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1.
The POLAR 5 rocket experiment carried an electron accelerator on a “daughter” payload which injected a 0,1 A beam of 10 keV electrons in a pulsed mode every 410ms. With spin and precession, injections were made over a wide range of pitch angles. Measurements from a double probe electric field instrument and from particle detectors on the “mother” payload and from a crude R.P.A. on the “daughter” payload are interpreted to indicate that the “daughter” charges to a potential between several hundred volts and 1 kV. The neutralizing return current to the “daughter” is shown to be assymetrically distributed with the majority being collected from the direction of the beam. The additional electrons necessary to neutralize the daughter are thought to be produced and heated through beam-plasma interactions postulated by Maehlum et al. (1980b) and Grandal et al. (1980) to explain the particle and optical measurements. Significant electric fields emanating from the charged “daughter” and the beam are seen at distances exceeding 100 m at the “mother” payload.  相似文献   

2.
Rocket-borne double probes for electric field measurements can be intermittently operated in special, diagnostic modes involving current bias and low-impedance shunts to obtain information on the properties of the ambient ionospheric plasma along the flight path. Several such modes, and the information that they can provide, are analyzed. For example, in a low-impedance mode with asymmetric bias, the attenuation ratio (i.e. signal amplitude in this mode over the signal amplitude in the electric-field measuring mode) is in a simple way related to the electron temperature of the ambient plasma. The special surface coatings (Aquadag or vitreous carbon) normally used for electric field probes provide very homogeneous surface properties, a feature which also contributes to the reliability of the electron temperature measurements. In addition to electron temperature, the modes analyzed can be used to measure electron density and to give some information on ion temperature. The data from four rocket flights from ESRANGE are discussed in the light of these results. Electron temperature was measured in three of these flights. In all cases the temperature profile is in good agreement with theoretically predicted profiles based on the CIRA 1965 reference atmosphere and the solar illumination prevailing during the respective flights (twilight). Electron density profiles obtained by means of the double probe are in good agreement with the density measured by the Langmuir probe in the two flights for which both kinds of data are available. They are also in agreement with the electron density data available from ionosondes. Finally, pulses occurring when one of the probes passed through the rocket's shadow, are used to determine the photoelectron yield of the probe coatings (Aquadag or vitreous carbon). The values obtained, (7 ± 3) × 10?6 A/m2 for Aquadag and (4 ± 2) × 10?6 A/m2 for vitreous carbon are in good agreement with expectations based on laboratory data and solar Lyman α radiation.  相似文献   

3.
The POLAR 5 sounding rocket, launched from Andøya, Norway, on February 1, 1976, was of the “mother-daughter” configuration.A rocket-borne electron accelerator, mounted on the “daughter,” produced a pulsed electron beam with a maximum current of 130 mA and electron energies up to 10 kev.Using a photometer the luminescence at 391.4nm produced by electrons colliding with ambient nitrogen molecules was studied. The observed light at 391.4 nm consisted of low background, with occasional flashes due to the natural auroral excitations, and intense sparkles when the electron beam was emitted.Below 130 km the light observed during beam injection can be explained by excitations of ambient N2 due to high energy beam electrons.In the altitude range from 150 km to apogee at 220 km, the observed light level during beam emission is fairly constant and much larger than that produced by the high energy beam electrons. A possible source of this light is the excitation of ambient N2 by an enhanced population of low energy electrons, created by the presence of a beam plasma discharge in the vicinity of the “daughter” payload.  相似文献   

4.
A space charge sheath is found to be formed whenever a high-velocity magnetized plasma stream penetrates a gas cloud. The sheath is always located at the head of the plasma stream, and its thickness is very small compared to the length of the plasma stream. Soon after the sheath is formed it quickly slows down to the Alfvén critical velocity. The plasma behind the sheath continues to move at higher velocity until the whole plasma stream is retarded to the critical velocity. In the interaction at gas density 1019 m–3 the sheaths are observed to be accompanied by a single loop of current with current density of 105 Å m–2. Maximum potential in the sheath ranges between 50 and 200 V.Presently available models for the sheath may explain the initiation of the sheath formation. Physical processes like heating of the electrons and ionization of the gas cloud which come into play at a later stage of the interaction are not included in these models. These processes considerably alter the potential structure in the sheath region. A schematic model of the observed sheath is presented here.Experiments reveal a threshold value of the magnetic field for plasma retardation to occur. This seems to correspond to the threshold condition for excitation of the modified two-stream instability which can lead to the electron heating. The observed current are found sufficient to account for the plasma retardation at a gas density of 1017 m–3.  相似文献   

