata containing gangue provides significant theoretical guidance for understanding, predicting, and controlling fracture network morphology in coal reservoirs. These findings are instrumental for the efficient development of deep coalbed methane.

Exploring volatility transmission in Capesize freight contracts: Insights from energy and commodity markets.

Analyzing the interactions between spot and time charter freight is crucial for the maritime industry. While numerous studies have explored the relationship between average freight indices and spillover effects, a gap remains in understanding the deeper connections between inter-regional shipping routes and chartering contracts. This research investigates the role of Capesize freight dynamics in shaping the regional dry bulk freight market, with a focus on the influence of energy and commodity price fluctuations. Utilizing the TVP-VAR model, we identify distinct trends across various investment horizons. The analysis reveals that short-term spillovers dominate the system, with crude oil serving as a consistent shock transmitter within the time charter network. The China-Brazil route drives spillovers across all periods, while the Australia-China route transitions from absorbing short-term volatility to transmitting long-term shocks. Similarly, the Tubarão-Rotterdam and Bolivar-Rotterdam routes display comparable shifts, transmitting short-term spillovers but absorbing long-term volatility. These findings offer valuable insights for stakeholders seeking to manage risks amidst economic and geopolitical uncertainties.

Tunable Casimir equilibria in dual-liquid system

The Casimir effect, a macroscopic manifestation of quantum phenomena, arises from zero-point energy and thermal fluctuations. When two objects are brought into close proximity, the Casimir effect manifests as a repulsive force, while at greater separations, it transforms into an attractive force. There exists a specific distance at which the Casimir force vanishes, which is referred to as the stable Casimir equilibrium. Stable Casimir equilibrium arises from the curve minimum value of the Casimir energy, which can create spatial trapping. The manipulation of stable Casimir equilibrium provides promising applications in fields such as tunable optical resonators and self-assembly. This work presents a scheme for achieving tunable Casimir equilibrium in a dual-liquid system. The system comprises a multilayered stratified structure with a gold substrate. Above the gold substrate, a stratified liquid system is formed due to the immiscibility between organic solutions and water. The lower-density solution is at the top, while the higher-density solution is at the bottom. Our results suggest that a stable Casimir equilibrium for a suspended gold nanoplate can be realized, when the suspended gold nanoplate is immersed in organic solution of toluene or benzene. Moreover, the height of the suspended gold nanoplate, determined by the stable Casimir equilibrium, can be precisely tuned by changing the thickness of the water layer. The effects of finite temperature and ionic concentration on the Casimir equilibria are also analyzed in this work. The results suggest that the separation height of Casimir equilibrium decreases with the increase of temperature. Interestingly, when the Debye shielding length is comparable to or smaller than the separation length, the ion concentration in water significantly affects the Casimir pressure allowing for extensive modulations of Casimir equilibrium. This work opens up a new avenue for adjusting Casimir equilibrium and has important applications in “quantum trapping” of micro-nano particles.

Intra-layer and inter-layer monitoring of laser powder bed fusion defects based on airborne acoustic and gn-Res model: pore and deformation

ABSTRACT Macroscopic deformation and microscopic pores are the main defects affecting the comprehensive performance of laser powder bed fusion (LPBF) parts. The LPBF process involves highly coupled multiple physical mechanisms over a wide time scale, making it difficult to obtain strongly correlated defect characteristics and achieve online monitoring. Thus, this study proposes an acoustic-based macro–micro defect synchronous monitoring technology. It enables monitoring by analysing process information progressively from intra-layer to inter-layer. The research identifies that high energy density leads to deformation defects, with helical scan strategy energy fluctuations exacerbating deformation. A correlation between keyhole pores and high-frequency signal components allows quantitative pore analysis directly from acoustic signals. Furthermore, an intelligent diagnosis model (gn-Res_SC) is proposed, incorporating high-order information interaction and residual structure for in-depth process analysis. The model demonstrates superior performance with accuracy (90.70%), recall (90.70%) and F1-score (90.40%) in LPBF acoustic monitoring signal evaluation.

Unusual Endotaxy Growth of Hexagonal Nanosheets by the Self-Assembly of a Homopolymer.

A classical crystallization usually grows epitaxially from a crystal nucleus. Presented in this study is an unusual endotaxy growth manner of a crystalline homopolymer to form hexagonal nanosheets. The amphiphilic homopolymer, poly(3-(4-(phenyldiazenyl)phenoxy)propyl methacrylate) (PAzoPMA), is first annealed in isopropanol to afford a hexagonal nut-like structure. Then, the PAzoPMA crystallizes from the inner wall to the center to form a thin bottom, which grows upwards along the bottom, leading to the formation of the evenly hexagonal nanosheets. The energy fluctuation by Molecular Dynamics (MD) simulation during self-assembly confirms the packing state of PAzoPMA chains in different solvents. In isopropanol, the total energy is the lowest, demonstrating the tight regular arrangement of polymer chains. In addition, the non-bonding interaction energy is the lowest, leading to the favorable contact with solvent molecules and the formation of hexagonal nanosheets. Otherwise, nanowires and giant large compound micelles are formed in ethanol and n-butanol. Overall, an unusual endotaxy crystallization manner of an amphiphilic homopolymer is observed during the preparation of hexagonal nanosheets, which brings fresh insight for understanding crystallization behavior of polymers and preparing functional soft nanomaterials.

