Polar Mesospheric Summer Echoes (PMSE) during artificial heating

2021 ◽  
Author(s):  
Tinna Gunnarsdottir ◽  
Arne Poggenpohl ◽  
Ove Havnes ◽  
Ingrid Mann
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Initial Density ◽  
Space Physics ◽  
Dust Particles ◽  
Typical Result ◽  
Geophysical Research ◽  
Ice Particles ◽  
Radar Scattering ◽  
Summer Echoes

<p>Polar Mesospheric Summer Echoes (PMSE) are regions of enhanced radar backscatter at 80 to 90 km that are assumed to form in the presence of neutral air turbulence and charged ice particles as a result of spatial variations in the electron density. Changes in the electron temperature, as can be generated by the EISCAT heater, influence the electron diffusivity as well as the charging of the ice particles and both are parameters that influence the radar scattering. In many cases, an overshoot effect [1] can be observed when the backscattered power is reduced during heater-on and rises above the initial signal during heater-off. We present observations made on the 11-12 and 15-16 of August 2018 with the EISCAT VHF radar during PMSE conditions. The EISCAT heating facility, operated at 5.423 MHz, was run in identical cycles where the heater was on for 48 seconds and off for 168 seconds. The observations clearly show the overshoot effect, caused by the cyclic heating of PMSE.  The surface charge of the ice particles increases during the heater-on intervals because of the higher electron temperature. As the heater is turned off the electrons are quickly cooled. The dust particles, however, still carry a higher charge, i.e. more electrons, so that the electrons cannot immediately obtain the initial density distribution. The typical result is that the electron density gradients are increased, which in turn lead to increased radar scattering, an overshoot. During the heater off phase, dust and plasma conditions are expected to relax back to undisturbed conditions. A theory was developed by Havnes [1] to explain the overshoot and we use a dusty plasma code [2] based on this theory to calculate the overshoot curves. They agree well with the average of the observational data. There is clear indication that during high precipitation the PMSE cloud is not affected by the heater and accordingly does not show an overshoot effect. </p><p> </p><p>1.     Havnes, O. (2004). Polar Mesospheric Summer Echoes (PMSE) overshoot effect due to cycling of artificial electron heating. Journal of Geophysical Research: Space Physics, 109(A2).</p><p>2.     Biebricher, A., Havnes, O., Hartquist, T. W., & LaHoz, C. (2006). On the influence of plasma absorption by dust on the PMSE overshoot effect. Advances in Space Research, 38(11), 2541-2550.</p>

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

2005 ◽  
Vol 23 (12) ◽  
pp. 3633-3643 ◽  
Author(s):  
M. Kassa ◽  
O. Havnes ◽  
E. Belova
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Electron Density Profile ◽  
Dust Particles ◽  
High Electron ◽  
Heating Effect ◽  
Ion Temperature ◽  
Degree Of Ionization ◽  
Electron Heating ◽  
Transmitter Power

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 90km, where noctilucent clouds (NLC) and the radar phenomenon PMSE (Polar Mesospheric Summer Echoes) are observed. With an electron density profile without bite-outs, the heated electron temperature Te,hot will generally decrease smoothly with height in the PMSE region or there may be no significant heating effect present. Within a bite-out Te,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 Te,hot/Ti, where Ti 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 EISCAT 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 Te,hot/Ti is found to vary in proportion to the transmitter power. We also looked for signatures of electron bite-outs by examining the variation of Te,hot/Ti with height for the three other days. We find that the height variation of Te,hot/Ti 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 density 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 (933MHz) 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.

scholarly journals Diagnostics of dusty plasma properties in planar magnetron sputtering device

2019 ◽  
Vol 13 (26) ◽  
pp. 64-75
Author(s):  
Qusay A. Abbas
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Discharge Current ◽  
Plasma Potential ◽  
Dust Particles ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Radial Profiles ◽  
Planar Magnetron ◽  
Radial Axis

