1,498 research outputs found
Cyclotron waves in a collisionless plasma
Plasma waves with resonances near electron cyclotron frequency investigated in long collisionless plasma column - wavelength dispersion curves and relation
Experimental investigation of the fundamental modes of a collisionless plasma quarterly report no. 3, sep. 11 - dec. 10, 1964
Plasma waves between electron cyclotron frequency and upper hybrid frequency in collisionless hydrogen plasm
On the origin of eccentricities among extrasolar planets
Most observed extrasolar planets have masses similar to, but orbits very
different from, the gas giants of our solar system. Many are much closer to
their parent stars than would have been expected and their orbits are often
rather eccentric. We show that some of these planets might have formed in
systems much like our solar system, i.e. in systems where the gas giants were
originally on orbits with a semi-major axis of several au, but where the masses
of the gas giants were all rather similar. If such a system is perturbed by
another star, strong planet-planet interactions follow, causing the ejection of
several planets while leaving those remaining on much tighter and more
eccentric orbits. The eccentricity distribution of these perturbed systems is
very similar to that of the observed extrasolar planets with semi-major axis
between 1 and 6 au.Comment: Accepted for publication in MNRAS Letter
Creative clusters and innovation (C.Chapain, P.Cooke, L.De Propris, S.MacNeill, J.Mateos-Garcia, NESTA)
Copyright @ 2012 Intellec
The instability of planetary systems in binaries: how the Kozai mechanism leads to strong planet-planet interactions
In this letter we consider the evolution of a planetary system around a star
inside a wide binary. We simulate numerically the evolution of the planetary
orbits for both co-planar and highly-inclined systems. We find that the Kozai
mechanism operates in the latter case. This produces a highly eccentric outer
planet whose orbit crosses those of some of the inner planets. Strong
planet-planet interactions then follow resulting in the ejection of one or more
planets. We note that planetary systems resembling our solar system, formed
around single stars in stellar clusters may exchange into binaries and thus
will be vulnerable to planet stripping. This process will reduce the number of
solar-system like planetary systems, and may produce at least some of the
observed extra-solar planets.Comment: 5 pages, 2 figures, accepted for publication in MNRAS Letter
The effects of fly-bys on planetary systems
Most of the observed extrasolar planets are found on tight and often
eccentric orbits. The high eccentricities are not easily explained by
planet-formation models, which predict that planets should be on rather
circular orbits. Here we explore whether fly-bys involving planetary systems
with properties similar to those of the gas giants in the solar system, can
produce planets with properties similar to the observed planets. Using
numerical simulations, we show that fly-bys can cause the immediate ejection of
planets, and sometimes also lead to the capture of one or more planets by the
intruder. More common, however, is that fly-bys only perturb the orbits of
planets, sometimes leaving the system in an unstable state. Over time-scales of
a few million to several hundred million years after the fly-by, this
perturbation can trigger planet-planet scatterings, leading to the ejection of
one or more planets. For example, in the case of the four gas giants of the
solar system, the fraction of systems from which at least one planet is ejected
more than doubles in 10^8 years after the fly-by. The remaining planets are
often left on more eccentric orbits, similar to the eccentricities of the
observed extrasolar planets. We combine our results of how fly-bys effect
solar-system-like planetary systems, with the rate at which encounters in young
stellar clusters occur. For example, we measure the effects of fly-bys on the
four gas giants in the solar system. We find, that for such systems, between 5
and 15 per cent suffer ejections of planets in 10^8 years after fly-bys in
typical open clusters. Thus, encounters in young stellar clusters can
significantly alter the properties of any planets orbiting stars in clusters.
As a large fraction of stars which populate the solar neighbourhood form in
stellar clusters, encounters can significantly affect the properties of the
observed extrasolar planets.Comment: 22 pages, 15 figures, 5 tables. Accepted for publication in MNRA
The origin of very wide binary systems
The majority of stars in the Galactic field and halo are part of binary or
multiple systems. A significant fraction of these systems have orbital
separations in excess of thousands of astronomical units, and systems wider
than a parsec have been identified in the Galactic halo. These binary systems
cannot have formed through the 'normal' star-formation process, nor by capture
processes in the Galactic field. We propose that these wide systems were formed
during the dissolution phase of young star clusters. We test this hypothesis
using N-body simulations of evolving star clusters and find wide binary
fractions of 1-30%, depending on initial conditions. Moreover, given that most
stars form as part of a binary system, our theory predicts that a large
fraction of the known wide 'binaries' are, in fact, multiple systems.Comment: 4 pages, 1 figure, to appear in the proceedings of IAU Symposium 266,
eds. R. de Grijs & J.R.D. Lepin
Experimental investigation of the fundamental modes of a collisionless plasma Final report, 10 Mar. 1964 - 31 Oct. 1967
Propagation of electron cyclotron waves and effects of low frequency noise in collisionless plasm
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