Nonlinear Evolution of a 3D Inertial Alfvén Wave and Its Implication in Particle Acceleration

A simulation based on a pseudo-spectral method has been performed in order to study particle acceleration. A model for the acceleration of charged particles by field localization is developed for the low-\(\upbeta\) plasma. For this purpose, a fractional diffusion approach has been employed. The nonlinear interaction between a 3D inertial Alfvén wave and a slow magnetosonic wave has been examined, and the dynamical equations of these two waves in the presence of ponderomotive nonlinearity have been solved numerically. The nonlinear evolution of the inertial Alfvén wave in the presence of slow magnetosonic wave undergoes a filamentation instability and results in field intensity localization. The results obtained show the localization and power spectrum of inertial Alfvén wave due to nonlinear coupling. The scaling obtained after the first break point of the magnetic power spectrum has been used to calculate the formation of the thermal tail of energetic particles in the solar corona.     

Formation of Coherent Structures and Impact on Turbulence Scaling in Solar-Wind Plasma

The governing dynamical equations of the right-handed circularly polarized dispersive Alfvén wave (DAW), which becomes dispersive owing to the finite frequency of the wave, and the slow Alfvén wave have been obtained using a two-fluid model. The wave localization at different instants of time and its power spectrum have been investigated. The ponderomotive force associated with the pump wave results in intense localized structures. The steepening of spectra is observed from the inertial range to the dispersive range. The results imply that the DAW may play a significant role in solar-wind turbulence. In addition, the formation of DAW localized structures is further examined considering two primary approaches, parametric instability (filamentation) and the reconnection-based model, to study the impact on the turbulent spectrum in more detail.     

Remote Sensing-Based Yield Forecasting for Sugarcane (<Emphasis Type="Italic">Saccharum officinarum</Emphasis> L.) Crop in India

Early yield assessment at local, regional and national scales is a major requirement for various users such as agriculture planners, policy makers, crop insurance companies and researchers. This current study explored a remote sensing-based approach of predicting sugarcane yield, at district level, using Vegetation Condition Index (VCI), under the FASAL programme of the Ministry of Agriculture & Farmers’ Welfare. 13-years’ historical database (2003–2015) of NDVI was used to derive the VCI. NDVI products (MOD-13A2) of MODIS instrument on board Terra satellite at 16-day interval from first fortnight of June to second fortnight of October (peak growing period) were used to calculate the VCI. Stepwise regression technique was used to develop empirical models between VCI and historical yield of sugarcane over 52 major sugarcane-growing districts in five states of India. For all the districts, the empirical models were found to be statistically significant. A large number of statistical parameters were computed to evaluate the performance of VCI-based models in predicting district-level sugarcane yield. Though there was variation in model performance in different states, overall, the study showed the usefulness of VCI, which can be used as an input for operational sugarcane yield forecasting.     

Role of 3d-dispersive Alfven waves in coronal heating

Coronal heating is one of the unresolved puzzles in solar physics from decades. In the present paper we have investigated the dynamics of vortices to apprehend coronal heating problem. A three dimensional (3d) model has been developed to study propagation of dispersive Alfvén waves (DAWs) in presence of ion acoustic waves which results in excitation of DAW and evolution of vortices. Taking ponderomotive nonlinearity into account, development of these vortices has been studied. There are observations of such vortices in the chromosphere, transition region and also in the lower solar corona. These structures may play an important role in transferring energy from lower solar atmosphere to corona and result in coronal heating. Nonlinear interaction of these waves is studied in view of recent simulation work and observations of giant magnetic tornadoes in solar corona and lower atmosphere of sun by solar dynamical observatory (SDO).     

Some plane symmetric inhomogeneous cosmological models in the scalar-tensor theory of gravitation

The present study deals with the inhomogeneous plane symmetric models in scalar-tensor theory of gravitation. We used symmetry group analysis method to solve the field equations analytically. A new class of similarity solutions have been obtained by considering the inhomogeneous nature of metric potential. The physical behavior and geometrical aspects of the derived models are also discussed.     

Lyra's cosmology of hybrid universe in Bianchi-V space-time

In this paper we have searched for the existence of Lyra's cosmology in a hybrid universe with minimal interaction between dark energy and normal matter using Bianchi-V space-time. To derive the exact solution, the average scale factor is taken as a =(t~ne~(kt))1/m which describes the hybrid nature of the scale factor and generates a model of the transitioning universe from the early deceleration phase to the present acceleration phase. The quintessence model makes the matter content of the derived universe remarkably able to satisfy the null, dominant and strong energy condition. It has been found that the time varying displacement β(t) co-relates with the nature of cosmological constant Λ(t). We also discuss some physical and geometrical features of the universe.     

