Exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds

Context. Magnetic clouds (MCs) are twisted magnetic structures ejected from the Sun and probed by in situ instruments. They are typically modeled as flux ropes (FRs). Aims. Magnetic field measurements are only available along the 1D spacecraft trajectory. The determination of the FR global character...

Descripción completa

Guardado en:
Detalles Bibliográficos
Autores principales: Démoulin, P., Dasso, S., Janvier, M.
Formato: JOUR
Materias:
Magnetic fields
Sun: coronal mass ejections (CMEs)
Sun: heliosphere
Eigenvalues and eigenfunctions
Rope
Axis orientation
In-situ instruments
Magnetic clouds
Minimum variance
Spacecraft trajectories
Sun: coronal mass ejection
Temporal profile
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00046361_v619_n_p_Demoulin
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_00046361_v619_n_p_Demoulin
record_format dspace
spelling todo:paper_00046361_v619_n_p_Demoulin2023-10-03T14:01:21Z Exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds Démoulin, P. Dasso, S. Janvier, M. Magnetic fields Sun: coronal mass ejections (CMEs) Sun: heliosphere Eigenvalues and eigenfunctions Rope Axis orientation In-situ instruments Magnetic clouds Minimum variance Spacecraft trajectories Sun: coronal mass ejection Sun: heliosphere Temporal profile Magnetic fields Context. Magnetic clouds (MCs) are twisted magnetic structures ejected from the Sun and probed by in situ instruments. They are typically modeled as flux ropes (FRs). Aims. Magnetic field measurements are only available along the 1D spacecraft trajectory. The determination of the FR global characteristics requires the estimation of the FR axis orientation. Among the developed methods, the minimum variance (MV) is the most flexible, and features only a few assumptions. However, as other methods, MV has biases. We aim to investigate the limits of the method and extend it to a less biased method. Methods. We first identified the origin of the biases by testing the MV method on cylindrical and elliptical models with a temporal expansion comparable to the one observed in MCs. Then, we developed an improved MV method to reduce these biases. Results. In contrast with many previous publications we find that the ratio of the MV eigenvalues is not a reliable indicator of the precision of the derived FR axis direction. Next, we emphasize the importance of the FR boundaries selected since they strongly affect the deduced axis orientation. We have improved the MV method by imposing that the same amount of azimuthal flux should be present before and after the time of closest approach to the FR axis. We emphasize the importance of finding simultaneously the FR axis direction and the location of the boundaries corresponding to a balanced magnetic flux, so as to minimize the bias on the deduced FR axis orientation. This method can also define an inner flux-balanced sub-FR. We show that the MV results are much less biased when a compromize in size of this sub-FR is achieved. Conclusions. For weakly asymmetric field temporal profiles, the improved MV provides a very good determination of the FR axis orientation. The main remaining bias is moderate (lower than 6°) and is present mostly on the angle between the flux rope axis and the plane perpendicular to the Sun-Earth direction. © ESO 2018. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00046361_v619_n_p_Demoulin
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Magnetic fields
Sun: coronal mass ejections (CMEs)
Sun: heliosphere
Eigenvalues and eigenfunctions
Rope
Axis orientation
In-situ instruments
Magnetic clouds
Minimum variance
Spacecraft trajectories
Sun: coronal mass ejection
Sun: heliosphere
Temporal profile
Magnetic fields
spellingShingle Magnetic fields
Sun: coronal mass ejections (CMEs)
Sun: heliosphere
Eigenvalues and eigenfunctions
Rope
Axis orientation
In-situ instruments
Magnetic clouds
Minimum variance
Spacecraft trajectories
Sun: coronal mass ejection
Sun: heliosphere
Temporal profile
Magnetic fields
Démoulin, P.
Dasso, S.
Janvier, M.
Exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds
topic_facet Magnetic fields
Sun: coronal mass ejections (CMEs)
Sun: heliosphere
Eigenvalues and eigenfunctions
Rope
Axis orientation
In-situ instruments
Magnetic clouds
Minimum variance
Spacecraft trajectories
Sun: coronal mass ejection
Sun: heliosphere
Temporal profile
Magnetic fields
description Context. Magnetic clouds (MCs) are twisted magnetic structures ejected from the Sun and probed by in situ instruments. They are typically modeled as flux ropes (FRs). Aims. Magnetic field measurements are only available along the 1D spacecraft trajectory. The determination of the FR global characteristics requires the estimation of the FR axis orientation. Among the developed methods, the minimum variance (MV) is the most flexible, and features only a few assumptions. However, as other methods, MV has biases. We aim to investigate the limits of the method and extend it to a less biased method. Methods. We first identified the origin of the biases by testing the MV method on cylindrical and elliptical models with a temporal expansion comparable to the one observed in MCs. Then, we developed an improved MV method to reduce these biases. Results. In contrast with many previous publications we find that the ratio of the MV eigenvalues is not a reliable indicator of the precision of the derived FR axis direction. Next, we emphasize the importance of the FR boundaries selected since they strongly affect the deduced axis orientation. We have improved the MV method by imposing that the same amount of azimuthal flux should be present before and after the time of closest approach to the FR axis. We emphasize the importance of finding simultaneously the FR axis direction and the location of the boundaries corresponding to a balanced magnetic flux, so as to minimize the bias on the deduced FR axis orientation. This method can also define an inner flux-balanced sub-FR. We show that the MV results are much less biased when a compromize in size of this sub-FR is achieved. Conclusions. For weakly asymmetric field temporal profiles, the improved MV provides a very good determination of the FR axis orientation. The main remaining bias is moderate (lower than 6°) and is present mostly on the angle between the flux rope axis and the plane perpendicular to the Sun-Earth direction. © ESO 2018.
format JOUR
author Démoulin, P.
Dasso, S.
Janvier, M.
author_facet Démoulin, P.
Dasso, S.
Janvier, M.
author_sort Démoulin, P.
title Exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds
title_short Exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds
title_full Exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds
title_fullStr Exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds
title_full_unstemmed Exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds
title_sort exploring the biases of a new method based on minimum variance for interplanetary magnetic clouds
url http://hdl.handle.net/20.500.12110/paper_00046361_v619_n_p_Demoulin
work_keys_str_mv AT demoulinp exploringthebiasesofanewmethodbasedonminimumvarianceforinterplanetarymagneticclouds
AT dassos exploringthebiasesofanewmethodbasedonminimumvarianceforinterplanetarymagneticclouds
AT janvierm exploringthebiasesofanewmethodbasedonminimumvarianceforinterplanetarymagneticclouds
_version_ 1782030783180963840

Ejemplares similares