Rotation Parameters Research Articles

Entropy analysis of MHD hybrid nanofluid in a rotating channel filled with porous material

This study investigates entropy generation of MHD hybrid nanofluid in a rotating channel filled with porous material. The hybrid nanofluid, which uses Cu and alumina nanoparticles along with water as the base fluid, has been used. The hybrid model equations were solved numerically using MATLAB’s ode15s which employs Runge-Kutta–Fehlberg scheme. Effects of entropy generation and other system variables were investigated. Parametric analysis reveals that, hybrid nanofluids show better heat transport capacities with a higher Nusselt number than Cu–water and alumina-water nanofluids. Thus, because of its improved thermal characteristics, the hybrid nanofluid transfers more heat, which makes it a better option for applications that need effective heat dissipation. The results show that, increasing the Biot number reduces temperature, while hybrid nanofluids yield a higher Bejan number, indicating more efficient heat transfer with minimized entropy generation. The study identifies increased friction between fluid and porous media as the cause of temperature rise with higher porous media resistance and shape factor parameters. It is also depicted that, the rate of entropy generation decreases as the Biot number Bi rises, this happens as a result of the channel’s temperature gradient being less pronounced at higher Bi, which reduces thermal irreversibility and, in turn, entropy generation. The findings also demonstrate that the presence of a magnetic field reduces axial velocity while increasing transverse velocity. Consequently, skin friction increases in the axial direction and decreases in the transverse direction. In addition, the increase of rotational parameter has been found to reduce skin friction to the greatest extent. These findings underscore the potential of hybrid nanofluids in optimizing thermal systems by reducing entropy generation and enhancing heat transfer efficiency.

High resolution laser diode spectroscopy of the hot bands of C2HD in the first overtone region of C-H stretching

The frequencies of C2HD hot bands ro-vibrational lines of the first overtone of C-H stretching were measured using tunable diode lasers. To expand the measuring range to the region of the large rotational numbers, a heated gas cell was used. Measurements were made in the range R1–R36 and P2–P14 for the transition (2,0,0,1,0) ← (0,0,0,1,0), and in the range R1–R18 for the transition (2,0,0,0,1) ← (0,0,0,0,1). The rotational parameters of the upper and lower states for the band (2,0,0,1,0) ← (0,0,0,1,0) were determined. The doublet structure of ro-vibrational lines was studied. For the transition (2,0,0,1,0) ← (0,0,0,1,0), a sharp increase in the splitting value was detected at J > 25.

High resolution analysis of the CD[formula omitted] deuterated methane: Extended investigation of the pentad region

A highly accurate rotational–vibrational analysis of Fourier transform infrared spectra of the 12CD4 molecule is presented. The high resolution infrared spectra were measured with a IFS125 HR Fourier transform interferometer from Bruker at an optical resolution of 0.003 cm−1 and analyzed in the 1750–2400 cm−1 region. Here the 2ν2, ν2+ν4, 2ν4, ν1 and ν3 bands (altogether, nine sub-bands of different symmetry) of the pentad are located. The number of 1213/1993/1576/77/1582 transitions with the Jmax = 23/23/23/14/32 were assigned to the 2ν2, ν2+ν4, 2ν4, ν1 and ν3 bands of 12CD4. The obtained experimental data were used for the determination of the upper ro-vibrational energy values. To provide more correct values of the upper energies, more than 7800 highly accurate “hot” transitions from the dyad region were additionally processed. In general, 4088 upper ro-vibrational energies of the pentad (for comparison, 2525 upper ro-vibrational energies with the value of Jmax=20 are known in the modern literature up to now) were determined, which were used then in the weighted fit procedure with a goal to determine the spectroscopic parameters (band centers, rotational, centrifugal distortion, tetrahedral splitting and resonance interaction parameters) of the effective Hamiltonian. The obtained drms value is 5.5×10−4 cm−1 which is almost one hundred times better than the reproduction of the same set of experimental data by the parameters known in the earlier literature.

