Damghan University PressIranian Journal of Astronomy and Astrophysics2322-492410220231002Detecting a New Type of Stokes V Profiles Observed by Hinode in a Sunspot13915235210.22128/ijaa.2023.724.1165ENHashem HamedivafaPhysics Department,
Faculty of Science,
Imam Khomeini International UniversityJournal Article20230901A part of a mature sunspot including of umbrae and penumbrae is observationally examined to find photospheric dynamics. We analyze spectro-polarimetric observations of photospheric Fe~I lines with the Solar Optical Telescope aboard Hinode to find signatures of Doppler velocities on the Stokes V profiles. Stokes V profiles characterized by humps on both blue and red lobes with the same magnetic polarity as the sunspot umbrae were detected in both umbrae and penumbrae. These types of profiles have not been previously reported. Pixels whose Stokes V profiles show humps on, at least, either blue or red lobe are ubiquitous: 42.1\% show both humps; 36.8\% (3.7\%) show only blue (red) hump. Umbra shows profiles having both blue and red humps. Investigating the Stokes V profiles characterized by humps implies that all types of these profiles are the same entity with different hump amplitudes. This means that both blue and red humps alter the Stokes V profiles either as explicit humps or as tail extension of the lobes. The magnetic fields of these hidden structures have to be weak and almost vertical. This implies that two humps cannot belong to a single-2nd-component. Bidirectional flows propagating along vertical magnetic fields as the result of redirection of outflows along the vertical magnetic field, after a magnetic reconnection, gives a possible mechanism producing adjacent upflows and downflows. Blue and red humps can be the Doppler effect signatures of these upflows and downflows, respectively.https://ijaa.du.ac.ir/article_352_551c3234fc32f631a0054156bde7c764.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-492410220231002Quantum Thermodynamic Properties of a Moving Particle Next to a Surface in the Presence of Electromagnetic Field15316435710.22128/ijaa.2023.672.1144ENMarjan JafariDepartment of Physics, Faculty of Science, Imam Khomeini International University, P.O.Box 34148-96818, Qazvin, IranJournal Article20230412In this paper, we investigate the effect of the motion of a magnetodielectric particle on the quantum thermodynamic properties of a system. Specifically, we study the behavior of a polarizable and magnetizable dielectric particle moving above a semi-infinite bulk dielectric in the presence of an electromagnetic field. Using a microscopic approach, we propose a covariant Lagrangian for the combined system and obtain a dynamical covariant response of the moving particle. We calculate the emitted power from the work extracted by the electric and magnetic dipoles of the moving particle. We explicitly determine the behavior of the main thermodynamic functions of the system, including thermal correlation functions, free energy, mean energy, entropy, and heat capacity. It is found that the thermodynamic properties of the moving particle in the electromagnetic field depend on the properties of the semi-infinite bulk dielectric. Moreover, we demonstrate that the formulation of quantum thermodynamics for an electromagnetic system in uniform relative motion differs from its formulation in the rest-frame.https://ijaa.du.ac.ir/article_357_3026ccd7161e25bf0f4fad0dab909975.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-492410220231010Low-Redshift Observational Constraints on Dark Energy Cosmologies16519036010.22128/ijaa.2023.719.1164ENMohammad MalekjaniDept. of Physics. Bu-Ali Sina UniversityJournal Article20230828Applying the Markov chain Monte Carlo algorithm and using low-redshift observational data, we put cosmological constraints on dark energy cosmologies. Our main aim is to show the influence of each data sample on the procedure of constraining. The main results of our analysis are as follows. In the case of the Pantheon catalog of supernovae, one can put approximately three times tighter constraints on the cosmological parameters compared to the early Gold dataset. Combining the Pantheon with the Hubble data, we obtain $\sim 1.5$ times tighter constraints compared to the Pantheon solely. We show that in cluster scale due to low growth rate data with large error bars, one cannot put tight constraints on the cosmological parameters. Combining the expansion and growth rate data leads to tighter constraints on the cosmological parameters. While the local value of Hubble constant $H_0$ has a $\sim 3.4 \sigma$ tension with Planck inferred result, we show that by combining the expansion and growth data with local $H_0$ data, the tension is alleviated to a $1.7 \sigma$. Finally joining the Pantheon, Hubble data, growth rate, $H_0$ with the BAO measurements gets roughly $7-8\%$ tighter constraints on the matter density and Hubble constant parameters.https://ijaa.du.ac.ir/article_360_19410b203537edb44fb33f87cf345c3c.