Clumpy Langmuir waves in type III radio sources - Comparison of stochastic-growth theory with observations

1993 ◽  
Vol 407 ◽  
pp. 790 ◽  
Author(s):  
P. A. Robinson ◽  
I. H. Cairns ◽  
D. A. Gurnett
Keyword(s):  
Growth Theory ◽  
Radio Sources ◽  
Langmuir Waves ◽  
Stochastic Growth ◽  
Type Iii

scholarly journals Statistics of auroral Langmuir waves

2008 ◽  
Vol 26 (12) ◽  
pp. 3885-3895 ◽  
Author(s):  
M. Samara ◽  
J. LaBelle ◽  
I. H. Cairns
Keyword(s):  
Electric Field ◽  
High Frequency ◽  
Large Range ◽  
Auroral Zone ◽  
Sounding Rocket ◽  
Growth Theory ◽  
Langmuir Waves ◽  
Stochastic Growth ◽  
Gaussian Form ◽  
Frequency Wave

Abstract. The Physics of Auroral Zone Electrons II (PHAZE II) sounding rocket was launched in February 1997 into active pre-midnight aurora. The resulting high frequency wave data are dominated by Langmuir waves. Consistent with many previous observations the Langmuir waves are sporadic, occurring in bursts lasting up to a few hundred ms. We compute statistics of the electric field amplitudes of these Langmuir waves, with two results. First, the shape of the distribution of running averages of the electric field amplitudes remains approximately stationary for a large range of widths of running average less than ~0.3 ms and for a large range of widths exceeding about 1 ms. The interpretation of this transition timescale is unclear but appears unlikely to be of instrumental origin. Second, for 2.6-ms running averages, corresponding to the latter range, the distribution of the logarithm of electric field amplitudes matches a Gaussian form very well for all nine cases studied in detail, hence the statistics are lognormal. These distributions are consistent with stochastic growth theory (SGT).

Connection between ambient density fluctuations and clumpy Langmuir waves in type III radio sources

1992 ◽  
Vol 387 ◽  
pp. L101 ◽  
Author(s):  
P. A. Robinson ◽  
I. H. Cairns ◽  
D. A. Gurnett
Keyword(s):  
Density Fluctuations ◽  
Radio Sources ◽  
Langmuir Waves ◽  
Type Iii

scholarly journals First test of stochastic growth theory for Langmuir waves in Earth's foreshock

1997 ◽  
Vol 24 (4) ◽  
pp. 369-372 ◽  
Author(s):  
Iver H. Cairns ◽  
P. A. Robinson
Keyword(s):  
Growth Theory ◽  
Langmuir Waves ◽  
Stochastic Growth

Clumpy Langmuir waves in type III radio sources

Solar Physics ◽  
1992 ◽  
Vol 139 (1) ◽  
pp. 147-163 ◽  
Author(s):  
P. A. Robinson
Keyword(s):  
Radio Sources ◽  
Langmuir Waves ◽  
Type Iii

scholarly journals Polarization and Position Measurements of Type III Bursts

1980 ◽  
Vol 86 ◽  
pp. 315-322 ◽  
Author(s):  
S. Suzuki ◽  
G.A. Dulk ◽  
K. V. Sheridan
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Open Field ◽  
Langmuir Waves ◽  
Type Iii ◽  
Brightness Temperatures ◽  
Polarization Characteristics ◽  
Field Lines ◽  
Cosine Law ◽  
The Magnetic Field

We report on the positional and polarization characteristics of Type III bursts in the range 24–220 MHz as measured by the Culgoora radioheliograph, spectrograph and spectropolarimeter. Our study includes 997 bursts which are of two classes: fundamental-harmonic (F-H) pairs and “structureless” bursts with no visible F-H structure. In a paper published elsewhere (Dulk and Suzuki, 1979) we give a detailed description and include observations of source sizes, heights and brightness temperatures. Here we concentrate on the polarization of the bursts and the variation of polarization from centre to limb. The observed centre-to-limb decrease in polarization approximately follows a cosine law. This decrease is not as predicted by simple theory but is consistent with other observations which imply that open field lines from an active region diverge strongly. The observed o-mode polarization of harmonic radiation implies that the wave vectors of Langmuir waves are always parallel, within about 20°, to the magnetic field, while the constancy of H polarization with frequency implies that the ratio fB/fP, the Alfvén speed vA and the plasma beta are constant with height on the open field lines above an active region. Finally, we infer that some factor, in addition to the magnetic field strength, controls the polarization of F radiation.

The Effect of Scattering on Solar Radio Sources at 80 MHz

1972 ◽  
Vol 2 (2) ◽  
pp. 98-100 ◽  
Author(s):  
A. C. Riddle
Keyword(s):  
Plasma Level ◽  
Electron Density ◽  
Solar Radio ◽  
Brightness Distribution ◽  
Time Profile ◽  
Radio Sources ◽  
Density Structure ◽  
Localized Source ◽  
Type Iii

Scattering of radiation from solar radio sources by in homogeneities in the electron density structure of the corona can have marked effects on the observed time profile and the brightness distribution. These effects are appreciable for any localized source emitting a brief burst of radiation and are most pronounced when the radiation propagates close to the plasma level; it is such sources, illustrated here by those of type III bursts, that will be considered in this paper.

scholarly journals High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

2004 ◽  
Vol 11 (3) ◽  
pp. 411-420 ◽  
Author(s):  
G. Thejappa ◽  
R. J. MacDowall
Keyword(s):  
Short Wavelength ◽  
Langmuir Wave ◽  
Linear Process ◽  
Radio Bursts ◽  
Sound Waves ◽  
Burst Source ◽  
Langmuir Waves ◽  
Type Iii ◽  
Resonant Wave ◽  
Source Regions

Abstract. Short wavelength ion sound waves (2-4kHz) are detected in association with the Langmuir waves (~15-30kHz) in the source regions of several local type III radio bursts. They are most probably not due to any resonant wave-wave interactions such as the electrostatic decay instability because their wavelengths are much shorter than those of Langmuir waves. The Langmuir waves occur as coherent field structures with peak intensities exceeding the Langmuir collapse thresholds. Their scale sizes are of the order of the wavelength of an ion sound wave. These Langmuir wave field characteristics indicate that the observed short wavelength ion sound waves are most probably generated during the thermalization of the burnt-out cavitons left behind by the Langmuir collapse. Moreover, the peak intensities of the observed short wavelength ion sound waves are comparable to the expected intensities of those ion sound waves radiated by the burnt-out cavitons. However, the speeds of the electron beams derived from the frequency drift of type III radio bursts are too slow to satisfy the needed adiabatic ion approximation. Therefore, some non-linear process such as the induced scattering on thermal ions most probably pumps the beam excited Langmuir waves towards the lower wavenumbers, where the adiabatic ion approximation is justified.

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