Stable reduction to the pole at the magnetic equator

1998 ◽  
Author(s):  
Yaoguo Li ◽  
Douglas W. Oldenburg
Keyword(s):  
Magnetic Equator ◽  
Reduction To The Pole ◽  
Stable Reduction

Stable reduction to the pole at the magnetic equator

Geophysics ◽  
2001 ◽  
Vol 66 (2) ◽  
pp. 571-578 ◽  
Author(s):  
Yaoguo Li ◽  
Douglas W. Oldenburg
Keyword(s):  
Fourier Transform ◽  
Magnetic Equator ◽  
Magnetic Data ◽  
Good Representation ◽  
Wavenumber Domain ◽  
Power Spectral ◽  
Reduction To The Pole ◽  
The Fourier Transform ◽  
Stable Reconstruction ◽  
Estimated Error

The solution of reduction to the pole (RTP) of magnetic data in the wavenumber domain faces a long standing difficulty of instability when the observed data are acquired at low magnetic latitudes or at the equator. We develop a solution to this problem that allows stable reconstruction of the RTP field with a high fidelity even at the magnetic equator. The solution is obtained by inverting the Fourier transform of the observed magnetic data in the wavenumber domain with explicit regularization. The degree of regularization is chosen according to the estimated error level in the data. The Fourier transform of the RTP field is constructed as a model that is maximally smooth and, at the same time, has a power‐spectral decay common to all fields produced by the same source. The applied regularization alleviates the singularity associated with the wavenumber‐domain RTP operator, and the imposed power spectral decay ensures that the constructed RTP field has the correct spectral content. As a result, the algorithm can perform the reduction to the pole stably at any magnetic latitude, and the constructed RTP field yields a good representation of the true field at the pole even when the reduction is carried out at the equator.

Strategic Scripts and Nuclear Disarmament

2018 ◽  
Author(s):  
Matthew Harries ◽  
Benedict Wilkinson
Keyword(s):  
Nuclear Weapons ◽  
Analytical Tool ◽  
The Other ◽  
Nuclear Disarmament ◽  
Stable Reduction ◽  
The Way

This chapter spans Freedman’s earliest focus on nuclear weapons and his development of strategic scripts as an analytical tool over three decades later. It discusses the way in which opposing logics of disarmament and armament co-existed in relation to nuclear weapons. It deploys the notion of strategic scripts to explain the contradictions inherent in approaches to nuclear disarmament, developing the concept of strategic scripts as it does so. The notion of scripts can be used to explore and even to promote nuclear disarmament. Two scripts, one of ‘stable reduction’, the other of ‘disarmament’, each serve to frame thinking. These scripts and the interactions they generate facilitate understanding of the way in which opposite instinctive reactions and, stemming from these, scripts about nuclear weapons co-exist, but are fragile as either an analytical or a strategic tool.

scholarly journals A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

1997 ◽  
Vol 15 (8) ◽  
pp. 1048-1056 ◽  
Author(s):  
R. L. Balthazor ◽  
R. J. Moffett
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Ionospheric Disturbance ◽  
Magnetic Equator ◽  
Ionospheric Disturbances ◽  
Atmospheric Gravity Waves ◽  
Opposite Hemisphere ◽  
Travelling Ionospheric Disturbances ◽  
F Region ◽  
Atmospheric Gravity

Abstract. A global coupled thermosphere-ionosphere-plasmasphere model is used to simulate a family of large-scale imperfectly ducted atmospheric gravity waves (AGWs) and associated travelling ionospheric disturbances (TIDs) originating at conjugate magnetic latitudes in the north and south auroral zones and subsequently propagating meridionally to equatorial latitudes. A 'fast' dominant mode and two slower modes are identified. We find that, at the magnetic equator, all the clearly identified modes of AGW interfere constructively and pass through to the opposite hemisphere with unchanged velocity. At F-region altitudes the 'fast' AGW has the largest amplitude, and when northward propagating and southward propagating modes interfere at the equator, the TID (as parameterised by the fractional change in the electron density at the F2 peak) increases in magnitude at the equator. The amplitude of the TID at the magnetic equator is increased compared to mid-latitudes in both upper and lower F-regions with a larger increase in the upper F-region. The ionospheric disturbance at the equator persists in the upper F-region for about 1 hour and in the lower F-region for 2.5 hours after the AGWs first interfere, and it is suggested that this is due to enhancements of the TID by slower AGW modes arriving later at the magnetic equator. The complex effects of the interplays of the TIDs generated in the equatorial plasmasphere are analysed by examining neutral and ion winds predicted by the model, and are demonstrated to be consequences of the forcing of the plasmasphere along the magnetic field lines by the neutral air pressure wave.

scholarly journals Small-scale (∼3 m)Eregion irregularities at and off the magnetic equator

1998 ◽  
Vol 103 (A9) ◽  
pp. 20761-20773 ◽  
Author(s):  
B. V. Krishna Murthy ◽  
Sudha Ravindran ◽  
K. S. Viswanathan ◽  
K. S. V. Subbarao ◽  
A. K. Patra ◽  
...  
Keyword(s):  
Magnetic Equator ◽  
Small Scale
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