Hot Ions Research Articles

Solitary dispersive Alfvén wave in a plasma composed of hot positrons, cold electrons and ions

The nonlinear solitary structure of the dispersive Alfvén wave in an three-component plasma with hot positron, cold electron and ion is studied from the multi-fluid theory. It is found that when the equilibrium number density ratio of ion to electron is finite, there only exists the super-Alfvén rarefactive solitons. The increase of the ion concentration or the speed of soliton will lead a deeper depletion of the electron number density. The width of soliton decreases with the increase of the speed of soliton and the ion concentration. When the equilibrium number density ratio of ion to electron is much less than unity, there are only sub-Alfvén rarefactive solitons. In the case, the larger speed of soliton or the smaller concentration of ions result the deeper depletion of the electron number density. The width of the soliton increases with the ion concentration and the speed of soliton. The results obtained may be related to the observations and experimental results in the electron positron plasma.

Evening corotating patches (ECP) observed by DMSP/SSUSI

Evening corotating patches (ECP) are a special type of aurora, which occur at subauroral latitude. In the present work we have used the images observed by DMSP/SSUSI instruments to investigate the ECP in a global perspective. This study indicates that the ECP occur in the recovery phase of magnetic storms. The ECP were observed between 58° and 68° magnetic latitude (MLAT) in the evening sector between 16:00 and 20:00 magnetic local time (MLT). The ECP cororate with the Earth but they occur at same MLAT, this suggest that the source region related to ECP is inside the plasmasphere. Particle observations indicate that ECP are produced by energetic ions with energies above ∼20 keV, without much electron precipitations. We argue that the energetic ions producing ECP originates from the ring current, which is assumed to be filled with hot ions during the recovery phase of magnetic storms.

The new exact solitary wave solutions and stability analysis for the (2+1)-dimensional Zakharov\u2013Kuznetsov equation

In this paper, a new generalized exponential rational function method is employed to extract new solitary wave solutions for the Zakharov–Kuznetsov equation (ZKE). The ZKE exhibits the behavior of weakly nonlinear ion-acoustic waves in incorporated hot isothermal electrons and cold ions in the presence of a uniform magnetic field. Furthermore, the stability for the governing equations is investigated via the aspect of linear stability analysis. Numerical simulations are made to shed light on the characteristics of the obtained solutions.

Comment on ‘Electron acoustic super solitary waves in a magnetized plasma’, J. Plasma Phys. 84, 905840406 (2018)

The plasma model used in a recent paper by Kamalam et al. (J. Plasma Phys., vol. 84, 2018, 905840406) assumes a Boltzmann description for two hot ion species, in the presence of two adiabatic (fluid) electron species, for the study of obliquely propagating acoustic-type nonlinear solitary waves with respect to a static magnetic field. We argue that the assumption of Boltzmann distributions for the hot ions is incorrect, thus invalidating their conclusions, in particular about the possible occurrence of supersolitons in magnetized plasmas.

Kinetic Alfvén waves generated by ion beam and velocity shear in the Earth's magnetosphere

Generation of Kinetic Alfvén Waves (KAWs) in a generalized three component plasma model consisting of the background cold ions, hot electrons, and hot ion beams, where all the three species have non-uniform streaming and velocity shear, is discussed. First, the role played by the ion beam solely in exciting KAWs is analyzed. Next, how this behavior gets modified when the velocity shear is present along with the streaming ion beam is discussed. The effects of other parameters such as temperature, number density, and propagation angle on the growth of KAWs are explored. It is found that when shear is positive and ions are streaming along the ambient magnetic field, KAWs are stabilized. On the other hand, with positive shear and an anti-parallel ion beam or vice-versa, KAWs with a larger growth rate are excited as compared to the case of waves excited by the ion beam alone. Also, for the first time, we have shown the combined effect of the ion beam and velocity shear on the generation of KAWs. The theoretical model can generate ultra-low frequency waves with frequencies up to ≈60 mHz for the plasma parameters relevant to auroral/polar cusp field lines.

