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Results for “INTERPLANETARY MAGNETIC FIELD”

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1964

Interplanetary magnetic fields.

Interplanetary magnetic fields discussing effects of solar plasma on origin, properties, irregularities and disturbances

SOLAR WIND↗
NASA NTRS1977

On the existence of finite amplitude, transverse Alfven waves in the interplanetary magnetic field

Interplanetary magnetic field data from the Mariner 10 spacecraft were examined for evidence of small and finite amplitude transverse Alfven waves, general finite amplitude Alfven waves, and magnetosonic waves. No evidence for transverse Alfven waves was found. Instead, the field fluctuations were found to be dominated by the general finite amplitude Alfven wave. Such wave modes correspond to non-plane-wave solutions of the nonlinear magnetohydrodynamic equations.

Sari, J. W.↗
NASA NTRS1976

Mariner 10 interplanetary magnetic field results

Interplanetary magnetic field data obtained by Mariner 10 between November 1973 and March 1974 are examined. Though large variations in the field due to the effects of high speed streams and stream-stream interactions were observed, on average the large scale interplanetary magnetic field radial component was found to have a distance dependence of r to the minus 2.0 plus or minus 0.3, while the azimuthal field component was found to vary as r to the minus 1.3 plus or minus 0.4, and a dependence of r to the minus 1.4 plus or minus 0.6 was found for the component normal to the solar equatorial plane. A close correspondence was found between the magnetic field stream signatures and persistent but evolving coronal hole regions on the sun, and a clear pattern of large southward fields in stream interaction regions and high levels of field fluctuations within the high-speed streams was detected.

Behannon, K. W.↗
NASA NTRS1991

The structure of helical interplanetary magnetic fields

The interplanetary magnetic field is known to be highly helical. Although the detailed spatial structure of the fields has yet to be elucidated, the helicity spectrum has been conjectured to result from a random walk in the direction of a constant magnitude magnetic field vector. A model using three-dimensional fluctuations with variations in B is demonstrated giving a good fit to the helicity spectrum as well as to other properties of the interplanetary magnetic field.

Goldstein, M. L.↗
NASA NTRS1975

A survey of long term interplanetary magnetic field variations

Interplanetary magnetic field data from 10 IMP, AIMP, and HEOS spacecraft were merged into a composite data set spanning 1963 to 1974. A consideration of the mutual consistency of the individual data sets reveals agreement typically to within 0.2 gamma. Composite data set analysis reveals: (1) whereas 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 heliolatitude 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 heliolatitude-dependent dominant polarity effect exhibits a complex sign reversal in the 1968 to 1971 period and a measure of symmetry in 1972 to 1974 not found in earlier data.

King, J. H.↗
NASA NTRS1975

A survey of the interplanetary magnetic field

All interplanetary magnetic field measurements from near-earth satellites have been collected in the form of hourly averages for the years 1963-1974. Solar cycle variations of the field and the exceptional events of this cycle are discussed in relation to the associated cosmic ray events, and statistical properties of the field over this period are presented. The presence of magnetic blobs as a permanent feature of the field is demonstrated and explained. The implications of these results for the theory of cosmic ray modulation are presented and analyzed.

Barouch, E.↗
NASA NTRS1991

The sun and interplanetary magnetic field

The interplanetary magnetic field (IMF) serves as a link between the sun, the response of the earth to solar activity and variations in galactic cosmic radiation. The IMF originates as a solar-coronal magnetic field that is transported into space by the solar wind. The close connection between solar magnetic fields and the origin and structure of the solar wind is described. The solar wind forms the heliosphere, a cavity containing the magnetized solar plasma from which the interstellar plasma and field are excluded. The entry of galactic cosmic rays into the heliosphere and their strong interaction with the IMF are discussed, this topic being of primary importance to the production and temporal variations of radiogenic elements. The profound influence of the IMF on geomagnetic activity and the aurora is discussed within the context of merging or reconnection with the planetary field. The physical connection is thus established between solar magnetic fields, magnetic storms and aurora. The state of the solar wind and IMF during the Maunder minimum is considered and an explanation for the (relative) absence of sunspots and aurora is proposed. The mechanism is an interruption of the oscillatory solar dynamo, a consequent reduction in the heating of the corona, a cessation of the supersonic solar wind and a weakening or absence of southward-directed magnetic fields in the vicinity of the earth.

Smith, Edward J.↗
NASA NTRS1983

Solar cycle variations in the interplanetary magnetic field

ISEE 3 interplanetary magnetic field measurements have been used to extend the NSSDC hourly averaged IMF composite data set through mid-1982. Most of sunspot cycle 20 (start:1964) and the first half of cycle 21 (start:1976) are now covered. The average magnitude of the field was relatively constant over cycle 20 with approx. 5-10% decreases in 1969 and 1971, when the Sun's polar regions changed polarity, and a 20% decrease in 1975-6 around solar minimum. Since the start of the new cycle, the total field strength has risen with the mean for the first third of 1982 being about 40% greater than the cycle 20 average. As during the previous cycle, an approx. 10% drop in IMF magnitude accompanied the 1980 reversal of the solar magnetic field. While the interplanetary magnetic field is clearly stronger during the present solar cycle, another 5-7 years of observations will be needed to determine if cycle 21 exhibits the same modest variations as the last cycle. Accordingly, it appears at this time that intercycle changes in IMF magnitude may be much larger than the intracycle variations.

Slavin, J. A.↗