Unique determination of model coronal magnetic fields using photospheric observations

Solar Physics ◽  
1993 ◽  
Vol 143 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Xuepu Zhao ◽  
J. Todd Hoeksema
Keyword(s):  
Magnetic Fields ◽  
Unique Determination ◽  
Coronal Magnetic Fields

UNIQUE DETERMINATION OF CONDUCTIVITY, SUSCEPTIBILITY, SIZE, AND DEPTH IN MULTIFREQUENCY ELECTROMAGNETIC EXPLORATION

Geophysics ◽  
1959 ◽  
Vol 24 (3) ◽  
pp. 531-546 ◽  
Author(s):  
Stanley H. Ward
Keyword(s):  
Magnetic Fields ◽  
Eddy Currents ◽  
Intermediate Frequency ◽  
Unique Determination ◽  
Frequency Range ◽  
Lower Range ◽  
Ore Body ◽  
Eddy Current Density ◽  
Magnetic Sphere

The response of a conductive, magnetic sphere in a uniform, alternating magnetic field is a function of the conductivity, permeability, and radius of the sphere and of the frequency of the alternations. Over one range of frequencies, eddy‐current density in any given sphere and secondary magnetic fields of the sphere are relatively constant and high. Over a much lower range of frequencies eddy currents are negligible, but the secondary magnetic fields may be of large constant amplitude but of polarity reversed to that of the higher frequency range. At some intermediate frequency the secondary magnetic fields will be entirely quadrature with respect to the inducing field. Utilization of this peculiar frequency dependence and of the geometry of the secondary magnetic fields permits unique determination of the conductivity, permeability, radius, and depth to the center of a buried sphere. The procedure for obtaining these variables is described in this article. As an added feature, it is shown that by completing a gravity survey as well as an electromagnetic survey over a dense, magnetic, conductive spherical ore body, it is possible to determine the above variables, plus density, uniquely. Precise identification of the material of the sphere is seen as a possible result of the application of this technique.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

scholarly journals Boundary Fitting Problems Associated with Coronal Magnetic Models

1974 ◽  
Vol 57 ◽  
pp. 89-91 ◽  
Author(s):  
Kenneth H. Schatten
Keyword(s):  
Magnetic Fields ◽  
Legendre Polynomial ◽  
Magnetic Monopole ◽  
Polynomial Fit ◽  
Coronal Magnetic Fields ◽  
Boundary Fitting

The calculation of coronal magnetic fields was first suggested by Gold (1958). Altschuler and Newkirk (1969) and Newkirk et al. (1968) used a Legendre polynomial fit to the photospheric observations of magnetic fields whereas Schatten (1968) with Wilcox and Ness (Schatten et al., 1969) use a magnetic monopole fit, first incorporated by Schmidt (1964).

AMBIPOLAR DIFFUSION AND TURBULENT MAGNETIC FIELDS IN MOLECULAR CLOUDS

2011 ◽  
Vol 26 (04) ◽  
pp. 235-249 ◽  
Author(s):  
MARTIN HOUDE ◽  
TALAYEH HEZAREH ◽  
HUA-BAI LI ◽  
THOMAS G. PHILLIPS
Keyword(s):  
Magnetic Fields ◽  
Molecular Clouds ◽  
Ambipolar Diffusion ◽  
Star Forming ◽  
Star Forming Regions ◽  
Spin Interactions ◽  
Line Narrowing ◽  
Weakly Ionized ◽  
Novel Method

We review the introduction and development of a novel method for the characterization of magnetic fields in star-forming regions. The technique is based on the comparison of spectral line profiles from coexistent neutral and ion molecular species commonly detected in molecular clouds, sites of star formation. Unlike other methods used to study magnetic fields in the cold interstellar medium, this ion/neutral technique is not based on spin interactions with the field. Instead, it relies on and takes advantage of the strong cyclotron coupling between the ions and magnetic fields, thus exposing what is probably the clearest observational manifestation of magnetic fields in the cold, weakly ionized gas that characterizes the interior of molecular clouds. We will show how recent development and modeling of the ensuing ion line narrowing effect leads to a determination of the ambipolar diffusion scale involving the turbulent component of magnetic fields in star-forming regions, as well as the strength of the ordered component of the magnetic field.

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