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Kiran Jain

Bio: Kiran Jain is an academic researcher from Physical Research Laboratory. The author has contributed to research in topics: Solar cycle & Sunspot. The author has an hindex of 16, co-authored 89 publications receiving 982 citations. Previous affiliations of Kiran Jain include University of Surrey & Indian Institute of Astrophysics.


Papers
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Journal ArticleDOI
TL;DR: A review of the empirical data on intrinsic states of odd-$A$ nuclei in the mass range $151\ensuremath{\le}A\enuremath{1/2}193$ and $A \ensuremath{ge}221$ is presented in this paper.
Abstract: A review of the empirical data on intrinsic states of odd-$A$ nuclei in the mass range $151\ensuremath{\le}A\ensuremath{\le}193$ and $A\ensuremath{\ge}221$ is presented. Global summaries of the data are presented in tables for each isotopic and isotonic chain, wherein the excitation energy, the $log\mathrm{ft}$ values, the moment-of-inertia parameter, and the decoupling parameter (for $K=\frac{1}{2}$ bands) are listed for single-particle, vibrational admixed, and pure vibrational states. Similar data are separately presented for three-quasiparticle excitations in the rare-earth region. Taking guidance from the systematics on nuclear deformation, the single-particle deformed potential for axially symmetric and reflection-symmetric shapes (the Nilsson model) modified by the hexadecapole deformation is used to interpret the data. Other variations of the Nilsson model, which include axially asymmetric shapes ($\ensuremath{\gamma}$ deformation) and especially reflection-asymmetric shapes (octupole deformation), have also been used to interpret the data in certain limited regions. Systematics for the intrinsic excitations are presented and discussed in terms of these models. The newly emerging regions of the octupole-quadrupole deformation and superdeformation are also discussed.

162 citations

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TL;DR: In this paper, the authors performed a systematic theoretical study of the mass-180 region and showed that the simpler blocked BCS theory gives a good approximation to the multi-quasiparticle spectra if the pairing strength is chosen appropriately.

73 citations

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TL;DR: In this article, the authors studied the time and latitudinal properties of acoustic modes that are sensitive probes of the subsurface layers and found evidence that a sudden enhancement in amplitude occurs in just the last few hundred kilometers.
Abstract: Manifestations of the solar magnetic activity through periodicities of about 11 and 2 years are now clearly seen in all solar activity indices. In this paper, we add information about the mechanism driving the 2-year period by studying the time and latitudinal properties of acoustic modes that are sensitive probes of the subsurface layers. We use almost 17 years of high-quality resolved data provided by the Global Oscillation Network Group to investigate the solar cycle changes in p-mode frequencies for spherical degrees l from 0 to 120 and 1600 μHz ≤ν ≤ 3500 μHz. For both periodic components of solar activity, we locate the origin of the frequency shift in the subsurface layers and find evidence that a sudden enhancement in amplitude occurs in just the last few hundred kilometers. We also show that, in both cases, the size of the shift increases toward equatorial latitudes and from minimum to maximum solar activity, but, in agreement with previous findings, the quasi-biennial periodicity (QBP) causes a weaker shift in mode frequencies and a slower enhancement than that caused by the 11-year cycle. We compare our observational findings with the features predicted by different models, that try to explain the origin of this QBP and conclude that the observed properties could result from the beating between a dipole and quadrupole magnetic configuration of the dynamo.

