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11.
Ram Ajor Maurya Jongchul Chae Hyungmin Park Heesu Yang Donguk Song Kyuhyoun Cho 《Solar physics》2013,288(1):73-88
We study chromospheric oscillations including umbral flashes and running penumbral waves in a sunspot of active region NOAA 11242 using scanning spectroscopy in Hα and Ca?ii 8542 Å with the Fast Imaging Solar Spectrograph (FISS) at the 1.6 meter New Solar Telescope at the Big Bear Solar Observatory. A bisector method is applied to spectral observations to construct chromospheric Doppler-velocity maps. Temporal-sequence analysis of these shows enhanced high-frequency oscillations inside the sunspot umbra in both lines. Their peak frequency gradually decreases outward from the umbra. The oscillation power is found to be associated with magnetic-field strength and inclination, with different relationships in different frequency bands. 相似文献
12.
In the present article, a family of static spherical symmetric well behaved interior solutions is derived by considering the
metric potential g
44=B(1−Cr
2)−n
for the various values of n, such that (1+n)/(1−n) is positive integer. The solutions so obtained are utilised to construct the heavenly bodies’ like quasi-black holes such
as white dwarfs, neutron stars, quarks etc., by taking the surface density 2×1014 gm/cm3. The red shifts at the centre and on the surface are also computed for the different star models. Moreover the adiabatic
index is calculated in each case. In this process the authors come across the quarks star only. Least and maximum mass are
fond to be 3.4348M
Θ and 4.410454M
Θ along with the radii 21.0932 km and 23.7245 km respectively. 相似文献
13.
We present a multi-wavelength analysis of an eruption event that occurred in active region NOAA 11093 on 7 August 2010, using
data obtained from SDO, STEREO, RHESSI, and the GONG Hα network telescope. From these observations, we inferred that an upward
slow rising motion of an inverse S-shaped filament lying along the polarity inversion line resulted in a CME subsequent to
a two-ribbon flare. Interaction of overlying field lines across the filament with the side-lobe field lines, associated EUV
brightening, and flux emergence/cancelation around the filament were the observational signatures of the processes leading
to its destabilization and the onset of eruption. Moreover, the time profile of the rising motion of the filament/flux rope
corresponded well with flare characteristics, viz., the reconnection rate and hard X-ray emission profiles. The flux rope was accelerated to the maximum velocity as a CME
at the peak phase of the flare, followed by deceleration to an average velocity of 590 km s−1. We suggest that the observed emergence/cancelation of magnetic fluxes near the filament caused it to rise, resulting in
the tethers to cut and reconnection to take place beneath the filament; in agreement with the tether-cutting model. The corresponding
increase/decrease in positive/negative photospheric fluxes found in the post-peak phase of the eruption provides unambiguous
evidence of reconnection as a consequence of tether cutting. 相似文献
14.
D.K. Pal T. Bhattacharyya P. Chandran S.K. Ray P.L.A. Satyavathi S.L. Durge P. Raja U.K. Maurya 《Quaternary International》2009,209(1-2):6
Smectitic parent material from the weathering Deccan basalt has been deposited in the lower piedmont plains, valleys and microdepressions during a previous wetter climate. The cracking clay soils (Vertisols) were developed in such alluvium during drier climate of the Holocene period. In India they occur in humid tropical (HT), sub-humid moist (SHM), sub-humid dry (SHD), semi-arid moist (SAM), semi-arid dry (SAD) and arid dry (AD) climatic environments and thus indicate an array of soils in a climosequence.The soils show a change in their morphological, physical, chemical and micromorphological properties in the climosequence. Soils of HT climate are dominated by Ca++ ions in their exchange complex throughout depth. However, in the sub-humid climates Mg++ ions tend to dominate in the lower horizons. The sub-humid moist to aridic climatic environments caused a progressive formation of pedogenic calcium carbonates (PC) with the concomitant increase in Na+ ions in soil solution. This facilitated the translocation of Na-clay in the soil profile. This is responsible for the increase in pH, decrease in Ca/Mg ratio of exchange sites with depth and finally in the development of subsoil sodicity. The reduction in mean annual rainfall (MAR) from sub-humid moist to arid climates accelerated the formation of PC and thus the soils of semi-arid and arid climates (SAM, SAD and AD) are more calcareous and sodic than soils of other climates (SHM and SHD).Formation of PC, illuviation of clay and the development of subsoil sodicity are concurrent, contemporary and active pedogenetic processes operating during the climate change of the Holocene period. These processes impaired the hydraulic properties of soils in general, and in soils of drier climates in particular. As a result, cracking pattern, chemical composition and plasmic fabric were more modified in soils of the drier climates. Such modifications in soil properties have a place in the rationale of Vertisol order of the US Soil Taxonomy. The soils of wetter climates (HT, SHM and SHD) are grouped in Typic Haplusterts whereas the soils of drier climates (SAM, SAD and AD) are classified as Aridic Haplusterts, Sodic Haplusterts and Sodic Calciusterts. The present study demonstrates how the intrinsic soil properties of the cracking clay soils in a climosequence may help in inferring the change in climate in a geologic period. 相似文献
15.
