Active Plasma Experiment Research Articles

Overview of APEX Project Results

The APEX mother-daughter project (Active Plasma EXperiments) was launched into an elliptical polar orbit (440 –-- 3080 km) in December 1991. It consisted of the main Russian Interkosmos--25 (IK--25) satellite and the Czech MAGION--3 subsatellite, both with international scientific payloads. The mission used intensive modulated electron beam emissions and xenon plasma or neutral releases from the main satellite for studies of dynamic processes in the magnetosphere and upper ionosphere. Its main scientific objectives were to simulate an artificial aurora and to study optical and radio emissions from the aurora region, and to investigate the dynamics and relaxation of modulated electron and plasma jets, artificially injected into the ionospheric plasma. The experiments studied the Critical Ionization Velocity phenomenon and a diamagnetic cavity formation during the xenon releases, local and distant effects of the electron beam injection, spacecraft charging and potential balance, and plasma-wave interactions during the artificial emissions. Attempts were performed to utilize the modulated electron beam as an active transmitting antenna in the space. The theory of ballistic wave propagation across plasma barrier was tested in a joint active experiment with the Dushanbe ionospheric heater facility. In the paper, we give a short overview of the IK--25/MAGION--3 scientific instrumentation and methodology of experiments with artificial beam injections and we provide a review of the main APEX active experiments results, many of which have been published only in the Russian language so far. From a historical 25-years-long perspective, we try to put the results of the APEX experiments into the context of other active experiments in the space plasma.

Measurement of Energy Spectra of Ions during Space Experiment "Koltso" (The Ring) on Board International Space Station

Details of design and functionality of the device "Region" developed for control of active plasma experiment "Koltso" (the Ring) on board the International Space Station are specified. We consider the problem of enhancing measurement accuracy on the basis of reducing influence of factors of space medium, in particular, variation of temperature regimes. For its resolving, the authors suggest the method of thermofunctional hypermodeling. Results of application of the method are considered.

Transformation of Space‐Charge Wave to Electromagnetic Wave in Active Space Experiments

AbstractIn this paper, we analyze the transformation from the space‐charge wave into the electromagnetic wave when electron beams pass through the concentration step of cold anisotropic plasma along the geomagnetic field. We focus our analysis on several typical conditions such as weak magnetic field approximation, whistler wave excitation, and low frequency approximation. We first derive the dispersion relation and the wave number of the space‐charge wave under small signal assumption, and then calculate the amplitude of the wave excitation in the concentration step of the plasma, using the electromagnetic component and the boundary condition of the velocity of the electron beam. We obtain the approximate solution to the coefficient of the transformation from the space‐charge wave into the electromagnetic wave, and provide the Poynting vector presentation of the corresponding wave radiation. We demonstrate the principle possibility of the Alfven wave and whistler wave excitation in inhomogeneous plasma by the modulated electron beam with transition radiation mechanism. These results can be used to analyze the experimental data collected in the active plasma experiment in space.

High-Frequency Wave Excitation by the Modulated Electron Beam From Spacecraft Injected Into the Ionosphere Plasma

Waves excitation in the ionosphere by the modulated electron beams was observed in some active plasma experiments in space. In the active beam-plasma experiments electromagnetic wave can be excited by injecting modulated electron beam into the ionosphere, by various mechanisms according to different experimental conditions. The frequency of this sort of radioemission is determined by the beam modulation; it can lie in the whistler band or in the high frequency band (higher than electron plasma frequency). This article gives a theoretical analysis as well as quantitative calculation of the radioemission of semi-restricted thin modulated electron beam injected from the spacecraft into the ionosphere plasma along the geomagnetic field. The result shows that when the modulated electron beams are injected along the magnetic field line, they can produce high-frequency electromagnetic radiations in the ionosphere plasma. This electromagnetic radiation is mainly observed in the plane that is perpendicular to the velocity direction of the injected electron beam. Estimations show that the radiated power is high enough to be detected.

Artificially Created Airglow by Neutral Gas Release

电离层中分子性的离子与电子的复合要比氧离子与电子的辐射性复合快得多,因此火箭发动机产生的尾气和空间等离子体主动实验中主动释放的中性气体会对电离层有很大的影响,这么大的电离层扰动现象在过去的实验中经常可以观测到.根据中性气体在热层背景中的扩散方程,考虑电离层F区主要的离子化学反应,研究了H2,H2O和CO2气体在电离层高度上的扩散过程和电离层对所释放气体的响应,计算了气辉的体发射系数和发射强度.结果表明,中性气体在电离层高度上扩散非常迅速,在F区的一些高度上,主要正离子成分由O+转变为其他分子离子,且在释放过程中伴随气辉发射,发射气辉的波长和特征与释放物质的种类有关.