5.
A “mother-daughter” rocket was launched from Andøya, Norway, February 1 1976 over two auroral structures. The “daughter” payload carried a 10keV electron accelerator and the “mother” carried a series of diagnostic instruments for monitoring optical and wave effects generated through beam-atmospheric interactions and production of secondary electrons.The experimental details are presented in this paper together with a survey of some of the results. This paper is also intended as a reference for a series of accompanying papers.  相似文献   

6.
Electron densities throughout the D- and E-regions of the ionosphere have been measured during two rocket flights from Woomera, Australia; one in the daytime and one at night. The detailed distributions have a height resolution of much better than a km over the majority of the height range which was 66–175 km on the day flight and 83–184 km at night. This resolution has enabled sharp changes in electron density to be observed such as those associated with positive ion changes near 85 km (Reid 1970) and with sporadic-E layers.The detail and large dynamic range in electron density (102 to 3 × 105 cm?3) were achieved by combining the data from an LF radio propagation experiment with those from a probe experiment. The radio equipment allowed measurement of both the phase and amplitude of the wavefield above a ground transmitter. The method of deducing electron density from the phase velocity of the penetrating component of the wavefield is explained in detail. A comparison of the probe current and electron density has shown that the ratio between them varies slowly with height.  相似文献   

7.
Possible waves and oscillations in the lunar photoelectron layer (PEL) are investigated. The steady state PEL is reviewed as a basis for discussing PEL motions. Magnetic fields are neglected, so that there are four possible wave modes to consider. The propagation through the PEL of the two electromagnetic modes is discussed. Positive-ion waves, the third mode, are dismissed and plasma waves are considered at length. It is concluded that there are no propagating waves in the PEL other than electromagnetic. However, there is a type of oscillation which appears to be new and which may not be strongly damped. With these oscillations, termed flight-time oscillations, the height of the PEL fluctuates as does the electric field. These oscillations appear to be analogous to the height oscillations of the vertical jet of water in a city park water fountain. If flight-time oscillations are not much damped then it would be simplest to interpret them as plasma oscillations continually driven by the upwelling photoelectron stream. A possible laboratory investigation of these oscillations is discussed. For the surfaces of the Moon and the planet Mercury, the flight-time oscillation frequency,ω F, is found to be respectively ç 4 × 106 and ç 107 rad s?1. The PEL's of those surfaces may be in a state of continual vertical ‘quivering’ due to flight-time oscillations, or may be quiescent.  相似文献   

8.
High resolution electric field and particle data, obtained by the S23L1 rocket crossing over a discrete prebreakup arc in January 1979, are studied in coordination with ground observations (Scandinavian Magnetometer Array—SMA, TV and all-sky cameras) in order to clarify the electrodynamics of the arc and its surroundings. Height-integrated conductivities have been calculated from the particle data, including the ionization effects of precipitating protons and assuming a steady state balance between ion production and recombination losses. High resolution optical information of arc location relative to the rocket permitted a check of the validity of this assumption for each flux tube passed by the rocket. Another check was provided by a comparison between calculated (equilibrium values) and observed electron densities along the rocket trajectory. A way to compensate for the finite precipitation time when calculating the electron densities is outlined. The height-integrated HalI-Pedersen conductivity ratio is typically 1.4 within the arc and about 1 at the arc edges, indicative of a relatively softer energy spectrum there. The height-integrated conductivities combined with the DC electric field measurements permitted calculation of the horizontal ionospheric current vectors (J⊥), Birkeland currents (from div J⊥) and energy dissipation through Joule heating (ΣpE2). An eastward current of typically 1 A m?1 was found to be concentrated mainly to the arc region and equatorward of it. A comparison has been made with the equivalent current system deduced from ground based magnetometer data (SMA) showing a generally good agreement with the rocket results. An intense Pedersen current peak (1.2 A m?1) was found at the southern arc edge. This edge constituted a division line between a very intense (> 10 μA m?1) and localized (~ 6 km) downward current sheet to the south, probably carried by upward flowing cold ionospheric electrons and a more extended upward current sheet (> 10 μA m?2) over the arc carried by measured precipitating electrons. Joule and particle heating across the arc were anticorrelated, consistent with the findings of Evans et al. (1977) with a total value of about 100mW m?2.  相似文献   