The effect of Al dust particles on glow discharge regions, dischargevoltage, discharge current, plasma potential, floating potential,electron density and electron temperature in planar magnetronsputtering device has been studied experimentally. Four cylindricalLangmuir probes were employed to measure plasma parameters atdifferent point on the radial axis of plasma column. The resultsshows the present of Al dust causes to increase the discharge voltageand reduce the discharge current. There are two electron groups inthe present and absent of Al dust particles. The radial profiles ofplasma parameters in the present of dust are non- uniform. Thefloating potential of probe becomes more negatively while theplasma potential becomes positive when the dust immersed intoplasma region. The electron density increases in the present of dustparticle which lead to decreases the electron temperature.

scholarly journals The research on small-scale structures of ice particle density and electron density in the mesopause region

2019 ◽  
Author(s):  
Ruihuan Tian ◽  
Jian Wu ◽  
Jinxiu Ma ◽  
Yonggan Liang ◽  
Hui Li ◽  
...  
Keyword(s):  
Electron Density ◽  
Particle Density ◽  
Small Scale ◽  
Mesopause Region ◽  
Ice Particles ◽  
Summer Echoes ◽  
Outer Atmosphere ◽  
Moist Condition ◽  
Scale Structures ◽  
Small Scale Structures

Abstract. In this paper, a growth and motion model is developed to investigate the evolution of radius, velocity, and number density of ice particles in mesopause region. In the growth model, meteoric dust from outer atmosphere and grains moving with the upward neutral wind from the mesosphere bottom serve as nuclei upon which water vapor can condense in the cold and moist condition. And the motion of the ice particles is mainly controlled by the gravity and the neutral drag force. It is shown that the radius of ice particles increases linearly with time. But the particle velocity has a complicated relationship with the radius due to the different mass densities of condensation nuclei and absorbed ice. For certain condensation core radius, the velocity of particles can be reversed at particular height, which leads to local gathering of particles near the boundary layer and small-scale structures of ice particle density on the order of a few meters. Based on the obtained small-scale ice particle distribution, the mean particle charge number and corresponding distributions of electrons are calculated by combining the dust charging processes and quasi-neutrality condition. It shows that the absorption of electrons by ice particles results in the formation of small-scale electron density structures, which can be important to the research on the cause of polar mesosphere summer echoes (PMSE).

A Comparison of Two Algorithms for Electron-Density Map Improvement by Introduction of Atomicity: Skeletonization, and Map Sorting Followed by Refinement

1998 ◽  
Vol 54 (1) ◽  
pp. 81-85 ◽  
Author(s):  
F. M. D. Vellieux
Keyword(s):  
Electron Density ◽  
Initial Density ◽  
Acta Cryst ◽  
Density Maps ◽  
Resolution Electron ◽  
Crystallographic Symmetry ◽  
Density Map ◽  
Ornithine Transcarbamoylase ◽  
Electron Density Map ◽  
Pseudo Atom

A comparison has been made of two methods for electron-density map improvement by the introduction of atomicity, namely the iterative skeletonization procedure of the CCP4 program DM [Cowtan & Main (1993). Acta Cryst. D49, 148–157] and the pseudo-atom introduction followed by the refinement protocol in the program suite DEMON/ANGEL [Vellieux, Hunt, Roy & Read (1995). J. Appl. Cryst. 28, 347–351]. Tests carried out using the 3.0 Å resolution electron density resulting from iterative 12-fold non-crystallographic symmetry averaging and solvent flattening for the Pseudomonas aeruginosa ornithine transcarbamoylase [Villeret, Tricot, Stalon & Dideberg (1995). Proc. Natl Acad. Sci. USA, 92, 10762–10766] indicate that pseudo-atom introduction followed by refinement performs much better than iterative skeletonization: with the former method, a phase improvement of 15.3° is obtained with respect to the initial density modification phases. With iterative skeletonization a phase degradation of 0.4° is obtained. Consequently, the electron-density maps obtained using pseudo-atom phases or pseudo-atom phases combined with density-modification phases are much easier to interpret. These tests also show that for ornithine transcarbamoylase, where 12-fold non-crystallographic symmetry is present in the P1 crystals, G-function coupling leads to the simultaneous decrease of the conventional R factor and of the free R factor, a phenomenon which is not observed when non-crystallographic symmetry is absent from the crystal. The method is far less effective in such a case, and the results obtained suggest that the map sorting followed by refinement stage should be by-passed to obtain interpretable electron-density distributions.

