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[en] Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number from 1957 to 2008. It was found that the relationship between the sunspot number and great storm number weakened as the activity of the storms strengthened. There was no obvious relationship between the annual sunspot number and great storm number with Dst≤−300 nT. Secondly, we studied the relationship between the peak Dst and peak Bz in detail. It was found that the condition Bz≤−10 nT is not necessary for storms with Dst≤−100 nT, but seems necessary for storms with Dst≤−150 nT. The duration for Bz≤−10 nT has no direct relationship with the giant storm. The correlation coefficient between the Dst peak and Bz peak for the 89 storms studied is 0.81. After removing the effect of solar wind dynamic pressure on the Dst peak, we obtained a better correlation coefficient of 0.86. We also found the difference between the Dst peak and the corrected Dst peak was proportional to the Dst peak.
[en] Based on the rate of expansion of the solar wind, the plasma should cool rapidly as a function of distance to the Sun. Observations show this is not the case. In this work, a magnetic pumping model is developed as a possible explanation for the heating and the generation of power-law distribution functions observed in the solar wind plasma. Most previous studies in this area focus on the role that the dissipation of turbulent energy on microscopic kinetic scales plays in the overall heating of the plasma. However, with magnetic pumping, particles are energized by the largest-scale turbulent fluctuations, thus bypassing the energy cascade. In contrast to other models, we include the pressure anisotropy term, providing a channel for the large-scale fluctuations to heat the plasma directly. A complete set of coupled differential equations describing the evolution, and energization, of the distribution function are derived, as well as an approximate closed-form solution. Numerical simulations using the VPIC kinetic code are applied to verify the model's analytical predictions. The results of the model for realistic solar wind scenario are computed, where thermal streaming of particles are important for generating a phase shift between the magnetic perturbations and the pressure anisotropy. In turn, averaged over a pump cycle, the phase shift permits mechanical work to be converted directly to heat in the plasma. Here, the results of this scenario show that magnetic pumping may account for a significant portion of the solar wind energization.
[en] In recent years, intense laser facilities have been widely used in laboratory astrophysics,and with the development of imaging and analyzing techniques, important advances have been made in this field. These include self-organized electromagnetic field structures in laser-produced counter-streaming plasmas, turbulent amplification of magnetic fields in laboratory laser-produced shock waves, laboratory formation of a scaled protostellar jet by coaligned poloidal magnetic fields, and modeling of the interaction of the solar wind with a dipole magnetic field using the intense Shenguang II lasers. The results achieved have promoted our understanding of protostellar bodies, jets of Herbig-Haro objects, the shockwave of supernova remains, and the earth's magnetosphere near the pole regions. This article will present an overview of the above topics,as well as some outlook on future laboratory astrophysics research. (authors)
[en] Wave energy up conversion of high frequency plasma wave in presence of low frequency plasma wave are studied in both space and laboratory plasma. In the ionosphere different forms of free energy sources are coexisting and energy exchange process takes place among plasma waves and particles. Through plasma maser effect ionospheric plasma particles may be transferred energy nonlinearly to high frequency mode through a modulated electric field in the presence of electron density gradients. In this paper it has been explained how energy from drift wave is transferred to non-resonant ion sound wave. Including plasma inhomogeneity effect in our model the growth rate of ion sound wave in the Earth’s ionosphere in presence of drift wave turbulence estimated using observational data
[en] : Sunspots occur due to magnetic disturbances on the surface of the sun. The sunspot activity effects weather on earth and also affect the earth temperature. In this research paper, various spectral estimation techniques for estimation of universal cyclic behavior of sunspot numbers are discussed. Spectral analysis has been based on two different approaches, namely parametric and non-parametric estimation. The performance of various parametric and non-parametric spectral estimation methods has been compared and frequency of occurrence of sunspots is calculated. MATLAB computer simulations have been extensively used for various estimator settings to arrive at correct results. The results show that the parametric spectral estimation techniques show better and consistent performance as compared to non-parametric spectral estimation techniques. (author)
