531 research outputs found
The effect of the interplanetary magnetic field on sidereal variations observed at medium depth underground detectors
It has been known for some years that the intensity variations in sidereal time observed by muon detectors at moderate underground depths are sensitive to the polarity of the interplanetary magnetic field (ipmf) near the Earth. There are differences in the response to these anisotropies as observed in the Norhtern and southern hemispheres. When fully understood, the nature of the anisotropy seems likely to provide information on the 3-dimensional structure of the heliomagnetosphere, its time variations, and its linking with the local interstellar field. The summation harmonic dials for the sidereal diurnal variation during 1958 to 1982 show that there is a strong dependence on whether the ipmf near the Earth is directed outwards from the Sun or inwards it
Long-term modulation of cosmic rays during solar cycle 21
A preliminary result concerning the rigidity dependence of the longer-term solar cycle modulation is reported. The long-term modulation, using monthly mean intensities and referred to November 1977 as a normalizing level, appear to be in accordance with the exponent gamma = 1, provided only Brisbane and Hobart data are used. Darwin data do not conform to this pattern except perhaps during the early years of the cycle until about the end of 1980, since when the Darwin long-term intensity has been largely steady, apart from Forbush-type decreases and the as yet unidentified vector from the observed SI vector. The true SI vector of galactic origin can be obtained. The resultant vector has the amplitude of 0.031% and the phase of 2.3h. The present result seems to be consistent with those so far reported
Energetic solar particle events
Studies of the arrival directions of energetic solar particles during ground level enhancements (CLE's) observed by neutron monitors have shown that, in general, in the first hour of the event most of the particles arrive with a distribution of pitch angles peaked about the garden hose field direction in the vicinity of Earth. During the first hour some of the particles arrive from the antisolar direction, while in later stages of the event the intensity becomes more nearly isotropic as a result of scattering of particles in interplanetary space. An attempt is made to determine the arrival directions of the particles during the early stages of the GLE of 16 February 1984 using the data currently available from high latitude neutron monitors near sea level where the cut off is essentially atmospheric (approx. LGV)
Sidereal variations deep underground in Tasmania
Data from the deep underground vertically directed muon telescopes at Poatina, Tasmania, have been used since 1972 for a number of investigations, including the daily intensity variations, atmospheric influences, and checking for possible effects due to the interplanetary magnetic field. These telescopes have a total sensitive area of only 3 square meters, with the result that the counting rate is low (about 1680 events per hour) and the statistical errors on the results are rather large. Consequently, it was decided several years ago to construct larger detectors for this station. The first of these telescopes has been in operation for two complete years, and the results from it are presented. Results from the new, more stable equipment at Poatina appear to confirm the existence of a first harmonic in the daily variations in sidereal time reported earlier, and are consistent with small or non-existent first harmonics in solar and anti-sidereal time. All the second harmonics appear to be small, if not zero at these energies
Atmospheric effects on the underground muon intensity
It has previously been reported that the barometric pressure coefficient observed for muons at Poatina (vertical absorber depth 357 hg/sq cm) appears to be appreciably higher than would be expected from atmospheric absorption alone. There is a possibility that the effect is due to an upper atmospheric temperature effect arising from an inverse correlation of surface pressure with stratospheric temperature. A new proportional telescope is discussed which has been operating at Poatina since about the beginning of 83 and which has a long term stability suitable for studying variations of atmospheric origin
Relativistic Proton Production During the 14 July 2000 Solar Event: The Case for Multiple Source Mechanisms
Protons accelerated to relativistic energies by transient solar and
interplanetary phenomena caused a ground-level cosmic ray enhancement on 14
July 2000, Bastille Day. Near-Earth spacecraft measured the proton flux
directly and ground-based observatories measured the secondary responses to
higher energy protons. We have modelled the arrival of these relativistic
protons at Earth using a technique which deduces the spectrum, arrival
direction and anisotropy of the high-energy protons that produce increased
responses in neutron monitors. To investigate the acceleration processes
involved we have employed theoretical shock and stochastic acceleration
spectral forms in our fits to spacecraft and neutron monitor data. During the
rising phase of the event (10:45 UT and 10:50 UT) we find that the spectrum
between 140 MeV and 4 GeV is best fitted by a shock acceleration spectrum. In
contrast, the spectrum at the peak (10:55 UT and 11:00 UT) and in the declining
phase (11:40 UT) is best fitted with a stochastic acceleration spectrum. We
propose that at least two acceleration processes were responsible for the
production of relativistic protons during the Bastille Day solar event: (1)
protons were accelerated to relativistic energies by a shock, presumably a
coronal mass ejection (CME). (2) protons were also accelerated to relativistic
energies by stochastic processes initiated by magnetohydrodynamic (MHD)
turbulence.Comment: 38 pages, 9 figures, accepted for publication in the Astrophysical
Journal, January, 200
Bright source of spectrally uncorrelated polarization-entangled photons with nearly single-mode emission
We present results of a bright polarization-entangled photon source operating
at 1552 nm via type-II collinear degenerate spontaneous parametric
down-conversion in a periodically poled potassium titanyl phosphate crystal. We
report a conservative inferred pair generation rate of 123,000 pairs/s/mW into
collection modes. Minimization of spectral and spatial entanglement was
achieved by group velocity matching the pump, signal and idler modes and
through properly focusing the pump beam. By utilizing a pair of calcite beam
displacers, we are able to overlap photons from adjacent down-conversion
processes to obtain polarization-entanglement visibility of 94.7 +/- 1.1% with
accidentals subtracted.Comment: 4 pages, 7 color figures. Revised manuscript includes the following
changes: corrected pair generation rate from 44,000/s/mW pump to 123,000/s/mW
pump; replaced Fig. 1b to enhance clarity; minor alterations to the title,
abstract and introduction; grammatical correction
Migrating to Cloud-Native Architectures Using Microservices: An Experience Report
Migration to the cloud has been a popular topic in industry and academia in
recent years. Despite many benefits that the cloud presents, such as high
availability and scalability, most of the on-premise application architectures
are not ready to fully exploit the benefits of this environment, and adapting
them to this environment is a non-trivial task. Microservices have appeared
recently as novel architectural styles that are native to the cloud. These
cloud-native architectures can facilitate migrating on-premise architectures to
fully benefit from the cloud environments because non-functional attributes,
like scalability, are inherent in this style. The existing approaches on cloud
migration does not mostly consider cloud-native architectures as their
first-class citizens. As a result, the final product may not meet its primary
drivers for migration. In this paper, we intend to report our experience and
lessons learned in an ongoing project on migrating a monolithic on-premise
software architecture to microservices. We concluded that microservices is not
a one-fit-all solution as it introduces new complexities to the system, and
many factors, such as distribution complexities, should be considered before
adopting this style. However, if adopted in a context that needs high
flexibility in terms of scalability and availability, it can deliver its
promised benefits
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