The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
M Sutton - One of the best experts on this subject based on the ideXlab platform.
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x Ray Intensity fluctuation spectroscopy by heterodyne detection
Journal of Synchrotron Radiation, 2006Co-Authors: F. Livet, F Bley, Francoise Ehrburgerdolle, E Geissler, Isabelle Morfin, M SuttonAbstract:A straightforward way of measuring X-Ray Intensity fluctuation spectroscopy in a small-angle X-Ray scattering configuration is demonstrated using heterodyne techniques. Two examples are presented: the Brownian motion of latex spheres in glycerol, and a Doppler velocity experiment demonstrating the motion and the relaxation of carbon-black-filled elastomers after uniaxial stretching. In the latter case the effects of mechanical relaxation can be separated from those of aggregate diffusion. The results suggest that the dynamics of these filled elastomers are similar to the universal features observed in disordered jammed systems.
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x Ray Intensity fluctuation spectroscopy
2006Co-Authors: M SuttonAbstract:At the outset let me stress that X-Ray Intensity fluctuation spectroscopy (XIFS) is a diffraction technique. As such, the intuition and expertise that you have developed for diffraction carries over to this new technique. The tendency in this chapter is to emphasize the aspects that are different from conventional diffraction but results learned from conventional diffraction will be called upon as needed.
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x Ray Intensity fluctuation spectroscopy studies on phase ordering systems
Physical Review Letters, 2005Co-Authors: Andrei Fluerasu, M Sutton, Eric M. DufresneAbstract:The order-disorder phase transition in ${\mathrm{C}\mathrm{u}}_{3}\mathrm{A}\mathrm{u}$ has been studied by x-Ray Intensity fluctuation spectroscopy. Following a quench from the high-temperature, disordered phase, the ordering kinetics is well described by a universal scaling form that can be measured by time-resolved (incoherent) x-Ray scattering. By using coherent scattering, we have measured the fluctuations about this universal scaling form. In the late stages of the ordering process, these fluctuations give a two-time correlation function $C(q,{t}_{1},{t}_{2})$ which has a scaling form with natural variables $\ensuremath{\delta}t=|{t}_{1}\ensuremath{-}{t}_{2}|$ and $\overline{t}=\frac{({t}_{1}+{t}_{2})}{2}$. The scaling form crosses over from linear in $\overline{t}$ to ${\overline{t}}^{1/2}$. These present the first such results for a nonconserved system.
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dynamics of block copolymer micelles revealed by x Ray Intensity fluctuation spectroscopy
Physical Review Letters, 1997Co-Authors: Simon G. J. Mochrie, M Sutton, A M Mayes, S. Brauer, G. B. Stephenson, Douglas L. Abernathy, Alec Sandy, Gerhard GrübelAbstract:We report x-Ray Intensity fluctuation spectroscopy measurements of the equilibrium dynamics of polymer micelle liquids, composed of polystyrene-polyisoprene block copolymer micelles within a polystyrene homopolymer matrix. The equilibrium dynamics were investigated for times between one and several hundred seconds, and for wave vectors from 0.003 to 0.015 A{sup -1}, far beyond wave vectors that can be studied with visible light. A wave-vector-dependent diffusion coefficient is found. {copyright} {ital 1997} {ital The American Physical Society}
Rajesh K. Mishra - One of the best experts on this subject based on the ideXlab platform.