Effect of hot dip galvanizing on the fatigue behavior of hot rolled and ion nitrided AISI 4340 steel

In this study, the effects of hot dip galvanizing on the fatigue strength of raw AISI 4340 and ion nitrided AISI 4340 steel in laboratory air atmosphere were studied. While the galvanizing process was applied at 451 °C for 1 min, the ion nitriding process was applied at 500 °C for 2 h using NH3 gas. It is known that hot dip galvanizing reduces the fatigue strength in steels. While the reduction in fatigue strength after galvanization was 36.7% in the hot rolled AISI 4340 steel, it was reduced to 7% when hot dip galvanizing was applied to the ion nitrided AISI 4340 steel. The use of ion nitriding before hot dip galvanizing has limited the decrease in fatigue strength caused by galvanizing. On all ion nitrided specimens, both hot dip galvanized and not, fatigue crack initiation was moved towards to core thus increasing the fatigue strength.

A Statistical Study of EMIC Waves Associated With and Without Energetic Particle Injection From the Magnetotail

AbstractTo understand the relationship between generation of electromagnetic ion cyclotron (EMIC) waves and energetic particle injections, we performed a statistical study of EMIC waves associated with and without injections based on the Van Allen Probes (Radiation Belt Storm Probes) and Geostationary Operational Environmental Satellite (GOES; GOES‐13 and GOES‐15) observations. Using 47 months of observations, we identified wave events seen by the Van Allen Probes relative to the plasmapause and to energetic particle injections seen by GOES‐13 and GOES‐15 on the nightside. We separated the events into four categories: EMIC waves with (without) injections inside (outside) the plasmasphere. We found that He+ EMIC waves have higher occurrence rate inside the plasmasphere, while H+ EMIC waves predominantly occur outside the plasmasphere. Meanwhile, the time duration and peak occurrence rate of EMIC waves associated with injections are shorter and limited to a narrower magnetic local time region than those without injections, indicating that these waves have localized source regions. He+ EMIC waves inside the plasmasphere associated with injection are usually accompanied by an increase in H+ flux within energies of 1–50 keV through all magnetic local time regions, while most wave events outside the plasmasphere show less relationship with H+ flux increase. From these observations, we suggest that injected hot ions are the major driver of He+ EMIC waves inside the plasmasphere during active time. Expanding plasmasphere during quiet times can provide broad wave source regions for He+ EMIC waves on the dayside. However, H+ EMIC waves outside the plasmasphere show different characteristics, suggesting that these waves are generated by other processes.

Hall Effect in Laboratory and Space Current Sheets

The role of the Hall effect in the formation of thin current sheets (CSs) is analyzed by comparing results of laboratory and satellite experiments. In spite of the strong difference in the plasma parameters, both laboratory and space CSs are characterized by the hot ion component and cold isotropic electron component. Such a relation between the ion and electron components would have to guarantee the predominant contribution of the ion diamagnetic drift current to the total current density. However, the Cluster spacecraft observations of thin CSs in the Earth’s magnetotail have revealed the predominance of a strong electron (rather than ion) current. This may be due to the Hall effect, which causes generation of electric fields, which redistribute the CS currents in favor of the electron currents at the expense of the ion currents. Observations demonstrate that the thinner the CS, the stronger this effect. A similar tendency was also observed in laboratory experiments on CS formation in plasma with ions of different mass, which made it possible to vary the CS relative thickness and monitor the consequences of the Hall effect. Comparison of results of satellite and laboratory experiments indicates that the Hall effect plays an important role in the formation of thin CSs in both magnetospheric and laboratory plasmas.

