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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1965

Interplanetary magnetic field.

Observations of interplanetary magnetic field by Mariner and Imp spacecraft confirm predictions based on behavior of cosmic rays

MARINER II SPACE PROBE↗
NASA NTRS1976

A survey of long-term interplanetary magnetic field variations

Interplanetary-magnetic-field data from the IMP-10, IMP-A, and Heos spacecraft have been merged into a composite data set spanning the period from 1963 to 1974. Consideration of the mutual consistency of the individual data sets reveals agrement typically to within 0.2 gamma. Analysis of the composite data set reveals the following: (1) although the yearly averaged magnitudes of all field vectors show virtually no solar-cycle variation, the yearly averaged magnitudes of positive- and negative-polarity field vectors show separate solar-cycle variations consistent with variations in the average azimuthal angles of positive- and negative-polarity field vectors; (2) there is no solar latitude dependence of long-time average field magnitudes; (3) field vectors parallel to the earth-sun line are on the average 1 gamma less in magnitude than field vectors perpendicular to this line; and (4) the solar latitude-dependent dominant polarity effect exhibits a complex sign reversal in the period from 1968 to 1971 and a measure of symmetry in 1972 through 1974 not found in earlier data.

King, J. H.↗
NASA NTRS1976

The August 1972 solar-terrestrial events - Interplanetary magnetic field observations

Interplanetary-magnetic-field measurements made by Pioneers 9 and 10, HEOS 2, and Explorer 41 during early August 1972 are reviewed. It is noted that the two Pioneers were nearly radially aligned during the flare events, with Pioneer 9 at a distance of 0.78 AU from the sun and Pioneer 10 at a distance of 2.2 AU. The data obtained by Pioneer 9, Pioneer 10, and the two near-earth satellites are analyzed separately, and the major flare-associated shocks are identified. An attempt is made to identify corresponding shocks at the different locations and to determine their propagation velocities in the region between 0.8 and 2.2 AU. It is found that there was an obvious tendency for the average shock velocities to decrease with increasing radial distance from the sun and that the local velocities at the Pioneer locations were significantly smaller than the appropriate average values. A comparison of these local velocities indicates that there was a large deceleration of the shocks between the sun and some distance within 0.8 AU but little, if any, deceleration beyond that distance. A plot of average shock velocities from the sun to 1.0 AU as a function of longitude separation between the flares and Pioneer 9 is shown to suggest a pronounced deviation of the shock fronts from spherical symmetry.

Smith, E. J.↗
NASA NTRS1972

Polar cap electric field distributions related to the interplanetary magnetic field direction

The correlations between the azimuthal direction of the interplanetary magnetic field and the most simple polar cap signatures are discussed. Only the spatial distribution of the dawn-dusk polar cap field is considered. For each OGO 6 traverse across the northern or southern polar cap, the simultaneous values of the interplanetary magnetic field in solar-equatorial coordinates were recorded by the Explorer 33 magnetometer. Histograms of these values are presented and are discussed. The high degree of correlation with the longitudinal angle indicates that the relative geometry of the interplanetary magnetic field and magnetospheric magnetic fields must be fundamental to explaining the distribution of polar cap electric fields. The sign of the solar-equatorial component perpendicular to the sun-earth line appears to be a more critical parameter than the sign of the component toward the sun. The Svalgaard-Mansurov correlation and the correspondence between fast convection and parallel magnetospheric and interplanetary magnetic fields are described.

Heppner, J. P.↗
NASA NTRS1972

Large-scale properties of the interplanetary magnetic field

Early theoretical work of Parker is presented along with the observational evidence supporting his Archimedes spiral model. Variations present in the interplanetary magnetic field from the spiral angle are related to structures in the solar wind. The causes of these structures are found to be either nonuniform radial solar wind flow or the time evolution of the photospheric field. Coronal magnetic models are related to the connection between the solar magnetic field and the interplanetary magnetic field. Direct extension of the solar field-magnetic nozzle controversy is discussed along with the coronal magnetic models. Effects of active regions on the interplanetary magnetic field is discussed with particular reference to the evolution of interplanetary sectors. Interplanetary magnetic field magnitude variations are shown throughout the solar cycle. The percentage of time the field magnitude is greater than 10 gamma is shown to closely parallel sunspot number. The sun's polar field influence on the interplanetary field and alternative views of the magnetic field structure out of the ecliptic plane are presented. In addition, a variety of significantly different interplanetary field structures are discussed.

