A sounding rocket observation of an apparent wake generated parallel electric field (original) (raw)
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Geophysical Research Letters, 1998
The three-axis electric field experiment on the Polar satellite provides direct observations of electric field components parallel and perpendicular to the local magnetic field with no arbitrary adjustment parameters. Approximately 750 perigee passes through each of the two southern auroral zones at a geocentric altitude of about two Earth radii have been computer-searched for parallel electric fields whose eight point (0.2 or 0.4 second) average exceeded 100 mV/m. After elimination of spurious events due to shadowing, saturation, and ten other effects, four events containing parallel fields of 200-300 mV/m, remain. These four events all occur in upward field aligned current regions, their parallel electric fields are all positive such that j • E > 0, and they occur at boundaries between regions of active and quiet perpendicular electric fields. Up-going ion beams are observed in the active field regions, and the plasma density is higher in the quiet field regions than in the adjacent active field regions. These boundaries are interpreted in terms of model equipotentials, some of which are below the spacecraft in the large field regions and all of which are above the spacecraft in the quiet field regions. In this model, the expected location of large parallel electric fields is where they are observed. That the potential difference measured by the electric field instrument along the vehicle trajectory and the kinetic energy of the up-going ions are equal lends further credence to the data and its interpretation. Discussion It is generally agreed that electric fields parallel to the background magnetic field exist in the auroral acceleration region to produce up-going ion beams and down-going inverted-V electrons. If these parallel fields are quasi-static and small compared to the 100-1000 mV/m perpendicular fields that are present, they cannot be detected by the electric field experiment on the Polar satellite. This is because uncertainties in the measured parallel field, arising primarily from angular uncertainties in the detector orientations, are comparable to or larger than such fields. However, strong double layer or electrostatic shock theories [Block, 1972; Kan, 1975; Swift, 1975; Swift, 1979] predict parallel fields that are comparable to or larger than the perpendicular field. Such fields can be measured easily if the spacecraft flies through a region containing them. It is the purpose of
Rocket spin effects on the current collected by a cylindrical probe in the ionosphere
Journal of Geophysical Research, 1976
The dc current collected by a rocket-borne cylindrical probe with various bias potentials has been measured, along with the plasma parameters (by in situ independent measurements on the same payload). Periodic variations synchronous with the rocket spin cycle appear; they are related to wake effects for the ion current and to both wake and ¾ x B effects for the electron current. The ion current modulations are quantitatively explained by a theory on the wake which takes account of the angle between the velocity and the rocket axis; the electron current modulations due to the V x B field are separated from the others and quantitatively explained by simple calculations. As a by-product the ion current outside the wake gives an unperturbed density measurement in agreement to within 15% with an independent measurement.
ASPI experiment: measurements of fields and waves on board the INTERBALL-1 spacecraft
Annales Geophysicae, 1997
The plasma-wave experiment ASPI (analysis of spectra of plasma waves and instabilities) on board the INTERBALL spacecraft is a combined wave diagnostics experiment. It performs measurements of the DC and AC magnetic ®eld vector by¯ux-gate and searchcoil sensors, the DC and AC electric ®eld vector by Langmuir double probes and the plasma current by Langmuir split probe. Preliminary data analysis shows the low noise levels of the sensors and the compatibility of new data with the results of previous missions. During several months of in-orbit operation a rich collection of data was acquired, examples of which at the magnetopause and plasma sheet are presented in second part of the paper.
The Electric Field and Waves Instruments on the Radiation Belt Storm Probes Mission
Space Science Reviews, 2013
The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by ∼15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the "highest quality" events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing et al. Space Sci. Rev. 2013).
Properties of the wake of small Langmuir probes on sounding rockets
Journal of Atmospheric and Terrestrial Physics, 1975
Split Langmuir probes have been used to study the near wake of small Langmuir probes on sounding rockets. The split Langmuir probe is a device which performs the usual measurement of current versus voltage for the two halves of a probe and, in addition, measures the difference current between the two halves to accuracies the order of IO4 times the single half plate current. Thus it is an ideal instrument for studying the near wake of a small probe. Experiments have been performed on two rocket flights using planar disk and cylindrical geometries and the results presented in this paper. Significant wake perturbations in plasma density and temperature were found due to the probe body itself, even though the probes were the order of or smaller than the Debye length. The largest effects of the wake are seen in the electron collection characteristics of the probe. The wvake of small probes show apparent magnetic field aligned structure, even though the probes were much smaller than the ion gyroradius. On one flight, a space charge potential large enough to substantially alter photoemission,-3.5 volts, was observed.
