2,161 research outputs found
Giant acceleration in slow-fast space-periodic Hamiltonian systems
Motion of an ensemble of particles in a space-periodic potential well with a
weak wave-like perturbation imposed is considered. We found that slow
oscillations of wavenumber of the perturbation lead to occurrence of directed
particle current. This current is amplifying with time due to giant
acceleration of some particles. It is shown that giant acceleration is linked
with the existence of resonant channels in phase space
Astrometric jitter of the sun as a star
The daily variation of the solar photocenter over some 11 years is derived
from the Mount Wilson data reprocessed by Ulrich et al. 2010 to closely match
the surface distribution of solar irradiance. The standard deviations of
astrometric jitter are 0.52 AU and 0.39 AU in the equatorial and the
axial dimensions, respectively. The overall dispersion is strongly correlated
with the solar cycle, reaching AU at the maximum activity in 2000.
The largest short-term deviations from the running average (up to 2.6 AU)
occur when a group of large spots happen to lie on one side with respect to the
center of the disk. The amplitude spectrum of the photocenter variations never
exceeds 0.033 AU for the range of periods 0.6--1.4 yr, corresponding to
the orbital periods of planets in the habitable zone. Astrometric detection of
Earth-like planets around stars as quiet as the Sun is not affected by star
spot noise, but the prospects for more active stars may be limited to giant
planets.Comment: Accepted in Ap
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