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Understanding of wave environments is critical for the understanding of how particles are accelerated and lost in space. This study shows that in the vicinity of Europa and Ganymede, that respectively have induced and internal magnetic fields, chorus wave power is significantly increased. The observed enhancements are persistent and exceed median values of wave activity by up to 6 orders of magnitude for Ganymede. Produced waves may have a pronounced effect on the acceleration and loss of particles in the Jovian magnetosphere and other astrophysical objects. The generated waves are capable of significantly modifying the energetic particle environment, accelerating particles to very high energies, or producing depletions in phase space density. Observations of Jupiter’s magnetosphere provide a unique opportunity to observe how objects with an internal magnetic field can interact with particles trapped in magnetic fields of larger scale objects.

One of the discoveries made by the radar sounder on the Mars Express spacecraft is the existence of magnetically controlled structures in the ionosphere of Mars, which result in bulges in the ionospheric electron density contours. These bulges lead in turn to oblique echoes, which show up as hyperbola-shaped features in the echograms. A hyperbola-shaped feature observed over an isolated region of strong crustal magnetic field is associated with a plasma cavity in the upper ionosphere and a corresponding density enhancement in the lower levels of the ionosphere. We suggest that along open magnetic field lines, the solar wind electrons are accelerated downward and the ionospheric ions are accelerated upward in a manner similar to the field line-driven auroral acceleration at Earth. This heating due to precipitating electrons may cause an increase in the scale height and may drive a loss of ionospheric plasma at high altitudes.

Enhanced topside electron densities in the dayside Martian ionosphere have been repetitively observed in areas of near-radial crustal magnetic fields, for periods of tens of days, indicating their long-term spatial and temporal stability despite changing solar wind conditions. We perform a statistical study of these density structures using the ionospheric mode of the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Mars Express. We estimate the apparent extents of these structures relative to the altitude of the surrounding ionosphere. The apex of the density structures often lies higher than the surrounding ionosphere (median vertical extent of 18 km), which indicates upwellings. These structures are much wider than they are high, with latitudinal scales of several degrees. The radar reflector regions are observed above both moderate and strong magnetic anomalies, and their precise locations and latitudinal extents match quite well with the locations and latitudinal extents of magnetic structures of given magnetic polarity (oblique to vertical fields), which happen to be regions where the field lines are open part of the time. The majority of the density structures occur in regions where ionospheric plasma is dominant, indicating closed field regions shielded from shocked solar wind plasma

Spacecraft radar sounding signals at frequencies higher than the ionospheric peak plasma frequency are not reflected by the ionosphere. Instead, they make it to the ground where they are reflected by the planetary surface. We analyze the intensity of the surface reflections measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) ionospheric radar sounder on board the Mars Express spacecraft. Apart from the surface reflectivity and the spacecraft altitude, the detected intensity of surface reflections is controlled primarily by the signal attenuation during the ionospheric propagation. We focus on the nightside region, where the ionospheric densities in the main layer are too low to cause a significant attenuation and allow sampling of the surface reflections at frequencies down to 3 MHz. The attenuation occurs mainly at altitudes below 100 km, where the electron-neutral collision frequency is a maximum. The intensity of surface reflections can thus serve as a proxy for electron densities at low altitudes not accessible by the direct ionospheric radar sounding. We analyze the intensity of surface reflections as a function of relevant controlling parameters. The intensity of surface reflections is lower at higher solar zenith angles on the nightside and during the periods of larger solar activity. Moreover, it exhibits a seasonal variation that is related to the dust storm occurrence. The intensity of surface reflections is lower in areas of closed magnetic field lines, suggesting that nightside electron densities behave rather differently at low altitudes than at higher altitudes. This is confirmed by comparison with simultaneous observations of the main ionospheric layer.

Enhanced topside electron densities in the dayside Martian ionosphere have been repetitively observed in areas of near-radial crustal magnetic fields, for periods of tens of days, indicating their long-term spatial and temporal stability despite changing solar wind conditions. We perform a statistical study of these density structures using the ionospheric mode of the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Mars Express. We estimate the apparent extents of these structures relative to the altitude of the surrounding ionosphere. The apex of the density structures often lies higher than the surrounding ionosphere (median vertical extent of 18 km), which indicates upwellings. These structures are much wider than they are high, with latitudinal scales of several degrees. The radar reflector regions are observed above both moderate and strong magnetic anomalies, and their precise locations and latitudinal extents match quite well with the locations and latitudinal extents of magnetic structures of given magnetic polarity (oblique to vertical fields), which happen to be regions where the field lines are open part of the time. The majority of the density structures occur in regions where ionospheric plasma is dominant, indicating closed field regions shielded from shocked solar wind plasma

