HR: 16:25h
AN: SA42B-01 INVITED     [Abstracts]
TI: The Parker Heliospheric Magnetic Field Model: A diagnostic of Ulysses Field and Particle Observations
AU: * Smith, E J
EM: edward.j.smith@jpl.nasa.gov
AF: Jet Propulsion Laboratory, M/S 169-506 4800 Oak Grove Dr, Pasadena, CA 91109, United States
AB: Although developed more than four decades ago, the Parker model is still the standard that is compared with observations of the heliospheric magnetic field. As such, it is a useful diagnostic in investigating physical conditions along field lines throughout the heliosphere and in explaining the observations. Numerous examples are provided by results from Ulysses, a spacecraft in a polar orbit that allows access to the Sun's polar regions. The conservation of the open magnetic flux (r2 BR, the radial component multiplied by the square of radial distance) along solar wind streamlines has been shown to be independent of helio-latitude at both solar minimum and maximum,revealing that the super-radial solar wind flow is driven by magnetic pressure of the solar field rather than by a stronger plasma pressure. The spiral angle, given by tangential and radial components, provides a quantitative measure of the extent to which non-radial field lines and solar wind expand near the Sun. Large departures of the field from the Parker spiral in solar wind rarefaction regions are explained by changes in the wind speed along the field lines as they transit polar coronal holes. The dependence of the field magnitude on distance departs from that predicted by the Parker model and demonstrates that the solar wind and magnetic field are pushed away from the solar equator by the interaction between fast and slow solar wind streams. Adaptation of the Parker field invoking random motion of the field lines in the Sun's photosphere explains why Galactic Cosmic Rays cannot easily access the Sun's polar caps. Alternatively, energetic particles accelerated by heliospheric shocks have easier access to the polar regions, a phenomenon explained by the diffusion of the particles across magnetic field lines and by a departure of the north-south magnetic field component from the Parker model that allows fields and particles to reach higher latitudes than predicted. These examples show that departures from and adaptations of the Parker model have been very productive in Ulysses investigations of the magnetic field and heliosphere in three dimensions.
DE: 2134 Interplanetary magnetic fields
DE: 2164 Solar wind plasma
DE: 2169 Solar wind sources
DE: 7524 Magnetic fields
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly