Interplanetary Field Enhancements: Observations from 0.3 AU to 1 AU

Interplanetary Field Enhancements are rare but very distinct increases in the magnetic field strength, reaching a nearly symmetric cusp-shaped peak. These increases are usually accompanied by a thin central current sheet. Their associations with the perihelion passages of the asteroid 2201 Oljato and with the comet De Vico have led to the hypothesis that these events are associated with the interaction of the solar wind with dust particles. In this paper we examine observations of these events with the Helios 1/2 spacecraft that flew as close to the Sun as 0.29 AU. These events are observed over the entire range of distances studied by Helios 1 and 2. The ponderomotive force exerted by the magnetic field strength decreases with radial distance roughly inversely proportional to the distance squared.