66 citations

Journal ArticleDOI
TL;DR: In this paper, the authors carried out a correlation analysis between the change in frequencies and several measures of the Sun's magnetic activity that are sensitive to changes at different levels in the solar atmosphere, and found that more than 90% of the variation in the oscillation frequencies in all activity phases can be explained by changes in both components of the magnetic field.
Abstract: We analyze intermediate-degree p-mode eigenfrequencies measured by Global Oscillation Network Group and Michelson Doppler Imager/Solar and Heliospheric Observatory over a solar cycle to study the source of their variability. We carry out a correlation analysis between the change in frequencies and several measures of the Sun's magnetic activity that are sensitive to changes at different levels in the solar atmosphere. The observations span a period of about 12 years starting from mid-1996 (the minimum of cycle 23) to early-2008 (near minimum of cycle 24), corresponding to a nearly complete solar activity cycle. We demonstrate that the frequencies do vary in phase with the solar activity indices, however, the degree of correlation differs from phase to phase of the cycle. During the rising and declining phases, the mode frequency shifts are strongly correlated with the activity proxies whereas during the high-activity period, the shifts have significantly lower correlation with all activity proxies, except for the 10.7 cm radio flux. In particular, the proxies that are only influenced by the variation of the strong component of the magnetic field in the photosphere have a much lower correlation at the high-activity period. On the other hand, the shifts are better correlated with the proxies sensitive to changes in the weak component of the magnetic field. Our correlation analysis suggests that more than 90% of the variation in the oscillation frequencies in all activity phases can be explained by changes in both components of the magnetic field. Further, the slopes obtained from the linear regression analysis also differ from phase to phase and show a strong correlation with the correlation coefficients between frequency shifts and solar activity.

50 citations

Journal ArticleDOI
TL;DR: In this paper, a correlation analysis of GONG p-mode frequencies with nine solar activity indices for the period from 1995 August to 1997 August is presented. But the analysis is limited to the period between 1995 and 1997.
Abstract: We present a correlation analysis of GONG p-mode frequencies with nine solar activity indices for the period from 1995 August to 1997 August. This study includes spherical harmonic degrees in the range 2-150 and the frequency range of 1500-3500 μHz. Using three statistical tests, the measured mean frequency shifts show strong to good correlation with activity indices. A decrease of 0.06 μHz in frequency during the descending phase of solar cycle 22 and an increase of 0.04 μHz in the ascending phase of solar cycle 23 are observed. These results provide the first evidence for change in p-mode frequencies around the declining phase of cycle 22 and the beginning of new cycle 23. This analysis further confirms that the temporal behavior of the solar frequency shifts closely follow the phase of the solar activity cycle.

42 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the development of this review article has evolved from work carried out by an international team of the International Space Science Institute (ISSI), Bern, Switzerland, and from work performed under the auspices of Scientific Committee on Solar Terrestrial Physics (SCOSTEP) regarding climate and weather of the Sun-Earth System (CAWSES).
Abstract: The development of this review article has evolved from work carried out by an international team of the International Space Science Institute (ISSI), Bern, Switzerland, and from work carried out under the auspices of Scientific Committee on Solar Terrestrial Physics (SCOSTEP) Climate and Weather of the Sun‐Earth System (CAWSES‐1). The support of ISSI in providing workshop and meeting facilities is acknowledged, especially support from Y. Calisesi and V. Manno. SCOSTEP is acknowledged for kindly providing financial assistance to allow the paper to be published under an open access policy. L.J.G. was supported by the UK Natural Environment Research Council (NERC) through their National Centre for Atmospheric Research (NCAS) Climate program. K.M. was supported by a Marie Curie International Outgoing Fellowship within the 6th European Community Framework Programme. J.L. acknowledges support by the EU/FP7 program Assessing Climate Impacts on the Quantity and Quality of Water (ACQWA, 212250) and from the DFG Project Precipitation in the Past Millennium in Europe (PRIME) within the Priority Program INTERDYNAMIK. L.H. acknowledges support from the U.S. NASA Living With a Star program. G.M. acknowledges support from the Office of Science (BER), U.S. Department of Energy, Cooperative Agreement DE‐FC02‐97ER62402, and the National Science Foundation. We also wish to thank Karin Labitzke and Markus Kunze for supplying an updated Figure 13, Andrew Heaps for technical support, and Paul Dickinson for editorial support. Part of the research was carried out under the SPP CAWSES funded by GFG. J.B. was financially supported by NCCR Climate–Swiss Climate Research.