scholarly journals Comparison of the measured and modelled electron densities and temperatures in the ionosphere and plasmasphere during 20-30 January, 1993

2000 ◽  
Vol 18 (10) ◽  
pp. 1257-1262 ◽  
Author(s):  
A. V. Pavlov ◽  
T. Abe ◽  
K.-I. Oyama
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Electron Temperature ◽  
Field Line ◽  
Electron Density ◽  
Magnetic Field Line ◽  
New Approach ◽  
Additional Heating ◽  
Vibrational Levels ◽  
The Magnetic Field

Abstract. We present a comparison of the electron density and temperature behaviour in the ionosphere and plasmasphere measured by the Millstone Hill incoherent-scatter radar and the instruments on board of the EXOS-D satellite with numerical model calculations from a time-dependent mathematical model of the Earth's ionosphere and plasmasphere during the geomagnetically quiet and storm period on 20–30 January, 1993. We have evaluated the value of the additional heating rate that should be added to the normal photoelectron heating in the electron energy equation in the daytime plasmasphere region above 5000 km along the magnetic field line to explain the high electron temperature measured by the instruments on board of the EXOS-D satellite within the Millstone Hill magnetic field flux tube in the Northern Hemisphere. The additional heating brings the measured and modelled electron temperatures into agreement in the plasmasphere and into very large disagreement in the ionosphere if the classical electron heat flux along magnetic field line is used in the model. A new approach, based on a new effective electron thermal conductivity coefficient along the magnetic field line, is presented to model the electron temperature in the ionosphere and plasmasphere. This new approach leads to a heat flux which is less than that given by the classical Spitzer-Harm theory. The evaluated additional heating of electrons in the plasmasphere and the decrease of the thermal conductivity in the topside ionosphere and the greater part of the plasmasphere found for the first time here allow the model to accurately reproduce the electron temperatures observed by the instruments on board the EXOS-D satellite in the plasmasphere and the Millstone Hill incoherent-scatter radar in the ionosphere. The effects of the daytime additional plasmaspheric heating of electrons on the electron temperature and density are small at the F-region altitudes if the modified electron heat flux is used. The deviations from the Boltzmann distribution for the first five vibrational levels of N2(v) and O2(v) were calculated. The present study suggests that these deviations are not significant at the first vibrational levels of N2 and O2 and the second level of O2, and the calculated distributions of N2(v) and O2(v) are highly non-Boltzmann at vibrational levels v > 2. The resulting effect of N2(v > 0) and O2(v > 0) on NmF2 is the decrease of the calculated daytime NmF2 up to a factor of 1.5. The modelled electron temperature is very sensitive to the electron density, and this decrease in electron density results in the increase of the calculated daytime electron temperature up to about 580 K at the F2 peak altitude giving closer agreement between the measured and modelled electron temperatures. Both the daytime and night-time densities are not reproduced by the model without N2(v > 0) and O2(v > 0), and inclusion of vibrationally excited N2 and O2 brings the model and data into better agreement.Key words: Ionosphere (ionospheric disturbances; ionosphere-magnetosphere interactions; plasma temperature and density)  

Influence of dust particles on the bulk electron density in radio frequency plasmas measured by microwave interferometry

2015 ◽  
Vol 22 (12) ◽  
pp. 123702 ◽  
Author(s):  
Carsten Killer ◽  
Thomas Wegner ◽  
André Melzer ◽  
Jürgen Meichsner
Keyword(s):  
Radio Frequency ◽  
Electron Density ◽  
Dust Particles ◽  
Microwave Interferometry

scholarly journals Machine Learning Prediction of Electron Density and Temperature from Optical Emission Spectroscopy in Nitrogen Plasma