Rotational Motion Compensation for ISAR Imaging Based on Minimizing the Residual Norm

In inverse synthetic aperture radar (ISAR) systems, image quality often suffers from the non-uniform rotation of non-cooperative targets. Rotational motion compensation (RMC) is necessary to perform refocused ISAR imaging via estimated rotational motion parameters. However, estimation errors tend to accumulate with the estimated processes, deteriorating the image quality. A novel RMC algorithm is proposed in this study to mitigate the impact of cumulative errors. The proposed method uses an iterative approach based on a novel criterion, i.e., the minimum residual norm of the signal phases, to estimate different rotational parameters independently to avoid the issue caused by cumulative errors. First, a refined inverse function combined with interpolation is proposed to perform the RMC procedure. Then, the rotation parameters are estimated using an iterative procedure designed to minimize the residual norm of the compensated signal phases. Finally, with the estimated parameters, RMC is performed on signals in all range bins, and focused images are obtained using the Fourier transform. Furthermore, this study utilizes simulated and real data to validate and evaluate the performance of the proposed algorithm. The experimental results demonstrate that the proposed algorithm shows dominance in the aspects of estimation accuracy, entropy values, and focusing characteristics.

Polar Motion Ultra-Short-Term Prediction of Least-Squares+Multivariate Autoregressive Hybrid Method by Using the Kalman Filter.

The polar motion (PM, including two parameters PMx and PMy) ultra-short-term prediction (1-10 days) is demanded in the real-time navigation of satellites and spacecrafts. Improving the PMx and PMy ultra-short-term predictions accuracies are a key to optimize the performance of these related applications. Currently, the least squares (LS)+autoregressive (AR) hybrid method is regarded as one of the most capable approaches for ultra-short-term predictions of PMx and PMy. The Kalman filter has proven to be effective in improving the ultra-short-term prediction performance of the LS+AR hybrid method, but the PMx and PMy ultra-short-term predictions accuracies are still not able to satisfy some related applications. In order to improve the performance of PM ultra-short-term prediction, it is worth exploring the combinations of existing methods. Throughout the existing predicted methods, the LS+multivariate autoregressive (MAR) hybrid method by using the Kalman filter has the potential to improve the accuracy of PM ultra-short-term prediction. In addition, a PM prediction performance analysis of the LS+MAR hybrid method by using the Kalman filter, namely the LS+MAR+Kalman hybrid method, is still missing. In this contribution, we proposed the LS+MAR+Kalman hybrid method for PM ultra-short-term prediction. The data sets for PM predictions, which range from 1 to 10 days, have been tested based on the International Earth Rotation and Reference Systems Service Earth Orientation Parameter (IERS EOP) 14 C04 series to assess the performance of the LS+MAR+Kalman hybrid model. The experimental results illustrated that the LS+MAR+Kalman hybrid method can effectively execute PMy ultra-short-term predictions. The improvement of PMy prediction accuracy can rise up to 12.69% for 10-day predictions, and the improvement of ultra-short-term predictions is 7.64% on average.

A numerical analysis of the rotational flow of a hybrid nanofluid past a unidirectional extending surface with velocity and thermal slip conditions

Abstract This work inspects 3D magnetohydrodynamic hybrid nanofluid flow on a permeable elongating surface. The emphasis of this paper is on the study of hybrid nanofluid flow within a rotating frame, taking into account the simultaneous impact of both thermal and velocity slip boundary conditions. The chosen base fluid is water, and the hybrid nanofluid comprises two nanoparticles Cu \text{Cu} and Al 2 O 3 {\text{Al}}_{2}{\text{O}}_{3} . The effect of the magnetic and porosity parameters is taken into account in the momentum equation. The thermal radiation, Joule heating, and heat source are considered in the energy equation. Using a similarity system, we transform the PDEs of the proposed model into ODEs, which are then solved numerically by the bvp4c technique. The magnetic field shows a dual nature on primary and secondary velocities. Enrich magnetic field decreases the primary velocity and enhances the secondary velocity. The rotation parameter has an inverse relation with both velocities. The temperature profile amplified with the escalation in heat source, magnetic field, rotation factor, and Eckert numbers. The skin friction is boosted with magnetic parameters while the Nusselt number drops.