9.
Using a well-known method for calculating the propagation of waves in an inhomogeneous medium, we have managed to reduce the problem of wave propagation in pulsar magnetospheres to a system of two ordinary differential equations that allow the polarization characteristics of the radio emission to be quantitatively described for any magnetic field structure and an arbitrary density profile of the outflowing plasma. We confirm that for ordinary pulsars (period P ∼ 1 s, magnetic field B 0 ∼ 1012 G, particle production multiplicity parameter λ ∼ 104), the polarization is formed inside the light cylinder at a distance of the order of a thousand neutron star radii. For reasonable magnetic field strengths and plasma densities on the emission propagation path, the degree of circular polarization is found to be ∼5–20%, in good agreement with observations.  相似文献   

10.
Pulses in electron intensity, occurring during the expansion phase of an auroral substorm, were studied using a Skylark sounding rocket launched from Kiruna, Sweden at 2226:50 UT on 2 March 1972. The pulses were typically of 5 s duration and occurred sporadically with a typical interval of 15 s. The rocket carried main and ejected payloads, and the pulses, occurring simultaneously at both, are found to be temporal rather than spatial in origin. Pitch-angle distributions changed little during a pulse, remaining slightly peaked towards larger pitch-angles. Precipitation is thought to be caused by pitch-angle diffusion under conditions where scattering angles are large compared with the opening angle of the loss cone. Enhanced scattering and variations in the temperature of the source plasma are both considered as possible causes of the pulse-like modulation. A dispersion in the times of occurrence of the pulses at different electron energies (3·8, 5·7, 9·0, > 18 and > 48 keV) indicates that the pulses originated at distances which varied between 41,000 ± 4000 km and 90,000 ± 7000 km during the flight. The larger distances are seen as evidence for temporary distortion of the local (L = 5·4) geomagnetic field lines whereby they are stretched to twice their normal (near-dipole) length. It appears that over a period of 100 s the field lines expanded and contracted at a speed of approximately 1000 km s?1. The further observation that the electron energy spectra were approximately Maxwellian, with a temperature equivalent to ～3 keV, helps to confirm the indications that the precipitation and its modulation were controlled directly by processes taking place in the plasma sheet. Other possible causes of the variable dispersion are considered, but found to be inconsistent with the present results.  相似文献   

11.
During the flight of a Petrel rocket, instrumented by the SRC Radio and Space Research Station with Geiger counters and launched westwards from South Uist, Outer Hebrides, Scotland (L=3.38), a transient increase was observed in the intensity of energetic electrons having pitch angles between 60 and 120°. The increase, by a factor of 20 above the quasi-steady intensity observed throughout the remainder of the flight, occurred in 0.8 sec and was simultaneous for both >45 keV and >110 keV electrons. Recorded ～0.5 sec later, on the ground, was a two-hop whistler. During the enhanced electron intensity event, the entire duration of which was ～6 sec, the four-, six- and eight-hop whistlers were also received. From an analysis of the whistlers' spectrogram, it is concluded that the whistlers were ducted through the magnetosphere along the L=3.3 ±0.1 field line; the electron density in the equatorial plane is found to be 330 ±10 cm?3, a value characteristic of conditions within the plasmapause. It is suggested that these temporally and/or spatially associated phenomena, rather than arising by a chance coincidence, were the result of a gyroresonant interaction between energetic electrons and whistler mode waves moving in opposite directions. For gyroresonance on this field line at the equator, the parallel component of energy of the electrons is 25 keV at 3 kHz in the whistler band, or 100 keV at 1 kHz below it. It is suggested that a magnetospheric event occurred, causing both sudden enhanced electron precipitation and favourable conditions for the propagation and/or amplification of whistlers. A possible explanation is that energetic electrons, having a sufficiently anisotropic distribution function and associated with those injected during an earlier auroral substorm, become unstable via the transverse resonance instability when they drift into the plasmasphere, a region of high density thermal plasma.  相似文献   

