All issues
Successor
Volume 32 (1980)
- Issue 12 Pages 721-
- Issue 11 Pages 671-
- Issue 10 Pages 585-
- Issue 9 Pages 507-
- Issue 8 Pages 431-
- Issue 7 Pages 365-
- Issue 6 Pages 309-
- Issue 5 Pages 265-
- Issue 4 Pages 181-
- Issue 3 Pages 129-
- Issue 2 Pages 67-
- Issue 1 Pages 1-
- Issue Supplement3 Pag･･･
- Issue Supplement2 Pag･･･
- Issue Supplement1 Pag･･･
Volume 43, Issue 10
Displaying 1-8 of 8 articles from this issue
- |<
- <
- 1
- >
- >|
-
T. IYEMORI, T. ARAKI1991 Volume 43 Issue 10 Pages 783-795
Published: 1991
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSGeomagnetic disturbances from the period April to June 1910 are analyzed to detect the possible effects of H the comet alley on the solar wind-magnetosphere interaction. Data from six mid-latitude geomagnetic observatories are used to calculate the longitudinally symmetric (i. e. Dst) and asymmetric fields. An application of a linear prediction filter to separate the solar wind dynamic pressure effect on the disturbances from that of the ring current, suggests that there exists a compressional variation in the Dst on May 18 which is around or slightly earlier than the time of estimated cometary tail encounter. The normal-run magnetogram from Agincourt on the dayside and that from Lu-Kia-Pang on the nightside, also indicate rather strong (i. e. 30-40nT) compressional variation. The disturbances characteristic to the solar wind-magnetosphere interaction under the southward IMF condition and that of the ring current development are seen during the period. An exponential recovery of the Dst also supports the above interpretation. These results suggest that the Earth's magnetosphere had been affected by a dense cometary plasma tail with high dynamic pressure, though the solar wind-magnetosphere interaction typically observed under the southward IMF condition had been taking place during the encounter. It is also suggested that the width of the cometary plasma tail was considerably greater (>0.09AU) than that of the theoretically expected though the possibility of overestimation caused by cometary tail fluttering can not be excluded.View full abstractDownload PDF (1460K) -
Vipin K. JAIN, Birbal SINGH1991 Volume 43 Issue 10 Pages 797-802
Published: 1991
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSPitch angle scattering and diffusion of inner belt electrons resonating with whistler-mode Decca signals of frequency 84.82kHz transmitted from Port Hedland, Australia (L=1.38) and observed at Kagoshima, Japan (L=1.2) are evaluated using quasi-linear theory of wave-particle interaction. The results show that the pitch angle scatterings are greater than 10-1 deg and lifetimes of the energetic electrons (ER=60keV) are -20min. These results indicate significant particle precipitation in the ionosphere. The evaluated precipitated flux is found to be 3.31×103el-cm-2-s-1 which in terms of energyflux is found to be 3.18×10-4ergs-cm-2-s-1. This is in good agreement with the precipitated flux observed in the low latitude zone of particle precipitation during magnetic storms.View full abstractDownload PDF (596K) -
Minoru FUNAKI, Hideo SAKAI1991 Volume 43 Issue 10 Pages 803-811
Published: 1991
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSMagnetization process of dirt-snow containing fine-grained magnetic minerals was investigated in order to understand the acquisition mechanism of natural remanent magnetization (NRM) by dirt-ice layers in Antarctica. Dirt-snow acquired NRM from the direction of geomagnetic field (GMF) direction at rooms -10°C and -20°C, and inclination becomes shallower than the GMF after 50 days.
The following two types of NRM acquisition mechanisms in the GMF are proposed; (1) magnetic grains align along the GMF when they drop onto the surfaces of underlying snow due to vaporization of snow; (2) the magnetic grains are rotated to align in the GMF direction on the snow surfaces by the torque with the GMF and the NRM. The compaction of the natural snow at formation of depth hoar works to flatten the NRM direction.
