Quasi-stationary corotating structure in the interplanetary medium

Abstract

A quasi‐stationary corotating structure in the interplanetary magnetic field has been observed with the Imp 1 satellite during 3 solar rotations. The interplanetary field is directed predominantly away from the sun for 2/7 of a rotation, then toward the sun for 2/7 of a rotation, then away from the sun for 2/7 of a rotation, and finally toward the sun for 1/7 of a rotation. The interplanetary magnetic field magnitude and the solar wind velocity, density, and flux are discussed with regard to this sector structure. As the structure rotates past the earth once every 27 days it influences geomagnetic activity and cosmic‐ray density. A recurring stream of protons of a few Mev energy is almost entirely contained within one sector. The solar source of the recurring geomagnetic storm of December 2, 1963, is associated with a ghost unipolar magnetic region in the solar photosphere.

The interplanetary magnetic field. Solar origin and terrestrial effects

“…This is consistent with the suggestion by WILCOX and NESS (1965) that the ghost UMR was associated with the source of the positive sector responsible for recurrent geomagnetic disturbance; since the associated UMR * Figure 48 was drawn using preliminary MIT values for solar wind velocity.…”

“…The data are 7.5-minute samples (BARTLEY et al, 1966). An approximation to the average shape shown in Figure 3_ can be seen in each individual sector (WILCOX and NESS, 1965). To find the equivalent equinoctial Kp from a given _ at a given date, say 7°at 20 January, draw a curve parallel to the given curves from this point to the vertical corresponding to the equinoxes, and read the value of _ there.…”

Large‐scale properties of the interplanetary magnetic field

“…This repeated every 27 days and formed a pattern which was given the name sector structure. This early sector structure pattern is shown in Figure 3 from Wilcox and Ness (1965).…”

Heliocentric distance dependence of the interplanetary magnetic field

“…High-speed streams were first identified in the Mariner 2 data of 1962 (Neugebauer and Snyder, 1966). Various correlations of the plasma and magnetic field measure ments on IMP I (Wilcox and Ness, 1965), Vela 3 (Ness et al, 1971) and Mariner 2 have shown that each high-speed stream has a predominant magnetic polarity, with one or more streams occurring within a single magnetic sector. The magnetic field magnitude is found to be enhanced in the leading part of a stream, which is the high density (compression) region, and reduced in the trailing part, which is the low density (rarefaction) region; These features have been predicted in dynamical models by Sakurai (1971), Matsuda andSakurai (1972) Urch (1972) and Nakagawa and Wellck (1973).…”