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard the European Space Agency's Mars Express (MEX) spacecraft routinely detects evidence of localized plasma density structures in the Martian dayside ionosphere. Such structures, likely taking the form of spatially extended elevations in the plasma density at a given altitude, give rise to oblique reflections in the Active Ionospheric Sounder data. These structures are likely related to the highly varied Martian crustal magnetic field. In this study we use the polar orbit of MEX to investigate the repeatability of the ionospheric structures producing these anomalous reflections, examining data taken in sequences of multiple orbits which pass over the same regions of the Martian surface under similar solar illuminations, within intervals lasting tens of days. Presenting three such examples, or case studies, we show for the first time that these oblique reflections are often incredibly stable, indicating that the underlying ionospheric structures are reliably reformed in the same locations and with qualitatively similar parameters. The visibility, or lack thereof, of a given oblique reflection on a single orbit can generally be attributed to variations in the crustal field within the ionosphere along the spacecraft trajectory. We show that, within these examples, oblique reflections are generally detected whenever the spacecraft passes over regions of intense near-radial crustal magnetic fields (i.e., with a “cusp-like” configuration). The apparent stability of these structures is an important feature that must be accounted for in models of their origin.

Electron densities in the Martian nightside ionosphere are more than 90% of time too low to be detected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding radar sounder on board the Mars Express spacecraft. However, the relative number of ionograms with peak electron density high enough to be detected represents a good statistical proxy of the ionospheric density. We focus on solar energetic particle (SEP) events, and we analyze their effects on ionospheric formation. SEP time intervals were identified in situ using the background counts recorded by the ion sensor of the ASPERA-3 instrument on board Mars Express. We show that peak electron densities during the SEP events are large enough to be detected in more than 30% of measurements, and, moreover, the reflections of the sounding signal from the ground almost entirely disappear. Nightside electron densities during SEP events are thus substantially increased as compared to normal nightside conditions.

We present evidence of a substantial ionospheric response to a strong interplanetary coronal mass ejection (ICME) detected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board the Mars Express (MEX) spacecraft. A powerful ICME impacted the Martian ionosphere beginning on 5 June 2011, peaking on 6 June, and trailing off over about a week. This event caused a strong response in the charged particle detector of the High-Energy Neutron Detector (HEND) on board the Odyssey spacecraft. The ion mass spectrometer of the Analyzer of Space Plasmas and Energetic Atoms instrument on MEX detected an increase in background counts, simultaneous with the increase seen by HEND, due to the flux of solar energetic particles (SEPs) associated with the ICME. Local densities and magnetic field strengths measured by MARSIS and enhancements of 100 eV electrons denote the passing of an intense space weather event. Local density and magnetosheath electron measurements and remote soundings show compression of ionospheric plasma to lower altitudes due to increased solar wind dynamic pressure. MARSIS topside sounding of the ionosphere indicates that it is extended well beyond the terminator, to about 116° solar zenith angle, in a highly disturbed state. This extension may be due to increased ionization due to SEPs and magnetosheath electrons or to plasma transport across the terminator. The surface reflection from both ionospheric sounding and subsurface modes of the MARSIS radar was attenuated, indicating increased electron content in the Mars ionosphere at low altitudes, where the atmosphere is dense.

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard the European Space Agency's Mars Express (MEX) spacecraft routinely detects evidence of localized plasma density structures in the Martian dayside ionosphere. Such structures, likely taking the form of spatially extended elevations in the plasma density at a given altitude, give rise to oblique reflections in the Active Ionospheric Sounder data. These structures are likely related to the highly varied Martian crustal magnetic field. In this study we use the polar orbit of MEX to investigate the repeatability of the ionospheric structures producing these anomalous reflections, examining data taken in sequences of multiple orbits which pass over the same regions of the Martian surface under similar solar illuminations, within intervals lasting tens of days. Presenting three such examples, or case studies, we show for the first time that these oblique reflections are often incredibly stable, indicating that the underlying ionospheric structures are reliably reformed in the same locations and with qualitatively similar parameters. The visibility, or lack thereof, of a given oblique reflection on a single orbit can generally be attributed to variations in the crustal field within the ionosphere along the spacecraft trajectory. We show that, within these examples, oblique reflections are generally detected whenever the spacecraft passes over regions of intense near-radial crustal magnetic fields (i.e., with a “cusp-like” configuration). The apparent stability of these structures is an important feature that must be accounted for in models of their origin.

As the saturnian magnetoplasma sweeps past Enceladus, it experiences both a decrease in electron content and sharp slowdown in the northern hemisphere region within similar to 5 Enceladus Radii (R-e). This slowdown is observed by Cassini in regions not obviously associated with the southern directed plume-originating ions. We suggest herein that the decrease in northern hemisphere electron content and plasma slowdown could both be related to the presence of fine dust grains that are being accelerated by the Lorentz force created within the saturnian magnetic field system.