Effects of nonthermality on dust-acoustic surface waves with dust rotation

Abstract Dust Acoustic Surface Waves (DASWs) real frequency and group velocity are investigated for semi-bounded dusty plasma whose electrons and ions are modeled by Cairn s Distribution Function (CDF) while massive particles i.e. dust are treated Maxwellian. Kinetic approach based on Vlasov-Poisson s set of equations is used for the derivation of plasma dispersion relation. It is observed that in the presence of rotational parameter r and the variation of nonthermal index α affect both real frequency and group velocity of the wave significantly. This study has wide astrophysical applications.

Schwarzschild modelling of barred s0 galaxy NGC 4371

ABSTRACT We apply the barred Schwarzschild method developed by Tahmasebzadeh et al. (2022) to a barred S0 galaxy, NGC 4371, observed by IFU instruments from the TIMER and ATLAS3D projects. We construct the gravitational potential by combining a fixed black hole mass, a spherical dark matter halo, and stellar mass distribution deprojected from 3.6 μm S$^4$G image considering an axisymmetric disc and a triaxial bar. We independently modelled kinematic data from TIMER and ATLAS3D. Both models fit the data remarkably well. We find a consistent bar pattern speed from the two sets of models with $\Omega _{\rm p} = 23.6 \pm 2.8 \, \mathrm{km \, s^{-1} \, kpc^{-1} }$ and $\Omega _{\rm p} = 22.4 \pm 3.5 \, \mathrm{km \, s^{-1} \, kpc^{-1} }$, respectively. The dimensionless bar rotation parameter is determined to be $\mathcal {R} \equiv R_{\rm cor}/R_{\rm bar}=1.88 \pm 0.37$, indicating a likely slow bar in NGC 4371. Additionally, our model predicts a high amount of dark matter within the bar region ($M_{\rm DM}/ M_{\rm total}$$\sim 0.51 \pm 0.06$), which, aligned with the predictions of cosmological simulations, indicates that fast bars are generally found in baryon-dominated discs. Based on the best-fitting model, we further decompose the galaxy into multiple 3D orbital structures, including a BP/X bar, a classical bulge, a nuclear disc, and a main disc. The BP/X bar is not perfectly included in the input 3D density model, but BP/X-supporting orbits are picked through the fitting to the kinematic data. This is the first time a real barred galaxy has been modelled utilizing the Schwarzschild method including a 3D bar.

Comparative numerical study between MHD Forchheimer nano and hybrid nanofluid flows over stretching sheet under aligned magnetic field in the presence of radiation absorption

ABSTRACT This study investigates the mass and heat transfer properties of Ag-H2O nanofluid MHD Forchheimer flows and Ag-MoS2/H2O hybrid nanofluid over two-dimensional linear stretching surfaces in aligned magnetic fields with absorption of radiation. The fluid experiences rotational motion around the vertical axis at a consistent angular speed. The system of nonlinear ODEs is derived from the set of nonlinear PDEs by use of similarity transformations. The BVP-5C shooting approach in MATLAB is then employed to solve the associated system of ODEs. As the Forchheimer number, porosity parameter, rotation parameter and aligned magnetic field exhibit an ascent, the velocity profile along the x-axis and y-axis experiences a decrement. Simultaneously, an augmentation in the magnetic parameter, thermal radiation and rotation parameter induces a heightened temperature profile. Additionally, greater values of the Forchheimer number, rotation parameter and magnetic parameters correspond to an increase in concentration profile. Furthermore, the results indicated an increased temperature profile in the Ag-MoS2/H2O hybrid nanofluid compared to that in the Ag-H2O nanofluid for magnetic, rotation and radiation parameters. Also, the concentration profile of magnetic and rotation parameters along with the Forchheimer number were noted to be higher in the Ag-MoS2/H2O hybrid nanofluid compared to that in the Ag-H2O nanofluid.

