A new interpretation on the origin of enhanced ion acoustic fluctuations in the upper ionosphere

Forme, F.

doi:10.1029/93gl02490

Cited by 50 publications

(67 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Muschietti et al (1994), Newman et al (1994) and Forme (1993). The beam parameters we have used are well within the limits given by these authors.…”

Section: Discussionmentioning

confidence: 62%

“…The ®rst formulation of this model by Forme (1993) was not able to explain some of the observed spectral signature like simultaneously propagating ion-acoustic waves in parallel and antiparallel (with respect to the magnetic ®eld) direction. This study shows that the parametric decay of beam generated Langmuir waves can lead to up-going and down-going ion-acoustic waves, propagating separately or simultaneously.…”

Section: Resultsmentioning

confidence: 96%

“…(1) we produce a matching condition that can be written as k rp % 2 k m x À 1. What actually selects the wave vector of the driven Langmuir mode is the beam energyĩ and the background density n. Estimates of the beam energy have been given by Forme (1993) for di erent background densities.…”

Section: Discussionmentioning

confidence: 99%

“…A completely di erent approach has been advanced by Forme (1993). It was suggested that the enhanced ionacoustic¯uctuations are due to the Langmuir wave decay l 3 l¢+s.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Parametric decay of beam-driven Langmuir wave and enhanced ion-acoustic fluctuations in the ionosphere: a weak turbulence approach

Forme¹

1999

Ann Geophysicae

Self Cite

View full text Add to dashboard Cite

Abstract. We present a model that describes the decay of beam generated Langmuir waves into ion-acoustic waves in the topside ionosphere. This calculation is done within the frame of the weak turbulence approximation. We study the spectral signature of such a process as seen by a VHF incoherent scatter radar. An incoherent scatter (IS) spectrum is characterized by two maxima at k r d r and Àk r d r , the right and left ion lines respectively. It is shown that, for reasonable beam parameters, the parametric decay of beam-generated Langmuir waves can enhance either the right, the left or both ion lines simultaneously. The shape of the spectrum can change drastically on time scale of about 0.1 to 1 s. The role of the beam parameter as well as the ionospheric parameters is also investigated. For a given beam number density, the beam energy or the background density are important to trigger either the left or the right ion line. A large energy spread of the beam or low electron collision frequencies can explain the simultaneous observations of the left and the right ion line. The importance of the electron collision frequency can explain the altitude distribution of the coherent echoes observed by incoherent scatter radars.

show abstract

“…Muschietti et al (1994), Newman et al (1994) and Forme (1993). The beam parameters we have used are well within the limits given by these authors.…”

Section: Discussionmentioning

confidence: 62%

Section: Resultsmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

“…A completely di erent approach has been advanced by Forme (1993). It was suggested that the enhanced ionacoustic¯uctuations are due to the Langmuir wave decay l 3 l¢+s.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Parametric decay of beam-driven Langmuir wave and enhanced ion-acoustic fluctuations in the ionosphere: a weak turbulence approach

Forme¹

1999

Ann Geophysicae

Self Cite

View full text Add to dashboard Cite

show abstract

“…St.-Maurice et al [ 1996] discuss the inferred field-aligned currents in terms of intense parallel electric fields of up to a few hundred microvolts per meter in magnitude together with horizontal scales of a few hundred meters or less. Forme [1993] has suggested that ion-acoustic fluctuations may be due to parametric decay of Langmuir waves, and Wahlund et al [1992a] propose a theory based on ion-ion two-stream instabilities. Foster et al [1988] using the Millstone Hill 440-MHz radar at angles of at least 11 ø away from the local magnetic field direction revealed echoes that could easily have been mistaken for satellite passes had they not had a consistent altitude profile and come from a fixed region of space.…”

mentioning

confidence: 99%

Coherent EISCAT Svalbard Radar spectra from the dayside cusp/cleft and their implications for transient field‐aligned currents

Sedgemore-Schulthess¹,

Lockwood²,

Trondsen³

et al. 1999

J. Geophys. Res.

View full text Add to dashboard Cite

Abstract. Naturally enhanced incoherent scatter spectra from the vicinity of the dayside cusp/cleft, interpreted as being due to plasma turbulence driven by short bursts of intense field-aligned current, are compared with high-resolution narrow-angle auroral images and meridian scanning photometer data. Enhanced spectra have been observed on many occasions in association with nightside aurora, but there has been only one report of such spectra seen in the cusp/cleft region. Narrow-angle images show considerable change in the aurora on timescales shorter than the 10-s radar integration period, which could explain spectra observed with both ion lines simultaneously enhanced. Enhanced radar spectra are generally seen inside or beside regions of 630-nm auroral emission, indicative of sharp F region conductivity gradients, but there appears also to be a correlation with dynamic, small-scale auroral forms of order 100 rn and less in width.

show abstract

On the relation of Langmuir turbulence radar signatures to auroral conditions

2014

View full text Add to dashboard Cite

We present a statistical study of anomalous radar echoes observed in the auroral ionosphere thought to be signatures of Langmuir turbulence (LT). Data obtained with the European Incoherent Scatter Svalbard radar during the international polar year (IPY) were searched for these anomalous echoes in the auroral F region. In incoherent scatter radar experiments LT may in certain circumstances be observed as enhanced backscattered radar power at the ion line frequencies, plasma line frequencies, and at zero Doppler shift. The power enhancement at zero Doppler shift could arise due to Bragg scattering from nonpropagating density fluctuations caused by strong LT. In the IPY data set, around 0.02% of the data comply with our search criteria for altitudes above 190 km based on the ion line spectrum including enhancement at zero Doppler shift. The occurrence frequency of the identified events peaks in the premidnight sector and increases with local geomagnetic disturbance. Enhanced backscattered power is observed with limited altitude extent (below 20 km in 70% of the events), and the altitude distribution of identified radar signatures in the ion line channel has a peak at about 220 km. Enhancement of the plasma line is observed with the ion line enhancements in more than 60% of the events. Two classes of enhanced plasma lines occur. In the first class, plasma lines are limited in frequency and altitude and occur at altitudes of ion line enhancements. In the second class, the plasma lines are spread in frequency and range and are observed at lower altitudes than the first class (at about 170 km) with frequencies close to 3 MHz. Available optical data available indicate that the identified events to occur during auroral breakup with high‐energy electron precipitation.

show abstract

A new interpretation on the origin of enhanced ion acoustic fluctuations in the upper ionosphere

Cited by 50 publications

References 21 publications

Parametric decay of beam-driven Langmuir wave and enhanced ion-acoustic fluctuations in the ionosphere: a weak turbulence approach

Parametric decay of beam-driven Langmuir wave and enhanced ion-acoustic fluctuations in the ionosphere: a weak turbulence approach

Coherent EISCAT Svalbard Radar spectra from the dayside cusp/cleft and their implications for transient field‐aligned currents

On the relation of Langmuir turbulence radar signatures to auroral conditions

Contact Info

Product

Resources

About