Schatten, K. H.↗
NASA NTRS1992

Venus internal magnetic field and its interaction with the interplanetary magnetic field

In a previous study, Knudsen et al. suggested that Venus has a weak internal magnetic dipole field of the order of 7 x 10 + 20 G cm(exp -3) that is manifested in the form of magnetic flux tubes threading the ionospheric holes in the Venus nightside ionosphere. They pointed out that any internal field of Venus, dipole or multipole, would be weakened in the subsolar region and concentrated in the antisolar region of the planet by the supersonic transterminator convection of the dayside ionosphere into the nightside hemisphere. The inferred magnitude of the dipole field does not violate the upper limit for an internal magnetic field established by the Pioneer Venus magnetometer experiment. The most compelling objection to the model suggested by Knudsen et al. has been the fact that it does not explain the observed interplanetary magnetic field (IMF) control of the polarity of the ionospheric hole flux tubes. In this presentation I suggest that a magnetic reconnection process analogous to that occurring at earth is occurring at Venus between the IMF and a weak internal dipole field. At Venus in the subsolar region, the reconnection occurs within the ionosphere. At Earth it occurs at the magnetopause. Reconnection will occur only when the IMF has an appropriate orientation relative to that of the weak internal field. Thus, reconnection provides a process for the IMF to control the flux tube polarity. The reconnection in the subsolar region takes place in the ionosphere as the barrier magnetic field is transported downward into the lower ionosphere by downward convection of ionospheric plasma and approaches the oppositely directed internal magnetic field that is diffusing upward. The reconnected flux tubes are then transported anti-Sunward by the anti-Sunward convecting ionospheric plasma as well as by the anti-Sunward-flowing solar wind. Reconnection will also occur in the Venus magnetic tail region, somewhat analogously to the reconnection that occurs in the magnetotail of the Earth. The possibility that reconnection is occurring between the IMF and an internal dipole field may be tested by measuring the orientation of the IMF projected into a plane perpendicular to the solar wind velocity during time intervals for which ionospheric holes are observed. The orientations of the IMV components should fall within a 180 deg angle.

Knudsen, W. C.↗
NASA NTRS1973

Further study of the theta component of the interplanetary magnetic field.

Measurements of the interplanetary magnetic field taken with Imp 3, Pioneer 6, and Explorer 34 constitute a large portion of the data available at low and moderate solar activity and provide nearly continuous coverage from mid-1965 through 1966 without radial effects. Study of these observations provides further evidence for the following B sub theta effect initially discovered with Mariners 2, 4, and 5. At low or moderate solar activity, the mean value of B sub theta is negative (approximately northward in the observations) above the solar equatorial plane and positive below it for an interplanetary field directed outward from the sun, and vice versa for an inward field. Thus, for an outward field, the r-theta component of a line of magnetic force above or below the equatorial plane was skewed relative to the average value of r in the direction away from the equatorial plane. Comparisons between different spacecraft are discussed.

Rosenberg, R. L.↗
NASA NTRS1975

Interplanetary magnetic field data book

An interplanetary magnetic field (IMF) data set is presented that is uniform with respect to inclusion of cislunar IMF data only, and which has as complete time coverage as presently possible over a full solar cycle. Macroscale phenomena in the interplanetary medium (sector structure, heliolatitude variations, solar cycle variations, etc.) and other phenomena (e.g., ground level cosmic-ray events) for which knowledge of the IMF with hourly resolution is necessary, are discussed. Listings and plots of cislunar hourly averaged IMP parameters over the period November 27, 1963, to May 17, 1974, are presented along with discussion of the mutual consistency of the IMF data used herein. The magnetic tape from which the plots and listings were generated, which is available from the National Space Science Data Center (NSSDC), is also discussed.

King, J. H.↗