Significance of tri‐hybrid nanoparticles on the dynamics of Ellis rotating nanofluid with thermal stratification

AbstractThe fluids flow containing nano size particles is essential in industrial applications, especially in nuclear cooling system and nuclear reactor to increase the energy performance. In connection to this, a trihybrid Ellis rotating nanofluid flow through a stretching surface for increasing the heat transportation is presented. By suspending three different types of nano size particles the trihybrid nanofluid is formed with distinct chemical and physical connection into base liquid. In this article, the nano size particles , and are mixed in (water). This type of mixture helps in degradation of noxious substances, cleaning environmental and many other appliances that requires the cooling effect. In addition, the linear thermal radiation is also considered. The governing equations of the flow and fluid temperature are minimized to ordinary differential equations and these equations are solved by Runge Kutta order fourth (RK45) approach. The approximate results are analyzed via graphs and the results reveal that thermal conductivity of trihybrid nano type fluid is more valuable as compared to hybrid and single nanofluid. Higher values of magnetic and rotational parameter have aggrandized the fluid temperature and opposite trend has observed for Ellis and thermal stratification parameter. Moreover, the results are compared with previous literature and found an excellent agreement.

Perfect Monomial Prediction for Modular Addition

Modular addition is often the most complex component of typical Addition- Rotation-XOR (ARX) ciphers, and the division property is the most effective tool for detecting integral distinguishers. Thus, having a precise division property model for modular addition is crucial in the search for integral distinguishers in ARX ciphers. Current division property models for modular addition either (a) express the operation as a Boolean circuit and apply standard propagation rules for basic operations (COPY, XOR, AND), or (b) treat it as a sequence of smaller functions with carry bits, modeling each function individually. Both approaches were originally proposed for the twosubset bit-based division property (2BDP), which is theoretically imprecise and may overlook some balanced bits.Recently, more precise versions of the division property, such as parity sets, threesubset bit-based division property without unknown subsets (3BDPwoU) or monomial prediction (MP), and algebraic transition matrices have been proposed. However, little attention has been given to modular addition within these precise models.The propagation rule for the precise division property of a vectorial Boolean function f requires that u can propagate to v if and only if the monomial πu(x) appears in πv(f). Braeken and Semaev (FSE 2005) studied the algebraic structure of modular addition and showed that for x ⊞ y = z, the monomial πu(x)πv(y) appears in πw(z) if and only if u + v = w. Their theorem directly leads to a precise division property model for modular addition. Surprisingly, this model has not been applied in division property searches, to the best of our knowledge.In this paper, we apply Braeken and Semaev’s theorem to search for integral distinguishers in ARX ciphers, leading to several new results. First, we improve the state-of-the-art integral distinguishers for all variants of the Speck family, significantly enhancing search efficiency for Speck-32/48/64/96 and detecting new integral distinguishers for Speck-48/64/96/128. Second, we determine the exact degrees of output bits for 7-round Speck-32 and all/16/2 output bits for 2/3/4-round Alzette for the first time. Third, we revisit the choice of rotation parameters in Speck instances, providing a criterion that enhances resistance against integral distinguishers. Additionally, we offer a simpler proof for Braeken and Semaev’s theorem using monomial prediction, demonstrating the potential of division property methods in the study of Boolean functions.We hope that the proposed methods will be valuable in the future design of ARX ciphers.

