A New Heliospheric Field Model: Implications for Energetic Particles

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

This is a proposal to explore the structure, dynamics, and evolution of the low solar corona. The main effort is theoretical analysis focused on four main questions: How does the heliospheric magnetic field reverse polarity from one solar cycle to the next? What controls the emergence of fast and slow solar wind? How is the dynamic evolution of the low corona tied to the structure and evolution of field and plasma in the heliosphere? For many decades the heliospheric magnetic field has been considered, on average, to execute a simple Archimedes spiral, typically termed the Parker spiral. . A magnetic field that is convected out radially with the solar wind, yet remains attached to a rigidly-rotating Sun will execute such a spiral pattern. Earlier work by these investigators showed how differential rotation in the photosphere and super-radial expansion of the solar wind not symmetric about the rotation axis lead to motion of heliospheric magnetic field footpoints near the solar wind source surface. These footpoint motions can cause strong systematic variations of the heliospheric magnetic field relative to a standard Archimedes spiral. The principles on which the new model was founded address a detailed connection between the dynamic evolution of the low corona and the heliospheric magnetic field. The new model has achieved some acceptance by the community, but many issues still remain. The investigators will test the correctness of the concepts by predicting their global consequences and comparing them to observations. To carry out these tests fully, idealized models must be generalized for the purpose of predictive modeling. The specific tasks to be carried out include: Obtain a more predictive model for footpoint motion that, in particular, does not rely on idealizations valid only during solar minimum; Use the generalized footpoint model to predict the global structure and evolution of the heliospheric magnetic field, and heliospheric plasma; Model the propagation of energetic particles and cosmic rays in the resultant heliospheric configurations and their evolution as the field is restructured during solar maximum.