Saturn's aurora has been studied at relatively lower latitudes mapping to closed field lines near the open closed field line boundary. Precipitation of electrons into the atmosphere of Saturn from resonant wave-particle interaction by whistler mode waves has been considered. Precipitation flux and UV intensities of four excitations: H Lyman-α from atomic H, H Lyman-α from dissociative excitation of molecular H2, Lyman and Werner bands of H2 have been estimated. In this study observed whistler mode wave data and observed electron distribution function have been used. Calculations have been performed for the range 4.5–7.5 of L-shells. In the sub range of L-shells 5.5–7.5, the calculated UV intensities are: 0.8 R, 120−134 R, 594−664 R and 631−706 R for H Lyman-α from atomic H, H Lyman-α from molecular H2, Lyman and Werner bands of H2, respectively. The UV intensities are found negligibly small for the range of L-shells 4.5–5.5. It is estimated that higher UV intensities would be expected for whistler mode upper band chorus waves. However, these waves are less frequent in the magnetosphere of Saturn and sufficient wave data is not available to calculate the auroral emissions.

In the present paper we have modeled diffuse auroral emissions, which have been observed at lower latitudes as compared to the main auroral arc at Saturn. It is generally accepted that these emissions are generated by precipitation of hot population of magnetospheric electrons on the closed field lines. We have considered the pitch angle diffusion by electrostatic electron cyclotron harmonic waves as the mechanism to diffuse trapped electrons into the atmospheric loss cone. Electrons are thereby precipitated into the atmosphere and excite the neutral atmospheric constituents producing auroral emissions. Calculation of ultraviolet emission intensities has been performed at two L‐shells 5.35 and 7.0. Observed hot electron distribution functions and observed electrostatic electron cyclotron harmonic wave characteristics have been used in the study. Intensities of Lyman‐alpha emission from excitation of atomic H and Lyman‐alpha produced from dissociative excitation of H 2 have been calculated, obtaining the values 20.1 R (1.8 R) and 1.6 kR (0.29 kR), respectively, for both L‐shells 7.0 (5.35).Further, intensities of Lyman and Werner bands of H 2 are also calculated. These have the values 7.50 kR (1.43 kR) and 7.52 kR (1.49 kR), respectively, for L‐shells 7.0 (5.35). It is observed that the volume excitation rates of these four excitations peak at an altitude of about 2,000 km. From the range‐energy relation in H 2 gas it is estimated that the electrons producing these excitations should have energies less than about 250 eV.

Diffuse auroral intensities of neutral atomic oxygen OI λ1356 Å emission on Ganymede due to whistler mode waves are estimated. Pitch angle diffusion of magnetospheric electrons into the loss cone due to resonant wave–particle interaction of whistler mode waves is considered, and the resulting electron precipitation flux is calculated. The analytical yield spectrum approach is used for determining the energy deposition of electrons precipitating into the atmosphere of Ganymede. It is found that the intensities (4–30 R) calculated from the precipitation of magnetospheric electrons observed near Ganymede are inadequate to account for the observational intensities (≤ 100 R). This is in agreement with the conclusions reached in previous works. Some acceleration mechanism is required to energize the magnetospheric electrons. In the present work we consider the heating and acceleration of magnetospheric electrons by electrostatic waves. Two particle distribution functions (Maxwellian and kappa distribution) are used to simulate heating and acceleration of electrons. Precipitation of a Maxwellian distribution of electrons can produce about 70 R intensities of OI λ1356 Å emission for electron temperature of 150 eV. A kappa distribution can also yield a diffuse auroral intensity of similar magnitude for a characteristic energy of about 100 eV. The maximum contribution to the estimated intensity results from the dissociative excitation of O2. Contributions from the direct excitation of atomic oxygen and cascading in atomic oxygen are estimated to be only about 1 and 2 % of the total calculated intensity, respectively. The findings of this work are relevant for the present JUNO and future JUICE missions to Jupiter. These missions will provide new data on electron densities, electron temperature and whistler mode wave amplitudes in the magnetosphere of Jupiter near Ganymede.