Coatings ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1221
Author(s):  
Jun-Hyoung Park ◽  
Ji-Ho Cho ◽  
Jung-Sik Yoon ◽  
Jung-Ho Song
Keyword(s):  
Machine Learning ◽  
Electron Temperature ◽  
Real Time ◽  
Electron Density ◽  
Emission Spectroscopy ◽  
Optical Emission Spectroscopy ◽  
Optical Emission ◽  
Plasma Parameters ◽  
Plasma Nitridation

We present a non-invasive approach for monitoring plasma parameters such as the electron temperature and density inside a radio-frequency (RF) plasma nitridation device using optical emission spectroscopy (OES) in conjunction with multivariate data analysis. Instead of relying on a theoretical model of the plasma emission to extract plasma parameters from the OES, an empirical correlation was established on the basis of simultaneous OES and other diagnostics. Additionally, we developed a machine learning (ML)-based virtual metrology model for real-time Te and ne monitoring in plasma nitridation processes using an in situ OES sensor. The results showed that the prediction accuracy of electron density was 97% and that of electron temperature was 90%. This method is especially useful in plasma processing because it provides in-situ and real-time analysis without disturbing the plasma or interfering with the process.

scholarly journals Diagnostics of low-pressure capacitively coupled RF discharge argon plasma

2019 ◽  
Vol 13 (27) ◽  
pp. 76-82
Author(s):  
Kadhim A. Aadim
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Langmuir Probe ◽  
Gas Flow ◽  
Low Pressure ◽  
Gas Pressure ◽  
Rf Discharge ◽  
Electrode Gap ◽  
Probe Characteristic ◽  
Capacitively Coupled

Low-pressure capacitively coupled RF discharge Ar plasma has been studied using Langmuir probe. The electron temperature, electron density and Debay length were calculated under different pressures and electrode gap. In this work the RF Langmuir probe is designed using 4MHz filter as compensation circuit and I-V probe characteristic have been investigated. The pressure varied from 0.07 mbar to 0.1 mbar while electrode gap varied from 2-5 cm. The plasma was generated using power supply at 4MHz frequency with power 300 W. The flowmeter is used to control Argon gas flow in the range of 600 standard cubic centimeters per minute (sccm). The electron temperature drops slowly with pressure and it's gradually decreased when expanding the electrode gap. As the gas pressure increases, the plasma density rises slightly at low gas pressure while it drops little at higher gas pressure. The electron density decreases rapidly with expand distances between electrodes.

scholarly journals Study of the Propagation Characteristics of Terahertz Waves in a Collisional and Inhomogeneous Dusty Plasma with a Ceramic Substrate and Oblique Angle of Incidence

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qingwen Rao ◽  
Guanjun Xu ◽  
Pengfei Wang ◽  
Zhengqi Zheng
Keyword(s):  
Electron Density ◽  
Dusty Plasma ◽  
Collision Frequency ◽  
Incident Angle ◽  
Ceramic Substrate ◽  
Dust Particles ◽  
Angle Of Incidence ◽  
Oblique Angle ◽  
Terahertz Waves ◽  
Thz Wave

In this paper, the propagation properties of a terahertz (THz) wave in a collisional and inhomogeneous dusty plasma with a ceramic substrate and oblique angle of incidence are studied using the scattering matrix method. The influence of the various corresponding parameters, such as the frequency of the THz wave, angle of incidence, electron density, radius and density of the dust particles, and the collision frequency, on the absorbance and transmittance is calculated. The results of the simulation indicate that an increase in the wave frequency increases the transmittance and decreases the absorbance. Moreover, the absorbance of a THz wave in a dusty plasma with a ceramic substrate increases with an increase in the incident angle, maximum electron density, coefficient of steepness, density and radius of the dust particles, and collision frequency. These results provide an important theoretical basis for the problem of communication blackout between ground and spacecraft.

Sign in / Sign up

Export Citation Format

Share Document