Evidence for the control of Pc 3,4 magnetic pulsations by the solar wind velocity
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Singer, H. J.↗
Engineering topics
Russell, C. T.
Publications and source records attributed to Russell, C. T..
Observations of magnetic merging and the formation of the plasma sheet in the earth's magnetotail
Particle and magnetic field observations of the field line merging process in the earth's magnetotail are presented. By analyzing the lunar shadow pattern of electron fluxes detected by the lunar-orbiting Apollo 16 subsatellite it has been possible to identify the topology and to measure the velocity of the magnetotail field lines. The observations reported here were made as the moon crossed the separatrix between premerging and merged field lines. The measured field line velocities toward the merging region were 30-60 km/s, and the thickness of the separatrix was estimated to be about 2000 km. Most of the magnetic energy released in the merging process appears to go into the energization of particles. The length and the thickness of the merging region are inferred to be of the order of about 10 earth radii and about 4000 km, respectively. The energized particles travel away from the merging region along the separatrix. Those headed earthward may form the plasma sheet by being trapped on closed field lines. The rate of energization and the energy spectrum of those particles are consistent with those required for formation of the plasma sheet.
Lin, R. P.↗
OGO 5 observations of Pc 5 waves - Particle flux modulations
An investigation is conducted concerning the modulations of particle fluxes associated with Pc 5 waves in the region beyond the plasmapause. A study of thermal flux modulations indicates that some of the density enhancements observed are not spatial structures but are spurious features caused by temporal flux variations associated with hydromagnetic waves. A resonance model of the energetic particle flux modulations is discussed. Energetic particle modulations are also considered. The reported observations reveal that modulations are dominant at energies of about 100 keV for electrons and at 100 keV to 1 MeV for protons. This may indicate that the bounce resonance interaction is not important for Pc 5 waves.
Kokubun, S.↗
The Venus ionosphere and solar wind interaction
The current state of knowledge of the chemistry, dynamics and energetics of the upper atmosphere and ionosphere of Venus is reviewed together with the nature of the solar wind-Venus interaction. Because of the weak, though perhaps not negligible, intrinsic magnetic field of Venus, the mutual effects between these regions are probably strong and unique in the solar system. The ability of the Pioneer Venus Bus and Orbiter experiments to provide the required data to answer the questions outstanding is discussed in detail.
Bauer, S. J.↗
The surface and interior of Venus
The present knowledge of Venus is reviewed with discussions of the nature and history of both the surface, crust and interior. Instrumentation on board the Pioneer Venus Orbiter, including the radar mapper, radio tracking and the fluxgate magnetometer, is described. Topographic, geological, Bouguer gravity, magnetic, and crustal thickness maps will be constructed from Orbiter data. These maps should provide information on composition and thermal history, the major geological or geophysical provinces, the rate of past and present tectonic activity, and evidence of past or present MHD dynamos.
Masursky, H.↗
Some comments on the topology of the geomagnetic tail
The magnetotail topology of the noon-midnight meridian is considered, taking into account the determination of the trajectory of the X line across the tail current sheet. The X line is the line in the current sheet that separates plasma sheet field lines from interplanetary field lines. Attention is given to recent measurements of the boundary layer, the entry layer, and a crossing of the separatrix at the orbit of the moon in terms of the topological sketches.
Russell, C. T.↗
The remanent magnetic field of the moon
Measurements of the moon's remanent magnetic field near the Apollo landing sites and from lunar orbit with the Apollo subsatellites are reviewed. Contour maps are presented for the intensity of the radial, eastward, and northward components of the remanent field as measured with Apollo subsatellite magnetometers at altitudes of 10 to 170 km. Attempts to fit the subsatellite measurements to various models are discussed along with indirect measurements of the remanent field. It is shown that scale sizes of field sources range from 1 to at least 100 km, that the magnetic fields on the far side are stronger and more variable than those on the near side, and that the lunar remanent field apparently exhibits a significant latitude dependence. The origin of the field responsible for the remanent magnetization is considered.
