Physics MDPI

📢 We are excited to share the good news that Physics MDPI received a new Impact Factor of 1.5, ranking Q2 in the "PHYSICS, MULTIDISCIPLINARY" category; new CiteScore of 3. 🎉 Thanks for the support of Editorial Board Members, reviewers and authors! MDPI; #OpenAccess #physics

Heating and Cooling in Transversely Oscillating Coronal Loops Powered by Broadband, Multi-Directional Wave Drivers | Article by Thomas Howson and Ineke De Moortel https://lnkd.in/grGaVX7u University of St Andrews; University of Oslo; MDPI #solar #corona #MHD #magnetohydrodynamics #oscillations #physics This article belongs to the Special Issue: A Themed Issue in Honor of Professor Marcel Goossens on the Occasion of His 75th Birthday https://lnkd.in/eQhx9x5A #Abstract Recent studies have identified the potential for coronal wave heating to balance radiative losses in a transversely oscillating low-density loop undergoing resonant absorption, phase mixing and the Kelvin–Helmholtz instability. This result relied on a continuous, resonant oscillatory driver acting on one of the loop footpoints and similar setups with non-resonant driving produce insufficient heating. Here, we consider broadband and multi-directional drivers with power in both resonant and non-resonant frequencies. Using three-dimensional magnetohydrodynamic simulations, we impose transverse, continuous velocity drivers at the footpoints of a coronal loop, which is dense in comparison to the background plasma. We include the effects of optically thin radiation and a uniform background heating term that maintains the temperature of the external plasma but is insufficient to balance energy losses within the loop. For both broadband and multi-directional drivers, we find that the energy dissipation rates are sufficient to balance the average energy losses throughout the simulation volume. Resonant components of the wave driver efficiently inject energy into the system and these frequencies dominate the energetics. Although the mean radiative losses are balanced, the loop core cools in all cases as the wave heating rates are locally insufficient, despite the relatively low density considered here.

Editor's Choice 📢 Electron as a Tiny Mirror: Radiation from a Worldline with Asymptotic Inertia | Communication by Michael R. R. Good and Yen Chin Ong https://lnkd.in/gTQMQBSB This article belongs to the Special Issue Vacuum Fluctuations (https://lnkd.in/giM8cvCX) Nazarbaev University;National Taiwan University; Yangzhou University; Shanghai Jiao Tong University; MDPI #acceleration #radiation #moving #mirrors #charges #quantum #blackholes #Davies-Fulling-Unruh effect #physics #Abstract We present a moving mirror analog of the electron, whose worldline possesses asymptotic constant velocity with corresponding Bogoliubov 𝛽 coefficients that are consistent with finite total emitted energy. Furthermore, the quantum analog model is in agreement with the total energy obtained by integrating the classical Larmor power.

The Impact of Radio Frequency Waves on the Plasma Density in the Tokamak Edge | Article by Dirk Van Eester and Nil Tournay https://lnkd.in/g8cSrXce Laboratory for Plasma Physics - ERM/KMS MDPI #radio #frequency #waves #ponderomotive #force #physics #Abstract A simple model is presented to describe how the radio frequency electromagnetic field modifies the plasma density the antenna faces in tokamaks. Aside from “off-the-shelf” equations standardly used to describe wave-plasma interaction relying on the quasilinear approach, it invokes the ponderomotive force in presence of the confining static magnetic field. The focus is on dynamics perpendicular to the 𝐵𝑜 magnetic field. Stronger fields result in density being pushed further away from the launcher and in stronger density asymmetry along the antenna.

Quantum Configuration and Phase Spaces: Finsler and Hamilton Geometries | Article by Saulo Albuquerque, Valdir B. Bezerra, Iarley P. Lobo, Gabriel Macedo, Pedro H. Morais, Ernesto Rodrigues, Luis C. N. Santos and Gislaine Varão https://lnkd.in/gWb-iwqP This article belongs to the Special Issue New Advances in Quantum Geometry (https://lnkd.in/gUDzYj3C) Universidade Federal da Paraíba;Universidade Federal de Lavras;MDPI #quantum #gravity #phenomenology #Finsler #geometry #Hamilton #geometry #physics

Advances in the Implementation of the Exactly Energy Conserving Semi-Implicit (ECsim) Particle-in-Cell Method | Article by Giovanni Lapenta KADOC-University of Leuven Center for mathematical Plasma Astrophysics; MDPI This article belongs to the Special Issue A Themed Issue in Honor of Professor Marcel Goossens on the Occasion of His 75th Birthday https://lnkd.in/eQhx9x5A #particle-in-cell; #energy #conservation; #subcycling #Abstract The energy-conserving semi-implicit (ECsim) method presented by the author in 2017, is a particle-in-cell (PIC) algorithm for the simulation of plasmas. Energy conservation is achieved within a semi-implicit formulation that does not require any non-linear solver. A mass matrix is introduced to linearly express the particle-field coupling. With the mass matrix, the algorithm preserves energy conservation to machine precision. The construction of the mass matrix is the central nature of the method and also the main cost of the computational cycle. Here, three methods that modify the construction of the mass matrix are analyzed. First, the paper considers how the sub-cycling of the particle motion modifies the mass matrix. Second, a form of smoothing that reduces the noise while retaining exact energy conservation is introduced. Finally, an approximation of the mass matrix is discussed that transforms the ECsim scheme to the implicit moment method.