We apply the hybrid simulation code AIKEF (adaptive ion kinetic electron fluid) to the interaction between Enceladus' plume and Saturn's magnetospheric plasma. For the first time, the influence of the electron-absorbing dust grains in the plume on the plasma structures and magnetic field perturbation, the Alfven wing, is taken into account within the framework of a global simulation. Our work continues the analytical calculations by Simon et al. (2011), who showed that electron absorption within the plume leads to a negative sign of the Hall conductivity. The resulting twist of the magnetic field, referred to as the Anti-Hall effect, has been observed during all targeted Enceladus flybys between 2005 and 2010. We show that (1) applying a plume model that considers both, the neutral gas and the dust allow us to quantitatively explain Cassini Magnetometer (MAG) data, (2) dust enhances the anti-Saturnward deflection of the ions, causing asymmetries which are evident in the MAG data, and (3) the ions in the plume are slowed down below 1 km s(-1); and we compare our results to MAG data in order to systematically analyze variations in the plume activity and orientation for selected pairs of similar flybys: (E5, E6), (E7, E9) and (E8, E11).

According to existing theory, electrons are accelerated up to ultra-relativistic energies(1) inside Jupiter's magnetic field by betatron and Fermi processes as a result of radial diffusion towards the planet and conservation of the first two adiabatic invariants(2-4). Recently, it has been shown that gyro-resonant electron acceleration by whistler-mode waves(5,6) is a major, if not dominant(7), process for accelerating electrons inside the Earth's outer radiation zone, and has redefined our concept for producing the Van Allen radiation belts(8). Here, we present a survey of data from the Galileo spacecraft at Jupiter, which shows that intense whistler-mode waves are observed outside the orbit of the moon Io and, using Fokker-Planck simulations, are strong enough to accelerate electrons to relativistic energies on timescales comparable to that for electron transport. Gyroresonant acceleration is most effective between 6 and 12 jovian radii (R-j) and provides the missing step in the production of intense synchrotron radiation from Jupiter(1,9).

This document discusses the Main Electronics Package, two Electric Field Preamps and Search Coil Magnetometer. The AFGL 701 SPACERAD instrumentation on the CRRES (Combined Release and Radiation Effects Satellite) project. This document discusses the scientific objectives and the importance of the Plasma Wave Experiment in the CRRES SPACERAD mission and describes the instrument design rational and the instrument development philosophy. The instrument description describes the instrument commands and their verifications. This document also discusses the testing and operations of the experiment and contains a schematic drawing of the instrumentation electrons and lists of the schematics, drawings, and wiring diagrams that describe the as- built configuration of the Plasma Wave Experiment instrumentation. Problems encountered during the construction and testing of the instrument and their resolutions are discussed. Test results from already completed environmental and EMC/RFI tests have already been submitted to AFGL and to the Air Force Headquarters Space Division Space Test Program. The recertification of the calibration of the instrument is recommended in the near future under a new contract covering the re-delivery (necessitated due to the removal during the launch-delay storage period), pre-launch, and launch operations. Keywords: Plasma wave experiment; Search coil magnetometer; Passive plasma sounder; Spectrum analyzer; Sweep frequency receiver; Electric fields; Magnetic fields.

By scattering particles and causing dissipation, waves in a collisionless shock play a role similar to collisions in an ordinary gas. The transition region is usually characterized by an abrupt broadband burst of electrostatic noise extending from below the lower hybrid resonance to near the electron plasma frequency, and by a broadband burst of whistler mode electromagnetic noise at frequencies below the electron cyclotron frequency. The electrostatic noise is believed pe p to be the primary mechanism by which heating and dissipation takes place at the shock. This noise is believed to be driven either by a current or an electron beam in the shock. Upstream of the shock electron plasma oscillations, ion acoustic waves, and intense ultra-low-frequency (ULF) magnetohydrodynamic waves are frequently observed. The electron plasma oscillations occur in the electron foreshock and are driven by suprathermal electrons escaping into the region upstream of the shock. The region downstream of the shock is usually very chaotic. Electrostatic waves, similar to the broadband noise in the transition region but less intense, often extend long distances into the downstream region. Whistler mode emissions also frequently are observed in the downstream region. Some of these waves may be locally generated, and others may be convected downstream from the shock.

This is a list of papers, etc. on Plasma Wave Instrument on the AMPTE/IRM Spacecraft. Each entry, of which there are 12, lists authors, titles of articles, journals where entered or conference where given, volume, pages and date., Rept. on Publications/Patents/Presentations/Honors Report.

By scattering particles and causing dissipation, waves in a collisionless shock play a role similar to collisions in an ordinary gas. In describing the waves and instability that occur near a shock three regions must be considered: (1) the transition region, (2) the upstream region, and (3) the downstream region. The transition region is usually characterized by an abrupt broadband burst of electrostatic noise extending to frequencies well above the ion plasma frequency, and by a broadband burst of whistler-mode electromagnetic noise at frequencies below the electron cyclotron frequency. The burst of electrostatic noise is believed to be the primary mechanism by which heating and dissipation takes place at the shock. This noise is believed to be ion-acoustic noise driven either by a current or an electron beam in the shock. Electrostatic lower-hybrid waves are also sometimes observed in the transition region. These waves are excited by ions reflected by the shock, and can be very effective at heating both ion and electrons. This paper reviews all of the above waves and comments on the similarities between waves observed near the bow shocks of earth, Venus, Jupiter and Saturn, and interplanetary shocks. Possible mechanisms for generating each type of wave are also considered.

