Iranian Journal of Astronomy and Astrophysic
Volume:9 Issue: 2, Summer 2022

In this article, we analyzed the abnormal thickness of the chromosphere above the coronal holes (CH) at the poles of the Sun for 13 years (2010-2022), on the 15th of every month, by using AIA/SDO telescope data. We used the light emitted from helium-2 (He II) at a wavelength of 304 {AA} at about 50,000 K to investigate the solar holes in its north and south poles. This light is emitted from the chromosphere and the transition region. According to the values of the graphs obtained by the MATLAB program and the comparison between solar cycles during the 2010-2022 years, it was seen that the Full width of the intensity curves at half maximum (FWHM) in the poles, and as a result the magnetic activity of the sun and especially the activity of coronal cavities as the main source of the solar dipole magnetic field before cycle 25 is significantly greater than this thickness before cycle 24. According to the relationship between the number of sunspots and the solar activity in the coronal holes at the solar poles with a time delay of 2 to 5 years, we expect the maximum increasing in the number of sunspots around the year 2025. As a result,in terms of the number of sunspots, the height of the solar cycle 25 probably is higher than the cycle 24, which was a low sunspot number cycle. We also concluded that the thickness of the Chromosphere has an inverse relationship with solar dynamo magnetic activity cycle.

In this paper, the Joule-Thomson (JT) adiabatic expansion isinvestigated for generalized Ayon-Beato-Garcia (ABG)\textcolor[rgb]{0.00,0.00,1.00}{regular} black hole. It has amagnetic charge which makes central region of the black holemetric to be AdS spacetime and so become non singular.\textcolor[rgb]{0.00,0.00,1.00}{Thus we not need to use anadditional cosmological parameter coming from ADS/CFTcorrespondence for production of pressure coordinate in the blackhole equation of state. Form this point of view our work is a newapproach versus to conventional methods which are addressed in thereferences of this paper. However we will see important behaviorof parameters of this modified ABG black hole on possibility ofbeing of JT adiabatic expansion.} This black hole is characterizedby five parameters including mass $m$, magnetic charge $q$, andthree \textcolor[rgb]{0.00,0.00,1.00}{other} parameters related toform of used nonlinear electromagnetic interaction fields.\textcolor[rgb]{0.00,0.00,1.00}{Inversion points are in fact aparticular T-P curve at constant enthalpy and it separates coolingand heating phase of the modified AdS ABG black hole.}

Observational results of the infrared dark clouds (IRDCs) reveal that these clouds exhibit a clumpy structure with directional line-of-sight velocity gradients. Recent research by Vahadanian \& Nejad-Asghar~(2022, hereafter VN22) focused on the observational results of IRDC G34.43+00.24 (G34). The study concluded that G34 behaves like a rolling cylinder within the plane of the Galaxy,exhibiting a slow angular velocity of approximately $\Omega\sim 5.7\times 10^{-14}\, \mathrm{s}^{-1}$. Using a simplified approximation for the mismatch of opposite charges, denoted by the parameter $\zeta$, researchers demonstrated that the rotation-induced electric current can generate magnetic fields with strengths on the order of thousands of micro-Gauss in certain regions of G34. This study specifically examines the clumps within the IRDCs and employs a simplified model that incorporates a density-dependent function for the parameter $\zeta$. Our research focuses on analyzing the magnetic field morphology within a clump. To address this investigation, we examine three specific clumps - MM1, MM2, and MM3 - within G34. The findings reveal that the magnetic field strength is higher near the axis of rotation compared to distant regions from the axis. Additionally, increasing values of the angular velocity $\Omega$ and the mismatch of opposite charges $\zeta$ lead to stronger magnetic field strengths. On the other hand, the results indicate that the strength of the magnetic field is not significantly influenced by the angle between the rotational axis of the IRDC and the boundary magnetic field. These findings offer valuable insights for researchers studying the distribution of star-forming cores within clumps.

An array of five scintillation detectors has been installed in Sharif University of Technology to record extensive air showers. ‎‎‎By using the time lags of the secondary particles of air showers relative to each other and the location of each of these ‎particles‎ relative to the core of the shower, the arrival direction of the primary particle producing each air shower has been ‎obtained.‎‎‎These data show that the distribution of time intervals of successive events in all directions of arrival into‎ the atmosphere is a random distribution‎. The distribution of the time intervals between successive events in different ‎seasons‎ has also been obtained and the seasonal effect has been ‎investigated‎. The effects of the environment‎, ‎including temperature and pressure‎, on the cosmic ray count rate have been investigated‎. ‎The distribution of zenith and azimuth angles‎, ‎as well as‎ the ‎solar,‎ sidereal, and antisidereal time distributions of cosmic rays‎, ‎have been obtained‎.

We study the stability of a model of magnetized accretion disk, in whichoutflows play a significant role in driving the inflow, and magnetic field is generated bya dynamo operating in the disk. We present a local and linear analysis of the stabilityin the presence of self-gravity and winds. The numerical results show the model withself-gravity is unstable in all parts, while in a model without self-gravity, instabilitycan be observed only in regions near the central body. Eventually, the effect of windcooling on the model stability was discussed. According to the results, in systemswithout self-gravity, wind cooling can help the system towards stability, but in thepresence of self-gravity, it is shown that our model will remain unstable in all regions.Comparison of these result with observational evidence shows that this model can besuitable for the explaining the behavior of the disks surrounding young stellar objects.

A solar flare is a sudden flash that occurs near the solar surface. Thisresults in the emission of an extensive range of energy from the surface of the Sun.These giant explosions generally contain X-rays and energy that tend to travel in alldirections at the speed of light. Coronal mass ejections (CMEs) are types of explosionsthat occur on the solar surface. A CMEs releases a large amount of plasma and magneticfield. Our main goal in this research is to prove that the reason for the release of chargedparticles, protons, electrons and X-ray radiation, followed by the release of solar winds,is the occurrence of flares and CMEs. The occurrence of this phenomenon is relatedto other phenomena, such as the magnetic field of the Sun’s surface, the cycle of theSun’s activity, sunspots, the emission of charged particles of electrons and protonsfrom the solar corona, the rate of occurrence of CMEs from the corona, the averageand maximum speed of CME and X-ray radiation in the category Class X, which is thehighest energy category for X-ray radiation, is directly and closely related.