Dipole-like Field Research Articles

A long-period Pi 2 associated with a mini-substorm observed by the Japanese satellite JIKIKEN (EXOS-B).

Being associated with a typical mini-substorm, a very-long-period Pi 2 event was observed simultaneously at both Onagawa, Japan, and the satellite, JIKIKEN, at 14-15 hUT on December 11, 1978. The fundamental period of the Pi 2 attained to 220 sec and the range of the substorm at Onagawa on the 23h local time meridian was only 2nT. The plasmapause was observed by JIKIKEN on the 21h local time meridian to be at L>6.3.This Pi 2 event in the extreme case is well explained by such an odd-mode model that a temporal odd-mode torsional oscillation of the dipole-like field lines anchored in the auroral ovals is observed as Pi 2. The analysis reveals that the ignition region for this mini-substorm must be |X|>16RE in the magnetotail and that the tail-like configuration of the field line must be changed to the dipole-like one within several min. This event provides valuable information on one of the smallest cases of the magnetospheric substorm.

Dipole-like neuronal sources of theta rhythm in dorsal hippocampus, dendate gyrus and cingulate cortex of the urethane-anesthetized rat

Spatial distribution of theta activity was investigated in the dorsal hippocampal formation and overlying neocortex of the urethaneanesthetized rat. Laminar phase profiles from semi-microelectrode penetrations showed approximately 180° phase shifts combined with small amplitude values in stratum radiatum of CA1, in stratum moleculare of the dentate gyrus and in layer V/VI of the cingulate cortex at theta peak frequency. Evidence has been presented that layers of neurons in CA1, in the dorsal granular layer and in the cinguate cortex are the sources of dipole-like theta field potentials. A strong linear relationship between the neuronal theta sources in hippocampal CA1, dendate area and cingulate cortex was found.

Explorer 33 entry layer observations

Low fluxes of stagnant or irregularly flowing plasma along the inside of the magnetopause labeled as the entry layer by Haerendel and Paschmann, are observed on Explorer 33 orbits which cross the dayside magnetopause and on one orbit which skims the dawn flank. The data indicate that the entry layer is a permanent magnetospheric feature which extends across the dayside and along the flanks to large distances down the tail on dipolelike field lines between extensions of the northern and southern polar cusps. Pressure anisotropies are present in the entry layer but are often weaker and less frequent than those in the adjacent magnetosheath. These anisotropies give clues about the process of entry layer formation. The sense of anisotropy when it is present on both sides of the magnetopause is the same for magnetosheath fields with a southward component and opposite for fields with a northward component. These correlations are consistent with entry layer filling by bulk flow along field lines opened by magnetic merging in the one case and by diffusion onto closed field lines in the other.

Latitude dependence of the solar wind speed: Influence of the coronal magnetic field geometry

The dependence of solar wind speed on latitude as influenced by the magnetic field configuration of the inner corona is studied. It is found that in general, a dipolelike field geometry characteristic of a minimum-type corona tends to produce a solar wind speed distribution which increases with heliographic latitude, in accordance with observations. At very high coronal base densities and temperatures, however, this effect is minimal or even inverted. Physically, the field affects the wind speed through its area divergence, a larger divergence resulting in correspondingly lower speeds. During solar minimum, eclipse photographs suggest that the field divergence increases from pole to equator, a characteristic not apparent during solar maximum. Hence we expect the latitudinal increase in speed to be most pronounced at the minimum phase of solar activity.

Multipole Magnetic Fields in Upper-Main Stars

view Abstract Citations (3) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multipole Magnetic Fields in Upper-Main Stars Monaghan, J. J. Abstract Models of uniformly rotating, axisymmetric, upper-main-sequence stars with multipole magnetic fields have been constructed using a perturbation method. The boundary conditions do not specify the solution uniquely. For one class of solutions the equations form a nonlinear eigenvalue problem which is solved for a special choice of the field stream function. The ratio of external to total magnetic flux is found to decrease with increasing rotation for a fixed surface field as it does for the dipole-like field. Subject headings: hydromagnetics - magnetic stars Publication: The Astrophysical Journal Pub Date: December 1973 DOI: 10.1086/152531 Bibcode: 1973ApJ...186..631M full text sources ADS |

Hyperfine fields in ordered lithium ferrite

The experimental 57Fe spectra of Doroshev et al. are explained in terms of dipole-like fields.

Cerenkov scintillation ounter measurements of the intensity and modulation of low rigidity cosmic rays and features of the geomagnetic cutoff rigidity

The primary cosmic radiation has been measured with a Cerenkov scintillation counter at various times in the solar cycle at locations having nominal cutoff rigidities of 0.8, 1.6, and 2.7 bv. Results are used here to delineate spectral features of low rigidity protons and α particles and to examine the rigidity and charge dependence of the eleven-year solar modulation. Details of particle transmission near the geomagnetic cutoff are also examined. The measurements indicate: (1) The observed nonsharp cutoff appears to be primarily due to expected transmission effects in a dipole-like field and to instrumental effects, and the actual cutoff is quasi-sharp in the Stormer sense. This is true even though the observed cutoff may be reduced to half that to be expected from the internal field, presumably because of external current systems flowing in the magnetosphere and its boundary. (2) The rigidity dependence of the eleven-year modulation of protons and that of α particles are closely similar above ∼1.2 bv. None of the presently proposed models for this modulation agree with our results. The implications of this lack of agreement are discussed, and it is concluded that certain general features of particle motion in the interplanetary medium not considered in present models may be of importance. One such general feature may be diffusive deceleration in the radially expanding interplanetary medium, which is shown to have the same effect as a static heliocentric electric field. (3) The differential spectrum of galactic cosmic rays near sunspot minimum at about 1-bv rigidity is either flat or falling slightly toward lower rigidities. The measurements in the rigidity range below 1 bv are compared with recent observations in this range.