The image shows the heliospheric current sheet generated by the sun as it rotates. The current sheet separates magnetic fields of opposite polarity. Because the current sheet is tilted with respect to the Sun's rotation axis, the Earth will pass through regions of different polarity, called sectors, as it travels around the sun. Credit: Hundhausen, A. J., Coronal Expansion and the Solar Wind, Springer-Verlag, 1972. |
The coronal magnetic field resembles a dipole that has been distorted, its field lines pulled outward by the solar wind. The expansion of the solar wind along with the rotation of the Sun determines the large-scale magnetic field structure in interplanetary space. Regions of opposive polarity are separated by a current sheet in interplanetary space. The sun's rotation equator is offset by ~7 degrees from it's magnetic equator making the current sheet undulate in space and giving it the appearance of a ballerina skirt. High speed solar wind streams escape along the open field lines near the polar regions. The magnetic field seen by the Earth from its orbit around the sun is divided into sectors of opposite magnetic polarity. At the Earth's location, the stretched out solar field makes and angle of roughly 45 degrees with the radial direction joining the Sun and Earth. When the interplanetary magnetic field at 1 au has a southward component, conditions are favorable for magnetic storm activity at the Earth.
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