Ion Acoustic Wave Frequencies and Onset Times During Type 3 Solar Radio Bursts

摘要: Conflicting interpretations exist for the low-frequency ion acoustic (S) waves often observed by ISEE 3 in association with intense Langmuir (L) source regions of type III solar radio bursts near 1 AU. Two indirect lines observational evidence, as well plasma theory, suggest they are produced electrostatic (ES) decay L yields L(PRIME) + S. However, contrary to theoretical predictions, an existing analysis wave frequencies instead favors electromagnetic (EM) decays T S, where denotes EM frequency. This conflict is addressed here comparing and onset times predictions ES decays, calculated using time-variable electron beam magnetic field orientation data, rather than nominal values used previously. Field effects speed variations shown analytically produce factor-of-three effects, greater difference predicted decays; similar magnitude occur events analyzed here. The S-wave signals extracted hand from a sawtooth noise background, greatly improving between S waves. Very good agreement exists time-varying most (but not all) bursts. only after becomes kinematically allowed, which consistent proceeding producing signals. Good decay's significant fraction observations while allowed. data consistent, however, being dominant nonlinear process. Often sufficiently broadband overlap simultaneously frequency ranges decays. Coupling dominance this provides support previous suggestion that fundamental emission occurs when stimulated product periods observable (independently) harmonic emission. supports interpretation coalescence L(prime) beam-generated decay, at twice Analysis reveals ballistic propagation minimal energy loss, implying propagates state close time- volume-averaged marginal stability. confirms central tenet stochastic growth theory