12.
The spacecraft ISEE-3 was launched in August 1978 and subsequently placed in orbit about the Sun-Earth L1 libration point where it continuously monitored the particles and fields in interplanetary space until mid-1982. The ISEE-3 Energetic Proton Anisotropy Spectrometer makes 3-dimensional intensity measurements of 35–1600 keV, Z ? 1 ions. This data is used in conjunction with simultaneous solar wind plasma and magnetic field data from the same spacecraft to study the properties of ions in interaction regions lying at the leading edges of nine corotating high speed solar wind streams observed during October 1978–July 1979. Seven streams have an enhancement of ? 300 keV ions in the compressed fast stream plasma between the stream interface and interaction region trailing edge. These enhancements are associated with plasma heating to above 3 × 105 K, have soft spectra (spectral index ～ 4.5?6.0) and in five cases show anti-solar streaming in the solar wind frame.  相似文献   

13.
The suggestion is explored that the two-stream instability has little effect on the propagation of the electron streams which generate type III bursts because the time required (ti) for development of the instability is comparable with or greater than the time available (Δt) for growth of the waves. Inferred parameters for streams in the corona and measured parameters for streams at the orbit of the Earth are compatible with this suggestion. Quasi-linear relaxation, which should occur as the stream forms, ensures that equality ti = Δt is set up initially, and restricts the number of escaping electrons to N s ≈ 1031. The minimum density requirement on the stream for the two-stream instability to occur is found to be much less restrictive than the requirement that there should be many streaming electrons per Debye sphere.  相似文献   

14.
A rocket C.W. radio propagation experiment has been used to measure electron density profiles and the results compared with values calculated from ionograms. In general the agreement is satisfactory but significant discrepancies in the rocket measurements, during the up-leg portions of several rocket flights above 110 km were observed and possible causes are discussed. In one flight the effect of a travelling ionospheric disturbance on the N(h) profile was recorded. Sporadic E strata with thicknesses of 0.6–0.8 km were recorded in these flights.  相似文献   

15.
The POLAR 5 sounding rocket, launched from Andøya, Norway on 1 February, 1976 was of a “mother-daughter” configuration. An electron accelerator, mounted on the “daughter,” produced a pulsed electron beam with currents up to 130 mA and electron energies up to 10 keV. The waves, artificially stimulated by the injected electron beam, was studied using wave receivers, mounted on the “mother.” The receivers covered the frequency range from 0.1 kHz to 5 MHz.

In addition to the stimulated waves observed during beam injection, enhanced wave emissions were observed 10–20 ms after the end of beam injection. This emission seemed to be relatively independent of whether the electron beam is launched up or down along the geomagnetic field.

The high frequency emission observed after beam injection is found to be correlated with the passage through an auroral arc. In particular this emission is closely correlated with the flux of 4–5 keV auroral electrons.

The low frequency emissions observed after beam injection are concentrated in two bands below the lower hybrid frequency.

Different mechanisms for explaining the observed time delays between the beam injection and the observation of the emissions are discussed.  相似文献   


16.
This paper discusses the experimental results on electron precipitation in a diffuse aurora obtained by a sounding rocket launched from ANDENES (L ～ 6·2) on 3 November 1968. A considerable increase in the intensity of low energy electrons, Ee ? 5 keV, followed a large precipitation of more energetic electrons Ee ? 5 keV. From the observation of angular distributions and an estimate of the diffusion coefficient (Dα ? 10?3 (sec)?2), it is suggested that this higher energy precipitation is induced by gyroresonant interactions of magnetospheric electrons with radiation in the whistler mode. The lower energy precipitation separated in time and/or space, shows quasi-periodic modulations in the 5–15 sec range with periods close to the bounce period. It is suggested that this precipitation is the result of bounce-resonance interactions with electrostatic waves in the equatorial plane. Finally, from a comparison between the experimental energy spectra and plasma sheet spectra it can be concluded that these electrons are injected from the plasma sheet during a substorm and are then diffused and precipitated by energy dependent mechanisms.  相似文献   

