Prominence height and vertical gradient in magnetic field

2000 ◽  
Vol 26 (5) ◽  
pp. 322-327 ◽  
Author(s):  
B. P. Filippov ◽  
O. G. Den
Keyword(s):  
Magnetic Field ◽  
Vertical Gradient

A comparison of methods for approximating the vertical gradient of one‐dimensional magnetic field data

Geophysics ◽  
1986 ◽  
Vol 51 (9) ◽  
pp. 1725-1735 ◽  
Author(s):  
J. W. Paine
Keyword(s):  
Magnetic Field ◽  
Fourier Transform ◽  
Field Data ◽  
Total Error ◽  
Vertical Gradient ◽  
Magnetic Data ◽  
Total Field ◽  
One Dimensional ◽  
Convolution Filter ◽  
Principal Factors

The vertical gradient of a one‐dimensional magnetic field is known to be a useful aid in interpretation of magnetic data. When the vertical gradient is required but has not been measured, it is necessary to approximate the gradient using the available total‐field data. An approximation is possible because a relationship between the total field and the vertical gradient can be established using Fourier analysis. After reviewing the theoretical basis of this relationship, a number of methods for approximating the vertical gradient are derived. These methods fall into two broad categories: methods based on the discrete Fourier transform, and methods based on discrete convolution filters. There are a number of choices necessary in designing such methods, each of which will affect the accuracy of the computed values in differing, and sometimes conflicting, ways. A comparison of the spatial and spectral accuracy of the methods derived here shows that it is possible to construct a filter which maintains a reasonable balance between the various components of the total error. Further, the structure of this filter is such that it is also computationally more efficient than methods based on fast Fourier transform techniques. The spacing and width of the convolution filter are identified as the principal factors which influence the accuracy and efficiency of the method presented here, and recommendations are made on suitable choices for these parameters.

THE GEOMAGNETIC GRADIOMETER

Geophysics ◽  
1967 ◽  
Vol 32 (5) ◽  
pp. 877-892 ◽  
Author(s):  
Howard A. Slack ◽  
Vance M. Lynch ◽  
Lee Langan
Keyword(s):  
Magnetic Field ◽  
Vertical Gradient ◽  
Diurnal Variations ◽  
Resolving Power ◽  
Magnetic Intensity ◽  
Geophysical Prospecting ◽  
Total Field ◽  
Optically Pumped ◽  
Magnetic Gradient ◽  
The Difference

The geomagnetic gradiometer is a new geophysical prospecting tool which measures directly the vertical gradient of the earth’s magnetic field and the total field intensity. The system is composed of two simultaneously recording, optically pumped and monitored magnetometer sensors suspended from a helicopter. The sensors are separated vertically by a known distance so that the magnetic gradient can be determined from the difference in total magnetic intensity between the two sensors. Since the gradient is measured directly, the gradiometer allows geophysicists to make better use of LaPlace’s and Euler’s equations. The gradiometer increases the value of magnetic prospecting by: (1) greatly increasing resolving power, (2) discriminating between intrabasement and suprabasement anomalies, and (3) eliminating problems caused by diurnal variations.

scholarly journals Reconciliating the Vertical and Horizontal Gradients of the Sunspot Magnetic Field

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Véronique Bommier
Keyword(s):  
Magnetic Field ◽  
Aspect Ratio ◽  
Vertical Gradient ◽  
Spectral Lines ◽  
Horizontal Gradient ◽  
Plasma Anisotropy ◽  
Different Depths ◽  
Mhd Modeling ◽  
Horizontal Flux ◽  
The Magnetic Field

In the literature, we found 15 references showing that the sunspot photospheric magnetic field vertical gradient is on the order of 3-4 G/km, with field strength decreasing with height, whereas the horizontal gradient is nine times weaker on the order of 0.4-0.5 G/km. This is confirmed by our recent THEMIS observations. As a consequence, the vanishing of divB→ is not realized. In other words, a loss of magnetic flux is observed with increasing height, which is not compensated for by an increase of the horizontal flux. We show that the lack of spatial resolution, vertical as well as horizontal, cannot be held responsible for the nonvanishing observed divB→. The present paper is devoted to the investigation of this problem. We investigate how the magnetic field is influenced by the plasma anisotropy due to the stratification, which is responsible for an “aspect ratio” between horizontal and vertical typical lengths. On the example of our THEMIS observations, made of two spectral lines formed at two different depths, which enables the retrieval of the three components entering divB→, it is shown that once this aspect ratio is applied, the rescaled divB→ vanishes, which suggests a new methodology for MHD modeling in the photosphere.

Vertical gradient freeze growth of GaAs with a rotating magnetic field

2002 ◽  
Vol 245 (3-4) ◽  
pp. 237-246 ◽  
Author(s):  
O Pätzold ◽  
I Grants ◽  
U Wunderwald ◽  
K Jenkner ◽  
A Cröll ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Vertical Gradient ◽  
Rotating Magnetic Field ◽  
Vertical Gradient Freeze
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