2,809 research outputs found
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
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 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 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
Storm-time changes of geomagnetic field at MAGSAT altitudes (325-550 Km) and their comparison with changes at ground locations
The values of H, X, Y, Z at MAGSAT altitudes were first expressed as residuals delta H, delta X, delta Y, delta Z after subtracting the model HMD, XMD, YMD, ZMC. The storm-time variations of H showed that delta H (Dusk) was larger (negative) than delta H (Dawn) and occurred earlier, indicating a sort of hysteresis effect. Effects at MAGSAT altitudes were roughly the same (10% accuracy) as at ground, indicating that these effects were mostly of magnetospheric origin. The delta Y component also showed large storm-time changes. The latitudinal distribution of storm-time delta H showed north-south asymmetries varying in nature as the storm progressed. It seems that the central plane of the storm-time magnetospheric ring current undergoes latitudinal meanderings during the course of the storm
Quantum phases in a doped Mott insulator on the Shastry-Sutherland lattice
We propose the projected BCS wave function as the ground state for the doped
Mott insulator SrCu2(BO3)2 on the Shastry-Sutherland lattice. At half filling
this wave function yields the exact ground state. Adding mobile charge
carriers, we find a strong asymmetry between electron and hole doping. Upon
electron doping an unusual metal with strong valence bond correlations forms.
Hole doped systems are d-wave RVB superconductors in which superconductivity is
strongly enhanced by the emergence of inhomogeneous plaquette bond order.Comment: 4 pages, 3 figure
Estimation in Misclassified Size – Biased Log Series Distribution
A misclassified size-biased Log Series Distribution (MSBLSD) ............
Phase diagram of the disordered Bose-Hubbard model
We establish the phase diagram of the disordered three-dimensional
Bose-Hubbard model at unity filling, which has been controversial for many
years. The theorem of inclusions, proven in Ref. [1], states that the Bose
glass phase always intervenes between the Mott insulating and superfluid
phases. Here, we note that assumptions on which the theorem is based exclude
phase transitions between gapped (Mott insulator) and gapless phases (Bose
glass). The apparent paradox is resolved through a unique mechanism: such
transitions have to be of the Griffiths type when the vanishing of the gap at
the critical point is due to a zero concentration of rare regions where extreme
fluctuations of disorder mimic a {\it regular} gapless system. An exactly
solvable random transverse field Ising model in one dimension is used to
illustrate the point. A highly non-trivial overall shape of the phase diagram
is revealed with the worm algorithm. The phase diagram features a long
superfluid finger at strong disorder and on-site interaction. Moreover, bosonic
superfluidity is extremely robust against disorder in a broad range of
interaction parameters; it persists in random potentials nearly 50 (!) times
larger than the particle half-bandwidth. Finally, we comment on the feasibility
of obtaining this phase diagram in cold-atom experiments, which work with
trapped systems at finite temperature.Comment: 9 pages, 5 figure
- …