Solar Sector Structure

TL;DR

This paper discusses the large-scale sector structure of the interplanetary magnetic field, its relation to solar surface features, and the significance of Hale sector boundaries in understanding solar magnetic polarity patterns.

Contribution

It links the interplanetary magnetic sector structure to solar surface magnetic features, emphasizing the role of Hale sector boundaries in polarity switching.

Findings

Sector structure reflects solar magnetic polarity patterns.

Pattern appears at both interplanetary space and solar surface.

Hale sector boundary aligns with sunspot polarity switches.

Abstract

The interplanetary magnetic field near has a characteristic "sector" structure that reflects its polarity relative to the solar direction. Typically we observe large-scale coherence in these directions, with two or four "away" or "towards" sectors per solar rotation, from any platform in deep space and near the ecliptic plane. In a simple picture, this morphology simply reflects the idea that the sources of the interplanetary field lie mainly in or near the Sun, and that the solar-wind flow enforces a radial component in this field. Although defined strictly via the interplanetary field near one AU, recent evidence confirms that this pattern also appears clearly at the level of the photosphere, with signatures including not only the large-scale structures (e.g., the streamers) but also highly concentrated fields such as those found in sunspots and even solar flares. This association with small-scale fields strengthens at the Hale sector boundary, defining the Hale boundary as the one for which the polarity switch matches that of the leading-to-following polarity alternation in the sunspots of a given hemisphere.