Inter-annual variations of 6.5-day planetary waves and their relations with QBO

This paper studies inter-annual variations of 6.5-Day Waves(6.5 DWs) observed at altitudes 20-110 km between 52°S-52°N latitudes during March 2002-January 2021, and how these variations were related to the equatorial stratospheric Quasi-Biennial Oscillation(QBO). Temperature amplitudes of the 6.5 DWs are calculated based on SABER/TIMED observations. QBO zonal winds are obtained from an ERA5 reanalysis dataset. QBO phases are derived using an Empirical Orthogonal Functions(EOF) method. Wavelet analysis of the observed 6.5 DW variations demonstrates obvious spectral maximums around 28-38 months at 32°N-52°N, and around 26-30 months at 32°S-52°S. In the Northern Hemisphere, peak periods lengthened poleward;in the Southern Hemisphere, however,they were unchanged with latitude. Residual 6.5 DWs amplitudes have been determined by removing composite amplitudes from 6.5 DWs amplitudes. Comparisons between QBO and monthly maximum residual 6.5 DWs amplitudes(AMmax) show clear correlations between the QBO and 6.5 DWs in both hemispheres, but the observed relationship is stronger in the NH. When AMmax NH, the mean QBO profile was easterly at all levels from 70 to 5 hPa;when the AMmax below 30 hPa. Linear Pearson correlation coefficients between QBO phases and AMmax 20°N-52°N in April and around 64 km at 24°S in February, and large negative values from 80 to 110 km between 20°N-50°N in August and at 96-106 km between 20°S-44°S in February. These results indicate quantitative correlations between QBO and 6.5 DWs and provide credible evidences for further studies of QBO modulations on long-term variations of 6.5 DWs.

Gravitomagnetic Effects on Collective Plasma Oscillations in Compact Stars

The effects of gravitomagnetic force on plasma oscillations are investigated using the kinetic theory of homogeneous electrically neutral plasma in the absence of external electric or magnetic field. The random phase assumption is employed neglecting the thermal motion of the electrons with respect to a fixed ion background. It is found that the gravitomagnetic force reduces the characteristic frequency of the plasma thus enhancing the refractive index of the medium. The estimates for the predicted effects are given for a typical white dwarf, pulsar, and neutron star.

Improved functional-weight approach to oscillatory patterns in excitable networks

Studies of sustained oscillations on complex networks with excitable node dynamics received much interest in recent years.Although an individual unit is non-oscillatory,they may organize to form various collective oscillatory patterns through networked connections.An excitable network usually possesses a number of oscillatory modes dominated by different Winfree loops and numerous spatiotemporal patterns organized by different propagation path distributions.The traditional approach of the so-called dominant phase-advanced drive method has been well applied to the study of stationary oscillation patterns on a network.In this paper,we develop the functional-weight approach that has been successfully used in studies of sustained oscillations in gene-regulated networks by an extension to the high-dimensional node dynamics.This approach can be well applied to the study of sustained oscillations in coupled excitable units.We tested this scheme for different networks,such as homogeneous random networks,small-world networks,and scale-free networks and found it can accurately dig out the oscillation source and the propagation path.The present approach is believed to have the potential in studies competitive non-stationary dynamics.