Plasma Wave Observations Research Articles

Frequency-dispersed Ion Acoustic Waves in the Near-Sun Solar Wind: Signatures of Impulsive Ion Beams

This work reports a novel plasma wave observation in the near-Sun solar wind: frequency-dispersed ion acoustic waves. Similar waves have previously been reported in association with interplanetary shocks or planetary bow shocks, but the waves reported here occur throughout the solar wind sunward of ∼60 solar radii, far from any identified shocks. The waves reported here vary their central frequency by factors of 3–10 over tens of milliseconds, with frequencies that move up or down in time. Using a semiautomated identification algorithm, thousands of wave instances are recorded during each near-Sun orbit of the Parker Solar Probe spacecraft. Wave statistical properties are determined and used to estimate their plasma frame frequency and the energies of protons most likely to be resonant with these waves. Proton velocity distribution functions are explored for one wave interval, and proton enhancements that may be consistent with proton beams are observed. A conclusion from this analysis is that properties of the observed frequency-dispersed ion acoustic waves are consistent with driving by cold, impulsively accelerated proton beams near the ambient proton thermal speed. Based on the large number of observed waves and their properties, it is likely that the impulsive proton beam acceleration mechanism generating these waves is active throughout the inner heliosphere. This may have implications for the acceleration of the solar wind.

Exploring plasma phenomena with the Nizhnik–Novikov–Veselov formula: Analyzing ion-acoustic waves, solitons, and shocks

This paper delves into the intricacies of the ([Formula: see text])-dimensional asymmetric Nizhnik–Novikov–Veselov ([Formula: see text]) model, a nonlinear partial differential equation governing ion-acoustic wave propagation in plasma. By employing advanced analytical and numerical approaches, the study explores innovative solitary wave solutions, particularly focusing on the dynamics of isochoric flow. Isochoric flow analysis is crucial for unraveling the complex behaviors exhibited by incompressible fluids like elastomers and bio-elastomers, which maintain a constant density. The derivation of the ([Formula: see text])-dimensional [Formula: see text] equation stems from fluid equations governing plasma dynamics. This model serves as a valuable tool for simulating experimental observations of plasma waves. The computational methodology applied in this research demonstrates a commendable level of precision and consistency, yielding novel solitary wave solutions previously unreported in the [Formula: see text] model. These results underscore the study’s importance and novelty. The outcomes not only contribute to our understanding of incompressible fluid dynamics, but also lay the groundwork for future investigations in this domain. The revealed solitary wave solutions have the potential to inform the development of more accurate models for predicting fluid dynamics, thereby advancing the field.

Juno Plasma Wave Observations at Europa

AbstractJuno passed by Europa at an altitude of 355 km on 29 September, day 272, 2022. As one of Juno's in situ science instruments, the Waves instrument obtained observations of plasma waves that are essential contributors to Europa's interaction with its environment. Juno observed chorus, a band at the upper hybrid frequency providing the local plasma density, and electrostatic solitary structures in the wake. In addition, impulses due to micron‐sized dust impacts on Juno were recorded with a local maximum very close to Europa. The peak electron density near Europa was ∼330 cm−3 while the surrounding magnetospheric density was in the range of 50–150 cm−3. There was a significant separation between the Europa flyby and Juno's crossing of Jupiter's magnetic equator, enabling a unique identification of effects associated with the moon as opposed to magnetospheric phenomena normally occurring at the magnetic equator near 10 Jovian radii.

Observations of plasma waves generated by charged space objects

A sampling of the environment around inert space objects has determined, which linear and nonlinear waves are created by moving space debris of all sizes. Plasma waves excited by satellites and space debris moving through the Earth's plasma in low earth orbit have been measured with in situ electric field sensors on other satellites. These orbit driven plasma waves are of interest for proximity detection of space debris and sources of electrostatic and electromagnetic noise on spacecraft. Satellites and other space objects moving through the near-earth ionosphere between 200 and 1000 km altitude become electrically charged by both electron collection and photo emission in sunlight. These hypersonic, charged objects can excite a wide range of plasma waves. Measurements with the Radio Receiver Instrument (RRI) on the Swarm-E satellite have shown that electromagnetic plasma waves from known objects can be observed out to ranges of tens of kilometers. The amplitude, spectral, and polarization changes of the RRI data are consistent with electromagnetic, compressional Alfvén waves launched by charged space objects traveling across magnetic field lines. In addition, electrostatic lower hybrid waves or nonlinear ion acoustic pinned oscillations may have been self-generated and measured on the Swarm-E satellite. It is proposed that measurements of these waves with local electric field measurements or remote electromagnetic wave scatter may be useful to design systems for the location of orbiting objects. Spatial and temporal details of spacecraft charging are key to understanding the extent of waves associated with the object motion in space plasmas.

