@Article{OliveiraOlOjPiEcNi:2021:ReAmMa,
               author = "Oliveira, Rosemeire Aparecida Rosa and Oliveira, Marcos William da 
                         Silva and Ojeda-Gonzalez, Arian and Pillat, Valdir Gil and Echer, 
                         Ezequiel and Nieves-Chinchilla, Teresa",
          affiliation = "{Universidade do Vale do Para{\'{\i}}ba (UNIVAP)} and {Instituto 
                         Federal de Ci{\^e}ncia e Tecnologia de S{\~a}o Paulo (IFSP)} and 
                         {Universidade do Vale do Para{\'{\i}}ba (UNIVAP)} and 
                         {Universidade do Vale do Para{\'{\i}}ba (UNIVAP)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {NASA Goddard Space 
                         Flight Center}",
                title = "Resolving the Ambiguity of a Magnetic Cloud’s Orientation Caused 
                         by Minimum Variance Analysis Comparing it with a Force-Free 
                         Model",
              journal = "Solar Physics",
                 year = "2021",
               volume = "296",
               number = "12",
                pages = "e182",
                month = "Dec.",
             keywords = "Coronal mass ejections, interplanetary, Magnetic fields, 
                         interplanetary, Solar, disturbances.",
             abstract = "This study aims to incorporate an algebraic and computational 
                         method for calculating the angles of the magnetic clouds (MC) axis 
                         from the minimum variance analysis (MVA) and correcting them 
                         compared to a simulated model from the linear, force-free 
                         approximation. Consequently, it determines the type of flux-rope 
                         consistently and automatically. In general, MCs measured in situ 
                         at 1 Astronomical Unit (AU) may be approximated to have a 
                         cylindrical geometry, and the internal magnetic-field topology is 
                         traditionally described by a force-free equilibrium flux-rope 
                         model. Based on the Bz-rotation, the flux-rope configuration can 
                         be classified in eight groups. This classification is obtained 
                         from the angle of rotation of the magnetic-field vector and 
                         inclination of the flux-rope axis (\ϕ, \θ) in relation 
                         to the plane of the Ecliptic. The MVA is applied to interplanetary 
                         magnetic-field (IMF) observations to obtain the direction of the 
                         cylinder axis. However, MVA estimates may have an ambiguity of 180 
                         \∘ in this direction. This is directly affected by the 
                         eigenvector signal since eigenvalues in MVA are always positive. 
                         To apply the methodology, a sample of 50 MC events measured by the 
                         Advance Composition Explorer (ACE) spacecraft was investigated in 
                         the period from 1998 to 2003. 83.72 % of the analysed events 
                         achieved a satisfactory match between the maximum- and 
                         minimum-variance planes (from MVA) with the model (force-free) and 
                         (\ϕ, \θ) angles consistent with the MC geometry. 
                         Moreover, automatic classification of the MC or flux-rope tube 
                         type related to the MC-axis was consistent for 100 % of the events 
                         studied. This processing is organized in a computational tool 
                         described in this publication. We discuss the results and 
                         implications of our analysis of six magnetic cloud events in 2018 
                         during the solar minimum.",
                  doi = "10.1007/s11207-021-01921-2",
                  url = "http://dx.doi.org/10.1007/s11207-021-01921-2",
                 issn = "0038-0938 and 1573-093X",
             language = "en",
           targetfile = "Oliveira_resolvin.pdf",
        urlaccessdate = "27 abr. 2024"
}