Collisionless relaxation of the ion ring distribution in space plasma

Energetic processes often produce transversely-heated angular distributions of the magnetized core (lowest energy) plasma. This characteristic is found in solar wind ion pickup, resulting from cometary or interstellar gas ionization, in Earths’ ionosphere, and with hot ions formed around the Space Transportation System during gas releases. We investigate the thermalization of O+ ion pickup using the 2.5D hybrid simulation method (with fluid electrons and kinetic ions) of the ion pickup (ring) distributions, formed in the auroral ionosphere, with a range of ring velocities and thermal to magnetic pressure ratios. We find that in the unstable collisonless regime the anisotropy of the non-thermal distribution produces the ion-cyclotron instability, and the nonlinear relaxation is accompanied by wave-particle scattering that results in an emitted power of EMIC waves. We conclude that ionospheric pickup thermalization is slow due to the small ring speed compared to the thermal and Alfvén speeds, while in the solar wind and other space plasmas regions with larger ion-ring velocity the collisionless relaxation and thermalization is rapid in terms of O+ ion gyro-period.

Magnetotail Hall Physics in the Presence of Cold Ions

AbstractWe present the first in situ observation of cold ionospheric ions modifying the Hall physics of magnetotail reconnection. While in the tail lobe, Magnetospheric Multiscale mission observed cold (tens of eV) E × B drifting ions. As Magnetospheric Multiscale mission crossed the separatrix of a reconnection exhaust, both cold lobe ions and hot (keV) ions were observed. During the closest approach of the neutral sheet, the cold ions accounted for ∼30% of the total ion density. Approximately 65% of the initial cold ions remained cold enough to stay magnetized. The Hall electric field was mainly supported by the j × B term of the generalized Ohm's law, with significant contributions from the ∇·Pe and vc×B terms. The results show that cold ions can play an important role in modifying the Hall physics of magnetic reconnection even well inside the plasma sheet. This indicates that modeling magnetic reconnection may benefit from including multiscale Hall physics.

Analytic Representation for Parallel Flow of Hot Ions Produced by Tangential Neutral Beam Injection

Analytic Representation for Parallel Flow of Hot Ions Produced by Tangential Neutral Beam Injection

Laser spectroscopy of the 1001-nm ground-state transition in dysprosium

We present the first direct excitation of the presumably ultra-narrow $1001 \, \textrm{nm}$ ground state transition in atomic dysproium. By using resonance ionization spectroscopy with pulsed Ti:sapphire lasers at a hot cavity laser ion source, we were able to measure the isotopic shifts in the $1001 \, \textrm{nm}$ line between all seven stable isotopes. Furthermore, we determined the upper level energy from the atomic transition frequency of the $^{164} \textrm{Dy}$ isotope as $9991.004(1) \, \textrm{cm}^{-1}$ and confirm the level energy listed in the NIST database. Since a sufficiently narrow natural linewidth is an essential prerequisite for high precision spectroscopic investigations for fundamental questions we furthermore determined a lower limit of $2.9(1) \, \mu\textrm{s}$ for the lifetime of the excited state.

Wavelength dependence of laser plasma interaction related to shock ignition approach

AbstractThis paper provides a summary of recent research connected with the shock ignition (SI) concept of the inertial confinement fusion which was carried out at PALS. In the experiments, Cu planar targets coated with a thin CH layer were used. Two-beam irradiation experiment was applied to investigate the effect of preliminary produced plasma to shock-wave generation. The 1ω or 3ω main beam with a high intensity >1015W/cm2generates shock wave, while the other 1ω beam with the intensity below 1014W/cm2creates CH pre-plasma simulating the pre-compressed plasma related to SI. Influence of laser wavelength on absorbed energy transfer to shock wave was studied by means of femtosecond interferometry and measuring the crater volume. To characterize the hot electron and ion emission, two-dimensional (2D) Kα-imaging of Cu plasma and grid collector measurements were used. In single 1ω beam experiments energy transport by fast electrons produced by resonant absorption made a significant contribution to shock-wave pressure. However, two-beam experiments with 1ω main beam show that the pre-plasma is strongly degrading the scalelength which leads to decreasing the fast electron energy contribution to shock pressure. In both the single 3ω beam experiments and the two-beam experiments with the 3ω main beam, do not show any clear influence of fast electron transport on shock-wave pressure. The non-monotonic behavior of the scalelength at changing the laser beam focal radius in both presence and absence of pre-plasma reflects the competition of plasma motion and electron heat conduction under the conditions of one-dimensional and 2D plasma expansion at large and small focal radii, respectively.

