4,435 research outputs found
Criteria of interplanetary parameters causing intense magnetic storms (Dst less than -100nT)
Ten intense storms occurred during the 500 days of August 16, 1978 to December 28, 1979. From the analysis of ISEE-3 field and plasma data, it is found that the interplanetary cause of these storms are long-duration, large and negative IMF B sub Z events, associated with interplanetary duskward-electric fields greater than 5 mV/m. Because a one-to-one relationship was found between these interplanetary events and intense storms, it is suggested that these criteria can, in the future, be used as predictors of intense storms by an interplanetary monitor such as ISEE-3. These B sub Z events are found to occur in association with large amplitudes of the IMF magnitude within two days after the onset of either high-speed solar wind streams or of solar wind density enhancement events, giving important clues to their interplanetary origin. Some obvious possibilities will be discussed. The close proximity of B sub Z events and magnetic storms to the onset of high speed streams or density enhancement events is in sharp contrast to interplanetary Alfven waves and HILDCAA events previously reported, and thus the two interplanetary features corresponding geomagnetic responses can be thought of as being complementary in nature. An examination of opposite polarity B sub Z events with the same criteria show that their occurrence is similar both in number as well as in their relationship to interplanetary disturbances, and that they lead to low levels of geomagnetic activity
On the estimates of the ring current injection and decay
In the context of the space weather predictions, forecasting ring current strength (and of the Dst index) based on the solar wind upstream conditions is of specific interest for predicting the occurrence of geomagnetic storms. In the present paper, we have studied separately its two components: the Dst injection and decay. In particular, we have verified the validity of the Burton's equation for estimating the ring current energy balance using the equatorial electric merging field instead of the original parameter V Bs (V is the solar wind speed and Bs is the southward component of the Interplanetary Magnetic Field, IMF). Then, based on this equation, we have used the phasespace method to determine the best-fit approximations for the ring current injection and decay as functions of the equatorial merging electric field (Em). Results indicate that the interplanetary injection is statistically higher than in previous estimations using V Bs . Specifically, weak but not-null ring current injection can be observed even during northward IMF, when previous studies considered it to be always zero. Moreover, results about the ring current decay indicate that the rate of Dst decay is faster than its predictions derived by using V Bs . In addition, smaller quiet time ring current and solar wind pressure corrections are contributing to Dst estimates obtained by Em instead of V Bs . These effects are compensated, so that the statistical Dst predictions using the equatorial electric merging field or using V Bs are about equivalent
Neutron-proton analyzing power at 12 MeV and inconsistencies in parametrizations of nucleon-nucleon data
We present the most accurate and complete data set for the analyzing power
Ay(theta) in neutron-proton scattering. The experimental data were corrected
for the effects of multiple scattering, both in the center detector and in the
neutron detectors. The final data at En = 12.0 MeV deviate considerably from
the predictions of nucleon-nucleon phase-shift analyses and potential models.
The impact of the new data on the value of the charged pion-nucleon coupling
constant is discussed in a model study.Comment: Six pages, four figures, one table, to be published in Physics
Letters
A Search for H2O in the Strongly Lensed QSO MG 0751+2716 at z=3.2
We present a search for 183 GHz H_2O(3_13-2_20) emission in the
infrared-luminous quasar MG 0751+2716 with the NRAO Very Large Array (VLA). At
z=3.200+/-0.001, this water emission feature is redshifted to 43.6 GHz. As
opposed to the faint rotational transitions of HCN (the standard high-density
tracer at high-z), H_2O(3_13-2_20) is observed with high maser amplification
factors in Galactic star-forming regions. It therefore holds the potential to
trace high-density star-forming regions in the distant universe. If indeed all
star-forming regions in massively star-forming galaxies at z>3 have similar
physical properties as e.g. the Orion or W49N molecular cloud cores, the flux
ratio between the maser-amplified H_2O(3_13-2_20) and the thermally excited
CO(1-0) transitions may be as high as factor of 20 (but has to be corrected by
their relative filling factor). MG 0751+2716 is a strong CO(4-3) emitter, and
therefore one of the most suitable targets to search for H_2O(3_13-2_20) at
cosmological redshifts. Our search resulted in an upper limit in line
luminosity of L'(H_2O) < 0.6 x 10^9 K km/s pc^2. Assuming a brightness