Recent studies of wideband plasma wave data from the Voyager 1 and 2 flybys of Jupiter have revealed the existence of narrowband radio emissions in the frequency range 1 -12 kHz. These narrowband emissions are very similar to narrowband emissions previously discovered in the magnetospheres of Earth and Saturn, and are believed to be produced by mode conversion from electron cyclotron waves near the upper hybrid resonance frequency. This mode conversion process is apparently one of the basic mechanisms for generating planetary radio emissions. In this paper we describe the characteristics of the Jovian narrowband emissions and discuss possible mechanisms for generating these emissions. In this paper we describe the characteristics of the Jovian narrowband emissions and discuss possible mechanisms for generating these emissions., Sponsored in part by Grants, NGL-16-001-002, NGL-16-001-043 and Contract NASA-954012.

The electrostatic bursts analyzed in this paper have a frequency much greater than that of the chorus. The frequency is usually somewhat lower than the electron plasma frequency and is normally in the range from about 3 kHz up to kHz. As will be shown, the electrostatic bursts are longitudinal electrostatic waves with wave vectors aligned almost exactly along the ambient magnetic field. In some cases, the amplitude of the electrostatic bursts is shown to have a modulation at the chorus frequency. This modulation is indicative of a strong physical interaction between these two wave modes. This paper details the investigation of this interaction and provides strong evidence that the electrons responsible for the electrostatic bursts are trapped and accelerated by a Landau resonance interaction with the chorus wave. The primary data used in this work was obtained from the ISEE 1 and ISEE 2 (International Sun-Earth Explorer) spacecraft, which were launched into Earth orbit simultaneously on October 22, 1977. A description of the spacecraft orbital parameters is contained in Anderson et al. (1981). The plasma wave data used was obtained from the University of Iowa Plasma Wave Experiment, and the instrumentation is described in detail by Gurnett et al. (1978)., Sponsored in part by Grants NGL-16-001-002, NGL-16-001-043 and Contracts NAS5-26819, NAS5-11074 and NAS5-26257.

Simultaneous observations of field-aligned currents (FAC) and auroral kilometric radiation (AKR) are compared from the polar orbiting satellites Triad and Hawkeye. The Triad observations were restricted to the evening-to-midnight local time sector (19 to 01 hours magnetic local time) in the northern hemisphere. This is the region where it is believed the most intense storms of AKR originate. The Hawkeye observations were restricted to when the satellite was in the AKR 'emission cone' in the northern hemisphere and at radial distances = or 7 R(E) (earth radii) to avoid local propagation cutoff effects. A (R/7 R(E)2 normalization to the power flux measurements of the kilometric radiation from Hawkeye is used to take into account the radial dependence of this radiation and to scale all intensity measurements such that they are independent of Hawkeye's position in the emission cone. Integrated field-aligned current intensities from Triad are determined from the observed transverse magnetic field disturbances. Statistically, there is a good correlation between the AKR intensity and the integrated curreent sheet intensity of field-aligned currents. It is found that as the intensity of auroral kilometric radiation increases so does the integrated auroral zone current sheet intensity increase., Prepared in cooperation with Johns Hopkins Univ., Laurel, MD. Applied Physics Lab., Contract N00017-72-C-4401. Sponsored in part by Grant NAS1-13129.

Simultaneous observations of energetic electron precipitations and auroral kilometric radiation (AKR) were obtained from the polar orbiting satellites AE-D and Hawkeye. The Hawkeye observations were restricted to periods when the satellite was in the AKR emission cone in the northern hemisphere and at radial distances or = 7 R(E) to avoid local propagation cutoff effects. In addition, the AE-D measurements were restricted to complete passes across the auroral oval in the evening to midnight local time sector (from 20 to 01 hours magnetic local time). This is the local time region where the most intense bursts of AKR are believed to originate. A qualitative survey of AKR and electron particle precipitation shows that AKR is more closely associated with inverted-V electron precipitation than with plasma sheet precipitation. Quantitatively, a good correlation is found between the AKR intensity and the peak energy of inverted-V events. In addition, in the tail of the most field-aligned portion (approx. 0 deg. pitch angle) of the distribution functions of the inverted-V events, systematic changes are indicated as the associated AKR intensity increases., Sponsored in part by Grant NGL-16-001-043.

Observations of radio emissions by the Hawkeye 1 satellite at low altitudes over the southern hemisphere have now provided measurements at radial distances from about 1.5 to 2.5 R sub e along the auroral field lines, in the region where the intense nightside auroral kilometric radiation is believed to be generated. These measurements provide new evidence on the mode of propagation and origin of the auroral kilometric radiation. In the local evening region, where the intense auroral kilometric radiation is believed to be generated, a few events have been detected for which no low frequency cutoff is evident. In these cases the auroral kilometric radiation appears to merge essentially continuously into a band of intense auroral hiss which extends downward to frequencies as low as 1 kHz. These observations suggest that the generation of the whistler-mode auroral hiss and the escaping auroral kilometric radiation are very closely related. Possible mechanisms which could produce strong coupling between the whistler-mode and the escaping free space electromagnetic modes are discussed. (Author)