The role of electrostatic electron cyclotron harmonic (ECH) waves in producing diffuse auroral emission O I 1356 angstrom on Ganymede is investigated. Electron precipitation flux entering the atmosphere of Ganymede due to pitch-angle diffusion by ECH waves into the atmospheric loss-cone is calculated. The analytical yield spectrum approach for electron energy degradation in gases is used for calculating diffuse auroral intensities. It is found that calculated O I 1356 angstrom intensity resulting from the precipitation of magnetospheric electrons observed near Ganymede is insufficient to account for the observed diffuse auroral intensity. This is in agreement with estimates made in earlier works. Heating and acceleration of ambient electrons by ECH wave turbulence near the magnetic equator on the field line connecting Ganymede and Jupiter are considered. Two electron distribution functions are used to simulate the heating effect by ECH waves. Use of a Maxwellian distribution with temperature 100 eV can produce about 50-70 Rayleigh O I 1356 angstrom intensities, and the kappa distribution with characteristic energy 50 eV also gives rise to intensities with similar magnitude. Numerical experiments are performed to study the effect of ECH wave spectral intensity profile, ECH wave amplitude, and temperature/characteristic energy of electron distribution functions on the calculated diffuse auroral intensities. The proposed missions, joint NASA/ESA Jupiter Icy Moon Explorer and the present JUNO mission to Jupiter, would provide new data to constrain the ECH wave and other physical parameters near Ganymede. These should help confirm the findings of the present study.

The present study is aimed at resolving the issue of pitch-angle diffusion by whistler mode waves near Ganymede and to understand the interaction of Ganymede with magnetosphere of Jupiter. A new electron distribution function, which is a combination of Maxwellian and kappa loss-cone distribution, is used to calculate whistler mode wave growth rates. The distribution function is fitted to observed distribution near Ganymede. Wave growth rates have been used to obtain bounce-averaged pitch-angle diffusion coefficients along the field line connecting Ganymede and Jupiter. Variations of electron density and magnetic field along the particle bounce trajectory and a non dipolar field have been taken into account. Pitch-angle variation of diffusion coefficients is parameterized in a simple form ~Dο(sinα)p. Do is diffusion coefficient (independent of pitch angle). The calculated energy dependence of diffusion coefficients (Do) is in good agreement with observed energy dependence of coefficient Do. Wave magnetic field ~16pT is required to match observed and calculated diffusion coefficients. The exponent p takes values from ~1 to 4 for electron energies 15keV to 1MeV, respectively. It is found that contribution of Ganymede interaction region to pitch-angle scattering is quite small (~4% to 20%). Further analysis of Galileo energetic particle detector (EPD) and plasma wave data or new particle and wave data near Ganymede from JUNO mission to Jupiter are necessary to confirm the findings of present work.

Bounce-averaged pitch angle diffusion rates of electrons due to whistler mode waves have been calculated in the Jupiter's magnetosphere. Variations of electron density, magnetic field, wave intensity and upper cut-off frequency along the particle bounce trajectory have been taken into account. Field line tracing is performed to obtain the loss-cone size associated with the VIP 4 magnetic field model including the external field due to azimuthal current sheet. Numerical calculations have been carried out at L shells 10, 12, 15, 18, and 20. The longitudinal variations of electron energy precipitation into the atmosphere leading to diffuse aurora have been modelled. It is found that observed wave amplitudes at L <= 15 are insufficient to put electrons on strong pitch angle diffusion whereas at L=18 and 20 electrons of energies <= 30 keV can be put on strong diffusion. At L=10 electron energy precipitation supports auroral brightness of 25 kR in the northern and 36 kR in the southern hemisphere at west longitude similar to 10-60 degrees. At shells L=12 and 15 auroral brightness less than 10 kR is obtained. This is in accord with Voyager observation of jovian UV aurora just beyond the In torus (7-12R(J)). At L=18 maximum auroral brightness 73 kR in the northern hemisphere at west longitude of 16 degrees and 30 kR in the southern hemisphere for west longitudes <= 50 degrees are obtained. This is in agreement with the diffuse auroral brightness measured by Hubble Space Telescope (HST). Observations of longitudinal variation of diffuse auroral brightness are, however, required to ascertain the present findings. (C) 2013 Published by Elsevier Inc.

Pitch-angle diffusion coefficients of electrons have been calculated for resonant interaction with electrostatic electron-cyclotron harmonic (ECH) waves using quasi linear diffusion theory. Calculations have been performed for the planets Earth and Jupiter at three radial distances for each planet. Electron precipitation fluxes have also been calculated and compared with observed fluxes. At Earth, electrons of energy ≤200 eV may be put on strong diffusion at L = 10. At lower L values, observed ECH wave amplitudes are insufficient to put electrons on strong diffusion. At Jupiter, electrons can be put on strong diffusion at all L values. However, the energy of electrons which may be put on strong diffusion decreases from about 1 keV at L = 7 to ~100 eV at L = 17. It is concluded that ECH waves may be partly responsible for diffuse auroral precipitation of low energy electrons at Jupiter for lower L values. At Earth contribution of ECH waves to diffuse aurora is quite small.

