Solar cycle variation of the interplanetary magnetic field spiral

Journal Article · Fri Mar 01 04:00:00 EST 1991 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/169830· OSTI ID:5700958

Smith, C W; Bieber, J W ^[1]

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1. Delaware Univ., Newark (USA)

Interplanetary measurements spanning the time interval from 1965 through 1987 and a distance range from 0.7 to 15.9 AU are employed to test the Parker (1958) theory for the large-scale structure of the interplanetary magnetic field. Examination of data recorded by earth-orbiting spacecraft reveals that the interplanetary magnetic field spiral depends upon the phase of the solar cycle, such that the annual mean winding angle in the years surrounding solar maximum is about 10 deg larger than in the years surrounding solar minimum. The observed variation of the solar wind speed with the solar cycle is shown to account for much of the recorded variation in the winding angle. It is suggested that nonzero azimuthal field components arising from differential solar rotation may be convected into the corona to provide a steady source of azimuthal magnetic fields at the source point of the solar wind. A straightforward extension of the Parker theory shows how such seed fields would account for the observed discrepancy in the interplanetary spiral winding. 38 refs.

• OSTI ID: 5700958
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 370; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640104 -- Astrophysics & Cosmology-- Solar Phenomena
640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
INTERPLANETARY MAGNETIC FIELDS
MAGNETIC FIELDS
MORPHOLOGY
MOTION
ROTATION
SOLAR ACTIVITY
SOLAR CORONA
SOLAR CYCLE
SOLAR WIND
STELLAR ATMOSPHERES
STELLAR CORONAE
VELOCITY