Magnetic Field-line Length and Twist Distributions within Interplanetary Flux Fopes from Wind Spacecraft Measurements

Wednesday, 17 December 2014
Qiang Hu1, Jiong Qiu2, Sam Krucker3, Linghua Wang4, Bing Wang5, Yao Chen5 and Christian Moestl6, (1)University of Alabama in Huntsville, Department of Space Science and CSPAR, Huntsville, AL, United States, (2)Montana State University Bozeman, Bozeman, MT, United States, (3)Univ California, Berkeley, CA, United States, (4)Peking University, Beijing, China, (5)Shandong University at Weihai, Weihai, China, (6)University of Graz, Space Research Institute, Austrian Academy of Sciences, Graz, Austria
We report on the detailed and systematic study of field-line twist and length distributions within magnetic flux ropes embedded in Interplanetary Coronal Mass Ejections (ICMEs). In particular we will utilize energetic electron burst observations at 1 AU together with associated type III radio emissions detected by the Wind spacecraft to provide unique measurements of magnetic field-line lengths within selected ICME events. These direct measurements will be compared with flux-rope model calculations to help assess the fidelity of different models and to provide diagnostics of internal structures. The Grad-Shafranov reconstruction method will be utilized together with a constant-twist nonlinear force-free (Gold-Hoyle) flux rope model and the commonly known Lundquist (linear force-free) model to reveal the close relation between the field-line twist and length in cylindrical flux ropes, based on in-situ Wind spacecraft magnetic field and plasma measurements. We show that our initial analysis of field-line twist indicates clear deviation from the Lundquist model, but better consistency with the Gold-Hoyle model. We will also discuss the implications of our analysis of flux-rope structures on the origination and evolution processes in their corresponding solar source regions.