Electric Field, Magnetic Field, and Density Measurements on the Active Plasma Experiment Sounding Rocket

High-resolution, in situ measurements of dc and wave electric fields, magnetic fields, and plasma number density have been gathered by instruments on a diagnostic payload at which a high-velocity, overdense aluminum ion beam was directed from a separate payload spaced 468 m away. The experiment, called the Active Plasma Physics Experiment, was carried out in the Earth's high-latitude ionosphere at 360-km altitude using a sounding rocket. The experimental data clearly show a large diamagnetic cavity with a 93 % depletion of the Earth's magnetic field within a narrowly confined ( 1.5 V/m perpendicular to the magnetic field were observed that represented both the E × B bulk plasma velocity and a magnetosonic wave, which preceded the arrival of the beam that was also evident in the AB magnetometer data. The electric field data also show the presence of electric fields parallel to the magnetic field, including a bipolar electric field signature presumably set up to ensure current continuity. Other plasma waves associated with the release include Alfven perturbations, intense broadband turbulence extending to frequencies beyond 1 MHz, whistler-mode electromagnetic emissions at the ambient O + lower hybrid frequency, and ion acoustic turbulence. The measurements provide a self-consistent picture of the electrodynamics surrounding a high-velocity, overdense ion beam released in the high-latitude ionosphere.

Dynamics of the Active Plasma Experiment North Star Artificial Plasma Jet

Active Plasma Experiment North Star was launched from Poker Flat Research Range, Alaska, on 22 January 1999 at 13:57:03 UT, with two explosive-type generators that produced an artificial aluminum plasma jet. The purpose of this experiment was to study the interaction of the artificial plasma jet with the ambient plasma. The first release occurred at 363 km, and a ∼90% reduction of the geomagnetic field was observed on three separate daughter payloads. The diamagnetic signatures suggest that the plasma cloud was highly localized (i.e., cloud dimensions ∼Al + gyroradius) traveling with a velocity of roughly 25 km/s perpendicular to the geomagnetic field. A hybrid code simulation provided an estimate of the plasma distribution and a qualitative description of the evolution of the plasma cloud. The simulation showed that the plasma cloud polarized and E x B drifted while transferring momentum to the ambient plasma via an Alfvenie disturbance. The model results are in good qualitative agreement with data from the plasma diagnostics payload.

Spacecraft potential during an active experiment: a comparison of experimental results with a simple model

Abstract. The Active Plasma Experiment (APEX) used intensive electron beam and/or a release of the low-energy Xenon plasma to study dynamic processes in the magnetosphere and upper ionosphere. It was shown by Prech et al. (1999) that the release of the Xe plasma increases the spacecraft potential when the ambient plasma density is low, but decreases it when the density is high enough. In the present paper, a simple computer model of the dust particle charging has been adapted for a calculation of the potential difference between a planar probe and a spherical satellite moving in the ionospheric plasma. The influence of a quasineutral plasma emission on the measured spacecraft potential difference is discussed and the calculated results are compared with experimental data from the APEX project.Key words. Ionosphere (active experiments)

Actively produced high-energy electron bursts within the magnetosphere: the APEX project

Abstract. The APEX project (Active Plasma Experiment) has been launched into a polar orbit in December 1991 and consists of two satellites (IK-25 and MAGION-3), with a distance between them from 200 km to 10 000 km. The mission used intensive electron beam emission, complemented by a low-energy Xenon plasma generator during the electron beam injection, for the study of dynamic processes in the magnetosphere and upper ionosphere. The paper deals with short, intensive bursts of field-aligned electrons observed during the APEX mission on board the MAGION-3 satellite. These events are located pre-dominantly at the middle geomagnetic latitudes in the day-side magnetosphere. The time-energy structure of these electron bursts is similar to the inverted-V one, but the pitch-angle width is less than 10°. Electrons with an energy up to 700 keV are often observed during the events. We analyze the observed events, discuss the possible mechanisms of the particle spreading, and the role of the main satellite’s activity as a possible source of these events.Key words. Ionosphere (particle acceleration; particle precipitation) – Space plasma physics (active perturbation experiments)

Reduction of momentum transfer rates by parallel electric fields: A two-fluid demonstration

Momentum transfer between an ionized gas cloud moving relative to an ambient magnetized plasma is a general problem in space plasma physics. Obvious examples include the Io–Jupiter interaction, comets, and coronal mass ejections. Active plasma experiments have demonstrated that momentum transfer rates associated with Alfvén wave propagation are poorly understood. Barium injection experiments from the Combined Release and Radiation Effects Satellite (CRRES) have shown that dense ionized clouds are capable of E×B drifting over large distances perpendicular to the magnetic field. The CRRES “skidding” distances were much larger than predicted by magnetohydrodynamic theory and it has been proposed that parallel electric fields were a key component in the skidding phenomenon. A two-fluid code was used to demonstrate the role of parallel electric fields in reducing momentum transfer between two distinct plasma populations. In this study, a dense plasma was initialized moving relative to an ambient plasma and perpendicular to B. Parallel electric fields were introduced via a friction term in the electron momentum equation and the collision frequency was scaled in proportion to the field-aligned current density. The simulation results showed that parallel electric fields decreased the decelerating magnetic tension force on the plasma cloud through a magnetic diffusion/reconnection process.