A survey of the plasma wave data from the Hawkeye-1 spacecraft has been performed in search of ion cyclotron waves associated with the scattering and loss of ring current ions within and near the plasma-pause. During an 18 month period, consisting of about 270 orbits, a total of 5 events have been found with clearly detectable electric and magnetic fields at frequencies below the proton gyrofrequency. Comparisons of the electric and magnetic field amplitudes for these events provide strong evidence that these waves are ion cyclotron waves. All five events occurred during the recovery phase of a magnetic storm at radial distances within or very close to the plasmapause boundary. The results of this survey confirm and are consistent with the earlier identification of ion cyclotron waves by the Explorer 45 satellite. The Hawkeye-1 observations show that ion cyclotron waves of substantial amplitude occur at magnetic latitudes well away from the magnetic equator.

The r.m.s. field strengths of electrostatic and electromagnetic turbulence in the earth's bow shock, measured in the frequency range 20 Hz to 200 kHz with IMP-6 satellite, are found to correlate with specific solar wind parameters measured upstream of the bow shock., Sponsored in part by Grants NGL-16-001-002, and NGL-16-001-043.

Direction-finding measurements with the plasma wave experiments on the HAWKEYE 1 and IMP 8 satellites are used to find the source locations of type III solar radio bursts in heliocentric latitude and longitude in a frequency range from 31.1 kHz to 500 kHz. IMP 8 has its spin axis perpendicular to the ecliptic plane; hence, by analyzing the spin modulation of the received signals the location of the type III burst projected into the ecliptic plane can be found. HAWKEYE 1 has its spin axis nearly parallel to the ecliptic plane; hence, the location of the source out of the ecliptic plane may also be determined. Using an empirical model for the emission frequency as a function of radial distance from the sun the three-dimensional trajectory of the type III radio source can be determined from direction-finding measurements at different frequencies. Since the electrons which produce these radio emissions follow the magnetic field lines from the sun these measurements provide information on the three-dimensional structure of the magnetic field in the solar wind., Presented at the Workshop on Mechanisms for Solar Type III Radio Bursts, 8-9 May 75, Berkeley, Calif.

In addition to the intense and highly variable auroral kilometric radiation the earth also radiates a weak non-thermal continuum from energetic electrons in the outer radiation zone. The intensity of this continuum radiation decreases with increasing frequency and is usually below the cosmic noise level at frequencies above 100 kHz. In this paper it is shown that the frequency spectrum of the continuum radiation consists of two components, a trapped component, which is permanently trapped within the magnetosphere at frequencies below the solar wind plasma frequency, and an escaping component which propagates freely away from the earth at frequencies above the solar wind plasma frequency.

Papers Submitted to Refereed Journals -- Simulation and Non-Linear Stage of Electrostatic Waves Observed During the AMPTE Lithium Release in the Solar Wind; Electron Number Density from the AMPTE/IRM Plasma Wave Experiment During Solar Wind Lithium Releases; A Comparison of the Plasma Wave Spectra From 100 Hz to 100khz for the Eight AMPTE Chemical Releases; High Frequency Electrostatic Waves at Earth's Bow Shock; and Nature and the Nonlinear Evolution of Electrostatic Waves Associated with the AMPTE Solar Wind Releases; Papers Published in Refereed Journals--Electron Plasma Waves in the Solar WInd; AMPTE/IRM and UKS Observations; An Analysis of the Shocklike Electrostatic Noise Observed During AMPTE Solar Wind Ion Releases; Electron Cyclotron Harmonic Waves Observed by the AMPTE-IRM Plasma Wave Experiment Following a Lithium Release in the Solar Wind; AMPTE IRM Observations of Waves Associated with Flux Transfer Events in the Magnetosphere, and Observation of Nonlinear Wave Decay Processes in the Solar Wind by the AMPTE IRM Plasma Wave Experiment; Observations and Theory of the AMPTE Magnetotail Barium Releases.

The primary purposes of the Active Magnetospheric Particle Tracing Explorers (AMPTE) program were (1) to carry out the release and monitoring of lithium and barium ions in the solar wind and the distant magnetosphere in order to study the transport of energization of magnetospheric particles, and to investigate the instabilities and wave-particle interactions associated with the releases and subsequent evolution of the injected clouds, and (2) to carry out large releases of barium in the solar wind with the objective of producing artificial comets and studying the interaction of the injected plasma clouds with the solar wind., Original contains color plates: All DTIC and NTIS reproductions will be in black and white.

Electric field spectrum measurements from the Plasma Wave Instrument on the Dynamics Explorer-1 spacecraft are used to study the local electron density at high altitudes in the northern polar cap region. The electron density is determined from the upper cutoff of whistler mode radiation at the electron plasma frequency. This technique typically gives the electron density with; an accuracy better than 12%., Supported in part by Contract NAG5-310, Grants NGL-16-001-002 and NGL-16-001-043.

