Effect Of Rayleigh-Taylor Instability Research Articles

Effects of Rayleigh-Taylor instability and ionospheric plasma bubbles on the global navigation satellite System signal

Ionospheric disturbances induced by various natural (e.g., earthquakes, volcanic eruption, thunderstorms, meteorite showers, solar eclipses) or anthropogenic (e.g., nuclear explosions, launching of space shuttles) processes can be detected through change in Total Electron Content (TEC) in the F-layer. These ionospheric perturbations can be captured by worldwide expanding geodetic (GNSS) networks, mainly during the day time, when the solar radiation ionizes the air molecules. However, during post-sunset period, strong ionospheric irregularities (known as Equatorial Plasma Bubbles, EPBs) develop due to the classical configuration for the Rayleigh-Taylor (R-T) instability that diffracts navigation and communication signals. Here we use various instances of ionospheric disturbances triggered by natural processes (e.g., earthquakes and volcanic eruption), in the recent decade to investigate the spatiotemporal and seasonal effects of ionospheric irregularities on the GNSS signals. Our study suggests that in the low-latitudinal region (e.g., Sumatra, Mexico), such ionospheric irregularities can mask the ionospheric perturbations due to the higher production rate of EPBs. Hence detection of such co-seismic TEC anomaly becomes difficult. However, in the high-latitudinal region (e.g., Iceland, Alaska), due to the lower production rate of EPBs, ambient ionospheric irregularities are insignificant and hence coseismic TEC anomalies can be captured even during night time. We argue that the production rate of EPBs further depends upon seasonal and longitudinal parameters on the globe.

Is the magnetopause Rayleigh‐Taylor unstable sometimes?

At the terrestrial magnetopause the dense magnetosheath flowing around the magnetosphere interfaces with the normally much more tenuous magnetospheric plasma. Temporal variations in the solar wind dynamic pressure cause the magnetopause to be in continuous motion. When it decelerates and rebounds sunward after a strong and rapid drop in the solar wind dynamic pressure, we have a situation of a heavy‐over‐light plasma in an effective gravitational field. In this paper we investigate theoretically the conditions under which this configuration may become Rayleigh‐Taylor (RT) unstable. The motion of the magnetopause is studied using a gas‐dynamic model which takes into account forces arising from hypersonic flow past an object of prescribed shape. Thus the effect of the magnetic field near the magnetopause is not included. For sufficiently large and rapid dynamic pressure variations we obtain accelerations ≥ 1kms−2 lasting for periods of the order of 1–2 min. We discuss the possible instability of both global (λ ≫ Δ, thickness of the magnetopause) and internal (λ < Δ) modes, taking into account the stabilizing effects of (1) magnetic shear across the magnetopause and (2) viscosity of the magnetosheath plasma. We find that both modes are stable when the magnetic shear across the magnetopause is large. When the magnetosheath field points strongly northward, however, we find that both modes may be RT unstable. Among the effects of RT instability on the magnetopause and its environs are (1) large distortions of the magnetic field lines, (2) localized compressions of the magnetospheric magnetic field, (3) increased magnetopause thickness, and (4) reduced average density gradient across the magnetopause. (Since we only concentrate here on the linear stage of the development of the instability, no mass transfer into the magnetosphere is included.) These are all, in principle, observable effects, though the rapid motion of the magnetopause would require a fortuitous spacecraft‐magnetopause configuration for them to be actually seen in single‐spacecraft data. This work may be considered äs a contribution to the current research on the structure and physics of the low‐shear magnetopause.

The radio dynamical evolution of young supernova remnants

Numerical models of young supernova remnants (SNRs) are calculated using a spherically symmetric magnetohydrodynamic code to determine the effects of Rayleigh-Taylor instabilities on the radio properties of young SNRs. The instabilities arise from the deceleration of the remnant as it moves through an inhomogeneous medium. After accounting for momentum interactions, the resultant energy of the instability is sufficient to amplify ambient magnetic fields to strengths comparable to those found in yound SNRs. The effects of varying the initial explosion energy, mass ejected, and interstellar density on the flux and surface brightness are investigated. Under the assumption that a supply of relativistic electrons is present, the temporal evolution of the flux density and surface brightness has been calculated. Graphs of surface brightness versus remnant radius are also presented, and the dynamical evolution of the radio shell is investigated as a function of the initial parameters.