Instabilität der positiven Säule endlicher Länge im magnetischen Feld / Instability of the Positive Column of Finite Length in a Magnetic Field

1970 ◽  
Vol 25 (7) ◽  
pp. 992-1006
Author(s):  
G. Janzen ◽  
F. Moser ◽  
E. Räuchle
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Frequency Spectrum ◽  
Satisfactory Agreement ◽  
Finite Length ◽  
Positive Column ◽  
Longitudinal Magnetic Field ◽  
Gas Discharge ◽  
Plasma Parameters ◽  
Theory And Experiments

The instability of a diffusion-dominated positive column of a gas discharge in a longitudinal magnetic field is investigated both experimentally and theoretically. Dispersion relations are derived for the case of an m = l helical instability considering the finite length of the column. Regions of instability are calculated for various wavelengths of the instability.Experiments were carried out in a positive column of variable length, ranging from 8.5 to 40 cm. at varying pressures of about 0.1 Torr of Neon. There is a satisfactory agreement between theory and experiments. The main results are: a) in long tubes instability occurs at a distinct magnetic field, calculated first by Kadomtsev and Nedospasov. Stable intermediate regions are possible at higher fields depending on the relations between the plasma-parameters; b) in short tubes the column is stable again for higher magnetic fields; c) in very short tubes there is no instability of this kind. The observed frequency spectrum agrees with the theoretical values

Anomale Diffusion in der positiven Säule im longitudinalen Magnetfeld1

1962 ◽  
Vol 17 (11) ◽  
pp. 937-962
Author(s):  
K. H. Wöhler
Keyword(s):  
Magnetic Field ◽  
Charged Particle ◽  
Positive Column ◽  
Longitudinal Magnetic Field ◽  
Diffusion Theory ◽  
Low Pressure ◽  
Gas Discharge ◽  
Critical Magnetic Field ◽  
Anomalous Behaviour

The positive column of a low pressure stationary gas discharge in a longitudinal magnetic field is investigated. Above a critical magnetic field the charged particle losses of the discharge increase rapidly in contradiction to the diffusion theory of the positive column. This effect has become known as LEHNERT-effect. Different theories and hypothesis are investigated and compared with the experiments to explain this phenomenon. It is shown that all experiments are most compatible with a theory of KADOMTSEV which states the anomalous behaviour of the positive column to be a turbulence like instability.

The Internal Magnetic Field of the Positive Column in a Longitudinal Magnetic Field

1975 ◽  
Vol 38 (1) ◽  
pp. 295-295
Author(s):  
Yoji Nagai ◽  
Shinogo Imazu ◽  
Takesuke Maruyama ◽  
Takeo Maruyama
Keyword(s):  
Magnetic Field ◽  
Positive Column ◽  
Longitudinal Magnetic Field ◽  
Internal Magnetic Field

An investigation of a high-current gas discharge in a longitudinal magnetic field

1957 ◽  
Vol 5 (1) ◽  
pp. 71-85
Author(s):  
A.L. Bezbatchenko ◽  
I.N. Golovin ◽  
D.P. Ivanov ◽  
V.D. Kirillov ◽  
N.A. Yavlinsky
Keyword(s):  
Magnetic Field ◽  
Longitudinal Magnetic Field ◽  
Gas Discharge ◽  
High Current

scholarly journals MOBSTER – III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic ‘identical twin’

2019 ◽  
Vol 490 (3) ◽  
pp. 4154-4165 ◽  
Author(s):  
M E Shultz ◽  
C Johnston ◽  
J Labadie-Bartz ◽  
V Petit ◽  
A David-Uraz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Light Curve ◽  
Line Profile ◽  
Longitudinal Magnetic Field ◽  
Stellar Structure ◽  
Line Profiles ◽  
Dipole Strength ◽  
Rotational Modulation ◽  
Brightness Modulation