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Solar Cycle Variation of Cosmic Ray Intensity along with Interplanetary and Solar Wind Plasma Parameters
Latvian Journal of Physics and Technical Sciences, 2008Co-Authors: Rajesh K. Mishra, Rekha Agarwal, Sharad TiwariAbstract:Solar Cycle Variation of Cosmic Ray Intensity along with Interplanetary and Solar Wind Plasma ParametersGalactic cosmic Rays are modulated at their propagation in the heliosphere by the effect of the large-scale structure of the interplanetary medium. A comparison of the variations in the cosmic Ray Intensity data obtained by neutron monitoring stations with those in geomagnetic disturbance, solar wind velocity (V), interplanetary magnetic field (B), and their product (V' B) near the Earth for the period 1964-2004 has been presented so as to establish a possible correlation between them. We used the hourly averaged cosmic Ray counts observed with the neutron monitor in Moscow. It is noteworthy that a significant negative correlation has been observed between the interplanetary magnetic field, product (V' B) and cosmic Ray Intensity during the solar cycles 21 and 22. The solar wind velocity has a good positive correlation with cosmic Ray Intensity during solar cycle 21, whereas it shows a weak correlation during cycles 20, 22 and 23. The interplanetary magnetic field shows a weak negative correlation with cosmic Rays for solar cycle 20, and a good anti-correlation for solar cycles 21-23 with the cosmic Ray Intensity, which, in turn, shows a good positive correlation with disturbance time index (Dst) during solar cycles 21 and 22, and a weak correlation for cycles 20 and 23.
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Transient phenomena in cosmic Ray Intensity during extreme events
Astrophysics, 2008Co-Authors: Rekha Agarwal, Rajesh K. MishraAbstract:In the present work an analysis has been made of the extreme events occurring during July 2005. Specifically, a rather intense Forbush decrease was observed at different neutron monitors all over the world during 16 July 2005. An effort has been made to study the effect of this unusual event on cosmic Ray Intensity as well as various solar and interplanetary plasma parameters. It is noteworthy that during 11 to 18 July 2005 the solar activity ranged from low to very active. Especially low levels occurred on 11, 15, and 17 July whereas high levels took place on 14 and 16 July 2005. The Sun is observed to be active during 11 to 18 July 2005, the interplanetary magnetic field Intensity lies within 15 nT, and solar wind velocity was limited to ∼500 kms-1. The geomagnetic activity during this period remains very quiet, the Kp index did not exceed 5, the disturbance storm time Dst index remains ∼-70 nT and no sudden storm commencement has been detected during this period. It is noted that for the majority of the hours, the north/south component of the interplanetary magnetic field, Bz, remains negative, and the cosmic Ray Intensity increases and shows good/high correlation with Bz, as the polarity of Bz tends to shift from negative to positive values, the Intensity decreases and shows good/high anti-correlation with Bz. The cosmic Ray Intensity tends to decrease with increase of interplanetary magnetic field strength (B) and shows anti-correlation for the majority of the days.
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Solar cycle phenomena in cosmic Ray Intensity up to the recent solar cycle
Physics Letters B, 2008Co-Authors: Rekha Agarwal, Rajesh K. MishraAbstract:Abstract A systematic correlative study has been performed since long to establish a significant relationship between cosmic Ray Intensity and different solar/heliospheric activity parameters and study is extended to recent solar cycle 23. In the present work yearly average of sunspot number (Rz), interplanetary magnetic field (B) have been used to correlate with yearly average cosmic Ray Intensity derived from the data of Moscow neutron monitor. It is noticed that for four different solar cycles 20–23 the cosmic Ray Intensity is found to anti-correlated with sunspot numbers (Rz) and interplanetary magnetic field (B) with some discrepancy. However, the interplanetary magnetic field B shows a good positive correlation with Rz for four different solar cycles. The interplanetary magnetic field strength (B) shows a weak negative correlation (−0.35) with cosmic Rays for the solar cycle 20, whereas it shows a high anti-correlation for the solar cycles 21–23 ( − 0.76 , − 0.69 ). Modulation of cosmic Rays during solar cycle 20 (1964–1976) presents discrepancies regarding the importance of IMF B for long-term modulation at 1 AU for the cycle 20. A significant contribution to modulation from the termination shock during solar cycle 20 could dilute the correlation of cosmic Rays with the interplanetary magnetic field B at 1 AU for that cycle. The perturbations of the heliosphere is weaker and less widely spread during solar cycle 20 than during other solar cycles. This might lead to a situation where the heliospheric perturbations are relatively small for cosmic Ray particles allowing these particles to reach the Earth as if it was a minimum solar activity period. This implies that the heliospheric perturbations caused by solar activity in the descending phase of solar cycle 20 were quite local and could not result in global modulation of cosmic Rays. These results demonstrate that the heliosphere evolved to the quite time structure very early in the declining phase of the solar cycle 20, implying an exceptionally fast recovery of the cosmic Ray level and a long flat cosmic Ray maximum during 1972–1977. This exceptional heliospheric evolution led to the negative lag between cosmic Ray and solar activity cycle observed in the declining phase of the solar cycle 20.