Maximal transport of non-Newtonian fluid in an anisotropic rotating porous channel with an inclined magnetic field

This study explores the flow characteristics of a viscous, incompressible, conducting Jeffrey fluid in a rotating channel filled with anisotropic porous medium with an inclined magnetic field. The study has relevance to fluid motion in striated rock formations and seepage flow in rotating systems across insulation or geological layers. The channel's rotation axis and a principal axis of the permeability tensor are perpendicular to the walls. The flow is described by the Darcy–Brinkman model under no-slip boundary conditions, applicable in regenerative heat exchangers. Key parameters include the rotation rate and the lateral permeabilities. They have significant impacts on flow behavior. Fluid velocity consists of a primary component aligned with the pressure gradient and a secondary component influenced by the Coriolis force. The variation in lateral permeabilities affects the convexity of the velocity profile, while the magnetic field allows for control of both velocity and volumetric flow rates. The Jeffrey parameter and the inclination angle further enhance the flow behavior. This study provides comprehensive analysis through tables and figures for various values of the anisotropic Darcy number and the rotation parameter, detailing the model's physical properties. The effects of the product of skin friction and the Reynolds number are also discussed, with results aligning with the existing literature for limiting cases. These findings offer valuable insights into fluid behavior in complex environments where rotation, porous structures, and magnetic fields interact with implications for process optimization, resource recovery, and sustainable engineering practices.

Bondi-Hoyle-Lyttleton accretion around the rotating hairy Horndeski black hole

Modeling of the shock cone formed around a stationary, hairy Horndeski black hole with Bondi-Hoyle-Lyttleton (BHL) accretion has been conducted. We model the dynamical changes of the shock cone resulting from the interaction of matter with the Horndeski black hole, where the scalar field and spacetime have a strong interaction. The effects of the scalar hair, the black hole rotation parameter, and the impacts of the asymptotic speed have been examined, revealing the influence of these parameters on the shock cone and the trapped QPO modes within the cone. Numerical calculations have shown that the hair parameter significantly affects the formation of the shock cone. As the absolute value of the hair parameter increases, the matter in the region of the shock cone is observed to move away from the black hole horizon. The rate of matter expulsion increases as h/M changes. After h/M < -0.6, a visible change in the physical structure of the shock cone occurs, ultimately leading to the complete removal out of the shock cone. On the other hand, it has been revealed that the asymptotic speed significantly affects the formation of the shock cone. As h/M increases in the negative direction and the asymptotic speed increases, the stagnation point moves closer to the black hole horizon. When the value of the hair parameter changes, the rest-mass density of the matter inside the cone decreases, whereas the opposite is observed with the asymptotic speed. Additionally, the formed shock cone has excited QPO modes. The deformation of the cone due to the hair parameter has led to a change or complete disappearance of the QPOs. Meanwhile, at asymptotic speeds of V ∞/c < 0.4, all fundamental frequency modes are formed, while at V ∞/c = 0.4, only the azimuthal mode is excited, and 1:2:3:4:… resonance conditions occur. No QPOs have formed at V ∞/c = 0.6. The results obtained from numerical calculations have been compared with theoretical studies for M87*, and it has been observed that the possible values of h/M found in the numerical simulations are consistent with the theory. Additionally, the results have been compared with those for the GRS 1915+105 black hole, and the hair parameters corresponding to the observed frequencies have been determined.

Flow past a rotating porous sphere in the existence of a toroidal magnetic field

This model consists of a porous spherical body rotating in an incompressible conducting fluid in the existence of a toroidal magnetic field. The toroidal field is generated by an electric dipole along the axis of symmetry. The model is split into two parts—the clear fluid region and the porous sphere. The clear fluid area is driven by the momentum equation and the permeable sphere region is driven by the Brinkman equation. The study is being done for the scenario where the impact of viscous force is much more than inertia force. The expression is found for fluid velocity and stream function by the superposition method. The results depict the impact of rotational parameters and the Darcy number on separation parameter. It is shown that the separation is low for the highly permeable sphere.