16.
Nirmala D. Desouza Baby Simon Muhammad S. Qureshi 《Meteorology and Atmospheric Physics》2011,114(3-4):107-121
The evolutionary characteristics of a dust storm over Oman on 2 February 2008 were studied by analyzing the weather associated with it. The National Center for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis wind flow pattern at 1,000?hPa showed a clockwise and outward wind flow pattern over the study region, a manifestation of a high-pressure cold air mass. In addition, ground truth observations for surface temperature and surface winds showed cold northerly winds until the early morning of 2 February 2008. A strong wind shear resulted from differences in wind speed between warm air and trapped cold air. This vertical wind shear enhanced instability. Furthermore, the weakening of the inversion in the lower troposphere and the formation of a mixed layer due to transfer of horizontal momentum from upper air towards the surface led to strong surface winds. These strong winds lifted a large amount of dust particles off the ground, resulting in the dust event of 2 February 2008. 相似文献
17.
Nirmala Devidas Desouza Rajnish Kurchania Muhammad Shums Qureshi 《Meteorology and Atmospheric Physics》2013,122(1-2):47-54
Dust storms commonly occur during the pre-monsoon (summer) season in north and northwest parts of India. Characteristics of dust events of the pressure gradient type are well understood. However, comprehensive studies on mechanism of convective dust storms in India are few. A convective dust storm which occurred on 21 April 2010 in association with a western disturbance over North India was hence studied. In the absence of in situ data, we used available satellite data to study the event. Dust storm that occurred on 20 April 2010 on the surface of the Thar Desert transported dust to northern and northwestern parts of India (Rajasthan, Haryana, Delhi and some parts of Uttar Pradesh). This formed a background of aerosols that affected the thunderstorm formed in association with western disturbance and the strong updraft in the thunderstorm carried the dust lingering in the atmosphere to higher altitudes. Large amount of aerosols carried to higher altitude suppressed the chance of precipitation by affecting the cloud top microphysics. Enhancement in evaporation due to an increase in aerosol concentration and strong downdrafts during dissipation of the thunderstorm resulted in emission of dust particles which led to the convective dust event of 21 April 2010. 相似文献
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Hyungmin Park Jongchul Chae Donguk Song Ram Ajor Maurya Heesu Yang Young-Deuk Park Bi-Ho Jang Jakyoung Nah Kyung-Suk Cho Yeon-Han Kim Kwangsu Ahn Wenda Cao Philip R. Goode 《Solar physics》2013,288(1):105-116
We observed solar prominences with the Fast Imaging Solar Spectrograph (FISS) at the Big Bear Solar Observatory on 30 June 2010 and 15 August 2011. To determine the temperature of the prominence material, we applied a nonlinear least-squares fitting of the radiative transfer model. From the Doppler broadening of the Hα and Ca ii lines, we determined the temperature and nonthermal velocity separately. The ranges of temperature and nonthermal velocity were 4000?–?20?000 K and 4?–?11 km?s?1. We also found that the temperature varied much from point to point within one prominence. 相似文献
20.
Similarity solutions are obtained for one-dimensional adiabatic flow behind a magnetogasdynamic cylindrical shock wave propagating in a rotating non-ideal gas in presence of an azimuthal magnetic field. The density of the medium ahead of the shock is assumed to be constant. In order to obtain the similarity solutions the angular velocity of the ambient medium is assumed to be obeying a power law and to be decreasing as the distance from the axis increases. It is found that the similarity solutions exist, in both the cases, when the initial magnetic field is constant or obeying a power law. The effects of an increase in the value of the index for variation of angular velocity of the ambient medium, in the value of the parameter of the non-idealness of the gas and in the strength of the initial magnetic field are obtained. 相似文献