Direct observation of relativistic broken plasma waves

Direct observation of relativistic broken plasma waves

Statistical Survey of Arase Satellite Data Sets in Conjunction With the Finnish Riometer Network

AbstractDuring disturbed geomagnetic conditions, the energetic particles in the inner magnetosphere are known to undergo precipitation loss due to interaction with various plasma waves. This study, investigates the energetic particle precipitation events statistically using coordinate observations from the ground riometer network and the inner‐magnetospheric satellite mission, Arase. We have compared cosmic noise absorption (CNA) data obtained from the Finnish ground riometer network located in the auroral/sub‐auroral latitudes with the comprehensive data set of omnidirectional electron/proton flux and plasma waves in ELF/VLF frequency range from the Arase satellite during the overpass intervals. The study period includes one and a half years of data between March 2017 and September 2018 covering Arase conjunctions with the riometer stations from all magnetic local time sectors. The relation between the plasma flux/waves observed at the satellite with the riometer absorptions are investigated statistically for CNA (absorption >0.5 dB) and non‐CNA (absorption <0.5 dB) cases separately. During CNA events, Arase observed elevated electron flux in the medium energy range (2–100 keV), and plasma wave activity in the whistler‐mode frequency range (0.5–3 kHz) of the spectra. Our study provides an estimate of the statistical dependence of the electron flux and plasma wave observations at Arase with the ground reality of actual precipitation.

Observational Evidence of the Excitation of Magnetosonic Waves by an He++ Ion Ring Distribution

AbstractWe report plasma wave observations of equatorial magnetosonic waves at integer harmonics of the local gyrofrequency of doubly ionized helium (). The waves were observed by Van Allen Probe A on 08 Feb 2014 when the spacecraft was in the afternoon magnetic local time sector near inside of the plasmasphere. Analysis of the complementary in‐situ energetic ion measurements (1–300 keV) reveals the presence of a helium ion ring distribution centered near 30 keV. Theoretical linear growth rate calculations suggest that the local plasma and field conditions can support the excitation of the magnetosonic waves from the unstable ring distribution. This represents the first report of the generation of magnetosonic equatorial noise via a ring distribution in energetic ions in the near‐Earth space plasma environment.

ARTEMIS Observations of Plasma Waves in Laminar and Perturbed Interplanetary Shocks

Abstract The “Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun” mission provides a unique opportunity to study the structure of interplanetary shocks and the associated generation of plasma waves with frequencies between ∼50 and 8000 Hz due to its long duration electric and magnetic field burst waveform captures. We compare wave properties and occurrence rates at 11 quasi-perpendicular interplanetary shocks with burst data within 10 minutes (∼3200 proton gyroradii upstream, ∼1900 downstream) of the shock ramp. A perturbed shock is defined as possessing a large amplitude whistler precursor in the quasi-static magnetic field with an amplitude greater than 1/3 the difference between the upstream and downstream average magnetic field magnitudes; laminar shocks lack these large precursors and have a smooth, step function-like transition. In addition to wave modes previously observed, including ion acoustic, whistler, and electrostatic solitary waves, waves in the ion acoustic frequency range that show rapid temporal frequency change are common. Three shocks had burst captures in the ramp; of these, the two laminar shocks contained a wide range of large amplitude wave modes in the ramp whereas the one perturbed shock contained no such waves. Thus, energy dissipation through wave–particle interactions is more prominent in these two laminar shocks than in the perturbed shock. Based on observations from all 11 shocks, the wave occurrence rates for laminar shocks are higher in the transition region, especially the ramp, than downstream. In contrast, perturbed shocks have approximately 2–3 times the wave occurrence rate downstream than laminar shocks.