Unusual Endotaxy Growth of Hexagonal Nanosheets by the Self‐Assembly of a Homopolymer

A classical crystallization usually grows epitaxially from a crystal nucleus. Presented in this study is an unusual endotaxy growth manner of a crystalline homopolymer to form hexagonal nanosheets. The amphiphilic homopolymer, poly(3‐(4‐(phenyldiazenyl)phenoxy)propyl methacrylate) (PAzoPMA), is first annealed in isopropanol to afford a hexagonal nut‐like structure. Then, the PAzoPMA crystallizes from the inner wall to the center to form a thin bottom, which grows upwards along the bottom, leading to the formation of the evenly hexagonal nanosheets. The energy fluctuation by Molecular Dynamics (MD) simulation during self‐assembly confirms the packing state of PAzoPMA chains in different solvents. In isopropanol, the total energy is the lowest, demonstrating the tight regular arrangement of polymer chains. In addition, the non‐bonding interaction energy is the lowest, leading to the favorable contact with solvent molecules and the formation of hexagonal nanosheets. Otherwise, nanowires and giant large compound micelles are formed in ethanol and n‐butanol. Overall, an unusual endotaxy crystallization manner of an amphiphilic homopolymer is observed during the preparation of hexagonal nanosheets, which brings fresh insight for understanding crystallization behavior of polymers and preparing functional soft nanomaterials.

Modeling interface roughness scattering with incorporation of potential energy and wave-function fluctuations: Enhancing mobility in AlN/GaN digital alloys

Interface roughness (IFR) scattering significantly impacts the mobility of two-dimensional electron gases (2DEGs) in heterostructures. While existing models for IFR scattering have advanced our understanding, they have notable limitations. The model developed by Jin et al. in 2007, while incorporating a realistic barrier height and roughness-induced changes in potential and subband wave-functions, employs a first-order roughness expansion. The formulation introduced by Lizzit et al. in 2014, although avoiding the first-order approximation for better higher-order effect modeling, omits IFR-induced change in electron density distribution. To address these limitations, we introduce a novel model that comprehensively accounts for all IFR-induced effects while avoiding any expansion approximations, by incorporating IFR-modified subband energies and wave-functions obtained from the numerical solution of the Schrödinger equation during the calculation of IFR scattering matrix elements. In addition, we have included models for other relevant scattering mechanisms, including charged dislocation lines, ionized impurities, acoustic phonons, and polar optical phonons. A comprehensive numerical analysis of carrier mobility has been performed for an AlN/GaN high electron mobility transistor, yielding results consistent with experimental data. Furthermore, to investigate the impact of device architecture on 2DEG mobility, we study the effects of layer thickness and modulation doping profiles in AlN/GaN digital alloys. Our findings reveal strategies for engineering high mobility at elevated 2DEG concentrations, potentially advancing the development of high-performance semiconductor devices.

Sub-Alfvénic Turbulence: Magnetic-to-kinetic Energy Ratio, Modification of Weak Cascade, and Implications for Magnetic Field Strength Measurements

We study the properties of sub-Alfvénic magnetohydrodynamic (MHD) turbulence, i.e., turbulence with Alfvén mach number M A = V L /V A < 1, where V L is the velocity at the injection scale and V A is the Alfvén velocity. We demonstrate that MHD turbulence can have different properties, depending on whether it is driven by velocity or magnetic fluctuations. If the turbulence is driven by isotropic bulk forces acting upon the fluid, i.e., is velocity driven, in an incompressible conducting fluid we predict that the kinetic energy is MA−2 times larger than the energy of magnetic fluctuations. This effect arises from the long parallel wavelength tail of the forcing, which excites modes with k ∥/k ⊥ < M A. We also predict that as the MHD turbulent cascade reaches the strong regime, the energy of slow modes exceeds the energy of Alfvén modes by a factor MA−1 . These effects are absent if the turbulence is driven through magnetic fluctuations at the injection scale. We confirm our predictions with numerical simulations. Since the assumption of magnetic and kinetic energy equipartition is at the core of the Davis–Chandrasekhar–Fermi (DCF) approach to measuring magnetic field strength in sub-Alfvénic turbulence, we conclude that the DCF technique is not universally applicable. In particular, we suggest that the dynamical excitation of long azimuthal wavelength modes in the galactic disk may compromise the use of the DCF technique. We discuss alternative expressions that can be used to obtain magnetic field strength from observations and consider ways of distinguishing the cases of velocity and magnetically driven turbulence using observational data.