Al-Doped ZnO Thin Films with 80% Average Transmittance and 32 Ohms per Square Sheet Resistance: A Genuine Alternative to Commercial High-Performance Indium Tin Oxide | Article by Ivan Ricardo Cisneros-Contreras, Geraldine López-Ganem, Oswaldo Sánchez-Dena, Yew Hoong Wong, Ana Laura Pérez-Martínez and Arturo Rodríguez-Gómez https://lnkd.in/g79vu4j7 Universidad Nacional Autónoma de México;Universidad Autónoma de Ciudad Juárez;Consejo Nacional de Ciencia y Tecnología (CONACYT);University of Malaya;MDPI #Al-doped #ZnO #alternative #commercial #TCOs #ultrasonic #spray #pyrolysis #transparent #Abstract In this study, a low-sophistication low-cost spray pyrolysis system built by undergraduate students is used to grow aluminum-doped zinc oxide thin films (ZnO:Al). The pyrolysis system was able to grow polycrystalline ZnO:Al with a hexagonal wurtzite structure preferentially oriented on the c-axis, corresponding to a hexagonal wurtzite structure, and exceptional reproducibility. The ZnO:Al films were studied as transparent conductive oxides (TCOs). Our best ZnO:Al TCO are found to exhibit an 80% average transmittance in the visible range of the electromagnetic spectrum, a sheet resistance of 32 Ω/□, and an optical bandgap of 3.38 eV. After an extensive optical and nanostructural characterization, we determined that the TCOs used are only 4% less efficient than the best ZnO:Al TCOs reported in the literature. This latter, without neglecting that literature-ZnO:Al TCOs, have been grown by sophisticated deposition techniques such as magnetron sputtering. Consequently, we estimate that our ZnO:Al TCOs can be considered an authentic alternative to high-performance aluminum-doped zinc oxide or indium tin oxide TCOs grown through more sophisticated equipment.

Thermosolutal Marangoni Convection for Hybrid Nanofluid Models: An Analytical Approach | Article by Ulavathi Shettar Mahabaleshwar, Rudraiah Mahesh and Filippos Sofos https://lnkd.in/gtAHcZ3g Davangere University, Davangere; University of Thessaly; MDPI #MHD #porous #media #thermal #radiation #heat #sink #hybrid #nanofluid #physics #Abstract The present study investigates the effect of mass transpiration on heat absorption/generation, thermal radiation and chemical reaction in the magnetohydrodynamics (MHD) Darcy–Forchheimer flow of a Newtonian fluid at the thermosolutal Marangoni boundary over a porous medium. The fluid region consists of H2O as the base fluid and fractions of TiO2–Ag nanoparticles. The mathematical approach given here employs the similarity transformation, in order to transform the leading partial differential equation (PDE) into a set of nonlinear ordinary differential equations (ODEs). The derived equations are solved analytically by using Cardon’s method and the confluent hypergeometric function. The solutions are further graphically analyzed, taking into account parameters such as mass transpiration, chemical reaction coefficient, thermal radiation, Schmidt number, Marangoni number, and inverse Darcy number. According to our findings, adding TiO2–Ag nanoparticles into conventional fluids can greatly enhance heat transfer. In addition, the mixture of TiO2–Ag with H2O gives higher heat energy compared to the mixture of only TiO2 with H2O.

Probability Distribution Functions of Solar and Stellar Flares | Article by Takashi Sakurai https://lnkd.in/gx_Zjn_C National Astronomical Observatory of Japan; MDPI #solar #physics #flares #Xrays #coronal #space #weather #stellar #statistical #openaccess This article belongs to the Special Issue: A Themed Issue in Honor of Professor Marcel Goossens on the Occasion of His 75th Birthday https://lnkd.in/eQhx9x5A #Abstract The paper studies the soft X-ray data of solar flares and found that the distribution functions of flare fluence are successfully modeled by tapered power law or gamma function distributions whose power exponent is slightly smaller than 2, indicating that the total energy of the flare populations is mostly due to a small number of large flares. The largest possible solar flares in 1000 years are predicted to be around X70 (a peak flux of 70 × 10−4 W m−2) in terms of the GOES (Geostationary Operational Environmental Satellites) flare class. The paper also studies superflares (more energetic than solar flares) from solar-type stars and found that their power exponent in the fitting of the gamma function distribution is around 1.05, which is much flatter than solar flares. The distribution function of stellar flare energy extrapolated downward does not connect to the distribution function of solar flare energy.

Study on the Thermodynamic Properties of Thin Film of FCC Interstitial Alloy AuSi at Zero Pressure Using the Statistical Moment Method | Article by Nguyen Thi Hoa, Nguyen Quang Hoc and Hua Xuan Dat https://lnkd.in/gRgkuTHg University of Transport and Communications; Hanoi National University of Education; MDPI #alloy #thinfilm #thermodynamic #statistical #physics #Abstract We built a model and proposed a theory about the thermodynamic properties of face-centered cubic (FCC) binary interstitial alloy’s thin films based on the statistical moment method and performed numerical calculations for AuSi (gold silicide). First, the statistical moment method (SMM) calculations for the thermodynamic properties of Au are compared with reported experiments and calculations that show a good agreement between the calculations in this paper and earlier studies. Additionally, the SMM calculations for thermodynamic properties of AuSi alloy films are performed, which show that the thermal expansion coefficient, the specific heat at constant volume, and the specific heat at constant pressure increases, while the isothermal elastic modulus decreases with increasing temperature and increasing interstitial atom concentration. Furthermore, when the number of layers reaches 100, the thermodynamic properties of the film are similar to those of the bulk material. The achieved theoretical results for AuSi films are novel and can be useful in designing future experiments.