Observation of acoustic plasma waves with a velocity approaching the speed of light

We investigate the electrodynamics of a disk-shaped two-dimensional electron system in the proximity of a screening gate. The two-dimensional plasmons in the system under study exhibit the linear dispersion characteristic of acoustic plasma waves. We experimentally achieve the limit when the velocity of acoustic waves approaches the speed of light. We show that retardation effects lead to strong coupling between acoustic plasmons and the light, which is manifested in the renormalization of the electron effective mass. We develop a theory to substantiate the observed phenomena.

High‐Density Magnetospheric He+ at the Dayside Magnetopause and Its Effect on Magnetic Reconnection

AbstractObservations from the Magnetospheric Multiscale (MMS) mission are used to quantify the maximum effect of magnetospheric H+ and He+ on dayside magnetopause reconnection. A data base of current‐sheet crossings from the first 2 years of the MMS mission is used to identify magnetopause crossings with the highest He+ concentrations. While all of these magnetopause crossings exhibit evidence of plasmaspheric plume material, only half of the crossings are directly associated with plasmaspheric plumes. The He+ density varies dramatically within the magnetosphere adjacent to the magnetopause, with density variations of an order of magnitude on timescales as short as 10 s, the time resolution of the composition instrument on MMS. Plasma wave observations are used to determine the total electron density, and composition measurements are used to determine the mass density in the magnetosheath and magnetosphere. These mass densities are then used with the magnetic field observations to determine the theoretical reduction in the reconnection rate at the magnetopause. The presence of high‐density plasmaspheric plume material at the magnetopause causes transient reductions in the reconnection rate of up to ∼40%.

Plasma Wave Investigation (PWI) Aboard BepiColombo Mio on the Trip to the First Measurement of Electric Fields, Electromagnetic Waves, and Radio Waves Around Mercury

The Plasma Wave Investigation (PWI) aboard the BepiColombo Mio (Mercury Magnetospheric Orbiter, MMO) will enable the first observations of electric fields, plasma waves, and radio waves in and around the Hermean magnetosphere and exosphere. The PWI has two sets of receivers (EWO with AM2P, SORBET) connected to two electric field sensors (MEFISTO and WPT) and two magnetic field sensors (SCM: LF-SC and DB-SC). After the launch on October 20, 2018, we began initial operations, confirmed that all receivers were functioning properly, and released the launch locks on the sensors. Those sensors are not deployed during the cruising phase, but the PWI is still capable performing magnetic field observations. After full deployment of all sensors following insertion into Mercury orbit, the PWI will start its measurements of the electric field from DC to 10 MHz using two dipole antennae with a 32-m tip-to-tip length in the spin plane and the magnetic field from 0.3 Hz to 20 kHz using a three-axis sensor and from 2.5 kHz to 640 kHz using a single-axis sensor at the tip of a 4.5-m solid boom extended from the spacecraft’s side panel. Those receivers and sensors will provide (1) in-situ measurements of electron density and temperature that can be used to determine the structure and dynamics of the Hermean plasma environment; (2) in-situ measurements of the electron and ion scale waves that characterize the energetic processes governed by wave–particle interactions and non-MHD interactions; (3) information on radio waves, which can be used to remotely probe solar activity in the heliocentric sector facing Mercury, to study electromagnetic-energy transport to and from Mercury, and to obtain crustal information from reflected electromagnetic waves; and (4) information concerning dust impacts on the spacecraft body detected via potential disturbances. This paper summarizes the characteristics of the overall PWI, including its significance, its objectives, its expected performance specifications, and onboard and ground data processing. This paper also presents the detailed design of the receiver components installed in a unified chassis. The PWI in the cruise phase will observe magnetic-field turbulence during multiple flybys of Earth, Venus, and Mercury. After the Mercury-orbit insertion planned at the end of 2025, we will deploy all sensors and commence full operation while coordinating with all payloads onboard the Mio and MPO spacecraft.

