scholarly journals Negative ions in the auroral mesosphere during a PCA event around sunset

1999 ◽  
Vol 17 (6) ◽  
pp. 782-793 ◽  
Author(s):  
C. F. del Pozo ◽  
E. Turunen ◽  
T. Ulich
Keyword(s):  
Electron Density ◽  
Negative Ions ◽  
Spectral Width ◽  
High Energy ◽  
Negative Ion ◽  
Ion Temperature ◽  
Ion Chemistry ◽  
Ion Chemistry And Composition ◽  
Proton Precipitation ◽  
Precipitation Events

Abstract. This is a study of the negative ion chemistry in the mesosphere above Tromsø using a number of EISCAT observations of high energy proton precipitation events during the last solar maximum, and in particular around sunset on 23 October, 1989. In these conditions it is possible to look at the relative importance of the various photodetachment and photodissociation processes controlling the concentration of negative ions. The data analysed are from several UHF GEN11 determinations of the ion-plasma ACF together with the pseudo zero-lag estimate of the `raw' electron density, at heights between 55 km and 85 km, at less than 1 km resolution. The power profiles from the UHF are combined with the 55-ion Sodankylä model to obtain consistent estimates of the electron density, the negative ion concentrations, and the average ion mass with height. The neutral concentrations and ion temperature are given by the MSIS90 model. These parameters are then used to compare the calculated widths of the ion-line with the GEN11 determinations. The ion-line spectrum gives information on the effects of negative ions below 70 km where they are dominant; the spectral width is almost a direct measure of the relative abundance of negative ions.Key words. Ionosphere (auroral ionosphere; ion chemistry and composition; particle precipitation).

Solitary Wave with Quantisation of Electron’s Orbit in a Magnetised Plasma in the Presence of Heavy Negative Ions

2020 ◽  
Vol 75 (3) ◽  
pp. 211-223 ◽  
Author(s):  
Manoj Kr. Deka ◽  
Apul N. Dev
Keyword(s):  
Magnetic Field ◽  
Solitary Wave ◽  
Electron Density ◽  
Maximum Amplitude ◽  
Negative Ions ◽  
Ion Concentration ◽  
Negative Ion ◽  
Maximum Height ◽  
Degenerate Plasma ◽  
Analytical Scheme

AbstractThe propagation characteristics of solitary wave in a degenerate plasma in the presence of Landau-quantised magnetic field and heavy negative ion are studied. The nature of solitary wave in such plasma under the influence of magnetic quantisation and the concentration of both electrons and negative ions, as well as in the presence of degenerate temperature, are studied with the help of a time-independent analytical scheme of the solution of Zakharov–Kuznetsov equation. The electron density, as well as the magnetic quantisation parameter, has an outstanding effect on the features of solitary wave proliferation in such plasma. Interestingly, for any fixed electron density, the magnetic quantisation parameter has an equal control on the maximum height and dispersive properties of the solitary wave. Toward higher temperatures and higher magnetic fields, the width of the solitary wave decreases. For a lower magnetic field, the maximum amplitude of the solitary wave decreases rapidly at higher values of degenerate temperature and negative ion concentration; however, at a lower value of degenerate temperature, the maximum amplitude increases with increasing negative ion concentration.

scholarly journals Sunset transition of negative charge in the D-region ionosphere during high-ionization conditions

2006 ◽  
Vol 24 (1) ◽  
pp. 187-202 ◽  
Author(s):  
P. T. Verronen ◽  
Th. Ulich ◽  
E. Turunen ◽  
C. J. Rodger
Keyword(s):  
Nitric Oxide ◽  
Negative Charge ◽  
Negative Ions ◽  
Solar Proton ◽  
Negative Ion ◽  
Proton Event ◽  
Minor Role ◽  
Cosmic Radio ◽  
Ion Chemistry ◽  
Visible Wavelengths