Eric M. Dufresne - One of the best experts on this subject based on the ideXlab platform.
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x Ray Intensity fluctuation spectroscopy studies on phase ordering systems
Physical Review Letters, 2005Co-Authors: Andrei Fluerasu, M Sutton, Eric M. DufresneAbstract:The order-disorder phase transition in ${\mathrm{C}\mathrm{u}}_{3}\mathrm{A}\mathrm{u}$ has been studied by x-Ray Intensity fluctuation spectroscopy. Following a quench from the high-temperature, disordered phase, the ordering kinetics is well described by a universal scaling form that can be measured by time-resolved (incoherent) x-Ray scattering. By using coherent scattering, we have measured the fluctuations about this universal scaling form. In the late stages of the ordering process, these fluctuations give a two-time correlation function $C(q,{t}_{1},{t}_{2})$ which has a scaling form with natural variables $\ensuremath{\delta}t=|{t}_{1}\ensuremath{-}{t}_{2}|$ and $\overline{t}=\frac{({t}_{1}+{t}_{2})}{2}$. The scaling form crosses over from linear in $\overline{t}$ to ${\overline{t}}^{1/2}$. These present the first such results for a nonconserved system.
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x Ray Intensity fluctuation spectroscopy studies on phase ordering systems
Physical Review Letters, 2005Co-Authors: Andrei Fluerasu, M R Sutton, Eric M. DufresneAbstract:The order-disorder phase transition in Cu3Au has been studied by x-Ray Intensity fluctuation spectroscopy. Following a quench from the high-temperature, disordered phase, the ordering kinetics is well described by a universal scaling form that can be measured by time-resolved (incoherent) x-Ray scattering. By using coherent scattering, we have measured the fluctuations about this universal scaling form. In the late stages of the ordering process, these fluctuations give a two-time correlation function C(q,t1,t2) which has a scaling form with natural variables deltat=/t1-t2/ and t =(t1+t2) / 2. The scaling form crosses over from linear in t to t1/2. These present the first such results for a nonconserved system.
G. A. Kovaltsov - One of the best experts on this subject based on the ideXlab platform.
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Reconstructing the long-term cosmic Ray Intensity: linear relations do not work
Annales Geophysicae, 2003Co-Authors: K. Mursula, I. G. Usoskin, G. A. KovaltsovAbstract:Abstract. It was recently suggested (Lockwood, 2001) that the cosmic Ray Intensity in the neutron monitor energy range is linearly related to the coronal source flux, and can be reconstructed for the last 130 years using the long-term coronal flux estimated earlier. Moreover, Lockwood (2001) reconstructed the coronal flux for the last 500 years using a similar linear relation between the flux and the concentration of cosmogenic 10 Be isotopes in polar ice. Here we show that the applied linear relations are oversimplified and lead to unphysical results on long time scales. In particular, the cosmic Ray Intensity reconstructed by Lockwood (2001) for the last 130 years has a steep trend which is considerably larger than the trend estimated from observations during the last 65 years. Accordingly, the reconstructed cosmic Ray Intensity reaches or even exceeds the local interstellar cosmic Ray flux around 1900. We argue that these unphysical results obtained when using linear relations are due to the oversimplified approach which does not take into account the complex and essentially nonlinear nature of long-term cosmic Ray modulation in the heliosphere. We also compare the long-term cosmic Ray Intensity based on a linear treatment with the reconstruction based on a recent physical model which predicts a considerably lower cosmic Ray Intensity around 1900. Key words. Interplanetary physics (cosmic Rays; heliopause and solar wind termination) – Geomagnetism and paleomagnetism (time variations, secular and long-term)
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Reconstructing the long-term cosmic Ray Intensity: linear relations do not work
