10,594 research outputs found
Orbital Dynamics of Multi-Planet Systems with Eccentricity Diversity
Since exoplanets were detected using the radial velocity method, they have
revealed a diverse distribution of orbital configurations. Amongst these are
planets in highly eccentric orbits (e > 0.5). Most of these systems consist of
a single planet but several have been found to also contain a longer period
planet in a near-circular orbit. Here we use the latest Keplerian orbital
solutions to investigate four known systems which exhibit this extreme
eccentricity diversity; HD 37605, HD 74156, HD 163607, and HD 168443. We place
limits on the presence of additional planets in these systems based on the
radial velocity residuals. We show that the two known planets in each system
exchange angular momentum through secular oscillations of their eccentricities.
We calculate the amplitude and timescale for these eccentricity oscillations
and associated periastron precession. We further demonstrate the effect of
mutual orbital inclinations on the amplitude of high-frequency eccentricity
oscillations. Finally, we discuss the implications of these oscillations in the
context of possible origin scenarios for unequal eccentricities.Comment: 12 pages, 9 figures, accepted for publication in the Astrophysical
Journa
Comparison of storm-time changes of geomagnetic field at ground and at MAGSAT altitudes, part 3
The latitudinal distributions of delta H, delta X, delta Y, and delta Z were studied for quiet and disturbed periods. For quiet periods, the average patterns showed some variations common to dusk and dawn, thus indicating probable ground anomaly. However, there were significant differences too between dusk and dawn, indicating considerable diurnal variation effects. Particularly in delta Y, these effects were large and were symmetric about the dip equator. For disturbed day passes, the quiet day patterns were considered as base levels and the latter were subtracted from the former. The resulting residual latitudinal patterns were, on the average, symmetric about the geographical equator. However, individual passes showed considerable north-south asymmetries, probably indicating meanderings of the central plane of the magnetospheric ring current
Comparison of storm-time changes of geomagnetic field at ground and MAGSAT altitudes
The MAGSAT data for the period Nov. 2-20, 1979 were studied. From the observed H, the HMD predicted by model was subtracted. The residue delta H = H-HMD shows storm-time variations similar to geomagnetic Dst, at least qualitatively. Delta H sub 0, i.e., equatorial values of delta H were studied separately for dusk and dawn and show some differences
Comparison of storm-time changes of geomagnetic field at ground and at MAGSAT altitudes, part 2
Geomagnetic field variations were studied by considering the parameter delta H which indicated H(observed) minus H(model), where H = (X squared + Y squared) (1/2) where X, Y, and Z are the components actually observed. Quiet time base values for 5 deg longitude belts were estimated. After subtracting these from the observed values, the residual delta H (dawn) and delta H (dusk) were studied for the two major storms. It was noticed that the dusk values attained larger (negative) values for a longer time, than the dawn value. Some changes in delta Y and delta Z were also noticed, indicating possibilities of either meridional currents and/or noncoincidence of the central plane of the ring current with the equatorial plane of the Earth. Other details are described
Comparison of storm-time changes of geomagnetic field at ground and at MAGSAT altitudes
Computations concerning variations of the geomagnetic field at MAGSAT altitudes were investigated. Using MAGSAT data for the X, Y, and Z components of the geomagnetic field, a computer conversion to yield the H component was performed. Two methods of determining delta H normalized to a constant geocentric distance R sub 0 = 6800 were investigated, and the utility of elta H at times of magnetic storms was considered. Delta H at a geographical latitude of 0 at dawn and dusk, the standard Dst, and K sub p histograms were plotted and compared. Magnetic anomalies are considered. Examination of data from the majority of the 400 passes of MAGSAT considered show a reasonable delta H versus latitude variation. Discrepancies in values are discussed
Heat and Mass Transfer in Cold Regions Soils
The work upon which this report is based was made possible by a cooperative
aid agreement between the U.S. Forest Service, Institute of Northern
Forestry, Fairbanks, Alaska, and the Institute of Water Resources, University
of Alaska. Contributions to this study were also made by the University of
California at Davis and Ohio State University. The collection of winter
data on pore pressures was made possible by a separate grant by the Office
of Water Research and Technology (project A-053 ALAS)
Quantum Spin Hall Effect in Graphene
We study the effects of spin orbit interactions on the low energy electronic
structure of a single plane of graphene. We find that in an experimentally
accessible low temperature regime the symmetry allowed spin orbit potential
converts graphene from an ideal two dimensional semimetallic state to a quantum
spin Hall insulator. This novel electronic state of matter is gapped in the
bulk and supports the quantized transport of spin and charge in gapless edge
states that propagate at the sample boundaries. The edge states are non chiral,
but they are insensitive to disorder because their directionality is correlated
with spin. The spin and charge conductances in these edge states are calculated
and the effects of temperature, chemical potential, Rashba coupling, disorder
and symmetry breaking fields are discussed.Comment: 4 pages, published versio
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