Abstract. The solar proton event of October 1989 and especially the sunset of 23 October is examined in this study of negative ion chemistry, which combines measurements of nitric oxide, electron density, and cosmic radio noise absorption with ion and neutral chemistry modelling. Model results show that the negative charge transition from electrons to negative ions during sunset occurs at altitudes below 80 km and is dependent on both ultraviolet and visible solar radiation. The ultraviolet effect is mostly due to rapid changes in atomic oxygen and O2(1Δg), while the decrease in NO3- photodetachment plays a minor role. The effect driven by visible wavelengths is due to changes in photodissociation of CO3- and the subsequent electron photodetachment from O-, and at higher altitudes is also due to a decrease in the photodetachment of O2-. The relative sizes of the ultraviolet and visible effects vary with altitude, with the visible effects increasing in importance at higher altitudes, and they are also controlled by the nitric oxide concentration. These modelling results are in good agreement with EISCAT incoherent scatter radar and Kilpisjärvi riometer measurements.

scholarly journals Effect of DC Biased Voltage and Ion Temperature on Bounded Ion-Ion Plasma

2020 ◽  
Vol 25 (1) ◽  
pp. 61-67
Author(s):  
Anish Maskey ◽  
Atit Deuja ◽  
Suresh Basnet ◽  
Raju Khanal
Keyword(s):  
Electric Field ◽  
Strong Electric Field ◽  
Negative Ions ◽  
Simulation Method ◽  
Negative Ion ◽  
Ion Temperature ◽  
Plasma Parameters ◽  
Degree Of Ionization ◽  
Particle In Cell ◽  
Ion Plasma

 A one dimensional particle-in-cell (PIC) simulation method has been employed to study the effect of DC voltage and ion temperature on the properties of ion-ion plasma bounded by two symmetrical but oppositely biased electrodes. It is assumed that the ion-ion plasma is collisionless and both the positive and negative ion species have the same mass, temperature, and degree of ionization. Simulation results show that the formation of sheath and presheath regions and fluctuation of plasma parameters in that region are affected by the biasing voltage and ion temperature. It was found that the magnitude of the electrostatic electric field at the vicinity of biasing electrodes was affected by the biasing voltage and ion temperature as well. This strong electric field close to the electrodes further prevents the flow of charged particles towards the electrodes. The presence of a non-zero electric field at the quasineutral region suggests a presheath region similar to the electron-ion plasma. In the quasineutral region, the density of ions increased with the increase in biasing voltage and decreased with the increase in temperature of isothermal ions. Furthermore, the phase space diagrams for the ions were obtained which indicated different regions of the plasma. The positive ions acquire negative velocity towards the negatively biased electrode and the negative ions acquire positive velocity towards the positively biased electrode.

The Boltzmann relation in electronegative plasmas: When is it permissible to use it?

2000 ◽  
Vol 64 (2) ◽  
pp. 131-153 ◽  
Author(s):  
R. N. FRANKLIN ◽  
J. SNELL
Keyword(s):  
Fluid Model ◽  
Negative Ions ◽  
Ionization Rate ◽  
Negative Ion ◽  
Simple Relationship ◽  
Ion Temperature ◽  
Ion Density ◽  
Positive Ions ◽  
Electronegative Plasmas ◽  
Low Pressures

This paper reports the results of computations to obtain the spatial distributions of the charged particles in a bounded active plasma dominated by negative ions. Using the fluid model with a constant collision frequency for electrons, positive ions and negative ions the cases of both detachment-dominated gases (such as oxygen) and recombination-dominated gases (such as chlorine) are examined. It is concluded that it is valid to use a Boltzmann relation ne = ne0exp(eV/kT) for the electrons of density ne, where the temperature T is approximately the electron temperature Te, and that the density nn of the negative ions at low pressures obeys nn = nn0exp(eV/kTn), where Tn is the negative-ion temperature. However, at high pressure in detachment-dominated gases where the ratio of negative-ion density to electron density is constant and greater than unity, and when the attachment rate is larger than the ionization rate, the negative ions are distributed with the same effective temperature as the electrons. In all other cases there is no simple relationship. Thus to put nn/ne = const, nn = ne0exp(eV/kTe) and nn = nn0exp(eV/kTn) simultaneously is mathematically inconsistent and physically unsound. Accordingly, expressions deduced for ambipolar diffusion coefficients based on these assumptions have no validity. The correct expressions for the situation where nn/ne = const are obtained without invoking a Boltzmann relation for the negative ions.