This paper reviews the principal types of electromagnetic plasma wave emissions produced in the high latitude auroral regions. Three types of radiation are described: auroral kilometric radiation, auroral hiss, and Z-mode radiation. Auroral kilometric radiation is a very intense radio emission generated in the free space R-X mode by electrons associated with the formation of discrete auroral arcs in the local evening. Current theories suggest that this radiation is an electron cyclotron resonance instability driven by an enhanced loss cone in the auroral acceleration region at altitudes of about 1 to 2 RE. Auroral hiss is a somewhat weaker whistler-mode emission generated by low energy (100 eV to 10 keV) auroral electrons. The auroral hiss usually has a V-shaped frequency-time spectrum caused by a frequency dependent beaming of the whistler mode into a conical beam directed upward or downward along the magnetic field. Z-mode radiation is a recently discovered broadband emission similar in some respects to auroral hiss, except that this radiation is propagating in the Z-mode., Presented at the Nobel Symposium on High Latitude Space Plasma Physics, 22-25 Mar 82, Kiruna (Sweden). Sponsored in part by Contracts NAS5-25690, NGL-16-001-002 and NGL-16-001-043.

The electric and magnetic field spectral densities of plasma waves in the earth's bow shock have been measured in the frequency range 20 Hz to 200 kHz using two 16-channel spectrum analyzers on the IMP-6 spacecraft. (Modified author abstract), Sponsored in part by Contract NAS5-11431, and Grant NGL-16-001-043.

Using the low-frequency cutoff of electromagnetic noise trapped in the magnetosphere at frequencies above the local plasma frequency it is now possible to make very accurate, plus or minus 1%, electron density measurements in the low density region between the magnetopause and plasmapause. This technique for measuring the total plasma density has been used, together with measurements of the suprathermal proton intensities with the LEPEDEA instrumentation on the IMP-6 spacecraft, to determine the thermal proton densities in the region between the plasmapause and magnetopause. (Modified author abstract), Sponsored in part by Contract NAS5-11039 and Grant NGL-16-001-043.

Naturally occurring radio noise at frequencies greater than the electron plasma frequency and less than the upper hybrid resonance frequency and less than the upper hybrid resonance frequency has been observed at relatively low altitudes in the ionosphere by several rocket- and spacecraft-borne radio noise experiments. Since the index of refraction for the extraordinary mode of propagation near the upper hybrid resonance is greater than one, it is generally believed that this noise is produced by Cerenkov radiation from super-thermal electrons. The University of Iowa plasma wave experiment on the IMP-6 spacecraft has detected a similar noise band believed to be associated with the upper hybrid resonance frequency at large radial distances in the magnetosphere. (Author), Sponsored in part by Grant NGL-16-001-043.

Satellite-borne electric field measurements using the double probe technique have now provided a comprehensive survey of convection electric fields at low altitudes in the magnetosphere. The most prominent features of the convection electric fields are reversals located at high magnetic latitudes, with generally anti-sunward convection poleward and sunward convection equatorward of the electric field reversal location. The electric field reversal is usually coincident with the 'trapping boundary' for electrons with energies E > 45 keV and is interpreted as the boundary between open and closed magnetic field lines. On the day side of the magnetosphere the electric field reversal is observed to coincide with the equatorward boundary of the polar cusp. (Author), Sponsored in part by Contract NAS1-2973.

Recent measurements of magnetospheric electric fields with the satellite Injun 5 have provided a comprehensive global survey of plasma convection at low altitudes in the magnetosphere. A persistent feature of these electric field observations is the occurrence of an abrupt reversal in the convection electric field at auroral zone latitudes. The plasma convection velocities associated with these reversals are generally directed east-west, away from the sun on the poleward side of the reversal, and toward the sun on the equatorward side of the reversal. The electric field reversal is observed to be coincident with the 'trapping boundary' for electrons with energies E>45 keV. Near local noon the region of anti-sunward convection poleward of the electric field reversal/trapping boundary corresponds to the low-altitude extension of the polar cusp plasma. Intense 'inverted V' electron precipitation events associated with auroral arcs are also observed near and poleward of the electric field reversal/trapping boundary. These observations are discussed in terms of a current model of magnetospheric convection. (Author), Sponsored in part by Contract NAS1-8141 and Grant NGL-16-001-043.

The paper reports on the operation and results of the double-probe DC electric field experiment on the low altitude polar orbiting Injun 5 satellite. At middle and low latitudes, where the convection electric field is generally very small, the operation of the double-probe electric field antenna is investigated by comparing measured electric fields with the vector V sub s cross the vector B electric field generated by the satellite motion through the ionosphere. Errors caused by sunlight shadows on the probes, wake effects, and antenna impedance variations are discussed. (Author), Sponsored in part by Contract NAS1-8141, NAS1-8144, NAS1-8150, and Grant NGL-16-001-043(97).

