Detection of collapsing Langmuir wave packets in solar type III radio bursts

2013 ◽  
Author(s):  
G. Thejappa ◽  
R. J. MacDowall ◽  
M. Bergamo
Keyword(s):  
Wave Packets ◽  
Langmuir Wave ◽  
Radio Bursts ◽  
Type Iii ◽  
Solar Type

scholarly journals Evidence for four- and three-wave interactions in solar type III radio emissions

2013 ◽  
Vol 31 (8) ◽  
pp. 1417-1428 ◽  
Author(s):  
G. Thejappa ◽  
R. J. MacDowall ◽  
M. Bergamo
Keyword(s):  
Wave Packet ◽  
Second Harmonic ◽  
Wave Packets ◽  
Spectral Peak ◽  
Wave Number ◽  
Radio Bursts ◽  
Langmuir Waves ◽  
Type Iii ◽  
Primary Peak ◽  
Solar Type

Abstract. The high time resolution observations obtained by the STEREO/WAVES experiment show that in the source regions of solar type III radio bursts, Langmuir waves often occur as intense localized wave packets with short durations of only few ms. One of these wave packets shows that it is a three-dimensional field structure with WLneTe ~ 10−3, where WL is the peak energy density, and ne and Te are the electron density and temperature, respectively. For this wave packet, the conditions of the oscillating two-stream instability (OTSI) and supersonic collapse are satisfied within the error range of determination of main parameters. The density cavity, observed during this wave packet indicates that its depth, width and temporal coincidence are consistent with those of a caviton, generated by the ponderomotive force of the collapsing wave packet. The spectrum of each of the parallel and perpendicular components of the wave packet contains a primary peak at fpe, two secondary peaks at fpe ± fS and a low-frequency enhancement below fS, which, as indicated by the frequency and wave number resonance conditions, and the fast Fourier transform (FFT)-based tricoherence spectral peak at (fpe, fpe, fpe + fS, fpe − fS), are coupled to each other by the OTSI type of four-wave interaction (fpe is the local electron plasma frequency and fS is the frequency of ion sound waves). In addition to the primary peak at fpe, each of these spectra also contains a peak at 2fpe, which as indicated by the frequency and wave number resonance conditions, and the wavelet-based bicoherence spectral peak at (fpe, fpe), appears to correspond to the second harmonic electromagnetic waves generated as a result of coalescence of oppositely propagating sidebands excited by the OTSI. Thus, these observations for the first time provide combined evidence that (1) the OTSI and related strong turbulence processes play a significant role in the stabilization of the electron beam, (2) the coalescence of the oppositely propagating up- and down-shifted daughter Langmuir waves excited by the OTSI probably is the emission mechanism of the second harmonic radiation, and (3) the Langmuir collapse follows the route of OTSI in some of the type III radio bursts.

WindSpacecraft Observations of Solar Impulsive Electron Events Associated with Solar Type III Radio Bursts

1998 ◽  
Vol 503 (1) ◽  
pp. 435-445 ◽  
Author(s):  
R. E. Ergun ◽  
D. Larson ◽  
R. P. Lin ◽  
J. P. McFadden ◽  
C. W. Carlson ◽  
...  
Keyword(s):  
Radio Bursts ◽  
Type Iii ◽  
Solar Type

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.

scholarly journals Distribution Functions of Type III Electrons Observed in Interplanetary Space

1980 ◽  
Vol 86 ◽  
pp. 311-313
Author(s):  
R. P. Lin ◽  
D. W. Potter ◽  
K. A. Anderson ◽  
J. Fainberg ◽  
R. G. Stone ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Energetic Particle ◽  
Solar Radio ◽  
Interplanetary Space ◽  
Energetic Electron ◽  
Distribution Functions ◽  
Radio Bursts ◽  
Type Iii ◽  
Solar Type ◽  
Good Energy

We present simultaneous energetic electron and solar radio observations from the ISEE−3 spacecraft of several solar type III radio bursts. The UC Berkeley energetic particle experiment measures from 2 to ~ 103 keV with good energy and pitch angle resolution while the Meudon/GSFC radio experiment tracks type III radio bursts at 24 frequencies in the range 30 kHz—2 MHz.

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