Multiwavelength Study of a Solar Eruption from AR NOAA 11112: II. Large-Scale Coronal Wave and Loop Oscillation     

Pankaj Kumar  K.-S. Cho  P. F. Chen  S.-C. Bong  Sung-Hong Park 《Solar physics》2013,282(2):523-541

We analyze multiwavelength observations of an M2.9/1N flare that occurred in AR NOAA 11112 on 16 October 2010. AIA 211 Å EUV images reveal the presence of a faster coronal wave (decelerating from ≈?1390 to ≈?830 km?s^?1) propagating ahead of a slower wave (decelerating from ≈?416 to ≈?166 km?s^?1) towards the western limb. The dynamic radio spectrum from Sagamore Hill radio telescope shows the presence of a metric type II radio burst, which reveals the presence of a coronal shock wave (speed ≈?800 km?s^?1). The speed of the faster coronal wave, derived from AIA 211 Å images, is found to be comparable to the coronal shock speed. AIA 171 Å high-cadence observations showed that a coronal loop, which was located at a distance of ≈?0.32R _⊙ to the west of the flaring region, started to oscillate by the end of the impulsive phase of the flare. The results indicate that the faster coronal wave may be the first driver of the transversal oscillations of coronal loop. As the slower wave passed through the coronal loop, the oscillations became even stronger. There was a plasmoid eruption observed in EUV and a white-light CME was recorded, having velocity of ≈?340?–?350 km?s^?1. STEREO 195 Å images show an EIT wave, propagating in the same direction as the lower-speed coronal wave observed in AIA, but decelerating from ≈?320 to ≈?254 km?s^?1. These observations reveal the co-existence of both waves (i.e. coronal Moreton and EIT waves), and the type II radio burst seems to be associated with the coronal Moreton wave.  相似文献   

Some anisotropic dark energy models in Bianchi type-V space-time     

Anil Kumar Yadav 《Astrophysics and Space Science》2011,335(2):565-575

The paper deals with Bianchi type V Universe, which has dynamical energy density. We consider Bianchi type V space-time, introducing three different skewness parameters along spatial directions to quantify the deviation of pressure from isotropy. To study the anisotropic nature of the dynamical dark energy, we assume that the skewness parameters are time dependent. It is found that the Universe achieves flatness in quintessence model. The physical behavior of the Universe has been discussed in detail.  相似文献   

A family of well behaved charge analogues of?a?well behaved neutral solution in?general relativity     

Sunil Kumar Maurya  Y. K. Gupta 《Astrophysics and Space Science》2011,332(2):481-490

A family of charge analogues of a neutral solution with g ₄₄=(1+Cr ²)⁶ has been obtained by using a specific electric intensity, which involves a parameter K. Both neutral and charged solutions are analysed physically subject to the surface density 2×10¹⁴ gm/cm³ (neutron star). The neutral solution is well behaved for 0.0<Ca ²≤0.10477 while its charge analogues are well behaved for a wide range of a parameter K (0≤K≤72) i.e. pressure, density, pressure-density ratio, velocity of sound is monotonically decreasing and the electric intensity is monotonically increasing in nature for the given range of the parameter K. The maximum mass and radius occupied by the neutral solution are 3.4126M _Θ and 18.9227 km for Ca ²=0.10447 respectively. While the red shift at centre Z ₀=0.9686 and red shift at the surface Z _a =0.4612. For the charged solution, the maximum mass and radius are 5.6111M _Θ and 17.2992 km respectively for K=3.0130 and Ca ²=0.2500, with the red shift Z ₀=3.0113 and Z _a =1.0538.  相似文献   

Seismic source zonation for NE India on the basis of past EQs and spatial distribution of seismicity parameters     

Borah  Niranjan  Kumar  Abhishek  Dhanotiya  Rajat 《Journal of Seismology》2021,25(6):1483-1506

Journal of Seismology - The North East (NE) of India is an earthquake (EQ) prone zone and has experienced considerable damages in the past due to high intensity EQs. With rapidly growing...  相似文献   

Dark energy models with anisotropic fluid in Bianchi Type-VI 0 space-time with time dependent deceleration parameter     

Anirudh Pradhan  Rekha Jaiswal  Kanti Jotania  Rajeev Kumar Khare 《Astrophysics and Space Science》2012,337(1):401-413

We present two dark energy (DE) models with an anisotropic fluid in Bianchi type-VI ₀ space-time by considering time dependent deceleration parameter (DP). The equation of state (EoS) for dark energy ω is found to be time dependent and its existing range for derived models is in good agreement with the recent observations. Under the suitable condition, the anisotropic models approach to isotropic scenario. We also find that during the evolution of the universe, the EoS parameter for DE changes from ω>−1 to ω=−1 in first model whereas from ω>−1 to ω<−1 in second model which is consistent with recent observations. The cosmological constant Λ is found to be a positive decreasing function of time and it approaches a small positive value at late time (i.e. the present epoch) which is corroborated by results from recent type Ia supernovae observations. The cosmic jerk parameter in our derived models is also found to be in good agreement with the recent data of astrophysical observations. The physical and geometric aspects of both the models are also discussed in detail.  相似文献   