Coleman, P. J., Jr.↗
Multiple satellite observations of pulsation resonance structure in the magnetosphere
Data from two intervals when pulsation activity was simultaneously observed on both ATS 1 and Ogo 5 satellites are presented. The first example, a Pc 4, indicates that this pulsation is caused by a field line near L = 7 resonating in its second-harmonic mode. This is inferred from both plasma density measurements and polarization characteristics. The wave was not observed at three ground stations in the vicinity of the satellite conjugate points. This indicates that Pc 4 waves are very localized in latitude and that a close array (less than 100 km) is needed to perform effective correlation with satellites. The second event, which is also in the Pc 4 band, can again be inferred to be a field line resonance from the polarization characteristics
Hughes, W. J.↗
The Venus bow shock - Detached or attached
Examination of the locations of the bow shock encounters of Mariner 5 and 10 and Venera 4, 6, and 9 suggests that the bow shock of Venus is on the average detached from the ionosphere. However, the standoff distance of the nose of the shock is closer to the planet than the distance that one would obtain by simply scaling the solar wind Venus interaction under the assumption that Venus completely deflects the solar wind. This fact implies that there is a significant influx of solar wind plasma into the Venus ionosphere. If the absorption of the solar wind by Venus is great enough, the shock may become attached to the ionosphere. The Mariner 10 bow shock encounter may have occurred during such a period. A rough estimate of the average fraction of the solar wind incident on the cross section of the planet that is absorbed is 29%.
Russell, C. T.↗
Structure of a quasi-parallel, quasi-laminar bow shock
A thick quasi-parallel bow shock structure was observed on February 14, 1969, with field and particle detectors of both Heos 1 and Ogo 5. The typical magnetic pulsation structure was at least 1-2 R-E thick radially and was accompanied by irregular but distinct (average) plasma distributions characteristic of neither the solar wind nor the magnetosheath. There appeared to be a separate 'interpulsation' regime occurring between bursts of large amplitude oscillations. This regime was magnetically similar to the upstream wave region but was characterized by disturbed plasma flux and enhanced noise around the ion plasma frequency. The shock structure appeared to be largely of an oblique whistler type, probably complicated by counterstreaming high-energy protons.
Greenstadt, E. W.↗
Linear magnetization feature associated with Rima Sirsalis
Measurements of the magnetic fields by the electron reflection method in the neighborhood of the long structural rille Rima Sirsalis show that a magnetic field with a strength of at least 100 nT (100 gammas) is present over a region of the order of 10 km in width and at least 300 km long. The center of the magnetized region closely parallels and is centered on the rille. The linear magnetization feature extends at least to latitude 8 deg S, 60 km beyond the place where the rille disappears at the edge of Oceanus Procellarum. This extension is coincident with the extrapolation of the rille based on photographs. However, the magnetization is much weaker or entirely absent at 5 deg S and has vanished at 0 deg latitude. These results suggest that the rille is indeed a structural feature and has associated with it magnetization, either in the form of intrusive magnetized rock or of a gap in an otherwise more or less uniformly magnetized layer of rock of large extent in two dimensions. Furthermore, the rille structure evidently is present for some distance beneath the lava flows of the Oceanus Procellarum basin.
Anderson, K. A.↗
Triggering of substorms by solar wind discontinuities
The probability of triggering of polar substorms by a large-scale magnetospheric compression associated with a discontinuity in the solar wind has been examined statistically using ground magnetogram data, AE index data and satellite geomagnetic data on 125 sudden storm commencements observed during 1967-1970. The triggering probability was found to depend on the amplitude of the sudden storm commencement and on the degree of preceding AE activity. In almost all cases the triggering occurred when the B-Z component of the interplanetary magnetic field was negative or decreasing during the 30 min before the passage of the discontinuity. Transient geomagnetic responses with a time scale of Alfven wave propagation in the polar cap also depend on interplanetary magnetic field conditions.