Whistlers received with the Injun 5 satellite are frequently observed to have bands with decreased signal amplitude at equally spaced frequency intervals. The frequency spacing between the bands is typically about 10 to 30 Hz. As many as 30 such bands have been observed on a single whistler. Subsequent investigations have shown that the bands are instead due to double or multiple strokes in the initial lightning discharge which result in destructive interference of the whistler signal at equally spaced frequency intervals. The frequency spacing between the interference bands is given by the inverse of the time interval between the lightning strokes. This simple explanation for these bands accounts for a number of peculiar characteristics which could not be accounted for with the gyrofrequency harmonic interaction hypothesis., Sponsored in part by NASA grants NAS1-8150 and NGR-16-001-043.

The Injun 5 satellite, launched into a low altitude (677 to 2528 km) polar orbit on August 8, 1968, carried a very-low-frequency (VLF) electric and magnetic fields experiment covering the frequency range from DC to 105 kHz for electric fields and 30 Hz to 10 kHz for magnetic fields. This paper describes the VLF experiment and presents initial results of immediate interest. Broad-band (30Hz to 10kHz) electric field intensities are found to be remarkably small, typically less than 100 microvolt/meter and seldom greater than 1 mvolt/meter. Most of the common types of VLF electromagnetic noise, electron and proton whistlers, chorus, ELF hiss, VLF hiss, and periodic emissions, have been observed simultaneously with both the electric and magnetic antennas, thus providing an excellent check on the operation of the electric antenna. Phase measurements between the electric and magnetic fields have been used to determine the direction of propagation, up or down the geomagnetic field. New phenomena observed include (1) spin modulation of lower hybrid resonance noise, (2) multiple frequency noise bands possibly related to lower hybrid resonance noise, (3) a narrow bandwidth electric field enhancement near the two-ion cutoff frequency, and (4) noise bands associated with harmonics of the proton gyrofrequency. (Author)

The direction of the Poynting flux, up or down the geomagnetic field, has been determined for several types of VLF radio noise phenomena observed with the Injun 5 satellite, thereby providing information about the source region of these waves and their propagation in the ionosphere. Determinations of the Poynting flux direction of proton whistlers show that they are propagating up the geomagnetic field lines in accordance with the accepted theory of proton whistler propagation, thus providing a good check on the experimental technique. Initial measurements are presented on the Poynting flux direction of the ELF hiss, periodic emissions, VLF hiss, and chorus. Of particular interest is a new type of VLF emission called a saucer which is found to be propagating upward from a source below the satellite. A qualitative explanation of the frequency-time shape of this new type of emission is presented. (Author), Sponsored in part by NAS1-8141, NAS1-8144, NAS8-8150 and Grant NGR-16-001-043.

Results of the Javelin 8.46 VLF electric and magnetic fields experiment flown from Ft. Churchill, Canada, on May 25, 1968, are discussed. This experiment carried three orthogonal magnetic loop antennas, three orthogonal long (3.16 meters) electric dipoles, two short (42 cm) electric dipoles, and six wideband (30 Hz to 10 kHz) receivers for amplifying signals from the various VLF antennas. Intense noise bursts with frequencies less than about 1.5 kHz were observed on all the electric antennas below 500 km altitude, but not on the loop antennas. The precession and spin modulation of these noise bursts suggest that the noise is generated by an interaction between the payload and the surrounding plasma. High frequency electrostatic noise bursts, from 5 to 30 kHz, were observed throughout the flight. These noise bursts, similar in some respects to lower-hybrid-resonance noise commonly observed with satellite VLF electric field experiments, also appear to involve an interaction between the payload and the surrounding plasma. Attenuation bands at harmonics of the proton gyrofrequency were also found in the frequency spectra of electric field noise observed during a portion of the flight. (Author)

Observations of intense bursts of very-low-frequency (VLF) radio noise at low altitudes near the magnetic equator are reported using data from the Injun 3 satellite. The spectral characteristics of these radio noise events typically consist of hiss extending from about 1 kHz to above 8.8 kHz (the highest frequency measured). These equatorial VLF hiss events are very similar to VLF hiss commonly found near the auroral zone. During the ten month lifetime of Injun 3, a total of ten VLF hiss events occurred below 35 degrees magnetic latitude with noise spectral densities exceeding 3 x 10 to the 10th power gamma squared/Hz. All of these events occurred below 350 km altitude and at L values less than 1.2. Nine of the events occurred below 20 degrees magnetic latitude. These equatorial VLF hiss events are noteworthy because of their unusual region of occurrence. Whereas auroral zone VLF hiss may be attributable to the precipitation of energetic (E = or < 10 keV) charged particles, no comparable flux of charged particles is known to exist in the region where the equatorial VLF hiss occurs. (Author)

An observation of electrostatic noise bands observed with the Javelin 8.46 sounding rocket is presented. It is shown that these noise bands are related to harmonics of the proton gyrofrequency. This observation is believed to be the first confirmation of ion gyrofrequency harmonic effects in the ionosphere. (Author)