Asteroseismic signatures of core magnetism and rotation in hundreds of low-luminosity red giants

ABSTRACT Red giant stars host solar-like oscillations which have mixed character, being sensitive to conditions both in the outer convection zone and deep within the interior. The properties of these modes are sensitive to both core rotation and magnetic fields. While asteroseismic studies of the former have been done on a large scale, studies of the latter are currently limited to tens of stars. We aim to produce the first large catalogue of both magnetic and rotational perturbations. We jointly constrain these parameters by devising an automated method for fitting the power spectra directly. We successfully apply the method to 302 low-luminosity red giants. We find a clear bimodality in core rotation rate. The primary peak is at $\delta \nu _{\mathrm{rot}}$ = 0.32 $\mu$Hz, and the secondary at $\delta \nu _{\mathrm{rot}}$ = 0.47 $\mu$Hz. Combining our results with literature values, we find that the percentage of stars rotating much more rapidly than the population average increases with evolutionary state. We measure magnetic splittings of 2$\sigma$ significance in 23 stars. While the most extreme magnetic splitting values appear in stars with masses $\gt $1.1 M$_{\odot }$, implying they formerly hosted a convective core, a small but statistically significant magnetic splitting is measured at lower masses. Asymmetry between the frequencies of a rotationally split multiplet has previously been used to diagnose the presence of a magnetic perturbation. We find that of the stars with a significant detection of magnetic perturbation, 43 per cent do not show strong asymmetry. We find no strong evidence of correlation between the rotation and magnetic parameters.

Hydromagnetic Turbulent Flow in Porous Media Over a Stretching Surface in a Rotating System with Heat

This study investigates the combined effects of magnetic fields, buoyancy forces, porosity, rotation, and Joule’s heating on fluid flow and heat transfer dynamics. The analysis is performed using a numerical approach, with the system oriented along three axes: the z-axis aligned with the plate, the y-axis perpendicular to the plate, and the x-axis orthogonal to the y-z plane. An infinite plate extends along the x and z axes, with a uniform transverse magnetic field applied parallel to the y-axis. By employing the finite difference method in MATLAB, we explore how various dimensionless parameters influence temperature and velocity profiles. Our findings reveal that an increase in the local temperature Grashof number enhances primary velocity while reducing secondary velocity near the fixed end. Temperature profiles show a decrease near the plate, increasing further away. The study also highlights that a higher Joule heating parameter leads to elevated primary velocity and temperature profiles but diminishes secondary velocity. Additionally, increasing rotational parameters is observed to decrease both primary and secondary velocities while augmenting temperature profiles near the plate. These results underscore the significant role that magnetic fields, rotational effects, and Joule heating play in modulating fluid flow and thermal behavior. The insights gained from this study can inform the design and optimization of engineering systems where control of velocity and temperature profiles is critical.

External parameter calibration of laser scanner based on the combination of plane-control-based and plane-constraints-based methods

Accurate calibration of the external parameters of a laser scanner is crucial to ensure consistency in data representation from multiple sources. Plane features, known for their simplicity and ease of extraction, are widely used in external parameter calibration. The use of control planes with known plane parameters enables the simultaneous estimation of both translation and rotation parameters, while the use of planes with unknown parameters allows for efficient self-calibration. In this paper, we introduce a novel method that combines the strengths of both types of plane calibration methods to calibrate the external parameters of a laser scanner. The approach, with the help of a Gauss-Helmert adjustment model, integrates control and constraint planes to calibrate the external parameters. The method boasts the ease and accessibility offered by the plane constraint method, utilizing fewer control features while successfully estimating the external parameters of the laser scanner. To evaluate the feasibility of this method, two sets of 12 calibration experiments were conducted on the mobile measurement system platform. Notably, the residual Root Mean Square Errors (RMSE) obtained from these experiments were comparable to those achieved using traditional plane-control-based method. Furthermore, the external parameter correlation aligns with that obtained using the plane-control-based method, while the plane parameter correlation exhibits similarity to that obtained using the plane-constraint-based method. These results confirm that our method effectively minimizes the requirement for control features and enables more convenient calibration of the external parameters of the laser scanner.

