1,310 research outputs found
Rigidity spectrum of Forbush decrease
Using data from neutron monitors and muon telescopes at surface and underground stations, the average rigidity spectrum of Forbush decreases (Fds) during the period of 1978-1982 were obtained. Thirty eight Ed-events are classified into two groups Hard Fd and Soft Fd according to size of Fd at Sakashita station. It is found that a spectral form of fractional-power type (P to the-gamma sub 1 (P+P sub c) to the -gamma sub2) is more suitable for the present purpose than that of power-exponential type or of power type with an upper limiting rigidity. The best fitted spectrum of fractional-power type is expressed by gamma sub1 = 0.37, gamma sub2 = 0.89 and P subc = 10 GV for Hard Fd and gamma sub1 = 0.77, gamma sub2 = 1.02 and P sub c - 14GV for Soft Fd
IMF-sense-dependent cosmic ray anisotropy produced from diffusion-convection in heliosphere
It was demonstrated that an interplanetary magnetic field (IMF) sense dependent 2nd order anisotropy is produced by the diffusion convection of cosmic rays in the heliomagnetosphere. The result implies that the anisotropy cannot be expressed only by the pitch angle with respect to the IMF axis
Long term variation of the solar diurnal anisotropy of galactic cosmic rays observed with the Nagoya multi-directional muon detector
We analyze the three dimensional anisotropy of the galactic cosmic ray (GCR)
intensities observed independently with a muon detector at Nagoya in Japan and
neutron monitors over four solar activity cycles. We clearly see the phase of
the free-space diurnal anisotropy shifting toward earlier hours around solar
activity minima in A>0 epochs, due to the reduced anisotropy component parallel
to the mean magnetic field. The average parallel component is consistent with a
rigidity independent spectrum, while the perpendicular component increases with
GCR rigidity. We suggest that this harder spectrum of the perpendicular
component is due to contribution from the drift streaming. We find that the
bidirectional latitudinal density gradient is positive in A>0 epoch, while it
is negative in A<0 epoch, in accord with the drift model prediction. The radial
density gradient, on the other hand, varies with ~11-year cycle with maxima
(minima) in solar maximum (minimum) periods, but there is no significant
difference seen between average radial gradients in A>0 and A<0 epochs. The
average parallel mean free path is larger in A0. We also find,
however, that parallel mean free path (radial gradient) appears to persistently
increase (decreasing) in the last three cycles of weakening solar activity. We
suggest that simple differences between these parameters in A>0 and A<0 epochs
are seriously biased by these long-term trends.Comment: accepted for the publication in the Astrophysical Journa
Self-tuning of threshold for a two-state system
A two-state system (TSS) under time-periodic perturbations (to be regarded as
input signals) is studied in connection with self-tuning (ST) of threshold and
stochastic resonance (SR). By ST, we observe the improvement of signal-to-noise
ratio (SNR) in a weak noise region. Analytic approach to a tuning equation
reveals that SNR improvement is possible also for a large noise region and this
is demonstrated by Monte Carlo simulations of hopping processes in a TSS. ST
and SR are discussed from a little more physical point of energy transfer
(dissipation) rate, which behaves in a similar way as SNR. Finally ST is
considered briefly for a double-well potential system (DWPS), which is closely
related to the TSS
Pressure-induced changes in the magnetic and valence state of EuFe2As2
We present the results of electrical resistivity, ac specific heat, magnetic
susceptibility, X-ray absorption spectroscopy (XAS) and X-ray magnetic circular
dichroism (XMCD) of the ternary iron arsenide EuFe2As2 single crystal under
pressure. Applying pressure leads to a continuous suppression of the
antiferromagnetism associated with Fe moments and the antiferromagnetic
transition temperature becomes zero in the vicinity of a critical pressure Pc
~2.5-2.7 GPa. Pressure-induced re-entrant superconductivity, which is highly
sensitive to the homogeneity of the pressure, only appears in the narrow
pressure region in the vicinity of Pc due to the competition between
superconductivity and the antiferromagnetic ordering of Eu2+ moments. The
antiferromagnetic state of Eu2+ moments changes to the ferromagnetic state
above 6 GPa. We also found that the ferromagnetic order is suppressed with
further increasing pressure, which is connected with a valence change of Eu
ions.Comment: 7 pages, 7 figures, accepted for publication in Phys. Rev.
PCN71 Value of Progression-Free Survival (PFS) in Refractory Non-Small Cell Lung Cancer (NSCLC): An Exploratory Modeling Analysis
- …