Related papers: Spicules: velocity, acceleration and scatter plots
We study general aspects of active motion with fluctuations in the speed and the direction of motion in two dimensions. We consider the case in which fluctuations in the speed are not correlated to fluctuations in the direction of motion,…
Light propagation through turbulence produces speckles, whose ensemble behavior is typically characterized by snapshot intensity statistics. Here, we track the spatiotemporal evolution of individual speckles and quantify fragmentation,…
Detailed comparisons are made between observations of scattered light upstream of the head of the HH~1 jet and predictions of simple scattering models. It is shown that, in order to unambiguously determine the velocity of the head of the…
We review the acceleration of energetic particles in relativistic astrophysical jets characterized by a significant velocity shear. The possible formation of power-law momentum spectra is discussed and typical acceleration timescales are…
We report numerical results for velocity correlations in dense, gravity-driven granular flow down an inclined plane. For the grains on the surface layer, our results are consistent with experimental measurements reported by Pouliquen. We…
Planetary transits provide a unique opportunity to investigate the surface distributions of star spots. Our aim is to determine if, with continuous observation (such as the data that will be provided by the Kepler mission), we can in…
Spicules are rapidly evolving fine-scale jets of magnetized plasma in the solar chromosphere. It remains unclear how these prevalent jets originate from the solar surface and what role they play in heating the solar atmosphere. Using the…
A knowledge of the particle escape time from the acceleration regions of many space and astrophysical sources is of critical importance in the analysis of emission signatures produced by these particles and in the determination of the…
We report on active region EUV dynamic events observed simultaneously at high-cadence with SUMER/SoHO and TRACE. Although the features appear in the TRACE Fe ix/x 171A images as jets seen in projection on the solar disk, the SUMER spectral…
The variation of the velocity of a periodic signal and its frequency along the world line of a standard emitter (at rest with an observer) are considered in a space with affine connections and metrics. It is shown that the frequency of the…
The question of the collimation of relativistic jets is the subject of a lively debate in the community. We numerically compute the apparent velocity and the Doppler factor of a non homokinetic jet using different velocity profile, to study…
We perform direct numerical simulations of a bi-disperse suspension of heavy spherical particles in forced, homogeneous, and isotropic three-dimensional turbulence. We compute the joint distribution of relative particle distances and…
Numerical simulations of the solar chromosphere have progressed towards reproducing spicules, which are transient features observed at the solar limb using spectral lines such as H$\alpha$, Ca II H&K, or Mg II h&k. Two types of spicules,…
We present a re-analysis of the optical spectroscopic data on SS433 from the last quarter-century and demonstrate that these data alone contain systematic and identifiable deviations from the traditional kinematic model for the jets:…
A distribution function approach is applied to describe the dynamics of the laser beam in the Earth atmosphere. Using a formal solution of the kinetic equation for the distribution function, we have developed an iterative scheme for…
We report new results from an HST archival program to study proper motions in the optical jet of the nearby radio galaxy M87. Using over 13 years of archival imaging, we reach accuracies below 0.1c in measuring the apparent velocities of…
While jets appear as a fundamental result of accretion processes onto compact objects in X-ray binaries, there is as yet no standard model for their underlying physics. The origin of the observed disk-jet coupling also remains largely…
Solar jets are fast-moving, elongated brightenings related to ejections seen in both images and spectra on all scales from barely visible chromospheric jets to coronal jets extending up to a few solar radii. The largest, most powerful jets…
The measurement of Doppler velocities in spectroscopic solar observations requires a reference for the local frame of rest. The rotational and radial velocities of the Earth and the rotation of the Sun introduce velocity offsets in the…
We analyze features that resemble type i spicules in two different 3D numerical simulations in which we include horizontal magnetic flux emergence in a computational domain spanning the upper layers of the convection zone to the lower…