[1] Comparison of results from a three-dimensional (3-D) finite difference time domain (FDTD) model of Schumann resonances (SR) with a set of classical eigenfrequency and quality factor solutions for laterally uniform spherically symmetric Earth-ionosphere cavity and recent SR observations during solar proton events (SPEs) and X-ray bursts demonstrate the potential and applicability of the FDTD technique for studies of realistic SR problems.Citation: Yang, H., and V. P. Pasko (2005), Three-dimensional finite difference time domain modeling of the Earth-ionosphere cavity resonances, Geophys. Res. Lett., 32, L03114,

[1] The conducting ionosphere and conducting surface of Titan, Venus, and Mars form a concentric resonator, which would support the possibility of the existence of global electromagnetic resonances. On Earth, such resonances are commonly referred to as Schumann resonances and are excited by lightning discharges. The detection of such resonances on other planets would give a support for the existence of the electrical discharges in the lower atmosphere on these planets. In this paper, a three-dimensional finite difference time domain modeling for the extremely low frequency propagation is employed to study the Schumann resonance problems on Titan, Venus, and Mars. The atmospheric conductivity profiles for these studies are derived from the previously reported ionospheric models for these planets. The Schumann resonance frequencies and Q factors on these planets are calculated and are critically compared with those obtained from the previously published models.

[1] The diurnal and seasonal variations of Schumann resonances (SR) have been reported in a number of experiments. In this paper, a three-dimensional FDTD model of the Earth-ionosphere cavity with a day-night asymmetric conductivity profile is employed to study the diurnal and seasonal variability of the power and frequency of the first Schumann resonance (SR) mode. Comparison of the FDTD results and recent experimental measurements shows a clear modulation in the SR power related to the local ionospheric height and global lightning activity. It is found that SR frequencies are not only a function of the local time but also are controlled by the global lightning activity changing with universal time.

No abstract

No abstract

[1] A three-dimensional Finite Difference Time Domain (FDTD) model of the Earthionosphere cavity with a realistic conductivity profile is employed to study the global lightning activity using the observed intensity variations of Schumann resonances (SR). Comparison of the results derived from our FDTD model and the previous studies by other authors on related subjects shows that Schumann resonance is a good probe to indicate the seasonal variations of lightning activity in three main thunderstorm regions (Africa, southeast Asia, and South America). An inverse method based on genetic algorithms is developed to extract information on lightning intensity in these three regions from observed SR intensity data. Seasonal variations of the lightning activity in three thunderstorm centers are clearly observed in our results. Different SR frequency variations associated with seasonal variations of global lighting activity are also discussed.

We report on two-color InAs/InP(100) quantum dot lasers with tunable wavelength gap. Two peaks of lasing emission were observed simultaneously, while the high energy peak undergoes continuous blueshift with the increase in the injection current, and the low energy peak is somewhat fixed. Sophisticated studies of the wavelength gap as a function of the laser power prove that the two-peak lasing and shifting is not caused by the effect of Rabi oscillation. Moreover, comparison of electroluminescence and lasing spectra under different injection currents reveal the blueshift of the high energy peak is most likely related to the state-filling effect.

The optical properties of two kinds of InGaN∕GaN quantum-wells light emitting diodes, one of which was doped with Si in barriers while the other was not, are comparatively investigated using time-integrated photoluminescence and time-resolved photoluminescence techniques. The results clearly demonstrate the coexistence of the band gap renormalization and phase-space filling effect in the structures with Si doped barriers. It is surprisingly found that photogenerated carriers in the intentionally undoped structures decay nonexponentially, whereas carriers in the Si doped ones exhibit a well exponential time evolution. A new model developed by O. Rubel, S. D. Baranovskii, K. Hantke, J. D. Heber, J. Koch, P. Thomas, J. M. Marshall, W. Stolz, and W. H. Rühle [J. Optoelectron. Adv. Mater. 7, 115 (2005)] was used to simulate the decay curves of the photogenerated carriers in both structures, which enables us to determine the localization length of the photogenerated carriers in the structures. It is found that the Si doping in the barriers not only leads to remarkable many-body effects but also significantly affects the carrier recombination dynamics in InGaN∕GaN layered heterostructures.