The APEX north star experiment: observations of high-speed plasma jets injected perpendicular to the magnetic field

Initial results from the Active Plasma EXperiment North Star experiment are presented. The North Star active experiment included two separate plasma jet injections, both perpendicular to the Earth's magnetic field. The objective of the experiment is to investigate the interaction of high-speed (7–40 km/s) plasma jets with the ionospheric plasma and the coupling to the magnetosphere and lower ionosphere. The plasma jets were produced using an Explosive Type Generator device. This device is a shaped-charge device that vaporizes porous aluminum inside the generator and forces the vaporized products out of a nozzle, resulting in the production of a high-speed, partially ionized aluminum plasma jet. Instrumentation on three different payloads was used to obtain multi-point observations of the plasma jet properties, optical radiation from the jets, and ionospheric perturbations. Imagery, high-speed photometry, and spectrographic imagery using ground- and space-based sensors were used to monitor the dynamics and spectral content of the plasma jet. This paper describes the experiment and summarizes the initial results from the North Star experiment.

Numerical simulation of ion thruster-induced plasma dynamics — the model and initial results

Recently, there is a strong interest in ion thrusters as propulsion devices for interplanetary missions. Apart from their propulsive efficiency, the operation of ion thrusters in space constitutes a very interesting active plasma experiment, and the associated plasma physical dynamics are only poorly understood. We give an overview of the thruster-induced plasma environment and describe the numerical simulation with which we attempt to explore the main dynamical phenomena in this environment. The simulation is applied to a simplified ion thruster neutralization regime. Initial results for an injection velocity ratio η = ν e0 th /ν i0 = 1 between electron thermal velocity and ion beam velocity reveal the occurrence of an electrostatic shock wave that provides a complete thermalization of the beam plasma.

Artificial ion beam effects on spacecraft potential

The Active Plasma Experiment (APEX) uses intensive electron beam emission for the study of dynamic processes in the magnetosphere and upper ionosphere. In order to balance the spacecraft potential while the electron beam is operating, a low-energy Xenon plasma generator emits an ion beam. This paper reports on the ability of the Xenon plasma generator to influence the vehicle potential which is estimated from the potential difference between a floating probe and the vehicle itself. The potential difference is measured under quiet conditions and with the plasma generator operating. We discuss the influence of the parameters of the ambient plasma, spacecraft position (altitudes up to 3000 km) and Xe injector working modes on the spacecraft charging/discharging process.

Evolution of the auroral oval during a weak substorm

The present paper deals with a detailed study of the dynamics of the polar cap boundaries. The study involves the data from two satellites of the APEX project, and the data from three DMSP satellites. The APEX (Active Plasma Experiment) satellites moving along the polar orbit provide charged particle measurements in a small spatial scale (due to variable distance between both spacecrafts), up to 2 000 km. The large scale changes are studied by the comparison of the APEX and the DMSP (Defense Meteorological Satellite Program) data. Different regions are identified using the characteristics of the precipitating particles in the energy range 0.1–20 keV which have been registered onboard all satellites. This satellite configuration allows us to determine the evolution of the small structures as well as the motion of the whole precipitating region. The main attention is concentrated on the rising phase of the substorms when the width of the auroral oval decreases with the increasing geomagnetic activity and the velocity of the auroral oval motion can reach 0.2° per minute. The observed phenomena are compared with the changes of the interplanetary magnetic field and the solar wind parameters as provided by the IMP-8 spacecraft.

