scholarly journals Electron Cyclotron Maser Emission near the Cutoff Frequencies

1983 ◽  
Vol 36 (5) ◽  
pp. 725 ◽  
Author(s):  
RG Hewitt ◽  
DB Melrose
Keyword(s):  
Growth Rate ◽  
Cutoff Frequency ◽  
Solar Radio Emission ◽  
Type I ◽  
Loss Cone ◽  
Spatial Growth ◽  
Lower Band ◽  
Wide Range ◽  
Narrow Frequency Band ◽  
Spatial Growth Rate

An earlier discussion of loss-cone driven cyclotron masers is extended to cover the case where the emission occurs close to the cutoff frequency of the 0 mode or the x mode. In general, wave growth may occur in one or two bands, and when two bands are allowed the lower band is close to the cutoff frequency. With the exception of the x mode at 8 = 1, growth in the lower band is allowed only for OJp/D. > 8 and cos28 > t for the 0 mode and for OJp/Q. > {s(s-I)}-!- and cos28 > (s-I)/8 for the x mode, and growth in the lower band has no particularly favourable features when allowed. For the X mode at 8 = 1 both bands are allowed for all OJp/D. $ 1 and growth in the lower band is possible over a wide range of angles in a very narrow frequency band. The spatial growth rate can be quite large due to the small group speed. However, the large spatial growth rate is offset by the short pathlengths for growth in a slowly spatially varying magnetic field due to the very narrow bandwidth of the growing waves. It is found that growth in the lower band is at best no more effective than growth in the upper band. We discuss the relative merits of growth in the two bands in a suggested application to terrestrial kilometric radiation. We also discuss cyclotron theories for type I solar radio emission, pointing out that our results do not favour such theories, and for solar microwave spike bursts.

scholarly journals Growth Rate of White Dwarf Mass in Binaries

1989 ◽  
Vol 114 ◽  
pp. 507-510
Author(s):  
Mariko Kato ◽  
Hideyuki Saio ◽  
Izumi Hachisu
Keyword(s):  
Growth Rate ◽  
Steady State ◽  
Star Formation ◽  
Neutron Star ◽  
Mass Loss ◽  
White Dwarf ◽  
Accretion Rate ◽  
Time Dependent ◽  
Type I ◽  
Wide Range

AbstractThe growth rate of a white dwarf which accretes hydrogen-rich or helium matter is studied. If the accretion rate is relatively small, unstable shell flash occurs and during which the envelope mass is lost. We have followed the evolutions of shell flashes by steady state approach with wind mass loss solutions to determined the mass lost from the system for wide range of binary parameters. The time-dependent models are also calculated in some cases. The mass loss due to the Roche lobe overflow are taken into account. This results seriously affects the existing scenarios on the origin of the type I supernova or on the neutron star formation induced by accretion.

Dispersion, spatial growth rate, and start current of a Cherenkov free-electron laser with negative-index material

2015 ◽  
Vol 22 (8) ◽  
pp. 083111 ◽  
Author(s):  
Yuanyuan Wang ◽  
Yanyu Wei ◽  
Dazhi Li ◽  
Keisuke Takano ◽  
Makoto Nakajima ◽  
...  
Keyword(s):  
Growth Rate ◽  
Free Electron ◽  
Free Electron Laser ◽  
Negative Index ◽  
Negative Index Material ◽  
Spatial Growth ◽  
Spatial Growth Rate

scholarly journals Long-wavelength asymptotics of unstable crossflow modes, including the effect of surface curvature

1995 ◽  
Vol 451 (1943) ◽  
pp. 515-541 ◽  
Keyword(s):  
Growth Rate ◽  
Asymptotic Methods ◽  
Three Dimensional ◽  
Wave Number ◽  
Shear Direction ◽  
Viscous Effects ◽  
Long Wavelength ◽  
Spatial Growth ◽  
Wall Shear ◽  
Spatial Growth Rate

Stationary vortex instabilities with wavelengths significantly larger than the thickness of the underlying three-dimensional boundary layer are studied with asymptotic methods. The long-wavelength Rayleigh modes are locally neutral and aligned with the direction of the local inviscid streamline. For a spanwise wave number β ≪ 1, the spatial growth rate of these vortices is O ( β 3/2 ). When β becomes O ( R -1/7 ), the viscous correction associated with a thin sublayer near the surface modifies the inviscid growth rate to the leading order. As β is further decreased through this regime, viscous effects assume greater significance and dominate the growth-rate behaviour. The spatial growth rate becomes comparable to the real part of the wave number when β = O ( R -¼ ). At this stage, the disturbance structure becomes fully viscous-inviscid interactive and is described by the triple-deck theory. For even smaller values of β , the vortex modes become nearly neutral again and align themselves with the direction of the wall-shear stress. Thus the study explains the progression of the crossflow-vortex structure from the inflectional upper branch mode to nearly neutral long-wavelength modes that are aligned with the wall-shear direction.

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