High Latitude Observations of Corotating Interaction Regions: Remote Sensing Using Energetic Particles
Edmond C. Roelof
	Johns Hopkins University/Applied Physics Laboratory

A startlingly unexpected result from the high latitude phases of the Ulysses mission was the persistence up to the highest latitude attained (80.1 deg) of 26-day recurrent variations of energetic particles (~50 keV electrons, ~1 MeV protons, and galactic cosmic rays). These recurrent events were observed both over the southern heliographic pole during the decline of solar activity (1994), and at high northern latitudes near solar minimum (1996). The variations in the particles were observed at latitudes far higher than where the signatures of corotating interaction regions (CIRs) could be identified in the solar wind plasma and magnetic field data. The continuous evolution of the profiles of the energetic particles from mid to high latitudes demonstrated that Ulysses was continuing to see variations associated with the CIRs at latitudes lower than 30 deg (even though the intensities of ~50 keV electrons and ~1 MeV protons diminished by a factor of 0.0001). This demanded magnetic connection from high latitudes at ~3 AU to low latitude CIRs at much greater helioradii ~15 AU. Fisk [1996] proposed a dramatic modification of the Parker model for the interplanetary field that provided a deterministic magnetic connection, while Kota and Jokipii [1999] invoked a stochastic magnetic connection. We now understand that there is an additional important process that must be includedthe energy loss of the particles. Roelof [1999] demonstrated that the energy loss is significant even in scatter-free propagation, and moreover that it depends only upon particle velocity and position while being independent of particle charge or rest mass. This explains immediately why the energetic particle variations observed by Ulysses as a function of latitude are ordered by particle velocity alone.