Statistical behavior of foreshock Langmuir waves observed by the Cluster wideband data plasma wave receiver

Abstract

Abstract. We present the statistics of Langmuir wave amplitudes in the Earth's foreshock using Cluster Wideband Data (WBD) Plasma Wave Receiver electric field waveforms from spacecraft 2, 3 and 4 on 26 March 2002. The largest amplitude Langmuir waves were observed by Cluster near the boundary between the foreshock and solar wind, in agreement with earlier studies. The characteristics of the waves were similar for all three spacecraft, suggesting that variations in foreshock structure must occur on scales greater than the 50-100 km spacecraft separations. The electric field amplitude probability distributions constructed using waveforms from the Cluster WBD Plasma Wave Receiver generally followed the log-normal statistics predicted by stochastic growth theory for the event studied. Comparison with WBD receiver data from 17 February 2002, when spacecraft 4 was set in a special manual gain mode, suggests nonoptimal auto-ranging of the instrument may have had some influence on the statistics.

Statistics of Langmuir wave amplitudes observed inside Saturn's foreshock by the Cassini spacecraft

“…This is in agreement with previous observations inside of Saturn's foreshock from Voyager 1 [ Boshuizen et al ., ] and Cassini [ Hospodarsky et al ., ]. Nevertheless, the largest observed amplitudes are lower by 1 order of magnitude than wave amplitudes observed inside Earth's foreshock [e.g., Bale et al ., ; Sigsbee et al ., ; Malaspina et al ., ]. The Langmuir wave amplitude distribution in a substantial part of the amplitude range follows the lognormal distribution (〈log E 〉=−1.170 ± 0.002, σ log E = 0.387 ± 0.001) as is predicted by the stochastic growth theory [e.g., Robinson , ] and shown by several observations of Earth's foreshock [e.g., Cairns and Robinson , ; Sigsbee et al ., ].…”

“…We find that larger amplitudes follow a power law distribution with the exponent −1.37 ± 0.01. The power law deviations of the amplitude distribution from the lognormal law was also shown for higher amplitudes by previous observations of planetary foreshocks [e.g., Bale et al ., ; Sigsbee et al ., ; Boshuizen et al. , ] and can be explained by observations of the probability distribution function over wide range of foreshock positions and during different conditions in the solar wind [ Boshuizen et al ., ].…”

“…The orientation of the receiving antenna with respect to the direction of the magnetic field therefore influences the measured wave amplitudes. A correction factor of 1/ cos θ , where θ is the angle between the dipole antenna and the magnetic field, was applied for each received waveform interval [ Sigsbee et al ., ]. When the angle between the antenna and the magnetic field is close to 90° (78° > θ > 101°), the correction factor becomes large and uncertainties of the measurements increase.…”

“…If nonlinear and thermal effects are neglected, the distribution of wave amplitudes should follow a lognormal distribution [ Robinson , ]. Event studies using experimental data observed during a time period of hours and covering only spatially limited regions found the distribution of amplitudes close to lognormal across most foreshock regions [e.g., Cairns et al ., ; Sigsbee et al ., ]. However, observations mixing a wide range of foreshock positions show amplitude distributions following a power law distribution at high amplitudes with an exponent ≈−1 [ Bale et al ., ; Cairns et al ., ; Boshuizen et al ., ].…”

Effect of Turbulence on Line Shapes in Astrophysical and Fusion Plasmas

“…Plasmas submitted to an energetic beam of particles or to a strong radiation can be found in many situations. In an astrophysical context, active galactic nuclei [6], pulsar radio sources [7], planetary foreshocks [8], or solar type III radio bursts [9] are possible candidates. Relevant laboratory plasmas are laser plasmas [10], radio experiments [11], or possibly also magnetic fusion plasma, since such plasmas can be affected by the energetic beams of runaway electrons [12].…”