Linear and nonlinear obliquely propagating ion-acoustic waves in magnetized negative ion plasma with non-thermal electrons

2013 ◽  
Vol 79 (5) ◽  
pp. 893-908 ◽  
Author(s):  
M. K. MISHRA ◽  
S. K. JAIN
Keyword(s):  
Acoustic Waves ◽  
Kdv Equation ◽  
Negative Ions ◽  
Ion Concentration ◽  
Negative Ion ◽  
Slow Mode ◽  
Ion Temperature ◽  
Ion Acoustic ◽  
Ion Acoustic Solitons ◽  
Ion Species

AbstractIon-acoustic solitons in magnetized low-β plasma consisting of warm adiabatic positive and negative ions and non-thermal electrons have been studied. The reductive perturbation method is used to derive the Korteweg–de Vries (KdV) equation for the system, which admits an obliquely propagating soliton solution. It is found that due to the presence of finite ion temperature there exist two modes of propagation, namely fast and slow ion-acoustic modes. In the case of slow-mode if the ratio of temperature to mass of positive ion species is lower (higher) than the negative ion species, then there exist compressive (rarefactive) ion-acoustic solitons. It is also found that in the case of slow mode, on increasing the non-thermal parameter (γ) the amplitude of the compressive (rarefactive) soliton decreases (increases). In fast ion-acoustic mode the nature and characteristics of solitons depend on negative ion concentration. Numerical investigation in case of fast mode reveals that on increasing γ, the amplitude of compressive (rarefactive) soliton increases (decreases). The width of solitons increases with an increase in non-thermal parameters in both the modes for compressive as well as rarefactive solitons. There exists a value of critical negative ion concentration (αc), at which both compressive and rarefactive ion-acoustic solitons appear as described by modified KdV soliton. The value of αc decreases with increase in γ.

scholarly journals The role of atomic oxygen concentration in the ionization balance of the lower ionosphere during solar proton events

2008 ◽  
Vol 26 (1) ◽  
pp. 131-143 ◽  
Author(s):  
A. Osepian ◽  
V. Tereschenko ◽  
P. Dalin ◽  
S. Kirkwood
Keyword(s):  
Electron Density ◽  
Oxygen Concentration ◽  
Atomic Oxygen ◽  
Negative Ions ◽  
Solar Proton ◽  
Negative Ion ◽  
Proton Event ◽  
Density Profiles ◽  
Oxygen Profile ◽  
Atomic Oxygen Concentration

Abstract. The influence of atomic oxygen concentration on the height distribution of the main positive and negative ions and on electron density in the mesosphere is studied for the conditions prevailing during the solar proton event on 17 January 2005. It is shown by numerical modeling that the electron and ion density profiles are strongly dependent on the choice of the atomic oxygen profile. Experimental measurements of the electron density are used as the criterion for choosing the atomic oxygen profile in the mesosphere. With the help of modeling, the atomic oxygen profile in the daytime in the winter mesosphere is found to lead to a model electron density profile best matching the electron density profile obtained experimentally. As a result, with the help of modeling, we find the atomic oxygen profiles at various solar zenith angles in the winter mesosphere which lead to model electron density profiles matching the electron density profiles obtained experimentally. Alteration of the atomic oxygen concentration leads to a redistribution of the abundance of both positive and negative ion constituents, with changes in their total concentrations and transition heights. In consequence this results in changes of the electron density and effective recombination coefficient. For conditions of low concentration of atomic oxygen (during a solar proton event), the formation of cluster ions is the key process determining electron and ion densities at altitudes up to 77 km. The complex negative CO3− ion is formed up to about 74 km and the final NO3− ion, which is stable in relation to the atomic oxygen, is the dominant negative ion up to 74 km. As a result the transition heights between cluster ions and molecular ions and between negative ions and electron density are located at 77 km and 66 km, respectively.

