455 research outputs found
On the solar cycle variation in the barometer coefficients of high latitude neutron monitors
Evaluation of barometer coefficients of neutron monitors located at high latitudes has been performed by using the results of the spherical harmonic analysis based on the records from around twenty stations for twelve years from January 1966 to December 1977. The average of data at eight stations, where continuous records are available for twelve years, show that the absolute value of barometer coefficient is in positive correlation with the cosmic ray neutron intensity. The variation rate of the barometer coefficient to the cosmic ray neutron intensity is influenced by the changes in the cutoff rigidity and in the primary spectrum
Long term changes in cosmic ray diurnal variations observed by ion chambers in Hong Kong and Japan
Yearly average solar diurnal variations of cosmic ray ion chamber data are inspected from a view point of the eleven and the 22 year solar activity cycle modulations. Ion chamber data and neutron data from various stations are added. From an inspection of observed data, a simple approximation that the 11 year and the 22 year variations of the solar diurnal variation are along 18-hour and 12-hour axes, respectively is proposed. The 18-hour component of diurnal variation in the 11 year cycle increases toward the solar active years. The 12-hour component is enhanced when the solar general magnetic field is parallel to the rotation vector, and is almost zero for the other state. The transition occurs when the amplitude of the 18-hour component is greater owing to the transition of the field during the maximum phase of solar activity. The 22 year shift is consistent with the drift modulation model in heliosphere
Electron-Positron Pairs in Hot Accretion Flows and Thin Disk Coronae
We investigate equilibrium accretion flows dominated by pairs. We
consider one- and two-temperature accretion disk coronae above a thin disk, as
well as hot optically thin two-temperature accretion flows without an
underlying thin disk; we model the latter in the framework of
advection-dominated accretion flows (ADAFs). In all three cases we include
equipartition magnetic fields. We confirm the previous result that the
equilibrium density of pairs in two-temperature ADAFs is negligible; and show
that the inclusion of magnetic fields and the corresponding synchrotron cooling
reduces the pair density even further. Similarly, we find that pairs are
unimportant in two-temperature coronae. Even when the corona has significantly
enhanced heating by direct transfer of viscous dissipation in the thin disk to
the corona, the inefficient Coulomb coupling between protons and electrons acts
as a bottleneck and prevents the high compactness required for pair-dominated
solutions. Only in the case of a one-temperature corona model do we find
pair-dominated thermal equilibria. These pair-dominated solutions occur over a
limited range of optical depth and temperature.Comment: 38 pages, including 10 figures, LaTeX; to appear in Ap
Burst size distributions in the digitized data of the ion chambers t Mt. Norikura and sea level stations
A practical and simple method for burst rejection is applied to the digitized data of cosmic ray ion chambers at Mt. Norikura, Tokyo and Kochi. As a result of burst rejection, the burst size frequency distributions in the digitized data at mountain altitude and sea level ion chambers is obtained. Results show that there are no significant differences between the digital and analog data processing in burst rejection
A Thermal-Nonthermal Inverse Compton Model for Cyg X-1
Using Monte Carlo methods to simulate the inverse Compton scattering of soft
photons, we model the spectrum of the Galactic black hole candidate Cyg X-1,
which shows evidence of a nonthermal tail extending beyond a few hundred keV.
We assume an ad hoc sphere of leptons, whose energy distribution consists of a
Maxwellian plus a high energy power-law tail, and inject 0.5 keV blackbody
photons. The spectral data is used to constrain the nonthermal plasma fraction
and the power-law index assuming a reasonable Maxwellian temperature and
Thomson depth. A small but non-negligible fraction of nonthermal leptons is
needed to explain the power-law tail.Comment: 5 pages, 2 PostScript figure, uses aipproc.sty, to appear in
Proceedings of Fourth Compton Symposiu
Recording system for the solar neutron monitoring at Mt. Norikura
To monitor solar neutron events, a new recording system will be installed at Mt. Norikura Cosmic Ray Observatory. The recording system is composed of a pulse counter with clock and a microcomputer with minifloppy disk. The counter and the microcomputer are connected through the General Purpose Interface Bus line. The one minute total count of the neutron monitor is recorded on the minifloppy disk
Multipole expansion for magnetic structures: A generation scheme for symmetry-adapted orthonormal basis set in crystallographic point group
We propose a systematic method to generate a complete orthonormal basis set
of multipole expansion for magnetic structures in arbitrary crystal structure.
The key idea is the introduction of a virtual atomic cluster of a target
crystal, on which we can clearly define the magnetic configurations
corresponding to symmetry-adapted multipole moments. The magnetic
configurations are then mapped onto the crystal so as to preserve the magnetic
point group of the multipole moments, leading to the magnetic structures
classified according to the irreducible representations of crystallographic
point group. We apply the present scheme to pyrhochlore and hexagonal ABO3
crystal structures, and demonstrate that the multipole expansion is useful to
investigate the macroscopic responses of antiferromagnets
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