Isotopic effect in microstability of electrostatic oscillations in magnetic mirror traps

It has been long known that Drift-Cyclotron Loss-Cone (DCLC) and Double-Humped (DH) oscillations can be unstable in a mirror trap because of the presence of an empty loss cone in the distribution of hot ions and that the instability can be suppressed by the addition of a small amount of warm ions with isotropic distribution. Unfortunately, previous analyses have been limited almost exclusively to the case when the populations of both hot and warm ions consist of the same single isotope. In the present paper, we studied the stability of DCLC and DH modes in a multispecies plasma with two different isotopes of hydrogen confined in a mirror trap. We found that both DCLC and DH microinstabilities can be suppressed by the addition of warm ions with isotropic Maxwellian distribution provided that the concentrations of different isotopes in the warm ion population are proportional to those in the population of hot ions. We came to the conclusion that overlapping of the full set of cyclotron harmonics of hot ions by the set of cyclotron harmonics of the warm ion mixture is essential for effective suppressing of the instability of DCLC and DH modes.

Phonon Lasing from Optical Frequency Comb Illumination of Trapped Ions.

We demonstrate the use of a frequency-doubled optical frequency comb to load, cool, and crystallize trapped atomic ions as an alternative to ultraviolet (UV) or even deep UV continuous-wave lasers. We find that the Doppler shift from the atom's oscillation in the trap, driven by the blue-detuned comb teeth, introduces additional cooling and amplification which gives rise to steady-state phonon lasing of the ion's harmonic motion in the trap. The phonon laser's gain saturation keeps the optical frequency comb from continually adding energy without bound. This protection allows us to demonstrate loading and crystallization of hot ions directly with the comb, eliminating the need for a continuous-wave cooling laser, a technique that is extendable to the deep UV.

Non-resonant Alfvénic instability activated by high temperature of ion beams in compensated-current astrophysical plasmas

Context. Compensated-current systems are established in response to hot ion beams in terrestrial foreshock regions, around supernova remnants, and in other space and astrophysical plasmas. Aims. We study a non-resonant reactive instability of Alfvén waves propagating quasi-parallel to the background magnetic field B0 in such systems. Methods. The instability is investigated analytically in the framework of kinetic theory applied to the hydrogen plasmas penetrated by hot proton beams. Results. The instability arises at parallel wavenumbers kz that are sufficiently large to demagnetize the beam ions, kzVTb/ωBi ≳ 1 (here VTb is the beam thermal speed along B0 and ωBi is the ion-cyclotron frequency). The Alfvén mode is then made unstable by the imbalance of perturbed currents carried by the magnetized background electrons and partially demagnetized beam ions. The destabilizing effects of the beam temperature and the temperature dependence of the instability threshold and growth rate are demonstrated for the first time. The beam temperature, density, and bulk speed are all destabilizing and can be combined in a single destabilizing factor αb triggering the instability at αb > αbthr, where the threshold value varies in a narrow range 2.43 ≤ αbthr ≤ 4.87. New analytical expressions for the instability growth rate and its boundary in the parameter space are obtained and can be directly compared with observations. Two applications to terrestrial foreshocks and foreshocks around supernova remnants are briefly discussed. In particular, our results suggest that the ions reflected by the shocks around supernova remnants can drive stronger instability than the cosmic rays.

Long-Term Monitoring of the Internal Energy Distribution of Isolated Cluster Systems.

A method is presented to monitor the internal energy distribution of cluster anions via delayed electron detachment by pulsed photoexcitation and demonstrated on Co_{4}^{-} in an electrostatic ion beam trap. In a cryogenic operation, we calibrate the detachment delay to internal energy. By laser frequency scans, at room temperature, we reconstruct the time-dependent internal energy distribution of the clusters. The mean energies of ensembles from a cold and a hot ion source both approach thermal equilibrium. Our data yield a radiative emission law and the absorptivity of the cluster for thermal radiation.

