scholarly journals Orbital effects of in-plane magnetic fields probed by mesoscopic conductance fluctuations

2004 ◽  
Vol 69 (12) ◽  
Author(s):  
D. M. Zumbühl ◽  
J. B. Miller ◽  
C. M. Marcus ◽  
V. I. Fal’ko ◽  
T. Jungwirth ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Conductance Fluctuations

Breakdown of universal scaling of conductance fluctuations in high magnetic fields

1992 ◽  
Vol 69 (8) ◽  
pp. 1248-1251 ◽  
Author(s):  
A. K. Geim ◽  
P. C. Main ◽  
P. H. Beton ◽  
L. Eaves ◽  
S. P. Beaumont ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
High Magnetic Fields ◽  
Universal Scaling ◽  
Conductance Fluctuations

Weak-localization effects and conductance fluctuations: Implications of inhomogeneous magnetic fields

1993 ◽  
Vol 48 (20) ◽  
pp. 15218-15236 ◽  
Author(s):  
Daniel Loss ◽  
Herbert Schoeller ◽  
Paul M. Goldbart
Keyword(s):  
Magnetic Fields ◽  
Weak Localization ◽  
Conductance Fluctuations

Conductance fluctuations in a rectangular dot at constant magnetic fields

1998 ◽  
Vol 58 (16) ◽  
pp. 10597-10601 ◽  
Author(s):  
I. V. Zozoulenko ◽  
A. S. Sachrajda ◽  
P. Zawadzki ◽  
K.-F. Berggren ◽  
Y. Feng ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Conductance Fluctuations

MESOSCOPIC FLUCTUATIONS IN HIGH MAGNETIC FIELDS — ARE THEY STILL UNIVERSAL?

1993 ◽  
Vol 07 (01) ◽  
pp. 1-12
Author(s):  
A. K. GEIM ◽  
P. C. MAIN ◽  
L. EAVES
Keyword(s):  
Magnetic Fields ◽  
Quantum Interference ◽  
Direct Consequence ◽  
High Magnetic Fields ◽  
Conductance Fluctuations ◽  
Breaking Length ◽  
Fluctuation Amplitude ◽  
Scattering Time ◽  
Universal Conductance ◽  
The Magnetic Field

Universal conductance fluctuations (UCF) arise in mesoscopic systems as a direct consequence of the quantum interference of electron waves. The universal feature of the fluctuations is that, at finite temperature, their behaviour can be expressed in terms of one parameter, the phase breaking length of electrons Lϕ. Though the mesoscopic fluctuations have also been observed in high magnetic fields, ω c τ > 1, where ω c is the cyclotron frequency and τ the electron scattering time, it was widely believed that the magnetic field had to suppress the fluctuations. However, experiments on an orthodox mesoscopic system have found out no signs of the suppression. The fluctuation amplitude remains unchanged in high magnetic fields while the period of fluctuations changes dramatically. This indicates the breakdown of universal scaling at high magnetic fields.

Conductance Fluctuations in Two-Dimensional Systems in Random Magnetic Fields

1993 ◽  
Vol 62 (11) ◽  
pp. 3979-3987 ◽  
Author(s):  
Tomi Ohtsuki ◽  
Keith Slevin ◽  
Yoshiyuki Ono
Keyword(s):  
Magnetic Fields ◽  
Two Dimensional ◽  
Conductance Fluctuations

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.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

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