1,045 citations

Journal ArticleDOI
TL;DR: The experimental and theoretical evidence for intrinsic reflection-asymmetric shapes in nuclei is reviewed in this article, and the theoretical methods discussed cover a wide spectrum, from mean field theory and its extensions to algebraic and cluster approaches.
Abstract: The experimental and theoretical evidence for intrinsic reflection-asymmetric shapes in nuclei is reviewed. The theoretical methods discussed cover a wide spectrum, from mean-field theory and its extensions to algebraic and cluster approaches. The experimental data for nuclear ground states and at low and high spin, cited as evidence for reflection asymmetry, are collected and categorized. The extensive data on electric dipole transition moments and their theoretical interpretation are surveyed, along with available data on electric octupole moments. The evidence for reflection-asymmetric molecular states in light nuclei is summarized. The application of reflection-asymmetric theories to descriptions of the fission barrier, bimodal fission, superdeformation, and hyperdeformations is reviewed, and some other perspectives in the wider context of nuclear physics are also given. [S0034-6861(96)00102-X]

462 citations

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TL;DR: In this article, the authors provide a framework for disentangling contributions from physics at different scales, building out from the set of dimension four and six effective operators that embody CP violation at the Fermi scale.

431 citations

Journal ArticleDOI
TL;DR: In this paper, a detailed overview of existing solar spectral irradiance (SSI) measurements and a comparison of models available to date is presented, along with a comprehensive approach for an issue that is usually addressed separately by different communities.
Abstract: The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE (SOlar Radiation and Climate Experiment) satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of recent chemistry-climate model (CCM) simulations have shown that this might have significant implications on the Earth's atmosphere. Motivated by these results, we summarize here our current knowledge of SSI variability and its impact on Earth's climate. We present a detailed overview of existing SSI measurements and provide thorough comparison of models available to date. SSI changes influence the Earth's atmosphere, both directly, through changes in shortwave (SW) heating and therefore, temperature and ozone distributions in the stratosphere, and indirectly, through dynamical feedbacks. We investigate these direct and indirect effects using several state-of-the art CCM simulations forced with measured and modelled SSI changes. A unique asset of this study is the use of a common comprehensive approach for an issue that is usually addressed separately by different communities. We show that the SORCE measurements are difficult to reconcile with earlier observations and with SSI models. Of the five SSI models discussed here, specifically NRLSSI (Naval Research Laboratory Solar Spectral Irradiance), SATIRE-S (Spectral And Total Irradiance REconstructions for the Satellite era), COSI (COde for Solar Irradiance), SRPM (Solar Radiation Physical Modelling), and OAR (Osservatorio Astronomico di Roma), only one shows a behaviour of the UV and visible irradiance qualitatively resembling that of the recent SORCE measurements. However, the integral of the SSI computed with this model over the entire spectral range does not reproduce the measured cyclical changes of the total solar irradiance, which is an essential requisite for realistic evaluations of solar effects on the Earth's climate in CCMs. We show that within the range provided by the recent SSI observations and semi-empirical models discussed here, the NRLSSI model and SORCE observations represent the lower and upper limits in the magnitude of the SSI solar cycle variation. The results of the CCM simulations, forced with the SSI solar cycle variations estimated from the NRLSSI model and from SORCE measurements, show that the direct solar response in the stratosphere is larger for the SORCE than for the NRLSSI data. Correspondingly, larger UV forcing also leads to a larger surface response. Finally, we discuss the reliability of the available data and we propose additional coordinated work, first to build composite SSI data sets out of scattered observations and to refine current SSI models, and second, to run coordinated CCM experiments.

334 citations

Journal ArticleDOI
06 May 1999-Nature
TL;DR: A small proportion of atomic nuclei can form highly excited metastable states, or isomers, and these isomers are among the longest-lived and have the potential to reach the highest energies as mentioned in this paper.
Abstract: A small proportion of atomic nuclei can form highly excited metastable states, or isomers. Of particular interest is a class of isomers found in deformed axially symmetric nuclei; these isomers are among the longest-lived and have the potential to reach the highest energies. By probing their properties, insights into nuclear structure have been gained. The possibility of stimulated isomer decay may ultimately lead to new forms of energy storage and γ-ray lasers.

306 citations