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1.
The horizontal electric field has been measured with balloons over the Pacific Ocean near the Sanriku Coast in Japan. By comparing the electric-field data obtained during magnetically disturbed periods, 16–17 October 1973, 6–7 October 1975 and 3–4 October 1977, with IMF Bz, auroral zone AU and AL, equatorial Dst and Δ(Dst)Δt, mid-latitude magnetic fields (H, D, Z at Kakioka), and the ionospheric electron density (?0F2 at Kokubunji), it is found that the observed electric fields of about 9 mVm?1 made the clockwise rotation during the growth and recovery stages of the magnetospheric substorms. Relations between high and middle latitude ionospheres and between the magnetosphere and the ionosphere are discussed in relation to the origin and propagation of these electric fields.  相似文献   

2.
The method of elimination of the nonrelativistic Doppler effect, suggested in 1960 by Badessa et al. allows the possibility of eliminating the influence of the first derivative of electron content ?N?t along the signal path. This gives in principal the possibility of measuring the second derivative of N and therefore of studying rapid small amplitude processes in the medium. Other possible reasons for the influence of the medium on the phase and frequency of signal stabilized with high accuracy (Δωω?10?12) are investigated. For example, the frequency shift appears due to the motion of the ionized medium. That allows under favourable conditions the study of large scale unbalanced electric fields in the ionosphere, magnetosphere and interplanetary space.  相似文献   

3.
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4.
An attempt has been made to estimate the east-west component (Ew) of the magnetospheric equatorial electric field near L = 1.12 during a magnetic storm period from the whistlers observed at our low latitude ground station, Nainital (geomag.lat. 19°1'N), on March 25, 1971 in the 0130–0500 IST sector. The method of measuring Ew from the observed cross L-motions of whistler ducts within the plasmasphere, indicated by changes in nose frequency of whistlers, has been outlined. The nose frequencies of non-nose whistlers under consideration have been deduced from Dowden-Allcock linear Q-technique. The variation of (?n)23 with local time has been shown, the slope of which can be directly related to the convection electric field. The estimated equatorial electric field at L? 1.12 is in the range 0.1–0.5 mV m?1 (in the 0130–0500 IST sector) during a storm period, which is in agreement with the results reported by earlier workers. The departure from a dipole field and the contribution of an induced electric field from the temporal changes have been discussed. The importance of an electric field study has been indicated.  相似文献   

5.
From an analysis of the local time distribution of the electron upper energy limit reached by the geostationary satellite GEOS-2 in cutting through the innermost part of the electron plasma sheet during fairly quiet conditions the following results have been obtained, among others. An electric field model given by E = ?▽{AR4sin(φ+π4)}, with the dusk singular point of the forbidden region boundary at 1500, instead of at 1800 M.L.T., is in quite good agreement with the observations. This means that effects due to the shielding by the hot plasma of the inner magnetosphere from the convection electric field are quite strong in situations of low disturbance level. The quiet-time convection electric field strength at 2100 M.L.T. in the geostationary orbit obtained from this analysis varies in the range 0.15–0.3 kV/Re. Six hours earlier or later in the satellite orbit the convection field is four times stronger. Also when the convection field varies, some information about its magnitude can be obtained from the keV electron measurements.  相似文献   

6.
The ionospheric electric field has been measured in the E region above the Churchill auroral research range under quiet and under disturbed conditions. Results were obtained 112 and 212 hr before local midnight over an altitude range of 115–165 km. The instruments and analysis differ from those used by other workers. An unusually advantageous vehicle motion resulted in dipole measurements along the magnetic field being modulated by the vehicle motion. Under quiet conditions and in the presence of a diffuse, east-west 2 kR auroral arc, the predominant vector component of the electric field was also quiet and between 35 and 40 mVm perpendicular to the magnetic field, southward. Parallel to the magnetic field, the vector component increased from ?17 mV/m at 130 km, reversed direction at 160 km during the latter third of the flight and fluctuated around + 6 mV/m between 155 and 135 km on the descent. Under disturbed conditions during the recovery phase of a large magnetic storm, the electric field was also more disturbed; however, there was no significant electric field along B. Analysis of effects caused when parts of the measurement system are connected by a common magnetic field line, and when one of the probes lies in the wake of the vehicle, shows that measurement perturbations produced by those effects are dominated by the magnetic field line connections and that wake effects are relatively unimportant.  相似文献   

7.
Ten years data set is used to separate the influence of IMF Bz-component and solar wind speed on the dawn-dusk component of magnetic variations in the summer polar cap. The reference level was chosen from most quiet periods of winter solstices (small polar cap and auroral zone conductivity) to exclude the inner source component. The linear regression analysis was then used to calculate the PC variation response to Bz under different ranges of solar wind speed. As a result, taking into account the value of polar cap conductivity and effects of induced currents, the response of dawn-dusk electric field component to Bz and V was obtained and the potential difference across the polar cap was estimated to be Δ?(kV) ≈ 6(V300)2 ? 9Bz(γ) for Bz ? + 1γ. The results give a proof for simultaneous operation in the magnetosphere of two electric field generation mechanisms, related to the boundary layer processes and magnetic field reconnection. The above-mentioned functional form was shown to correlate effectively with AE index (R = 0.73).  相似文献   