Hybrid simulation of instabilities in capacitively coupled RF CF4/Ar plasmas

2022 ◽  
Author(s):  
Wan Dong ◽  
Yi Fan Zhang ◽  
ZhongLing Dai ◽  
Julian Schulze ◽  
Yuan-Hong Song ◽  
...  
Keyword(s):  
Electric Field ◽  
Electron Temperature ◽  
Electron Impact ◽  
Electron Density ◽  
Etching Rate ◽  
Reaction Rates ◽  
High Energy ◽  
Density Fluctuations ◽  
Negative Ion ◽  
Capacitively Coupled

Abstract Radio frequency capacitively coupled plasmas (RF CCPs) sustained in fluorocarbon gases or their mixtures with argon are widely used in plasma-enhanced etching. In this work, we conduct studies on instabilities in a capacitive CF4/Ar (1:9) plasma driven at 13.56 MHz at a pressure of 150 mTorr, by using a one-dimensional fluid/Monte-Carlo (MC) hybrid model. Fluctuations are observed in densities and fluxes of charged particles, electric field, as well as electron impact reaction rates, especially in the bulk. As the gap distance between the electrodes increases from 2.8 cm to 3.8 cm, the fluctuation amplitudes become smaller gradually and the instability period gets longer, as the driving power density ranges from 250 to 300 W/m2. The instabilities are on a time scale of 16-20 RF periods, much shorter than those millisecond periodic instabilities observed experimentally owing to attachment/detachment in electronegative plasmas. At smaller electrode gap, a positive feedback to the instability generation is induced by the enhanced bulk electric field in the highly electronegative mode, by which the electron temperature keeps strongly oscillating. Electrons at high energy are mostly consumed by ionization rather than attachment process, making the electron density increase and overshoot to a much higher value. And then, the discharge becomes weakly electronegative and the bulk electric field becomes weak gradually, resulting in the continuous decrease of the electron density as the electron temperature keeps at a much lower mean value. Until the electron density attains its minimum value again, the instability cycle is formed. The ionization of Ar metastables and dissociative attachment of CF4 are noticed to play minor roles compared with the Ar ionization and excitation at this stage in this mixture discharge. The variations of electron outflow from and negative ion inflow to the discharge center need to be taken into account in the electron density fluctuations, apart from the corresponding electron impact reaction rates. We also notice more than 20% change of the Ar+ ion flux to the powered electrode and about 16% difference in the etching rate due to the instabilities in the case of 2.8 cm gap distance, which is worthy of more attention for improvement of etching technology.

Negative chlorine ion chemistry in the upper stratosphere and its application to an artificially created dense electron cloud

1995 ◽  
Vol 13 (3) ◽  
pp. 296-304 ◽  
Author(s):  
S. S. Prasad
Keyword(s):  
Major Ions ◽  
Negative Ions ◽  
Electron Cloud ◽  
Negative Ion ◽  
Cluster Ions ◽  
Aerosol Formation ◽  
Ion Chemistry ◽  
Catalytic Destruction ◽  
Three Body ◽  
Chlorine Ion