Probably the Antarctic dirt-ice has acquired NRM during the periods of accumulation of snow and magnetic grains and formation of the depth hoar. The NRM of dirt-snow and -ice are usuful for understanding the glacial dynamics and paleomagnetism of the Antarctic ice sheet, although many problems still remain.View full abstractDownload PDF (983K) -
M. K. TUNÇER, Y. HONKURA, N. OSHIMAN, Y. IKEDA, A. M. ISIKARA1991 Volume 43 Issue 10 Pages 813-823
Published: 1991
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSMeasurements of the geomagnetic total intensity were carried out in the western part of the North Anatolian Fault Zone. In particular, profile measurements were made across some fold structures in the graben. The data show anomalies presumably related to active folds, although fold structures are not necessarily accompanied by magnetic anomalies. The anomalies are similar to those found along the active faults in the North Anatolian Fault Zone, and they could be interpreted in terms of a dike-like structure model as was the case for the anomalies associated with the active faults. This implies that folding may be a surface manifestation of faulting at depth.View full abstractDownload PDF (1019K) -
Yasuharu SANO1991 Volume 43 Issue 10 Pages 825-837
Published: 1991
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSIt is demonstrated by a simple example and an elementary calculation that under certain conditions the moment of a dipole fitted to a distribution of magnetic potential is not necessarily the same as the dipole moment in the original magnetic potential. The dipole moment of the original magnetic potential which is a vector quantity specified by the first three coefficients in the spherical harmonic expansion is invariant, that is, independent of the choice of the origin of the coordinate system. Despite this, the moment of the fitted dipole can be different from the dipole moment in the original magnetic potential, depending on the choice of the optimum condition for the fitting. The optimum condition used here differs from that adopted in Schmidt's definition in that in the present definition coefficients of all degree and order are considered. The present definition becomes identical with Schmidt's definition when the harmonics of degrees higher than the quadrupole are truncated. When all the higher harmonics are included in the definition, we obtain a moment and location of the dipole different from those obtained from the classical method of Schmidt. Moreover, the obtained dipole moment and location are different from those deduced from a generalization of Schmidt's definition by inclusion of all harmonics to the infinite degree. For the present geomagnetic field, this method of analysis gives a dipole position shifted from the conventional eccentric dipole position roughly by 80km, and a moment reduced roughly by 20nT.View full abstractDownload PDF (1079K) -
1. The Adjoint System and Its SolutionsMasaru KONO, Paul H. ROBERTS1991 Volume 43 Issue 10 Pages 839-862
Published: 1991
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThe kinematic dynamo problem poses a non-self-adjoint eigenvalue problem. Corresponding to this eigenvalue system is its adjoint, which has the same eigenvalues but different eigenfunctions that are orthogonal to those of the dynamo system. The differential equations governing the two systems are the same, but the velocity appears with opposite signs; the α-effect (if present) is the same in each; the boundary conditions are different. The adjoint problem is useful in (a) examining why so often dynamos of dipole and quadrupole parity are excited with almost equal ease, (b) providing a check on the accuracy of numerical calculations, and (c) constructing weakly nonlinear solutions of the full MHD dynamo problem, at slightly supercritical magnetic Reynolds numbers, a topic postponed to sequels of this paper.
The adjoint system is deduced here both for spherical dynamos and for dynamos operating in containers of general form. The application of a technique developed by one of us previously (KONO, 1990), that rests on the use of computer algebra, is generalized to include the α-effect. Eigenvalues of both the dynamo system and its adjoint are derived numerically for a number of axisymmetric spherical dynamos of α2- and αω-type. Agreement between the eigenvalues of the two systems, and between those reported in earlier integrations, is demonstrated, as is the closeness of the eigenvalues of dipole and quadrupole type for α2-dynamos; their separation for αω-dynamos is greater.View full abstractDownload PDF (2403K) -
Senkichi SHIBUYA1991 Volume 43 Issue 10 Pages 863-869
Published: 1991
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSDownload PDF (607K) -
Hiroshi AMEMIYA, Yoshyuki SHIGUEOKA1991 Volume 43 Issue 10 Pages 871-881
Published: 1991
Released on J-STAGE: September 14, 2010
JOURNAL FREE ACCESSThermal electron energy distributions in the midlatitude ionosphere measured at dusk on September 16, 1983, by a Japanese rocket S-310-14, launched from Kagoshima Space Center, showed bumps appeared on the high energy tail at about 0.3eV between 98.3 and 171km. Densities of such non-thermal electrons were about 10-2 of those of thermal electrons. Above the height of 180km (F-layer), distributions had no bumps on the tail and only slightly deviated from Maxwellian. The mechanism of the appearance of non-thermal electrons is discussed from a point of super-elastic collisions between vibrationally excited nitrogen molecules and thermal electrons.View full abstractDownload PDF (891K)
- |<
- <
- 1
- >
- >|