Electromagnetic Ion Cyclotron Waves in Multi-Ions Hot Anisotropic Plasma in Auroral Acceleration Region-Particle Aspect Approach     

Soniya Patel  P. Varma  M. S. Tiwari 《Earth, Moon, and Planets》2012,109(1-4):29-41

Using particle aspect approach, the effect of multi-ions densities on the dispersion relation, growth rate, perpendicular resonant energy and growth length of electromagnetic ion cyclotron wave with general loss-cone distribution function in hot anisotropic multi-ion plasma is presented for auroral acceleration region. It is observed that higher He⁺ and O⁺ ions densities enhance the wave frequency closer to the H⁺ ion cyclotron frequency and growth rate of the wave. The differential heating of He⁺ ions perpendicular to the magnetic field is enhanced at higher densities of He⁺ ions. The waves require longer distances to achieve observable amplitude by wave-particle interactions mechanism as predicted by growth length. It is also found that electron thermal anisotropy of the background plasma enhances the growth rate and reduces the growth length of multi-ions plasma. These results are determined for auroral acceleration region.  相似文献   

Bulk viscous LRS Bianchi-I Universe with variable G and decaying Λ     

Anil Kumar Yadav  Anirudh Pradhan  Ajay Kumar Singh 《Astrophysics and Space Science》2012,337(1):379-385

The present study deals with spatially homogeneous and totally anisotropic locally rotationally symmetric (LRS) Bianchi type I cosmological model with variable G and Λ in presence of imperfect fluid. To get the deterministic model of Universe, we assume that the expansion (θ) in the model is proportional to shear (σ). This condition leads to A=ℓB ⁿ , where A, B are metric potential. The cosmological constant Λ is found to be decreasing function of time and it approaches a small positive value at late time which is supported by recent Supernovae Ia (SN Ia) observations. Also it is evident that the distance modulus curve of derived model matches with observations perfectly.  相似文献   

Dark energy model with variable q and ω in LRS Bianchi-II space-time     

Bijan Saha  Anil Kumar Yadav 《Astrophysics and Space Science》2012,341(2):651-656

The present study deals with spatial homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-II dark energy model in general relativity. The Einstein’s field equations have been solved exactly by taking into account the proportionality relation between one of the components of shear scalar $(\sigma^{1}_{1})$ and expansion scalar (?), which, for some suitable choices of problem parameters, yields time dependent equation of state (EoS) and deceleration parameter (DP), representing a model which generates a transition of universe from early decelerating phase to present accelerating phase. The physical and geometrical behavior of universe have been discussed in detail.  相似文献   

Assessment of Aphid Infestation in Mustard by Hyperspectral Remote Sensing     

Jitendra Kumar  Ananta Vashisth  V. K. Sehgal  V. K. Gupta 《Journal of the Indian Society of Remote Sensing》2013,41(1):83-90

Field experiment was conducted during 2009–10 and 2010–11 rabi season at research farm of IARI, New Delhi for assessing the aphid infestation in mustard. In aphid infested plant the LAI was 67 to 94% lower than healthy plant. Chlorophyll concentration decreased to 50% in infested plant as compared to healthy plant. Infestation was more severe in late sown crop and due to aphid infestation the percentage oil content and yield was reduced significantly. The spectral reflectance of aphid infested canopy and healthy canopy taken in the laboratory had significant difference in NIR region. In the visible region, the reflectance peak occurred in healthy canopy at around 550–560 nm while this peak was lower by 31% in the aphid infested canopy. The reflectance for healthy crop was found to be more in visible as well as NIR region as compared to aphid infested canopy. The most significant spectral bands for the aphid infestation in mustard are in visible (550–560 nm) and near infrared regions (700–1250 nm and 1950–2450 nm). The different level of aphid infestation can be identified in 1950–2450 nm spectral regions. Spectral indices viz NDVI, RVI, AI and SIPI had significant correlation with aphid infestation. Hence these indices could be used for identifying aphid infestation in mustard.  相似文献   

Effect of Different Growing Environments on Population Dynamics of Sucking Pests in Relation to Various Spectral Indices in Cotton     

Naresh Kumar  Ram Niwas  M. L. Khichar  R. K. Saini  Barun Biswas 《Journal of the Indian Society of Remote Sensing》2013,41(2):309-317

Present study was designed to determine the effect of various growing environments on sucking pest population dynamics in cotton and to work out their relation with spectral indices. Crop spectral reflectance in four IRS bands was measured with ground truth radiometer during 1000–1200 h in all the treatment combinations. Incidence of sucking pest in cotton was found out to be highly influenced by growing environments. The leafhopper and whitefly population was highest in 15 May sown cotton crop and was lowest in 15 April sown crop. Cultivar HS-6 was highly affected by both the sucking pest than the other cultivar H-1226. The spectral indices (SR, NDVI and TVI) were highest in 15 April sown crop at all the phenophases and were lowest in 15 May sown crop. The cultivar H-1226 showed higher values of spectral indices as compared to HS-6. The relationship of pests’ population with various spectral indices was established. Multiple regression models based on spectral indices can be used for prediction of sucking pest population more than 69 and 74 % accuracy in leafhopper and whitefly, respectively in cotton crop.  相似文献