Abstract. This paper discusses new potential reactions of chlorine-bearing anions (negative ions) in the upper stratosphere. These reactions are then applied to the negative-ion chemistry following the injection of an electron cloud of very high density, of the order of 106-107 e- cm-3, in the 40-45-km region. The idea is to evaluate the recently proposed scheme to mitigate ozone depletion by converting the reactive chlorine atoms at these altitudes into Cl- ions which are unreactive towards ozone, i.e., electron scavenging of Cl. We find that the previously neglected photodetachment from Cl- is fast. For an overhead sun, this process may have a rate coefficient of 0.08 s-1 when multiple scattering is included. The rate could be even higher, depending on the ground albedo. Switching reaction between Cl-·H2O and HCl might lead to the formation of Cl-·HCl anion. Possible reactions of Cl-·H2O and Cl-·HCl with O atoms could produce ClO- and Cl-2. The production of ClO- in this manner is significant because Cl- having a high photodetachment rate constant would be regenerated in the very likely reactions of ClO- with O. When these possibilities are considered, then it is found that the chlorine anions may not be the major ions inside the electron cloud due to the rapid photodetachment from Cl-. Furthermore, in such a cloud, there may be the hazard that the Cl--Cl-·H2O-ClO--Cl- cycle amounts to catalytic destruction of two O atoms. Thus, the scheme could be risky if practised in the altitude region where atomic oxygen is an important constituent. Similar conclusions apply even if the ClO- species forms ClO-3 by three-body association with O2, instead of reacting with O. It must be emphasized that the present study is speculative at this time, because none of the relevant reactions have been investigated in the laboratory as yet. Nevertheless, it is very safe to say that the scheme of ozone preservation by electron scavenging of the upper stratospheric Cl is much less certain than implied in the studies reported by its original proponents, because those studies neglected the photodetachment from Cl- and made the highly unlikely assumption that the Cl-·H2O anion neither photodissociates nor reacts any further. The situation at the lower altitudes could be even more complex due to the formation of large cluster ions and the ion-induced aerosol formation. The lower atmospheric situation, therefore, requires much more study. The uncertainties in the scavenging scheme due to the electrostatic repulsion in the cloud should also be addressed. Despite the uncertainties about its environmental engineering usefulness, the emerging technology for artificial creation of plasmas, with any desired density and charge in the stratosphere, could have significant pure scientific values in the studies of stratospheric ion chemistry and ion-induced aerosol formation. Such studies have perennially suffered from the extremely low densities of the naturally occurring plasma.

Hydrocarbon ions in fuel-rich, CH4–C2H2–O2 flames as a probe for the initiation of soot: interpretation of the ion chemistry

1982 ◽  
Vol 60 (22) ◽  
pp. 2766-2776 ◽  
Author(s):  
John M. Goodings ◽  
Scott D. Tanner ◽  
Diethard K. Bohme
Keyword(s):  
Charge Transfer ◽  
Proton Transfer ◽  
Reaction Zone ◽  
Negative Ions ◽  
Negative Ion ◽  
Ion Chemistry ◽  
Soot Precursors ◽  
Ion Profiles ◽  
Three Body ◽  
Positive Ion

The ion chemistry is discussed for fuel-rich, nearly sooting, methane–oxygen flames at atmospheric pressure with added acetylene. Different types of ion–molecule reactions, both positive and negative, which can contribute through chemical ionization (CI) processes are summarized including their dependence on temperature, pressure, and equivalence ratio [Formula: see text]. Extensive data were presented previously involving ion concentration profiles measured with a mass spectrometer as a function of distance along the axis of conical flames. An understanding of the dominant CI processes provides insight into the early chemical stage of soot formation associated with the flame reaction zone. The negative ion profiles show moderately unsaturated hydrocarbon ions upstream formed by proton transfer followed by progressive dehydrogenation; the highly unsaturated, carbonaceous ions observed downstream appear to arise by two- and three-body electron attachment, charge transfer, and H-atom stripping. The negative hydrocarbon ions can all be explained in terms of polyacetylene derivatives. The same build-up of carbonaceous species downstream is evident from the positive ion profiles. A major role is ascribed to proton transfer reactions with lesser contributions from charge transfer and ion–molecule condensation; three-body association is probably insignificant. Experiments with added acetylene indicate extensive fuel pyrolysis early in the reaction zone. There is no evidence that an ionic mechanism is dominant in forming soot precursors compared with neutral condensation reactions. Because of complexities in the positive ion chemistry, the negative ions appear to provide the more straightforward probe of the underlying neutral chemistry.

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