Kokubun, S.↗
On deducing the magnetization of the lunar surface from orbital surveys
A combination of orbital photographic, selenochemical, and magnetic surveys may elucidate the mechanism by which the lunar surface became magnetized and possibly yield an estimate of the intensity of the ancient magnetizing field and its time variation. The determination of the size and shape of the magnetized regions requires the measurement of the altitude dependence of field, especially at low altitudes (less than 100 km) and with a high enough sampling rate to resolve the profile at the edges of magnetized bodies. The planned Lunar Polar Orbiter may well provide the necessary data.
Russell, C. T.↗
Geologic-magnetic correlations on the moon - Apollo subsatellite results
Comparison of the magnetic-field measurements of the Apollo subsatellite magnetometers with USGS geologic maps suggests that the ancient lunar field may have been greater during the Imbrian Period than the earlier Pre-Nectarian and Nectarian periods. Further, the field seems to have varied in direction. These data are consistent with a model in which the ancient lunar magnetizing field arises from a core dynamo which does not form until the Imbrian Period. Impacts during this period then result in magnetized crater melt and ejecta blankets. It is emphasized, however, that the area sampled by the subsatellite magnetometers is but a small fraction of the lunar surface. These results must be confirmed with studies of independent regions of the lunar surface before they can be considered conclusive.
Russell, C. T.↗
On a correlation between surface remanent magnetism and chemistry for the lunar frontside and limbs
Image-processing techniques applied to orbital data have revealed an inverse correlation between lunar surface remanent magnetism and surface concentrations of Fe and Th on a scale of 250 km and greater. The effect can be understood in terms of the implantation of magnetism early in the history of the moon, coupled with the chronological sequence of highland-mare crustal differentiation. The exception seen at the Fra Mauro region suggests the presence of a source of magnetization sometime within 0.3-0.6 b.y. after formation of the moon.
Metzger, A. E.↗
Magnetic pulsations as a probe of the interplanetary magnetic field - A test of the Borok B index
A magnetic pulsation index based on the periods of Pc 2-4 pulsations as recorded in earth current measurements at the Borok Geophysical Observatory has been claimed to be a measure of the interplanetary field. Tests of this index for the period 1972 to June 1974 show only a 27% success rate. However, a simple recalibration of the index improves the success rate to 51%. The success of the index indicates that the source of many terrestrial magnetic pulsations is external to the magnetosphere.
Russell, C. T.↗
A statistical study of Pc 1 magnetic pulsations at synchronous orbit
The statistical properties of Pc 1 magnetic pulsations at synchronous orbit are examined by using measurements obtained with the UCLA flux-gate magnetometer on board ATS 1. In 1967, 121 intervals of Pc 1 activity occurred. These events typically had amplitudes of 1-7 gamma and periods of 2-5 sec. Most events lasted less than 30 min and occurred in the afternoon sector. Pc 1 waves were more probable during the main phase of a geomagnetic storm, within 1 hour of a substorm expansion. While they do not have the signature of IPDP (intervals of pulsations of diminishing periods) events at ATS, simultaneous ground records show the occurrence of rising frequency tones characteristic of IPDP events in seven out of ten cases. The wave frequency ranged principally from 0.1 to 0.2 of the local proton gyrofrequency, similar to observations of electron cyclotron waves. The observed Pc 1 activity is consistent with the generation by cyclotron resonance of 30-keV protons in a 30/cu cm plasma.
Bossen, M.↗
Simultaneous Pc 1 observations by the synchronous satellite ATS-1 and ground stations - Implications concerning IPDP generation mechanisms
Results are presented for an experimental study designed to examine the properties of Pc 1 activity observed simultaneously at ATS 1 and two Canadian ground stations. The Pc 1 activity is found to follow substorm expansion phase onsets and to occur most frequently at dusk. Dynamic spectra waves at both ground stations are that of IPDP (Intervals of Pulsations Diminishing by Period) type Pc 1. A previously proposed mechanism to explain IPDP generation, which required a rapid increase in the equatorial magnetic field to produce IPDP, is inconsistent with the dynamic spectra and magnetic field observations. Either purely azimuthal or a combination of azimuthal and radial inward drift of energetic resonant protons is an equally plausible mechanism to explain IPDP generation.
Bossen, M.↗