ASIC waveform receiver with improved environmental tolerance for probing space plasma waves in environments with high radiation and wide temperature variation

Plasma-wave observations are conducted under conditions of high radiation and wide temperature variation. The electrical characteristics of plasma-wave instruments should therefore be insensitive to these environmental factors. We have developed a new application-specific integrated circuit (ASIC) waveform receiver with a radhard [radiation-hardened] amplifier and a temperature-compensation circuit. The environmental tolerance of the conventional ASIC receiver is unsuitable for probing plasma waves in the range 1 Hz to 10 kHz in harsh space environments. Its weak radiation tolerance under 350 krad results in radiation-induced degradation in noise performance, such that weak plasma waves are lost in the noise floor. With an ambient temperature change of −40° C to +100° C, the gain response of the conventional ASIC receiver varies by more than ±1.0 dB, preventing accurate measurement of plasma waves around the cutoff frequency of 10 kHz. Our new ASIC receiver operates at a total dose rate of 350 krad without degradation in noise performance. Moreover, the temperature dependence of the gain response from −60° C to +100° C dramatically improved by ±0.05 dB due to the addition of a compensation circuit. Our new ASIC receiver can contribute to the measurement of plasma waves in challenging environmental conditions to further the understanding of magnetospheric dynamics.

Plasma Wave Observation in Space Via Scientific Satellites

Space plasmas are essentially collisionless. Kinetic energies of plasmas are transferred through wave-particle interactions. Since plasmas are dispersive media, plasma waves show various features depending on how and which plasma wave modes interact with particles. Plasma wave observations via scientific satellites have a key role in knowing physical processes in space. Plasma wave investigation systems on board satellites are dedicated to the observations of electric field and magnetic field components of plasma waves. They consist of sensors, receivers and an onboard digital processing unit. While dipole antennas are used for electric field sensors, search coil magnetometers or loop antennas are used for magnetic field sensors. Plasma wave receivers are a kind of sophisticated radio receivers. The recent plasma wave receiver is designed as a waveform receiver that can save its mass and size. In addition to waveforms, the waveform receiver provides frequency spectra which are calculated in the digital processing unit from the observed waveforms. The present paper introduces plasma wave observation by scientific satellites on the basis of the latest design of plasma wave investigation systems.

Automatic Detection of Lightning Whistlers Observed by the Plasma Wave Experiment Onboard the Arase Satellite Using the OpenCV Library

The automatic detection of shapes or patterns represented by signals captured from spacecraft data is essential to revealing interesting phenomena. A signal processing approach is generally used to extract useful information from observation data. In this paper, we propose an image analysis approach to process image datasets produced via plasma wave observations by the Arase satellite. The dataset consists of 31,380 PNG files generated from the dynamic power spectra of magnetic wave field data gathered from a one-year observation period from March 2017 to March 2018. We implemented an automatic detection system using image analysis to classify the various types of lightning whistlers according to the Arase whistler map. We successfully detected a large number of whistler traces induced by lightning strikes and recorded their corresponding times and frequencies. The various shapes of the lightning whistlers indicate different very-low-frequency propagations and provide important clues concerning the geospace electron density profile.

Development of a miniaturized spectrum-type plasma wave receiver comprising an application-specific integrated circuit analog front end and a field-programmable gate array

Plasma waves are an important target for satellite-based in situ observation to understand electromagnetic phenomena in space. Recent scientific satellites have carried fast Fourier transform (FFT)-based spectrum receivers; however, such receivers have a disadvantage because they use wideband analog parts. The new receiver overcomes the disadvantage by adding bandlimiting in the first stage of the analog part, and it covers the entire observation frequency range of each band by switching its cutoff frequency. In order to miniaturize circuit size, the new receiver comprises application-specific integrated circuits (ASICs) and a field-programmable gate array (FPGA). The ASIC chip includes the analog part of the receiver and the analog-to-digital converter, and the FPGA includes an FFT module and the controller of the receiver. The proposed spectrum receiver was successfully implemented with a size of 55 mm × 80 mm × 35 mm and a total power consumption of 948.3 mW. The time resolution of the receiver was 112 ms, and the frequency resolutions for frequency bands from 10 Hz to 1 kHz, from 1 kHz to 10 kHz, and from 10 kHz to 100 kHz were 13 Hz, 130 Hz, and 1.3 kHz, respectively. Overall, the developed receiver showed sufficient performance for plasma wave observation.