A proper motion study of the globular cluster M12(NGC 6218)

Using astrometric techniques developed by Anderson et al., we determine proper motions(PMs) in the ～14.60 × 16.53 arcmin~2 area of the kinematically "thick-disk" globular cluster M12. The cluster's proximity and sparse nature makes it a suitable target for ground-based telescopes. Archive images with time gap of ～11.1 years were observed with the wide-field imager(WFI) mosaic camera mounted on the ESO 2.2 m telescope. The median value of PM error in both components is ～0.7 mas yr~(-1) for the stars having V ≤ 20 mag. PMs are used to determine membership probabilities and to separate field stars from the cluster sample. In electronic form, a membership catalog of 3725 stars with precise coordinates, PMs and BV RI photometry is being provided. One of the possible applications of the catalog is demonstrated by gathering the membership information of the variable stars, blue stragglers and X-ray sources reported earlier in the cluster's region.     

Resource potential and planning for exploration of the Hebrus Valles,Mars

Mars is the only extraterrestrial body which could host primitive lifeforms and also has the potential to host a human base in the near future. Towards fulfilling these objectives, several remote sensing missions and rover based missions have been sent to Mars. Still, confirmation of existing or extinct life on this planet in any form has not been achieved and possibly human missions at selected sites in the future are the key to addressing this problem. Here, we have used remote sensing data from Mars Reconnaissance Orbiter(MRO; NASA), Mars Global Surveyor(MGS; NASA), Mars Odyssey(NASA) and Mars Express(MEX; ESA) to devise an exploration strategy for one such area known as Hebrus Valles, which is a potential site for human exploration of the surface of Mars. A geological context map of the Hebrus Valles and Hephaestus Fossae region has been prepared and a candidate landing site has been proposed in the Hebrus Valles region. Suitable rover paths have been worked out from the proposed landing site for harnessing the science and resource potential of the region. The proposed landing site is located in the equatorial region at(20?40′N, 126?23′E) and due to its proximity to the Potential Subsurface Access Candidates(PSACs) in the region, such as sinkholes and skylights and also other resources such as crater ejecta, silicate material and fluvial channels, the site is appropriate for exploration of the region.     

AstroSat observation of GX 5–1: spectral and timing evolution

We report on the first analysis of an AstroSat observation of the Z-source GX 5–1 on 2017 February 26-27. The hardness-intensity plot reveals that the source traced out the horizontal and normal branches. The 0.8-20 keV spectra from simultaneous SXT and LAXPC data at different locations of the hardness-intensity plot can be described well by disk emission and a thermal Comptonized component. The ratio of the disk flux to the total flux, i.e., the disk flux ratio, increases monotonically along the horizontal branch to the normal one. Thus, the difference between the normal and horizontal branches is that in the normal branch, the disk dominates the flux while in the horizontal one it is the Comptonized component which dominates. The disk flux scales with the inner disk temperature as T_(in)~(5.5 ) and not as T_(in)~4 , suggesting that either the inner radius changes dramatically or that the disk is irradiated by the thermal component changing its hardness factor. The power spectra reveal a quasi-periodic oscillation(QPO) whose frequency changes from ~30 Hz to 50 Hz. The frequency is found to correlate well with the disk flux ratio. In the 3-20 keV LAXPC band, the r.m.s. of the QPO increases with energy(r.m.s. ∝ E~(0.8)), while the harder X-rays seem to lag the soft ones with a time-delay of milliseconds. The results suggest that the spectral properties of the source are characterized by the disk flux ratio and that the QPO has its origin in the corona producing the thermal Comptonized component.     

In Situ Bioremediation of Toluene‐Polluted Vadose Zone: Integrated Column and Wetland Study

A vertical soil column setup integrated with wetlands is developed to study the biodegradation and transport of toluene, a light non‐aqueous phase liquid (LNAPL), in the subsurface environment. LNAPL‐contaminated water is applied to infiltrate from the top of the soil column. The observed and simulated breakthrough curves show high equilibrium concentration at top ports rather than at lower ports, indicating effective toluene biodegradation with soil depth. The observed equilibrium concentration of toluene is higher in the case of unplanted wetland, asserting an accelerated biodegradation rate in the planted case. A difference in the relative concentration of toluene between input and output fluxes at 100 h is found as 13.34% and 30.86% for planted and unplanted wetland setups, respectively. Estimated biodegradation rates show that toluene degradation is 2.5 times faster in the planted wetland setup. In addition, the difference in the observed bacterial count and dissolved oxygen prove that toluene degraded aerobically at a faster rate in the planted setup. Simulations show that as time reached 80–100 h, there is no significant change in concentration profile, thereby confirming the equilibrium condition. The results of this study will be useful to frame plant‐assisted bioremediation techniques for LNAPL‐contaminated soil–water resources in the field.