Radio Science, 1980
Two rocket payloads carrying plasma density probes with high spatial resolution have been flown in the auroral zone during active conditions. Simultaneous Wideband satellite scintillation and Chatanika incoherent scatter radar observations were made in order to study the properties of high-latitude irregularities and their effects on radio wave transmission. Unlike barium cloud striations and bottomside equatorial spread F, the observed power law dependence of the irregularities does not seem to be due to steepening of kilometer-scale structures, rather, a turbulent process seems to occur. In addition the power law indexes determined both from the probe and from the scintillation measurements indicates an in situ one-dimensional spectrum less steep than the k-2 value often reported. Both the probe and the scintillation data indicate absolute electron density fluctuations (An2•) •/2 of several times 109 m-3 during the expansion phase of an auroral substorm, with a layer thickness of several hundred kilometers. The observed S4 levels at VHF were in the range of 0.1-0.4. This level of scintillation, as well as the absolute density fluctuation levels and the power spectral density at the kilometer scale, are shown to be comparable with bottomside equatorial spread F. It is suggested that differences between the power spectral index in the present data set and the other ionospheric experiments mentioned above may be due to a highly conductive E layer and its effects upon the nonlinear evolution of irregularities. During another flight with lower magnetic activity but several bright auroral areas in the trajectory, much lower levels of absolute and relative density fluctuations were observed with a corresponding lower value for S 4. Two very sharp changes in electron density were observed (e-folding scales of 1.45 and 0.7 km) near the field line projected position of the auroral arcs. The associated density spectra were peaked at short wavelengths. The detection of very structured plasma within minutes of the poleward expansion phase of a substorm suggests that the Flayer irregularities were formed in the precipitation event. On the other hand, evidence is also presented for production or enhancement of irregularities in the presence of horizontal density gradients which suggests that plasma instabilities also play a role in the production of auroral zone irregularities. 1. INTRODUCTION New information concerning the phenomenology of equatorial and auroral scintillation has accrued from the successful operation of the Wideband satellite [Frernouw et al., 1977, 1978; Rino et al., Copyright ¸ 1980 by the American Geophysical Union. 1978]. These new data have encouraged further developments in the theory of ionospheric radio wave scintillations [Rino, 1980]. In addition, with the operation of Wideband and correlative groundbased measurements, notably the Chatanika radar, progress has begun toward understanding questions of physical mechanisms. In this paper we describe the results of rocket flights which probed the auroral 0048-6604 / 80/0506-1472501.00 491 492 KELLEY, BAKER, ULWICK, RINO, AND BARON plasma nearly simultaneous to an overpass of the Wideband satellite. Two of the rockets were launched in the midnight time period in November 1976 to altitudes of nearly 500 km. A third rocket in the series was launched at 0900 local time in March 1978 with an apogee of 320 km. All three were flown from the Poker Flat Research Range in Alaska, and the Chatanika radar was operated during each flight. In this paper we concentrate on the nighttime data. The daytime results will be discussed in a future publication. Details of the rocket payload have been presented elsewhere [Baker et al., 1978]. In brief the measurements were obtained by a 6-cm-diameter cylindrical probe extending 1 m along the forward spin axis of the rocket. The electron density of the plasma was derived by two techniques. The absolute density was determined from the RF impedance of the antenna. In addition, the variation in current to the hemispherical tip of this probe was measured while the probe was held at a fixed dc potential. The frequency response of both systems was high enough to provide measurements of electron density variations down to scale sizes of about a meter.
A measurement of perpendicular current density in an aurora
Journal of Geophysical Research, 1975
A Nike Tomahawk sounding rocket was launched into a 400-'y auroral substorm on February 7, 1972, from Esrange, Kiruna, Sweden. The rocket instrumentation included a split Langmuir probe plasma velocity detector and a double-probe electric field detector. Above 140-km altitude the electric field deduced from the ion flow velocity measurement and the electric field measured by the double probe agree to an accuracy within the uncertainties of the two measurements. The difference between the two measurements at altitudes below 140 km provides an in situ measurement of current density and conductivity. Alternatively, if values for the conductivity are assumed, the neutral wind velocity can be deduced. The heightintegrated current was 0.11 A/m flowing at an azimuth of 276 ø. The neutral winds were strong, exhibited substantial altitude variation in the east-west component, and were predominantly southward.
Journal of Geophysical Research, 1993
On January 28, 1990, the Dynamics Explorer 1 and Akebono satellites crossed a magnetic field structure at the equatorward edge of the polar cusp at altitudes of 22,000 and 5000 km, respectively, within 6 min of each other. Locally measured plasma particles and fields and magnetometer data from a ground station near the foot of the magnetic field line are more consistent with an interpretation of the structure as that of a standing Alfv•n wave than that of a quasi-steady field-aligned current sheet. We discuss the observations supporting this conclusion and other related observations of field-aligned currents, Alfv6n waves, and ion energization near the equatorward edge of the cusp. These observations suggest that Alfv6n waves are commonly present near the equatorward edge of the cusp.
Initial results from the POLAR magnetic fields investigation
Advances in Space Research, 1997
The POLAR magnetic field investigation was designed to provide a high temporal resolution and high sensitivity measurement of the magnetic field along the POLAR orbit from perigee at 2 R, to apogee at 9 R,. The objectives of the investigation include probing the field aligned currents that couple the solar wind interaction and the tail dynamics to the aurora1 ionosphere. The launch of the spacecraft on February 24, 1966 was nominal and the turn on of the instruments very successful. Comparisons with Tsyganenko's 1995 model of the external current systems show that at quiet times it reproduces the field well. POLAR is clearly observing the field aligned current systems and the ring current. On one occasion when the IMF was strongly northward and the solar wind dynamic pressure stronger than usual the high altitude, high latitude magnetosphere became filled with magnetosheath type plasma. This event was probably an encounter with the polar cusp near the cusp-magnetosheath interface.