[en] This study pertained to the relationship between critical frequency of F/sub 2/ layer (foF/sub 2/) and solar activity indices at three low latitude ionospheric stations during solar cycle 22 (1985-1996). The selected ionospheric stations lie in the latitudinal range of Pakistan: therefore, this investigation may also be useful to understand the impact of solar activity relevant to our region. The monthly median values of foF/sub 2/ for Okinawa, (26.3ON, 127.8O E), Guangzhou, (23.10O N, 113.4O E) and Chongqing (29.50O N, 106.40O E) have been plotted against sunspot number (SNN) and solar radio flux (F10.7cm). The main purpose of this analysis was to compare the foF/sub 2/ values at low latitude ionospheric stations. A comparison of different phases of solar activity with foF/sub 2/ at the subject stations revealed almost similar patterns. The correlation coefficients between SSN and critical frequency of F/sub 2/ layer (foF/sub 2/) on hourly basis for all months were compared. These trends helped in understanding foF/sub 2/ occupancy in the region of Pakistan during solar cycle 22. A strong dependence was observed between solar activity and foF/sub 2/ during this period. Ikubanni et al.  have already investigated the trends of F2 layer critical frequency at a low latitude station, during solar cycle 22. This comparative study of foF/sub 2/ was regarding Chongqing, Okinawa, and Guangzhou that have not been explored as yet. These studies emphasized the behavior of foF/sub 2/ for all these stations and identified the latitude dependency of foF/sub 2/ on solar activity. A better agreement was observed during the year of moderate solar activity (MSA). An International Reference Ionosphere (IRI) model has been used to reveal foF/sub 2/ missing values. (author)
[en] An examination is made of Antarctic dayside auroras to establish how they relate to solar wind strength under the quiet conditions of the recent extended solar minimum when the solar wind pressure was weak and the interplanetary magnetic field Bz is small. It is found that, during the many days of observation, the aurora is detected even with the most stable and quiet conditions. On such occasions the 630 nm OI emission can be as low as 50 R, but is unambiguously and continuously detectable through each noon. This is above an airglow intensity of about 30 R. For these quiet conditions there is no evident relation between the solar wind dynamic pressure or interplanetary magnetic field Bzand dayside auroral intensity. This suggests that there is no effective reconnection under these minimal conditions and the particle source for the dayside aurora could be within the magnetosphere. (author)
[en] A new Cassini magnetosheath data set is introduced that is based on a comprehensive survey of intervals in which the observed magnetosheath flow was encompassed within the plasma analyzer field of view and for which the computed numerical moments are therefore expected to be accurate. The data extend from 2004 day 299 to 2012 day 151 and comprise 19,155 416-s measurements. In addition to the plasma ion moments (density, temperature, and flow velocity), merged values of the plasma electron density and temperature, the energetic particle pressure, and the magnetic field vector are included in the data set. Statistical properties of various magnetosheath parameters, including dependence on local time, are presented. The magnetosheath field and flow are found to be only weakly aligned, primarily because of a relatively large z-component of the magnetic field, attributable to the field being pulled out of the equatorial orientation by flows at higher latitudes. A new procedure for using magnetosheath properties to estimate the upstream solar wind speed is proposed and used to determine that the amount of electron heating at Saturn's high Mach-number bow shock is ~4% of the dissipated flow energy. The data set is available as an electronic supplement to this paper.
[en] Among other stochastic models, fractional auto regressive integrating moving average (FARIMA) is distinct because of its appropriateness for modeling stationary time series with long range dependence (long memory or persistence). Results obtained in this manuscript shows appropriateness of FARIMA model for the analysis of sunspot number. Analyzing for stationary, each cycle out of the 24 sunspot cycles were modeled. FARIMA can be used for modeling using different techniques. In view of the parameters obtained by maximum likelihood test two most appropriate techniques are adopted. These two are Direct Method and Whittle approximation Method. Results are obtained by applying these two types of FARIMA, the significance of these two methods were observed and compared using significance tests. For FARIMA models the fractional differencing parameter d is most decisive for the determination of persistency. In this regard four types of model (0, d,0), (1, d,0), (0, d,1) and (1, d,1) are used. The adequacy of each of the models is determined with the help of Akaike, Bayesian-Schwarz and Hannan-Quinn Information criterion. The investigations made using these models are reliable for both short and long sunspot cycles. Finally, tail analysis is performed in view of the parameter (α) it is observed that heavy tails exist for each sunspots cycle confirming long range dependence. The study is useful to examine the sunspot historical data using the FARIMA model to understand their long term behavior. (author)
[en] In this paper we have performed the relationship between cosmic ray intensity (CRI) and Interplanetary Magnetic field (B) for the period 1976 to 2018. For this we have taken the data of Cosmic Ray Intensity (CRI) from various Neutron Monitor Stations, which are well maintained stations and provide reliable Cosmic Ray Data. Here we have taken the monthly and annual mean value of Cosmic Ray Intensity (CRI) from the Moscow (2.42GV), Russia Neutron Monitor Station. It has been found that Interplanetary Magnetic field (B) shows anti-phase with Cosmic Ray Intensity (CRI). It is found that Interplanetary Magnetic Field (IMF-B) shows decreasing trend with CRI and also shows negative correlation. Also we have taken interplanetary magnetic field (B), sunspot number (SSN) and index from omni web. (author)