Geodesic mode instability driven during ion cyclotron heating in tokamaks

The effect of a minor concentration of energetic particles produced by ion cyclotron resonance (ICR) heating on the stability of Geodesic Acoustic Modes (GAM) is studied using fully drift kinetic equation. Assuming the ICR layer position on the high field side of the tokamak magnetic axis, a minority ion distribution is modeled by the energetic ion tail and “triangle”-like pitch angle distribution with the maximum at the trapped-passing ion boundary. The resulting GAM instability is found when the hot ion thermal velocity is larger than the effective parallel GAM phase velocity Rqω and the geodesic frequency has the order of the energetic ion bounce frequency. The standard GAM frequency may be strongly reduced by some small concentration of the energetic ions allowing the mode to be unstable. Respective neoclassical polarization corrections (residual flow) driven by energetic ions are found to be negative and larger than that calculated by Rosenbluth and Hinton [Phys. Rev. Lett. 80, 724 (1998)]. Qualitative comparison of the theory with ICR heating experiments in tokamak is discussed.

Dust acoustic shock waves in magnetized dusty plasma

We have presented a theoretical study of the dust acoustic (DA) shock structures in a magnetized, electron depleted dusty plasma in the presence of two temperature superthermal ions. By deriving a Korteweg–de Vries–Burgers equation and studying its shock solution, we aim to highlight the effects of magnetic field and obliqueness on various properties of the DA shock structures in the presence of kappa-distributed two temperature ion population. The present model is motivated by the observations of Geotail spacecraft in the Earth's magnetotail and it is seen that the different physical parameters such as superthermality of the cold and hot ions, the cold to hot ion temperature ratio, the magnetic field strength, obliqueness and the dust kinematic viscosity greatly influence the dynamics of the shock structures so formed. The results suggest that the variation of superthermalities of the cold and hot ions have contrasting effects on both positive and negative polarity shock structures. Moreover, it is noted that the presence of the ambient magnetic field affects the dispersive properties of the medium and tends to make the shock structures less wide and more abrupt. The findings of present investigation may be useful in understanding the dynamics of shock waves in dusty plasma environments containing two temperature ions where the electrons are significantly depleted.

The Detached Auroras Induced by the Solar Wind Pressure Enhancement in Both Hemispheres From Imaging and In Situ Particle Observations

AbstractThis paper presents simultaneous detached proton auroras that appeared in both hemispheres at 11:06 UT, 08 March 2012, just 2 min after a sudden solar wind pressure enhancement (~11:04 UT) hit the Earth. They were observed under northward interplanetary magnetic field Bz condition and during the recovery phase of a moderate geomagnetic storm. In the Northern Hemisphere, Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observed that the detached arc occurred within 60°–65° magnetic latitude and covered a few magnetic local time (MLT) hours ranging from 0530 to 0830 MLT with a possible extension toward noon. At the same time (11:06 UT), Polar Orbiting Environment Satellites 19 detected a detached proton aurora around 1300 MLT in the Southern Hemisphere, centering ~62° magnetic latitude, which was at the same latitudes as the northern detached arc. This southern aurora was most probably a part of a dayside detached arc that was conjugate to the northern one. In situ particle observations indicated that the detached auroras were dominated by protons/ions with energies ranging from around 20 keV to several hundreds of keV, without obvious electron precipitations. These detached arcs persisted for less than 6 min, consistent with the impact from pressure enhancement and the observed electromagnetic ion cyclotron (EMIC) waves. It is suggested that the increasing solar wind pressure pushed the hot ions in the ring current closer to Earth where the steep gradient of cold plasma favored EMIC wave growth. By losing energy to EMIC waves the energetic protons (>20 keV) were scattered into the loss cone and produced the observed detached proton auroras.