Bounce-averaged pitch angle diffusion coefficients of electrons due to resonant interaction with electrostatic electron cyclotron harmonic (ECH) and whistler mode waves have been calculated. Temporal growth rates obtained by solving the appropriate dispersion relation have been used to represent the distribution of wave energy with frequency. Calculations have been performed at two spatial locations L=4.6 and L=6.8. The results obtained suggest that ECH waves can put electrons on strong pitch angle diffusion at both spatial locations. However, at L=4.6, electrons with energy <100eV and at L=6.8 electrons with energy up to ∼500eV can be put on strong diffusion contributing to diffuse auroral precipitation. Whistler mode waves can put electrons of energy ≤5keV on strong pitch angle diffusion at L=6.8 whereas at L=4.6 observed wave fields are insufficient to put electrons on strong diffusion. ECH waves contribute up to 17% of the total electron energy precipitation flux due to both ECH and whistler mode waves. A case study has been performed to calculate pitch angle diffusion coefficients using Gaussian function to represent wave energy distribution with frequency. It is found that, for electron energy <500eV, the calculated diffusion coefficients using Gaussian function to represent ECH wave energy distribution are several orders of magnitude smaller or negligible as compared to diffusion coefficients calculated by temporal growth rates. However, the calculated pitch angle diffusion coefficients using Gaussian function for whistler mode wave energy distribution are in very good agreement with diffusion coefficients calculated by temporal growth rates. It is concluded that representing the ECH wave energy distribution with frequency by a Gaussian function grossly underestimates the low energy (<500eV) electron precipitation flux due to ECH waves.

The general characteristic equation is derived for the helically cladded step-index optical fiber. The dispersion curves are drawn for the different pitch angles Ψ and mode order ν = 1. The effect of helix pitch angle on the dispersion characteristics and also on the modal cut-off condition is examined. Except for the lowest order mode, all the modes appear in pairs. The lowest order mode displays the negative dispersion for the some value of normalized frequency V and depends on the helix pitch angle Ψ.

This paper considers the problem of installation of additional facilities in water supply system to meet the demands of an increasing population. Dynamic programming has been used to minimize a performance index based on the waiting cost of the population needing water supply, and cost of unutilized capacity. These two costs will ensure the proper size of additional facilities to be installed at a particular time. Assuming that water requirement over a certain time period in future has been estimated, optimal installation times of additional facilities in water supply system and optimal number of such installations over the given time period have been determined. Though the present model does not involve the installation cost explicitly, it is inherently present in form of cost of unutilized capacity and optimal number of installations.

We consider an annular elliptic lightguide of constant radial width (CRWEG), whose guiding region cross section is bounded by two elliptical boundaries. Using Goell's point-matching method, we obtain the characteristic equation and dispersion curves for this waveguide. When the dispersion curves of this waveguide are compared with that of confocal and concentric elliptic lightguides (CFEG and CEG), it is found that they are less steep for CRWEG. It is also found that the cutoff value of the lowest order modes for this waveguide is greater than that for CFEG and CEG. This means that this waveguide supports fewer modes than CFEG and CEG. (C) 2001 John Wiley & Sons, Inc.

Bromine, a minor constituent in the Earth’s atmosphere - with its 50-fold higher efficiency of ozone destruction compared to chlorine - contributes significantly to the ozone hole formation and wintertime stratospheric ozone depletion over northern mid and high latitudes. In addition ozone episodes observed in the Arctic during polar sunrise are solely due to atmospheric bromine. CH3Br, CH2Br2 and CHBr3 are the major brominated gases in the atmosphere, of which CH3Br being most abundant, contributes about 50% and CH2Br2 around 7 to 10% of the total organic stratospheric bromine. Bromocarbons with shorter lifetimes like CHBr3, CH2BrCl, CHBr2Cl, CHBrCl2 and CH2Brl decompose before reaching the stratosphere, and are responsible for the ozone episodes. But for CH3Br, which has also significant anthropogenic sources, all the aforementioned bromocarbons are mostly of marine origin. Halons (H-1211, H-1301, H-2402, H-1202) are solely anthropogenic and are far more stable. They decompose only after reaching the stratosphere. It is estimated that 39% of the stratospheric organic bromine (≈ 7 pptv) loading is due to these halons. Increases are being still registered in the atmospheric abundance of halons in spite of production restrictions. Though extensively investigated, the existing knowledge with regard to the production and degradation of atmospheric bromine gases, is not commensurate with its importance.

The rotational analysis of the three bands (1,0), (0,0), and (0,1) of the B–X2 system of PbF has been carried out. The bands have been excited in a transformer discharge and photographed in the second order of a 35 ft concave grating spectrograph. The analysis has shown that the bands arise from a 2Σ+–2Π3/2 transition. The rotational constants of the upper and lower states have been determined.