temperature of T_b(H_2O) ~= 500 K for the maser emission and CO properties from
the literature, this translates to a H_2O(3_13-2_20)/CO(4-3) area filling
factor of less than 1%. However, this limit is not valid if the H_2O(3_13-2_20)
maser emission is quenched, i.e. if the line is only thermally excited. We
conclude that, if our results were to hold for other high-z sources, H_2O does
not appear to be a more luminous alternative to HCN to detect high-density gas
in star-forming environments at high redshift.Comment: 6 pages, 1 figure, to appear in ApJ (accepted May 19, 2006
Optical multi-trapping by Kinoform m-Bonacci lenses
[EN]
Optical manipulation is interfacing disciplines in the micro and nanoscale, from molecular biology to quantum computation. Versatile solutions for increasingly more sophisticated technological applications require multiple traps with which to maneuver dynamically several particles in three dimensions. The axial direction is usually overlooked due to difficulties in observing particles away from an objective-lens focal plane, a normal element in optical tweezers, and in managing interparticle distances along the trapping beam propagating direction, where strong radiation pressure and shadowing effects compromise the simultaneous and stable confinement of the particles. Here, aperiodic kinoform diffractive lens based on the m-Bonacci sequence are proposed as a newtrapping strategy. This lens provides split first-order diffractive foci whose separation depends on the generalized m-golden ratio. We show the extended manipulation capabilities of a laser tweezers system generated by these lens, in which concomitant trapping of particles in different focal planes takes place. Positioning particles in the axial direction with computer-controlled distances allows dynamic three-dimensional all-optical lattices, useful in a variety of microscale and nanoscale applications. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing AgreementMinisterio de Ciencia e Innovacion (PID2019-107391RB-I00); Generalitat Valenciana (PROMETEO/2019/048); Universitat Politecnica de Valencia (PAID-01-20-25).Muñoz-Pérez, FM.; Ferrando, V.; Furlan, WD.; Monsoriu Serra, JA.; Arias-Gonzalez, JR. (2022). Optical multi-trapping by Kinoform m-Bonacci lenses. Optics Express. 30(19):34378-34384. https://doi.org/10.1364/OE.4656723437834384301
Multiplexed vortex beam-based optical tweezers
The design and implementation of a multiplexed spiral phase mask in an
experimental optical tweezer setup are presented. This diffractive optical
element allows the generation of multiple concentric vortex beams with
independent topological charges. The generalization of the phase mask for
multiple concentric vortices is also shown. The design for a phase mask of two
multiplexed vortices with different topological charges is developed. We
experimentally show the transfer of angular momentum to the optically trapped
microparticles by enabling orbiting dynamics around the optical axis
independently within each vortex. The angular velocity of the confined
particles versus the optical power in the focal region is also discussed for
different combinations of topological charges
Key Ne states identified affecting -ray emission from F in novae
Detection of nuclear-decay rays provides a sensitive thermometer of
nova nucleosynthesis. The most intense -ray flux is thought to be
annihilation radiation from the decay of F, which is destroyed
prior to decay by the F(,)O reaction. Estimates of
F production had been uncertain, however, because key near-threshold
levels in the compound nucleus, Ne, had yet to be identified. This
Letter reports the first measurement of the
F(He,)Ne reaction, in which the placement of two
long-sought 3/2 levels is suggested via triton--
coincidences. The precise determination of their resonance energies reduces the
upper limit of the rate by a factor of at nova temperatures and
reduces the average uncertainty on the nova detection probability by a factor
of 2.1.Comment: 6 pages, 4 figure
New -ray Transitions Observed in Ne with Implications for the O(,)Ne Reaction Rate
The O(,)Ne reaction is responsible for breakout
from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of
resonances between and 5 MeV in Ne is crucial in the
calculation of this reaction rate. The spins and parities of these states are
well known, with the exception of the 4.14- and 4.20-MeV states, which have
adopted spin-parities of 9/2 and 7/2, respectively. Gamma-ray
transitions from these states were studied using triton--
coincidences from the F(He,)Ne reaction measured
with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure
Studies) at Argonne National Laboratory. The observed transitions from the
4.14- and 4.20-MeV states provide strong evidence that the values are
actually 7/2 and 9/2, respectively. These assignments are consistent
with the values in the F mirror nucleus and in contrast to previously
accepted assignments
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