Artificial electron and ion beam effects: Active Plasma Experiment

The Active Plasma Experiment uses intensive electron beam emission for the study of dynamic processes in the magnetosphere and upper ionosphere. The beam energy and current are as high as 8 keV and 100 mA and the pitch angle of the emission varies in the range from 50° to 80°. The basic cycle of electron injection is formed by current pulses of different duration, intensity, and frequency. The spacecraft potential is balanced by a low‐energy xenon plasma generator during the electron beam injection. The spacecraft potential is measured by the floating probe, and the response of the environment is studied by the charged particle spectrometer working in the energy range from 0.05 to 25 keV. During the neutral or ionized Xe release without the electron gun operation the spacecraft potential remains nearly unchanged and the observed energy spectra of charged particles do not exhibit the presence of any acceleration process. The spacecraft potential during electron beam emission does not exceed 50 V if the Xe plasma or the neutral gas was released together with the electrons. The electron gun firing creates a disturbance which produces a broad spectrum of energetic electrons extending up to 1.5 keV. The acceleration process can be explained by the introduction of the electric field with intensity of about 100 V/m. This intensity is in agreement with the observed E × B drift velocity. The spatial extent of the disturbance is established to be tens of meters.

Propagation of electron bursts in the low-latitude magnetosphere

The APEX project (Active Plasma Experiment) has been launched into a polar orbit in December 1991 and consists of two satellites (IK-25 and MAGION-3), with a distance from ≍ 200 km to 10 000 km between them. The paper deals with short intensive bursts of field-aligned electrons observed during the APEX mission on board the MAGION-3 satellite. These events are predominantly located at the middle geomagnetic latitudes in the day-side magnetosphere. The time–energy structure of these electron bursts is similar to the inverted-V one but the pitch–angle width is less than 10°. Electrons with an energy up to 700 keV are often observed during the events. We analyse the observed events, discuss the possible mechanisms of the particle spreading and the role of the activity of the main satellite as a possible source of these events.

Generation of Bernstein modes in space and laboratory plasmas by injection of an electron beam

The theory of electron-beam interaction with Bernstein plasma modes is developed for conditions of active space plasma experiments as well as experiments in large vacuum chambers. Translational movement of the beam along a magnetic field and Larmor rotation of the beam are considered as sources of free energy for wave build-up. Part of the energy of translational movement is lost to the excitation of Langmuir plasma oscillations. Bernstein modes then slowly grow owing to a ‘fan’-type instability. In this case the emission spectrum consists of lines near the half-harmonics of the electron gyrofrequency, ≈(n+½)ωc. Larmor gyration of the beam is not destroyed by the excitation of Langmuir turbulence, and thus there is strong hydrodynamic interaction of the rotated beam with the Bernstein modes. Integer harmonics of gyrofrequency nωc are generated in this case, with the spectral maximum near the upper-hybrid plasma frequency.

Charged Particle Behaviour during the Active Phase of the APEX Experiment.

The Active Plasma Experiment (APEX) uses intensive electron beam emission for the study of dynamic processes in the magnetosphere and upper ionosphere. The beam energy and current is as high as 8 keV and 100 mA and the pitch angle of the emission varies in the range from 50° to 80°. The basic cycle of electron injection is formed by current pulses of different duration, intensity and frequency. The spacecraft potential is balanced by a low energy xenon plasma generator during the electron beam injection. The response of the environment is studied by the PEAS charged particle spectrometer working in the energy range 0.1-25 keV. The common response to the beam emission is the increase of the intensity ofthe registered electrons with energy less than 2 keV. Under some circumstances (the satellite position, the injector regime, the beam direction with respect to the magnetic field etc.), strong electron fluxes of the order of 10 7 cm -2 sec -1 keV -1 have been observed. The energy of these fluxes is in general a rising function of the mean current ofthe emitted beam but never exceeds the beam energy. The energy-angular distribution exhibits a complicated structure with the maximum energy located at the pitch angle which corresponds to that of the emitted electron beam.

Active plasma experiment — Project APEX

Two particle beam injectors on board the INTERCOSMOS-25 spacecraft are the core of experiments of the APEX project. The subsatellite MAGION-3 with a payload covering the main plasma and wave measurements was used as an independent diagnostic package. Theory of VLF wave generation by Xe plasma beam is discussed and first results of the active plasma experiments are mentioned.

A behaviour of electron and ion energy and angular distribution during the active APEX experiment

The APEX project (Active Plasma Experiment) involves two spacecrafts moving along the same polar orbit (perigeum 440 km, apogeum 3080 km). The distance between these spacecrafts can be controlled in a wide range - from 1 to 1000 km, enabling a variety of two-point measurements. The principal feature of the experiment is an electron and ion gun, with variable parameters of injected beams, mounted on board the main satellite. Both objects are provided with fast ionelectron energy spectrometers having energy range from 50 eV to 30 keV. The spectrometers cover a full 4p of angular directions. This paper explains experimental possibilities offered by the APEX set-up, especially for the study of artificial disturbances created by the electron gun, and presents first results on the ion and electron distribution function measurements. The most interesting observation is a similarity between the undisturbed energy distribution in the polar region and that resulting from the electron beam-plasma interaction in lower latitudes.