Modeling Heliospheric Flux Ropes: A Comparative Study of Physical Quantities

Abstract

Large-scale heliospheric flux ropes are observed by in situ instruments onboard heliospheric observatories as magnetic structures embedded in interplanetary coronal mass ejections (ICMEs). They are known as the interplanetary counterpart of the coronal mass ejections (CMEs), and the main drivers of geomagnetic activity. These structures can be reconstructed by fitting an axial symmetric flux rope model to the data. By using a circular-cylindrical analytical flux rope model , the 3-D reconstruction provides information about the heliospheric orientation, geometry, magnetic field at the flux rope center, and force distribution along the radius. Other quantities that can be derived are the magnetic flux and helicity. This model is constrained by the current density distribution along the tube. Thus, this paper aims to evaluate how different current density profiles change the physical and geometrical quantities. We selected two Earth-directed ICME events from the Wind ICME catalog (wind.gsfc.nasa.gov) and fit the model parameters to the data using two model-cases with different current density profiles. In general, the orientation, geometry, magnetic field strength, relative helicity, and size seem well-defined quantities. However, in the case of the magnetic flux and number of turns, the reconstructions are more sensitive to the current density constraint. This comparative analysis of the variation of the quantity will allow us to constrain not only this model but also the coronal models and the dynamical evolution of ICMEs in the solar wind by comparing the physical quantities.