Large-scale Mapping of Magnetic Fields between the Sun and Earth

Abstract:

Magnetic field lines between the Sun and Earth in the solar equatorial plane are calculated and mapped, using near-Earth spacecraft data and a solar wind model. The model allows a nonzero azimuthal component of magnetic field at the source surface, contrasting with the Parker model. The mapping shows that, typically, but not always, the magnetic fields are open and Parker-like. Nevertheless, the predicted field lines sometimes deviate significantly from the Parker direction, corresponding to when the observed magnetic fields are more azimuthally-oriented than the Parker model. Examples of non-Parker-like and Parker-like cases are shown, both for solar maximum and minimum conditions. Often the predicted magnetic field configurations are stable over consecutive solar rotations. The mapping predictions have important implications for particle propagation studies and for estimates of the length of the actual field lines. The effects on the transport paths of solar energetic particles (SEPs) to Earth are demonstrated briefly for an unusually long-lived SEP event at Earth.