The Javelin 8.45 rocket VLF experiment flown from Wallops Island at 07:38 UT, 21 September 1967, to an altitude of 763 km is described and the experiment results are discussed. This experiment carried three electric dipole and three magnetic loop antennas, five wideband receivers (30 Hz to 10 KHz), one step frequency receiver (7 KHz to 70 KHz), an instrument to measure the phase and magnitude of the electric antenna impedance (20 KHz to 20 Hz) and a VLF transmitter in the nose cone. A noise band between about 7.5 KHz and 30 KHz was observed with both the electric and magnetic receivers. The field geometry of this noise suggests that the noise is propagating perpendicular to the geomagnetic field and that the lower cutoff frequency may be the lower hybrid resonance frequency. Some evidence suggests that this electric antenna noise may be generated by the motion of the payload. (Author)

A summary of recent satellite observations of VLF emissions and their association with energetic charged particles is presented. Using data from the Injun 3 satellite maps of the broadband intensity of magnetospheric VLF emissions are shown as a function of invariant latitude and magnetic local time. Examples of the simultaneous occurrence of VLF emissions and energetic charged particle precipitation are discussed. (Author), Prepared for presentation at the Advanced Study Institute on Earth's Particles and Fields, Freising, Germany, Jul 31-Aug 12 1967.

A statement is made of the theory and of the formulas used to derive the concentration of H(+) ion relative to the electron concentration and the ion temperature from the measurement of proton-whistlers. The potential results are discussed of measuring proton-whistlers from all of the Injun III VLF data based on a preliminary study of local summer day and winter night. Other measurements are suggested that can be made on VLF data to obtain the concentrations of He(+) and O(+) relative to the electron density., Available copy will not permit fully legible reproduction. Reproduction will be made if requested by users of DDC. Copy is available for public sale.

Broad-band VLF radio noises from about 4 kc/s to above 10 kc/s are frequently observed near the auroral zone with the Injun 3 satellite. These broad-band VLF radio noises are called VLF hiss. In this study we select VLF hiss events for analysis by requiring that the radio noise intensity from 5.5 to 8.8 kc/s exceed 3 x 10 to the -10th power gamma 2/cps (about 5 times the receiver noise level). The frequency spectra of the VLF hiss observed by Injun 3 is typically a flat noise spectrum with a distinct lower frequency cutoff. The lower frequency cutoff is often found to have a nearly symmetric latitude variation centered on a region of intense electron precipitation. The range of invariant latitudes (INV) for which VLF hiss typically occurs is about 10 wide and centered on 77 INV at 12.0 hours magnetic local time (MLT), decreasing to 72 INV at 23.0 hours MLT. On the high latitude side of the 40 keV trapping boundary, where VLF hiss usually occurs, intense fluxes of soft electrons are often accompanied by FLF hiss. It is found that the correlation between VLF hiss and intense fluxes (j > 2.5 x 10 to the 7th power (sq. cm ster sec)-1 of electrons (E > 10 keV) is dependent on the exponential folding energy E. The correlation is very good for E from 3 to 4 keV but poor for larger E values. (Author)

A method is discussed for determining H ion concentration, electron number density, and proton gyrofrequency in the vicinity of the satellite by measurements of the asymptotic frequency-time profile of a proton whistler near the proton gyrofrequency. This new technique is applied to proton whistlers received by the Injun 3 VLF receiver. The calculated values of H ion concentration and electron density are shown to be in good agreement with measurements by other experimenters at similar altitudes, latitudes, and local times. B values calculated from the proton gyrofrequency are compared with values calculated from the Jensen and Cain expansion for the geomagnetic field. It is shown that the wave energy of a proton whistler is guided very nearly along the geomagnetic field and that the parallel component of the group velocity is closely approximated by the group velocity for longitudinal propagation. (Author)

The authors describe the electric field noise phenomena observed by the S3-A spacecraft near the plasmapause during the magnetic storm of December 16-17, 1971. The most striking and unusual feature of these storm time electric field observations is the occurrence of a region of intense low-frequency (2O Hz to 500 Hz) electrostatic noise bursts just outside the plasmapause boundary. These noise bursts occurred concurrent with the rapid decrease in 24.3 < or = E < or = 35.1 keV ring current protons mirroring near the equator during this storm and may be responsible for the pitch angle diffusion and loss of these particles. The characteristics of other phenomena, such as whistlers, ELF hiss, and banded chorus, observed near the plasmapause during this period are also discussed. (Author), Sponsored in part by Grant NGL-16-001-043.

ELF and VLF radio noises observed by satellites in the ionosphere often have a very sharp lower cutoff frequency near the proton gyrofrequency. The paper summarizes the experimentally observed characteristics of this low frequency cutoff and proposes an explanation for the cutoff based on the reflection of downward propagating, extraordinary mode, waves near the two-ion cutoff frequency between the proton and helium gyrofrequencies. This explanation, if correct, provides the first direct evidence that chorus and ELF hiss emissions are generated at high altitudes (above 3000 km) and not near the base of the ionosphere. Ground-based observations of 700 Hz noise bands near the auroral zone, previously attributable to proton cyclotron radiation at low altitudes in the ionosphere, can now be explained by this reflection mechanism. Other possibly related effects (such as multiple ELF noise bands and the reflection of whistlers at the two-ion cutoff frequency) are discussed. (Author)