ABSTRACT HD 62658 (B9p V) is a little-studied chemically peculiar star. Light curves obtained by the Kilodegree Extremely Little Telescope (KELT) and Transiting Exoplanet Survey Satellite (TESS) show clear eclipses with a period of about 4.75 d, as well as out-of-eclipse brightness modulation with the same 4.75 d period, consistent with synchronized rotational modulation of surface chemical spots. High-resolution ESPaDOnS circular spectropolarimetry shows a clear Zeeman signature in the line profile of the primary; there is no indication of a magnetic field in the secondary. PHOEBE modelling of the light curve and radial velocities indicates that the two components have almost identical masses of about 3 M⊙. The primary’s longitudinal magnetic field 〈Bz〉 varies between about +100 and −250 G, suggesting a surface magnetic dipole strength Bd = 850 G. Bayesian analysis of the Stokes V profiles indicates Bd = 650 G for the primary and Bd < 110 G for the secondary. The primary’s line profiles are highly variable, consistent with the hypothesis that the out-of-eclipse brightness modulation is a consequence of rotational modulation of that star’s chemical spots. We also detect a residual signal in the light curve after removal of the orbital and rotational modulations, which might be pulsational in origin; this could be consistent with the weak line profile variability of the secondary. This system represents an excellent opportunity to examine the consequences of magnetic fields for stellar structure via comparison of two stars that are essentially identical with the exception that one is magnetic. The existence of such a system furthermore suggests that purely environmental explanations for the origin of fossil magnetic fields are incomplete.

scholarly journals Analysis of EUV, Microwave, and Magnetic Field Observations of Solar Plage

1993 ◽  
Vol 141 ◽  
pp. 291-294
Author(s):  
J W Brosius ◽  
J M Davila ◽  
H P Jones ◽  
W T Thompson ◽  
R J Thomas ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Longitudinal Magnetic Field ◽  
Emission Measure ◽  
Plasma Temperature ◽  
Microwave Emission ◽  
Plasma Parameters ◽  
Very Large Array ◽  
Hot Plasma ◽  
Iron Abundance ◽  
Bremsstrahlung Emission

AbstractWe obtained simultaneous images of solar plage on 7 May 1991 with Goddard Space Flight Center’s Solar EUV Rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and the NASA/NSO spectromagnetograph at Kitt Peak. Using intensity ratios of Fe XVI to Fe XV emission lines, we find that the coronal plasma temperature is 2.5 ± 0.3 ×lO6 K throughout the region. The column emission measure ranges from 2.6 × 1027 to 1.3 × 1028 cm−5. The calculated structure and intensity of the 20 cm wavelength thermal bremsstrahlung emission from the hot plasma observed by SERTS is quite similar to the observed structure and intensity of the 20 cm microwave emission observed by the VLA. Using the revised coronal iron abundance of Meyer (1991, 1992), we find no evidence for either cool absorbing plasma or for contributions from thermal gyroemission. Combining the observed microwave polarization and the SERTS plasma parameters, we calculate a map of the coronal longitudinal magnetic field. The resulting values, ~ 30 – 60 Gauss, are comparable to extrapolated values of the potential field at heights of 5,000 and 10,000 km.

scholarly journals The Magnetic Fields at Different Levels in the Active Regions of the Solar Atmosphere

1971 ◽  
Vol 43 ◽  
pp. 223-230 ◽  
Author(s):  
T. T. Tsap
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Longitudinal Magnetic Field ◽  
Active Regions ◽  
Close Correlation ◽  
Crimean Astrophysical Observatory ◽  
Different Depths ◽  
Different Levels ◽  
Made In

The strengths of the longitudinal magnetic fields recorded at different depths of active regions with a double magnetograph of the Crimean Astrophysical Observatory are compared.The recordings of the magnetic fields were made in the lines Fe Iλ5250Å, Ca Iλ6103Å, Na I D1, BIIλ4554Å, Mg Iλ5184Å, Hα, Hγ, Hδ.It is shown, that there is a close correlation between the longitudinal magnetic field at different levels.

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