Annales Geophysicae, 2003Co-Authors: K. Mursula, I. G. Usoskin, G. A. KovaltsovAbstract:It was recently suggested (Lockwood, 2001) that the cosmic Ray Intensity in the neutron monitor energy range is linearly related to the coronal source flux, and can be reconstructed for the last 130 years using the long-term coronal flux estimated earlier. Moreover, Lockwood (2001) reconstructed the coronal flux for the last 500 years using a similar linear relation between the flux and the concentration of cosmogenic 10 Be isotopes in polar ice. Here we show that the applied linear relations are oversimplified and lead to unphysical results on long time scales. In particular, the cosmic Ray Intensity reconstructed by Lockwood (2001) for the last 130 years has a steep trend which is considerably larger than the trend estimated from observations during the last 65 years. Accordingly, the reconstructed cosmic Ray Intensity reaches or even exceeds the local interstellar cosmic Ray flux around 1900. We argue that these unphysical results obtained when using linear relations are due to the oversimplified approach which does not take into account the complex and essentially nonlinear nature of long-term cosmic Ray modulation in the heliosphere. We also compare the long-term cosmic Ray Intensity based on a linear treatment with the reconstruction based on a recent physical model which predicts a considerably lower cosmic Ray Intensity around 1900.
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a physical reconstruction of cosmic Ray Intensity since 1610
Journal of Geophysical Research, 2002Co-Authors: I. G. Usoskin, K. Mursula, S K Solanki, M Schussler, G. A. KovaltsovAbstract:[1] The open solar magnetic flux has been recently reconstructed by Solanki et al. [2000, 2002] for the last 400 years from sunspot data. Using this reconstructed magnetic flux as an input to a spherically symmetric quasi-steady state model of the heliosphere, we calculate the expected Intensity of galactic cosmic Rays at the Earth's orbit since 1610. This new, physical reconstruction of the long-term cosmic Ray Intensity is in good agreement with the neutron monitor measurements during the last 50 years. Moreover, it resolves the problems related to previous reconstruction for the last 140 years based on linear correlations. We also calculate the flux of 2 GeV galactic protons and compare it to the cosmogenic 10 Be level in polar ice in Greenland and Antarctica. An excellent agreement between the calculated and measured levels is found over the last 400 years.
Rekha Agarwal - One of the best experts on this subject based on the ideXlab platform.
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Solar Cycle Variation of Cosmic Ray Intensity along with Interplanetary and Solar Wind Plasma Parameters
Latvian Journal of Physics and Technical Sciences, 2008Co-Authors: Rajesh K. Mishra, Rekha Agarwal, Sharad TiwariAbstract:Solar Cycle Variation of Cosmic Ray Intensity along with Interplanetary and Solar Wind Plasma ParametersGalactic cosmic Rays are modulated at their propagation in the heliosphere by the effect of the large-scale structure of the interplanetary medium. A comparison of the variations in the cosmic Ray Intensity data obtained by neutron monitoring stations with those in geomagnetic disturbance, solar wind velocity (V), interplanetary magnetic field (B), and their product (V' B) near the Earth for the period 1964-2004 has been presented so as to establish a possible correlation between them. We used the hourly averaged cosmic Ray counts observed with the neutron monitor in Moscow. It is noteworthy that a significant negative correlation has been observed between the interplanetary magnetic field, product (V' B) and cosmic Ray Intensity during the solar cycles 21 and 22. The solar wind velocity has a good positive correlation with cosmic Ray Intensity during solar cycle 21, whereas it shows a weak correlation during cycles 20, 22 and 23. The interplanetary magnetic field shows a weak negative correlation with cosmic Rays for solar cycle 20, and a good anti-correlation for solar cycles 21-23 with the cosmic Ray Intensity, which, in turn, shows a good positive correlation with disturbance time index (Dst) during solar cycles 21 and 22, and a weak correlation for cycles 20 and 23.
