Charged dust in the Earth's mesopause; effects on radar backscatter

Havnes, O.; Melandsø, Frank; Hoz, C. La; Aslaksen, T.; Hartquist, T. W.

doi:10.1088/0031-8949/45/5/022

Cited by 111 publications

(75 citation statements)

References 25 publications

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“…In an equilibrium process where ion-electron pairs are produced at a rate q, this will be balanced by a loss due to ion-electron recombination and absorption by dust particles (e.g. Havnes et al, 1992;Rapp and Lübken, 2001). The production rate q can vary between wide limits according to whether we have day or night conditions and/or quiet or disturbed conditions.…”

Section: The Electron Heating As Deduced From the Overshoot Charactermentioning

confidence: 99%

The effect of electron bite-outs on artificial electron heating and the PMSE overshoot

2005

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Abstract.We have considered the effect that a local reduction in the electron density (an electron bite-out), caused by electron absorption on to dust particles, can have on the artificial electron heating in the height region between 80 to 90 km, where noctilucent clouds (NLC) and the radar phenomenon PMSE (Polar Mesospheric Summer Echoes) are observed. With an electron density profile without biteouts, the heated electron temperature T e,hot will generally decrease smoothly with height in the PMSE region or there may be no significant heating effect present. Within a biteout T e,hot will decrease less rapidly and can even increase slightly with height if the bite-out is strong. We have looked at recent observations of PMSE which are affected by artificial electron heating, with a heater cycling producing the new overshoot effect. According to the theory for the PMSE overshoot the fractional increase in electron temperature T e,hot /T i , where T i is the unaffected ion temperature = neutral temperature, can be found from the reduction in PMSE intensity as the heater is switched on. We have looked at results from four days of observations with the EIS-CAT VHF radar (224 MHz), together with the EISCAT heating facility. We find support for the PMSE overshoot and heating model from a sequence of observations during one of the days where the heater transmitter power is varied from cycle to cycle and where the calculated T e,hot /T i is found to vary in proportion to the transmitter power. We also looked for signatures of electron bite-outs by examining the variation of T e,hot /T i with height for the three other days. We find that the height variation of T e,hot /T i is very different on the three days. On one of the days we see typically that this ratio can increase with height, showing the presence of a bite-out, while on the next day the heating factor mainly decreases with height, indicating that the fractional amount of dust is low, so that the electron density is hardly affected by it. On the third day there is little heating effect on the PMSE layer. This is probably due to a sufficiently high electron densityCorrespondence to: O. Havnes (oha003@asp.uit.no) in the atmosphere below the PMSE layer, so that the transmitted heater power is absorbed in these lower layers. On this day the D-region, as given by the UHF (933 MHz) observations, extends deeper down in the atmosphere than on the other two days, indicating that the degree of ionization in and below the PMSE layers is higher as well.

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Section: The Electron Heating As Deduced From the Overshoot Charactermentioning

confidence: 99%

The effect of electron bite-outs on artificial electron heating and the PMSE overshoot

2005

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“…n 2 z n 2 y and ε 3 n 2 y . These waves are used, in particular, for investigation of the mesospheric dusty plasma (Havnes et al, 1992(Havnes et al, , 2001. In this case the dispersion relation has the form…”

Section: Circularly Polarized Wavesmentioning

confidence: 99%

“…The accelerated dust winds and dust fluxes are observed in the cosmic environment and late-type stars (Spitzer Jr., 1978;Falceta-Goncalves and Jatenco-Pereira, 2002;Altobelli et al, 2003). Experiments are carried out on the interaction of radar beams with the mesospheric dusty plasma (Havnes et al, 1992(Havnes et al, , 2001). The ponderomotive force can be used, in particular, for removal of impurities (dust grains) from the plasma in laboratory devices.…”

Section: Introductionmentioning

confidence: 99%

Dust grain dynamics due to nonuniform and nonstationary high-frequency radiations in cold magnetoplasmas

Nekrasov

Feygin

2006

Ann. Geophys.

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Abstract.A general nonlinear theory for low-frequency electromagnetic field generation due to high-frequency nonuniform and nonstationary electromagnetic radiations in cold, uniform, multicomponent, dusty magnetoplasmas is developed. This theory permits us to consider the nonlinear action of all waves that can exist in such plasmas. The equations are derived for the dust grain velocities in the lowfrequency nonlinear electric fields arising due to the presence of electromagnetic cyclotron waves travelling along the background magnetic field. The dust grains are considered to be magnetized as well as unmagnetized. Different regimes for the dust particle dynamics, depending on the spatio-temporal change of the wave amplitudes and plasma parameters, are discussed. It is shown that induced nonlinear electric fields can have both an electrostatic and electromagnetic nature. Conditions for maximum dust acceleration are found. The results obtained may be useful for understanding the possible mechanisms of dust grain dynamics in astrophysical, cosmic and laboratory plasmas under the action of nonuniform and nonstationary electromagnetic waves.

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“…This represents at least an order of magnitude improvement over standard MST radar resolutions. For example, one of the theories proposed to explain the occurrence of PMSE is that of dust-hole scatter, attributed to Havnes et al (1992). It is assumed that horizontal vortex rolls are embedded in a ®eld of falling charged dust or ice aerosols.…”

Section: Introductionmentioning

confidence: 99%

Frequency domain interferometry mode observations of PMSE using the EISCAT VHF radar

Chilson

Kirkwood

Häggström

2001

Annales Geophysicae

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Abstract. During the summer of 1997 investigations into the nature of polar mesosphere summer echoes (PMSE) were conducted using the European incoherent scatter (EISCAT) VHF radar in Norway. The radar was operated in a frequency domain interferometry (FDI) mode over a period of two weeks to study the frequency coherence of the returned radar signals. The operating frequencies of the radar were 224.0 and 224.6 MHz. We present the ®rst results from the experiment by discussing two 4-h intervals of data collected over two consecutive nights. During the ®rst of the two days an enhancement of the FDI coherence, which indicates the presence of distinct scattering layers, was found to follow the lower boundary of the PMSE. Indeed, it is not unusual to observe that the coherence values are peaked around the heights corresponding to both the lower-and upper-most boundaries of the PMSE layer and sublayers. A Kelvin±Helmholtz mechanism is oered as one possible explanation for the layering structure. Additionally, our analysis using range-timepseudocolor plots of signal-to-noise ratios, spectrograms of Doppler velocity, and estimates of the positions of individual scattering layers is shown to be consistent with the proposition that upwardly propagating gravity waves can become steepened near the mesopause.

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Charged dust in the Earth's mesopause; effects on radar backscatter

Cited by 111 publications

References 25 publications

The effect of electron bite-outs on artificial electron heating and the PMSE overshoot

The effect of electron bite-outs on artificial electron heating and the PMSE overshoot

Dust grain dynamics due to nonuniform and nonstationary high-frequency radiations in cold magnetoplasmas

Frequency domain interferometry mode observations of PMSE using the EISCAT VHF radar

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