Estimation of the bias of the Minimum Variance technique in the determination of magnetic clouds global quantities and orientation

2007 ◽  
Vol 40 (12) ◽  
pp. 1881-1890 ◽  
Author(s):  
A.M. Gulisano ◽  
S. Dasso ◽  
C.H. Mandrini ◽  
P. Démoulin
Keyword(s):  
Minimum Variance ◽  
Magnetic Clouds ◽  
Variance Technique

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

2018 ◽  
Vol 619 ◽  
pp. A139 ◽  
Author(s):  
P. Démoulin ◽  
S. Dasso ◽  
M. Janvier
Keyword(s):  
Flux Rope ◽  
Field Measurements ◽  
Minimum Variance ◽  
Magnetic Clouds ◽  
The Sun ◽  
Axis Orientation ◽  
Axis Direction ◽  
Before And After ◽  
Elliptical Models

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.

New Metric for Minimum Variance Analysis Validation in the Study of Interplanetary Magnetic Clouds

Solar Physics ◽  
2020 ◽  
Vol 295 (3) ◽  
Author(s):  
Rosemeire Aparecida Rosa Oliveira ◽  
Marcos William da Silva Oliveira ◽  
Arian Ojeda-González ◽  
Victor De La Luz
Keyword(s):  
Minimum Variance ◽  
Variance Analysis ◽  
Magnetic Clouds

Determination of CRLB and Minimum Variance Unbiased Estimator of a DC Signal in AWGN Using Laplace Transform

2021 ◽  
Vol 40 (1) ◽  
pp. 79-86
Author(s):  
Abdi Abdalla
Keyword(s):  
Lower Bound ◽  
Gaussian Noise ◽  
Unbiased Estimator ◽  
Laplace Transformation ◽  
Additive White Gaussian Noise ◽  
Minimum Variance ◽  
Minimum Variance Unbiased Estimator ◽  
Mathematical Background ◽  
Alternative Approach

This paper presents an alternative approach for the determination of Cramer-Rao Lower Bound (CRLB) and Minimum Variance Unbiased Estimator (MVUE) using Laplace transformation. In this work, a DC signal in Additive White Gaussian Noise (AWGN) was considered. During the investigation, a number of experiments were conducted to analyze different possible outputs under different conditions, and then the patterns of the outcomes were studied. Finally closed-form expressions for the CRLB and MVUE were deduced employing the Laplace transformation. The resulting expressions show that the proposed method has almost the same number of steps as the existing method. However, the later requires only the knowledge of algebra to arrive at the CRLB expressions contrary to the existing approach where a strong mathematical background is required and hence making it superior over the existing method, in that sense.

The Influence of Operating Costs on Return on Assets at PT. Sinar Harapan in Jakarta

2019 ◽  
Vol 3 (1) ◽  
pp. 111
Author(s):  
Hendro Waryanto
Keyword(s):  
Standard Deviation ◽  
Hypothesis Testing ◽  
Financial Statements ◽  
Minimum Variance ◽  
Operating Costs ◽  
Return On Assets ◽  
Operational Costs ◽  
Maximum Variance ◽  
Analysis Technique

Company management must be able to manage everything that can affect the entire process in the company. This study aims to determine the effect of operational costs on Return on Assets at PT. Sinar Harapan in Jakarta. The method used was explanatory research with a sample of 5 years of financial statements. The analysis technique uses statistical analysis with regression testing, correlation, determination, and hypothesis testing. The results of this study variable operational costs obtained a minimum variance of 71.2 billion and a maximum variance of 89.8 billion with an average of 84.44 billion with a standard deviation of 75.11 billion. Return on Assets obtained a minimum variance of 0.7% and a maximum variance of 0.9% with a rating score of 8.04% with a standard deviation of 0.551%. Operating costs have a significant effect on Return on Assets with a regression equation Y = 17.517 + 0.0565X, and a correlation value of 0.885 or strong with a determination of 78.3%. Hypothesis testing obtained a significance of 0.046 <0.050.

About determination of coordinates of sources of geomagnetic perturbations according to the world network of magnetic observatories

2020 ◽  
Author(s):  
Beibit Zhumabayev ◽  
Ivan Vassilyev ◽  
Vladimir Protsenko ◽  
Saltanat Zhumabayeva
Keyword(s):  
Coordinate System ◽  
Geomagnetic Storms ◽  
Magnetic Clouds ◽  
The World ◽  
Relationship Of ◽  
The Relationship ◽  
Geomagnetic Perturbations ◽  
Magnetic Observatories ◽  
Single Coordinate

&lt;p&gt;A method for determining the coordinates of geomagnetic perturbation sources based on joint data processing of the world network of magnetic observatories is proposed. A large statistical material showed the relationship of large geomagnetic storms with the interaction of two or more magnetic clouds formed as a result of coronal mass ejections. To determine the coordinates of the sources of perturbations, it is proposed to use the data of magnetic observatories of the &quot;INTERMAGNET&quot; international network, which has more than 100 observation points distributed around the world and equipped with modern identical hardware. The results of geomagnetic field measurement obtained by magnetic observatories are brought to a single coordinate system. It was achieved by rotation of the axes of local stations, which allows determining the coordinates of the sources of perturbations and evaluating the accuracy of specifying the coordinate system of each local observatory.&lt;/p&gt;

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