1,419 research outputs found
Sporadic Aurora near Geomagnetic Equator: In the Philippines, on 27 October 1856
While low latitude auroral displays are normally considered to be a
manifestation of magnetic storms of considerable size, Silverman (2003, JGR,
108, A4) reported numerous "sporadic auroras" which appear locally at
relatively low magnetic latitudes during times of just moderate magnetic
activity. Here, a case study is presented of an aurora near the geomagnetic
equator based on a report from the Philippine Islands on 27 October 1856. An
analysis of this report shows it to be consistent with the known cases of
sporadic aurorae except for its considerably low magnetic latitude. The record
also suggests that extremely low-latitude aurora is not always accompanied with
large magnetic storms. The description of its brief appearance leads to a
possible physical explanation based on an ephemeral magnetospheric disturbance
provoking this sporadic aurora.Comment: 15 pages, 3 figures, accepted for publication in Annales Geophysicae
on 18 August 201
nature of the superdeformed band of and the evolution of the molecular structure
The relation between the superdeformed band of and molecular bands is studied by the deformed-base
antisymmetrized molecular dynamics with the Gogny D1S force. It is found that
the obtained superdeformed band members of have considerable
amount of the component. Above the superdeformed
band, we have obtained two excited rotational bands which have more prominent
character of the molecular band. These three
rotational bands are regarded as a series of
molecular bands which were predicted by using the unique
- optical potentil. As the excitation energy and principal
quantum number of the relative motion increase, the cluster structure becomes more prominent but at the same time, the band
members are fragmented into several states
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Breaking the Symmetry Between Interaction and Replacement in Evolutionary Dynamics on Graphs
We study the evolution of cooperation modeled as symmetric 2Ă2 games in a population whose structure is split into an interaction graph defining who plays with whom and a replacement graph specifying evolutionary competition. We find it is always harder for cooperators to evolve whenever the two graphs do not coincide. In the thermodynamic limit, the dynamics on both graphs is given by a replicator equation with a rescaled payoff matrix in a rescaled time. Analytical results are obtained in the pair approximation and for weak selection. Their validity is confirmed by computer simulations.MathematicsOrganismic and Evolutionary Biolog
Observation of "Partial Coherence" in an Aharonov-Bohm Interferometer with a Quantum Dot
We report experiments on the interference through spin states of electrons in
a quantum dot (QD) embedded in an Aharonov-Bohm (AB) interferometer. We have
picked up a spin-pair state, for which the environmental conditions are ideally
similar and have traced the AB amplitude in the range of the gate voltage that
covers the pair. The behavior of the asymmetry in the amplitude around the two
Coulomb peaks agrees with the theoretical prediction that relates a spin-flip
process in a QD to the quantum dephasing of electrons. These results consist
evidence of "partial coherence" due to an entanglement of spins in the QD and
the interferometer.Comment: 4 pages, 3 figures, RevTe
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Repeated Games and Direct Reciprocity Under Active Linking
Direct reciprocity relies on repeated encounters between the same two individuals. Here we examine the evolution of cooperation under direct reciprocity in dynamically structured populations. Individuals occupy the vertices of a graph, undergoing repeated interactions with their partners via the edges of the graph. Unlike the traditional approach to evolutionary game theory, where individuals meet at random and have no control over the frequency or duration of interactions, we consider a model in which individuals differ in the rate at which they seek new interactions. Moreover, once a link between two individuals has formed, the productivity of this link is evaluated. Links can be broken off at different rates. Whenever the active dynamics of links is sufficiently fast, population structure leads to a simple transformation of the payoff matrix, effectively changing the game under consideration, and hence paving the way for reciprocators to dominate defectors. We derive analytical conditions for evolutionary stability.MathematicsOrganismic and Evolutionary Biolog
The Great Space Weather Event during February 1872 Recorded in East Asia
The study of historical great geomagnetic storms is crucial for assessing the
possible risks to the technological infrastructure of a modern society, caused
by extreme space-weather events. The normal benchmark has been the great
geomagnetic storm of September 1859, the so-called "Carrington Event". However,
there are numerous records of another great geomagnetic storm in February 1872.
This storm, about 12 years after the Carrington Event, resulted in comparable
magnetic disturbances and auroral displays over large areas of the Earth. We
have revisited this great geomagnetic storm in terms of the auroral and sunspot
records in the historical documents from East Asia. In particular, we have
surveyed the auroral records from East Asia and estimated the equatorward
boundary of the auroral oval to be near 24.3 deg invariant latitude (ILAT), on
the basis that the aurora was seen near the zenith at Shanghai (20 deg magnetic
latitude, MLAT). These results confirm that this geomagnetic storm of February
1872 was as extreme as the Carrington Event, at least in terms of the
equatorward motion of the auroral oval. Indeed, our results support the
interpretation of the simultaneous auroral observations made at Bombay (10 deg
MLAT). The East Asian auroral records have indicated extreme brightness,
suggesting unusual precipitation of high-intensity, low-energy electrons during
this geomagnetic storm. We have compared the duration of the East Asian auroral
displays with magnetic observations in Bombay and found that the auroral
displays occurred in the initial phase, main phase, and early recovery phase of
the magnetic storm.Comment: 28 pages, 5 figures, accepted for publication in the Astrophysical
Journal on 31 May 201
A Great Space Weather Event in February 1730
Aims. Historical records provide evidence of extreme magnetic storms with
equatorward auroral extensions before the epoch of systematic magnetic
observations. One significant magnetic storm occurred on February 15, 1730. We
scale this magnetic storm with auroral extension and contextualise it based on
contemporary solar activity. Methods. We examined historical records in East
Asia and computed the magnetic latitude (MLAT) of observational sites to scale
magnetic storms. We also compared them with auroral records in Southern Europe.
We examined contemporary sunspot observations to reconstruct detailed solar
activity between 1729 and 1731. Results. We show 29 auroral records in East
Asian historical documents and 37 sunspot observations. Conclusions. These
records show that the auroral displays were visible at least down to 25.8{\deg}
MLAT throughout East Asia. In comparison with contemporary European records, we
show that the boundary of the auroral display closest to the equator surpassed
45.1{\deg} MLAT and possibly came down to 31.5{\deg} MLAT in its maximum phase,
with considerable brightness. Contemporary sunspot records show an active phase
in the first half of 1730 during the declining phase of the solar cycle. This
magnetic storm was at least as intense as the magnetic storm in 1989, but less
intense than the Carrington event.Comment: 30 pages, 5 figures, and 2 tables, accepted for publication in
Astronomy & Astrophysics on 25 April 2018. The figures and
transcriptions/translations of historical documents are partially omitted in
this manuscript due to the condition of reproduction. They are available in
the publisher versio
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