Analysis of shape-change capabilities for the two-stage tensegrity tower

Two-layer spliced tensegrity structure can be used to design a flight simulator. Structural motions are caused by the shape changes. So, it is necessary to investigate the structural deformation. Considering the tensegrity structure with redundant cables is more resistant to destruction, this paper is devoted to analyzing shape changes of the two-stage tensegrity tower with redundant cables. Based on the principle of the minimum number of cables with different lengths, structural parameters of a two-stage tensegrity tower composed of two prisms with opposite rotation and other parameters are determined. Further, this paper defines five shape-changes: stretching, shrinking, flexure, shear and torsion. According to the five shape-change types, the axial, coupling, and complex deformations of a tensegrity tower are analyzed. Based on the energy-efficient cable-actuation strategy, this paper also studies the drive mode with the least energy dissipation for shape changes. The results show that the deformation energy consumption ratios of shrinking and stretching deformations are 9.634 and 12.674, respectively, under the optimal driving mode. The significance of the shape-change analysis is that it can predict the driving mode of the cable.

Hybrid differential evolution algorithm for Falkner-Skan flow with rotation

A hybrid differential evolution algorithm is used in this work to study the rotating transport of Falkner-Skan flow. The problem is modeled as an equivalent optimization problem by using Padé rational approximation functions. The primary model of the governing partial differential equations is imposed to subjugate the error between profiles. A hybrid evolutionary algorithm based on differential evolution and a convergent version of Nelder-Mead direct search algorithm is employed to perform global exploratory search along with an enhanced exploitation to improve the accuracy of the proposed solution scheme. The resulting scheme is named as evolutionary Padé approximation (EPA) scheme. The performance of the proposed EPA scheme on the Falkner-Skan boundary value problem is investigated by considering various values of the rotation parameters. The developed optimizer in EPA scheme was able to minimize the residuals up to10−10. Results are displayed graphically in order to study the effect of various types of parameters. EPA scheme determined that angular velocity increases or decreases accordingly as fluid parameter (β) and the rotation parameter (λ) but shows inverse behavior with respect to power law index(n). Similarly, the response of velocity profile along y−axis was decreasing function of β as well as n but increasing function of λ. The performance of the proposed EPA scheme has been demonstrated by comparing results with a hybrid neural network scheme and found in excellent agreement.

Solar Rotation and Activity for Cycle 24 from SDO/AIA Observations

Differential rotation plays a crucial role in the dynamics of the Sun. We study the solar rotation and its correlation with solar activity by applying a modified machine learning algorithm to identify and track coronal bright points (CBPs) from the Solar Dynamics Observatory/Atmospheric Imaging Assembly observations at 193 Å during cycle 24. For more than 321,440 CBPs, the sidereal and meridional velocities are computed. We find the occurring height of CBPs to be about 5627 km above the photosphere. We obtain a rotational map for the corona by tracking CBPs at the formation height of Fe xii (193 Å) emissions. The equatorial rotation (14.°40 to 14.°54 day−1) and latitudinal gradient of rotation (−3.°0 to −2.°64 day−1) show very slightly positive and negative trends with solar activity (sunspots and flares), respectively. For cycle 24, our investigations show that the northern hemisphere has more differential rotation than the southern hemisphere, confirmed by the asymmetry of the midlatitude rotation parameter. The asymmetry (ranked) of the latitudinal gradient of the rotation parameter is concordant with the sunspot numbers for 7 yr within the 9 yr of the cycle; however, for only 3 yr, it is concordant with the flare index. The minimum horizontal Reynolds stress changes from about −2500 m2 s−2 (corresponding to high activity) in 2012 and 2014 to −100 m2 s−2 (corresponding to low activity) in 2019 over 5° to 35° latitudes within cycle 24. We conclude that the negative horizontal Reynolds stress (momentum transfer toward the Sun’s equator) is a helpful indication of solar activity.