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Transient phenomena in cosmic Ray Intensity during extreme events
Astrophysics, 2008Co-Authors: Rekha Agarwal, Rajesh K. MishraAbstract:In the present work an analysis has been made of the extreme events occurring during July 2005. Specifically, a rather intense Forbush decrease was observed at different neutron monitors all over the world during 16 July 2005. An effort has been made to study the effect of this unusual event on cosmic Ray Intensity as well as various solar and interplanetary plasma parameters. It is noteworthy that during 11 to 18 July 2005 the solar activity ranged from low to very active. Especially low levels occurred on 11, 15, and 17 July whereas high levels took place on 14 and 16 July 2005. The Sun is observed to be active during 11 to 18 July 2005, the interplanetary magnetic field Intensity lies within 15 nT, and solar wind velocity was limited to ∼500 kms-1. The geomagnetic activity during this period remains very quiet, the Kp index did not exceed 5, the disturbance storm time Dst index remains ∼-70 nT and no sudden storm commencement has been detected during this period. It is noted that for the majority of the hours, the north/south component of the interplanetary magnetic field, Bz, remains negative, and the cosmic Ray Intensity increases and shows good/high correlation with Bz, as the polarity of Bz tends to shift from negative to positive values, the Intensity decreases and shows good/high anti-correlation with Bz. The cosmic Ray Intensity tends to decrease with increase of interplanetary magnetic field strength (B) and shows anti-correlation for the majority of the days.
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Solar cycle phenomena in cosmic Ray Intensity up to the recent solar cycle
Physics Letters B, 2008Co-Authors: Rekha Agarwal, Rajesh K. MishraAbstract:Abstract A systematic correlative study has been performed since long to establish a significant relationship between cosmic Ray Intensity and different solar/heliospheric activity parameters and study is extended to recent solar cycle 23. In the present work yearly average of sunspot number (Rz), interplanetary magnetic field (B) have been used to correlate with yearly average cosmic Ray Intensity derived from the data of Moscow neutron monitor. It is noticed that for four different solar cycles 20–23 the cosmic Ray Intensity is found to anti-correlated with sunspot numbers (Rz) and interplanetary magnetic field (B) with some discrepancy. However, the interplanetary magnetic field B shows a good positive correlation with Rz for four different solar cycles. The interplanetary magnetic field strength (B) shows a weak negative correlation (−0.35) with cosmic Rays for the solar cycle 20, whereas it shows a high anti-correlation for the solar cycles 21–23 ( − 0.76 , − 0.69 ). Modulation of cosmic Rays during solar cycle 20 (1964–1976) presents discrepancies regarding the importance of IMF B for long-term modulation at 1 AU for the cycle 20. A significant contribution to modulation from the termination shock during solar cycle 20 could dilute the correlation of cosmic Rays with the interplanetary magnetic field B at 1 AU for that cycle. The perturbations of the heliosphere is weaker and less widely spread during solar cycle 20 than during other solar cycles. This might lead to a situation where the heliospheric perturbations are relatively small for cosmic Ray particles allowing these particles to reach the Earth as if it was a minimum solar activity period. This implies that the heliospheric perturbations caused by solar activity in the descending phase of solar cycle 20 were quite local and could not result in global modulation of cosmic Rays. These results demonstrate that the heliosphere evolved to the quite time structure very early in the declining phase of the solar cycle 20, implying an exceptionally fast recovery of the cosmic Ray level and a long flat cosmic Ray maximum during 1972–1977. This exceptional heliospheric evolution led to the negative lag between cosmic Ray and solar activity cycle observed in the declining phase of the solar cycle 20.
