POLAR observations of coherent electric field structures

Abstract. Electrostatic Solitary Waves (ESWs) have been observed by several spacecraft in the current layers of Earth's magnetosphere since 1982. ESWs are manifested as isolated pulses (one wave period) in the high time resolution waveform data obtained on these spacecraft. They are thus nonlinear structures generated out of nonlinear instabilities and processes. We report the first observations of ESWs associated with the onset of a super-substorm that occurred on 24 August 2005 while the Cluster spacecraft were located in the magnetotail at around 18-19 R E and moving northward from the plasma sheet to the lobes. These ESWs were detected in the waveform data of the WBD plasma wave receiver on three of the Cluster spacecraft. The majority of the ESWs were detected about 5 min after the super-substorm onset during which time 1) the PEACE electron instrument Correspondence to: J. S. Pickett (pickett@uiowa.edu) detected significant field-aligned electron fluxes from a few 100 eV to 3.5 keV, 2) the EDI instrument detected bursts of field-aligned electron currents, 3) the FGM instrument detected substantial magnetic fluctuations and the presence of Alfvén waves, 4) the STAFF experiment detected broadband electric and magnetic waves, ion cyclotron waves and whistler mode waves, and 5) CIS detected nearly comparable densities of H+ and O+ ions and a large tailward H+ velocity. We compare the characteristics of the ESWs observed during this event to those created in the laboratory at the University of California-Los Angeles Plasma Device (LAPD) with an electron beam. We find that the time durations of both space and LAPD ESWs are only slightly larger than the respective local electron plasma periods, indicating that electron, and not ion, dynamics are responsible for generation of the ESWs. We have discussed possible mechanisms for generating the ESWs in space, including the beam and kinetic Buneman type instabilities and the acoustic instabilities. Future studies will examine these mechanisms in more detail using Published by Copernicus Publications on behalf of the European Geosciences Union and the American Geophysical Union. 432 J. S. Pickett et al.: Electrostatic solitary waves in current layers the space measurements as inputs to models, and better relate the ESW space measurements to the laboratory through PIC code models.

Section: Introductionmentioning

confidence: 99%

Electrostatic solitary waves in current layers: from Cluster observations during a super-substorm to beam experiments at the LAPD

Pickett

Chen

Santolı́k

et al. 2009

“…Analysis of the high time resolution of the plasma wave data from GEOTAIL have shown that BEN in the plasma sheet boundary layer actually consists of short electrostatic solitary waves (ESWs) whose Fourier spectrum give rises to the broadband nature of the noise (Matsumoto et al, 1994). ESWs have been observed at/in the bow shock (Bale et al, 1998), the magnetosheath (Pickett et al, 2003), the polar cap boundary layer (Franz et al, 1998;Tsurutani et al, 1998), and in the auroral acceleration region (Ergun et al, 1998;Bounds et al, 1999). It is interesting to note that the electrostatic solitary structures are observed in the electric field parallel to the background magnetic field, are usually bipolar or tripolar, and their amplitudes are typically a few mV/m in the plasma sheet boundary layer, but they can be as large as 200 mV/m at polar altitudes (Cattell et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Study of nonlinear ion- and electron-acoustic waves in multi-component space plasmas

Lakhina

Singh

Kakad

et al. 2008

102

Abstract. Large amplitude ion-acoustic and electronacoustic waves in an unmagnetized multi-component plasma system consisting of cold background electrons and ions, a hot electron beam and a hot ion beam are studied using Sagdeev pseudo-potential technique. Three types of solitary waves, namely, slow ion-acoustic, ion-acoustic and electron-acoustic solitons are found provided the Mach numbers exceed the critical values. The slow ion-acoustic solitons have the smallest critical Mach numbers, whereas the electron-acoustic solitons have the largest critical Mach numbers. For the plasma parameters considered here, both type of ion-acoustic solitons have positive potential whereas the electron-acoustic solitons can have either positive or negative potential depending on the fractional number density of the cold electrons relative to that of the ions (or total electrons) number density. For a fixed Mach number, increases in the beam speeds of either hot electrons or hot ions can lead to reduction in the amplitudes of the ion-and electron-acoustic solitons. However, the presence of hot electron and hot ion beams have no effect on the amplitudes of slow ion-acoustic modes. Possible application of this model to the electrostatic solitary waves (ESWs) observed in the plasma sheet boundary layer is discussed.

“…Such large value of electric fields suggest that the nonlinear effects have a bearing in the generation of BEN. Electrostatic solitary structures have been observed in the auroral acceleration region (Temerin et al, 1982;Bostrom et al, 1988;Dubouloz et al, 1991a, b;Mozer et al, 1997;Ergun et al, 1998;Bounds et al, 1999), in Earth's high altitude polar magnetosphere (Franz et al, 1998), in Polar cap boundary layer (Tsurutani et al, 1998), in the plasma sheet boundary layer Omura et al, 1994), on cusp field lines (Cattell et al, 1999) and in AKR source region (Pottelette et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Electron acoustic solitary waves with non-thermal distribution of electrons

Singh

Lakhina

2004

122

Abstract. Electron-acoustic solitary waves are studied in an unmagnetized plasma consisting of non-thermally distributed electrons, fluid cold electrons and ions. The Sagdeev pseudo-potential technique is used to carry out the analysis. The presence of non-thermal electrons modifies the parametric region where electron acoustic solitons can exist. For parameters representative of auroral zone field lines, the electron acoustic solitons do not exist when either α > 0.225 or T c /T h > 0.142, where α is the fractional non-thermal electron density, and T c (T h ) represents the temperature of cold (hot) electrons. Further, for these parameters, the simple model predicts negatively charged potential structures. Inclusion of an electron beam in the model may provide the positive potential solitary structures.