On the Radiative Relaxation Time for the Hydrogen–Helium Atmosphere Estimated from Changes in the Activity Factor of Jupiter’s Hemispheres

2020 ◽  
Vol 36 (1) ◽  
pp. 12-16
Author(s):  
A. P. Vidmachenko
2017 ◽  
Vol 74 (5) ◽  
pp. 1533-1547 ◽  
Author(s):  
William J. M. Seviour ◽  
Darryn W. Waugh ◽  
Richard K. Scott

Abstract The Martian polar atmosphere is known to have a persistent local minimum in potential vorticity (PV) near the winter pole, with a region of high PV encircling it. This finding is surprising, since an isolated band of PV is barotropically unstable, a result going back to Rayleigh. Here the stability of a Mars-like annular vortex is investigated using numerical integrations of the rotating shallow-water equations. The mode of instability and its growth rate is shown to depend upon the latitude and width of the annulus. By introducing thermal relaxation toward an annular equilibrium profile with a time scale similar to that of the instability, a persistent annular vortex with similar characteristics as that observed in the Martian atmosphere can be simulated. This time scale, typically 0.5–2 sols, is similar to radiative relaxation time scales for Mars’s polar atmosphere. The persistence of an annular vortex is also shown to be robust to topographic forcing, as long as it is below a certain amplitude. It is therefore proposed that the persistence of this barotropically unstable annular vortex is permitted owing to the combination of short radiative relaxation time scales and relatively weak topographic forcing in the Martian polar atmosphere.


2016 ◽  
Vol 18 (7) ◽  
pp. 5219-5231 ◽  
Author(s):  
Mohamed El-Amine Madjet ◽  
Alexey V. Akimov ◽  
Fadwa El-Mellouhi ◽  
Golibjon R. Berdiyorov ◽  
Sahel Ashhab ◽  
...  

Non-adiabatic molecular dynamics simulations of non-radiative relaxation dynamics of charge carriers in hybrid perovskites show that the carrier relaxation time can be considerably increased by halide mixing.


2009 ◽  
Vol 75 (4) ◽  
pp. 517-528
Author(s):  
K. A. P. SINGH ◽  
B. N. DWIVEDI

AbstractWe study the propagation and damping of small-amplitude prominence oscillations invoking steady flow and radiative losses due to Newton's cooling with constant relaxation time. We find that the strength of steady flow has a large influence on the propagation (e.g. period, phase velocity) of wave modes. In the presence of steady flow, the thermal mode is a propagating wave and hence it can be observed in solar prominences. The thermal mode contributes to the non-thermal line broadening in the solar atmosphere. The steady flow does not affect the damping time of the wave modes. The damping of slow and thermal modes is highly dependent on the radiative relaxation time. The thermal perturbation, in the presence of steady flow, is found to be larger in the case of the thermal mode than in the slow and fast modes. The energy flux (~300 W m−2) associated with the thermal mode is sufficient to heat the quiet regions of the Sun. The slow mode contribution to non-thermal broadening has been estimated. The non-thermal broadening is found to be large in the case of the prominence with large characteristic length. The steady flow, in the presence of Newton's cooling, breaks the symmetry between the forward and backward propagating modes. No modes with negative energy have been found. For strong flows (above 10 km s−1), the canonical backward wave propagates in the forward direction, which can play an important role in wave detection and prominence seismology.


2018 ◽  
Vol 123 (7) ◽  
pp. 075101
Author(s):  
A. Novatski ◽  
A. Somer ◽  
F. G. Maranha ◽  
E. C. F. de Souza ◽  
A. V. C. Andrade ◽  
...  

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