Direct Observation of Plasma Waves and Dynamics Induced by Laser-Accelerated Electron Beams

Plasma wakefield acceleration (PWFA) is a novel acceleration technique with promising prospects for both particle colliders and light sources. However, PWFA research has so far been limited to a few large-scale accelerator facilities world-wide. Here, we present first results on plasma wakefield generation using electron beams accelerated with a 100-TW-class Ti:Sa laser. Due to their ultrashort duration and high charge density, the laser-accelerated electron bunches are suitable to drive plasma waves at electron densities in the order of $10^{19}$ cm$^{-3}$. We capture the beam-induced plasma dynamics with femtosecond resolution using few-cycle optical probing and, in addition to the plasma wave itself, we observe a distinctive transverse ion motion in its trail. This previously unobserved phenomenon can be explained by the ponderomotive force of the plasma wave acting on the ions, resulting in a modulation of the plasma density over many picoseconds. Due to the scaling laws of plasma wakefield generation, results obtained at high plasma density using high-current laser-accelerated electron beams can be readily scaled to low-density systems. Laser-driven PWFA experiments can thus act as miniature models for their larger, conventional counterparts. Furthermore, our results pave the way towards a novel generation of laser-driven PWFA, which can potentially provide ultra-low emittance beams within a compact setup.

New Plasma Wave Observations from Earth's Magnetosphere

The first simultaneous observations of multiple electromagnetic wave types in Earth’s magnetosphere may inaugurate a new field of inquiry into cross-frequency wave interactions.

Whistler Mode Waves Associated With Broadband Auroral Electron Precipitation at Jupiter

AbstractLarge amplitude electromagnetic plasma waves are observed simultaneously with intense fluxes of electrons precipitating on auroral field lines at Jupiter. Here we present plasma wave observations from the Juno Waves instrument obtained during an instance of very intense broadband electron precipitation observed by the Jupiter Energetic Particle Detector Instrument connecting to Jupiter's main auroral oval. The wave spectrum extends from 50 Hz to ~10 kHz with peak‐to‐peak amplitudes of ~10 nT in the magnetic channel and of ~1 V/m in the electric channel, representing some of the most intense plasma waves observed by Juno. The E and B fields of these electromagnetic waves are correlated and have apparent polarization perpendicular to Jupiter's magnetic field with a downward Poynting flux. We conclude the plasma waves are whistler mode emissions with a possible admixture of ion‐cyclotron or Alfvén waves and may be important in the broadband electron acceleration.

Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures

The icy surface of Jupiter’s moon, Europa, is thought to lie on top of a global ocean1–4. Signatures in some Hubble Space Telescope images have been associated with putative water plumes rising above Europa’s surface5,6, providing support for the ocean theory. However, all telescopic detections reported were made at the limit of sensitivity of the data5–7, thereby calling for a search for plume signatures in in-situ measurements. Here, we report in-situ evidence of a plume on Europa from the magnetic field and plasma wave observations acquired on Galileo’s closest encounter with the moon. During this flyby, which dropped below 400 km altitude, the magnetometer 8 recorded an approximately 1,000-kilometre-scale field rotation and a decrease of over 200 nT in field magnitude, and the Plasma Wave Spectrometer 9 registered intense localized wave emissions indicative of a brief but substantial increase in plasma density. We show that the location, duration and variations of the magnetic field and plasma wave measurements are consistent with the interaction of Jupiter’s corotating plasma with Europa if a plume with characteristics inferred from Hubble images were erupting from the region of Europa’s thermal anomalies. These results provide strong independent evidence of the presence of plumes at Europa.

Saturn's rings and associated ring plasma cavity: Evidence for slow ring erosion

We re-examine the radio and plasma wave observations obtained during the Cassini Saturn orbit insertion period, as the spacecraft flew over the northern ring surface into a radial distance of 1.3 Rs (over the C-ring). Voyager era studies suggest the rings are a source of micro-meteoroid generated plasma and dust, with theorized peak impact-created plasma outflows over the densest portion of the rings (central B-ring). In sharp contrast, the Cassini Radio and Plasma Wave System (RPWS) observations identify the presence of a ring-plasma cavity located in the central portion of the B-ring, with little evidence of impact-related plasma. While previous Voyager era studies have predicted unstable ion orbits over the C-ring, leading to field-aligned plasma transport to Saturn's ionosphere, the Cassini RPWS observations do not reveal evidence for such instability-created plasma ‘fountains’. Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend >109 years, and that there is limited evidence for prompt destruction (loss in <100Myrs).