17.
The NASA DS1 spacecraft encountered Comet P/Borrelly on September 22, 2001 at a distance of ∼2171 km on the sunward side of the comet. The flyby speed was ∼16.5 km s−1. Using high temporal resolution (50 μs) absolute electric field amplitude measurements from a ∼1 m dipole antenna, new features of plasma clouds created by cometary dust impacts have been detected. The pulses have 1/e exponential decays of ∼650 μs duration, exponentially shaped overshoots with rise times of ∼2 ms, and exponential-shaped overshoot decay times of ∼10 ms. Assuming a plasma temperature of 104 K, these pulse features have been explained as plasma cloud space charge effects from the electron, proton and heavy ion portions of the clouds passing the antenna. Complex pulse shapes were also detected. These are believed to be due to either plasma cloud scattering off of the spacecraft, or to secondary impacts. Small electric pulses of duration 10-15 ms of cometary origin were detected but are presently unexplained. The electric component of the plasma wave spectra at closest approach had an f−2.4 power law shape from 10 Hz to 1 kHz. The electron cyclotron frequency was approximately 1 kHz. One possible explanation of the wave spectrum is that whistler mode waves associated with phase steepened cometary plasma waves are dispersed, leading to the broad spectrum. Finally, based on the present results, a new type of low-cost, large-area dust detector is proposed.  相似文献   

18.
The interaction between an artificially produced narrow beam of electrons and the upper atmosphere has been studied by the POLAR 5 electron accelerator “mother”-“daughter” rocket. It is shown how the beam develops a “halo” of scattered electrons and how the low energy electron population in this “halo” is produced partly during the ionization process (at low altitudes), partly by a “wave-plasma” interaction which accelerates the ionospheric background electrons.  相似文献   

19.
A sounding rocket was flown during the predawn on 17 January, 1976 from Uchinoura, Japan, to measure directly the behaviour of the conjugate photoelectrons at magnetically low latitudes. On board the rocket were an electron energy analyzer, 630 nm airglow photometer, and plasma probes to measure electron density and temperature. The incoming flux of the photoelectrons was measured in the altitude range between 210 and 340 km. The differential flux at the top of the atmosphere was determined to be F = (1.3 ± 0.4) × 1011exp[?E(eV)12] electron · m?2 · sr?1 · s?1 in the energy range 10 ? E ? 50 eV. The emission rate of the 630 nm airglow was observed in the altitude range between 90 and 360 km. The apparent emission rate observed at 80 km was 32 ± 5 R. From a theoretical calculation of the optical excitation rate using the observed electron flux data along with a model distribution of atomic oxygen, it was estimated that more than 65% of the emission could be produced by direct impact of the photoelectrons with atomic oxygen in the thermosphere between 200 and 360 km. Using the observed electron density and the model distribution of oxygen molecules the residual of the emission was ascribed to the excitation of O(1D) through dissociative recombination, O2++e→O1 + O7. The direct collisional excitation by ambient electrons is estimated to be negligibly small at the level of observed electron temperature.  相似文献   

20.
Results are reported from a rocket experiment conducted at Søndre Strømfjord, Greenland, on 22 August 1976, at 16.00 M.L.T. A series of plasma, particles, and fields and wave experiments were carried on board the payload, and the venture was supported by data from the AE-C satellite and by groundbased ionosondes and magnetometers at the launch site and at Godhavn. Two regions of field-aligned electron precipitation, electron density and temperature enhancements, and field-aligned upflowing current sheets were intercepted by the rocket. The density enhancements were also observed by groundbased ionosondes. Significant discrepancies were found between the currents carried by the streaming electrons in the 0.15–10 keV range and the upflowing currents seen by the on board magnetometer, suggesting that the upflowing current could not be the primary driver of the electron acceleration mechanism. The E-region was unstable to the combined Gradient-Drift and Farley-Buneman instability, and plasma turbulence was observed in situ, but the absolute density fluctuations were too small to return detectable HF-radar power to the ground.  相似文献   

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