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-492410220231105Gravity-Assist might be a Solution to Save Earth from Global Warming19119936210.22128/ijaa.2023.733.1169ENSohrab RahvarDepartment of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran0000-0002-7084-5725Journal Article20230918Global warming is one of the problems of human civilization and decarbonization policy is the main solution to this problem. In this work, we propose an alternative method of using the gravity assist by the asteroids to increase the orbital distance of the Earth from the Sun. We can manipulate the orbit of asteroids in the asteroid belt by solar sailing and propulsion engines to guide them towards the Mars orbit and a gravitational scattering can put asteroids in a favorable direction to provide an energy loss scattering from the Earth. The result would be increasing the orbital distance of the earth and consequently cooling down the Earth's temperature. We calculate the increase in the orbital distance of the earth for each scattering. The time scale for lowering the orbit of an asteroid for a gravitational impact is $70$ years. For the consecutive of scatterings of asteroids, we investigate the feasibility of performing this project.https://ijaa.du.ac.ir/article_362_baef133b78ce6ec27144e8c318e1bad8.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-492410220231105Observation of Six Pre-Flare VLP Pulsations in Solar Corona20122036710.22128/ijaa.2023.720.1163ENMalihe JalaliradDepartment of Physics, Payame Noor University, Tehran, Iran.Narges FathalianDepartment of Physics, Payame Noor University, P.O.Box 19395-3697, Tehran, Iran.0000-0003-2824-1773Journal Article20230827Solar flares are sudden bursts in the solar atmosphere, which emit from radio wavelengths to gamma rays, and according to their energy, are classified into different classes (A, B, C, M, and X, respectively). Predicting the time of the flare occurrence and determining its class type can help reduce its destructive effects. One of the observable structures that can be seen before a flare occurs are oscillations with very long period pulsations (VLPs) of the order of 8-30 minutes, which occur about one to two hours before the flare onset. In this paper, using GOES data, we observed typical VLPs before flare-onset for six flares in Class C and M. Periodicities that we calculated for the VLPs of these flares are between 14.6 and 28.2 minutes, which is in agreement with the results of Tan et al. (2016). The number of pulses observed in each pre-flare is between 4 and 6. For the other two remaining flares of our selection, no typical pre-flare VLP was observed.https://ijaa.du.ac.ir/article_367_5d3775947e3b50392c789d50c2251261.pdfDamghan University PressIranian Journal of Astronomy and Astrophysics2322-492410220231108Magnetoacoustic Wave Dynamics and a Magnetic Null-Point22123136610.22128/ijaa.2023.731.1167ENZeinab ShajeiFaculty of Physics, University of Tabriz, Tabriz, IranZahra FazelFaculty of Physics, University of Tabriz, Tabriz0000-0001-8267-9528Soheil Vasheghani FarahaniDepartment of Physics, Tafresh University, Tafresh 39518-79611, IranHossein EbadiUniversity of TabrizJournal Article20230912The solar wind acceleration and the coronal heating are two aspects of the solar atmosphere that comprise many physical phenomena. Some features of the solar atmosphere are somehow independent but some seem to be part of a chain reaction. In this study, the interaction of a magnetoacoustic pulse is highlighted with a two dimensional magnetic null point. A simple two dimensional magnetic null-point in the (x, y) plane is subject to a circlular pulse where its initial starting point depends on the solar atmospheric conditions. An analytic relation is presented that governs the density perturbations due to the nearing of the magnetoacoustic pulse. This enables a deeper insight on the effects of the zero and finite plasma-β conditions on the density perturbations. The analytic results are accompanied by numerical plots using the PLUTO code. The results indicate that finite plasma- β conditions decrease the plasma density at the magnetic null-point. This proves adequate for considering atmospheric conditions to prevent inaccurate conclusions regarding the interaction and energy transfer.https://ijaa.du.ac.ir/article_366_89fdbc94652df1fa0042760f051816a7.pdf