8.
When observed noontime values of the maximum electron density, NMAX(F2), in the ionospheric F2 region are plotted as a function of magnetic latitude, a curve is produced which has two peaks, one on either side of the dip equator at ±16° dip latitude. This paper theoretically investigates the daily variation of this latitudinal distribution in NMAX(F2) (the so-called Appleton or equatorial anomaly) and specifically attempts to account for the longitudinal differences observed between the American and Asian sectors.In Part II, models of the neutral atmosphere, production, loss and diffusion rates, neutral wind, and electric field are described and the electron densities obtained by solving the continuity equation utilizing these models are presented. In each sector, the extent to which the equatorial anomaly's daily variation is affected by changes in the geomagnetic field configuration, neutral wind, and E × B drift is examined. It is found that development of the anomaly is most sensitive to the electric field model assumed, and that the observed differences at the magnetic equator between the American and Asian sectors could be accounted for by an upward E × B drift which commences an hour or two earlier in the Asian sector.  相似文献   

9.
Daytime Pc 3–4 pulsation activities observed at globally coordinated low-latitude stations [SGC (L = 1.8,λ = 118.0°W), EWA(1.15,158.1°W), ONW(1.3,141.5°E)] are evidently controlled by the cone angle θXB of the IMF observed at ISEE 3. Moreover, the Pc 3–4 frequencies (?) at the low latitudes and high latitude (COL; L = 5.6 and λ = 147.9°W) on the ground and that of compressional waves at geosynchronous orbit (GOES 2; L = 6.67 and λ = 106.7°W) are also correlated with the IMFmagnitude(BIMF).The correlation of ? of the compressional Pc 3–4 waves at GOES 2 against BIMF is higher than those of the Pc 3–4 pulsations at the globally coordinated ground stations, i.e., γ = 0.70 at GOES 2, and (0.36,0.60,0.66,0.54) at (COL, SGC, EWA, ONW), respectively. The standard deviation (σn = ± Δ? mHz) of the observed frequencies from the form ? (mHz) = 6.0 × BIMF (nT) is larger at the ground stations than at GOES 2, i.e., Δ? = ± 6.6 mHz atGOES 2, and ±(13.9, 9.1, 10.7, 12.1) mHz at (COL, SGC, EWA, ONW), respectively. The correlations between the IMF magnitude BIMF and Pc 3–4 frequencies at the low latitudes are higher than that at the high latitude on the ground, which can be interpreted by a “filtering action” of the magnetosphere for daytime Pc 3–4 magnetic pulsations. The scatter plots of pulsation frequency ? against the IMF magnitude BIMF for the compressional Pc 3–4 waves at GOES 2 are restricted within the forms ? = 4.5 × BIMFand ? = 7.5 × BIMF. The frequency distribution is in excellent agreement with the speculation (<ωscΩi = 0.3 ～ 0.5) of the spacecraft frame frequency of the magnetosonic right-hand waves excited by the anomalous ion cyclotron resonance with reflected ion beams with V6 = 650 ～ 1150 km s?1 in the solar wind frame observed by the ISEE satellite in the Earth's foreshock. These observational results suggest that the magnetosonic right-handed waves excited by the reflected ion beams in the Earth's foreshock are convected through the magnetosheath to the magnetopause, transmitted into the magnetosphere without significant changes in spectra, and then couple with various HM waves in the Pc 3–4 frequency range at various locations in the magnetosphere.  相似文献   

10.
Whistlers recorded at Eights (L ? 4) and Byrd (f ? 7), Antarctica have been used to study large-scale structure in equatorial plasma density at geocentric distances ?3–6 RE. The observations were made during conditions of magnetic quieting following moderate disturbance. The structures were detected by a “scanning” process involving relative motion, at about one tenth of the Earth's angular velocity or greater, between the observed density features and the observing whistler station or stations. Three case studies are described, from 26 March 1965, 11 May 1965 and 29 August 1966. The cases support satellite results by showing outlying high density regions at ?4–6 RE that are separated from the main plasmasphere by trough-like depressions ranging in width from ?0.2 to 1 RE. The structures evidently endured for periods of 12 hr or more. In the cases of deepest quieting their slow east-west motions with respect to the Earth are probably of dynamo origin. The cases observed during deep quieting (11 May 1965 and 29 August 1966) suggest the approximate rotation with the Earth of structure formed during previous moderate disturbance activity in the dusk sector. The third case, from 26 March 1965, may represent a structure formed near local midnight. The reported structures appear to be closely related to the bulge phenomenon. The present work supports other experimental and theoretical evidence that the dusk sector is one of major importance in the generation of outlying density structure. It is inferred that irregularities of the type reported here regularly develop near 4–5 RE during moderate substorm activity. This research suggests that at least a major class of the density structures that develop near 4 RE are tail-like in nature, joined to the main body of the plasmasphere. The apparent disagreement with Chappell's results from OGO 5, which are interpreted as showing regions of “detached” plasma beyond 5 RE, may be related to the pronounced spatial structure of electric fields observed in high-latitude ionospheric regions that are conjugate to the magnetospheric regions in which the OGO-5 observations were made.  相似文献   

11.
VLF-emissions with subharmonic cyclotron frequency from magnetospheric electrons have been detected by the S3-A satellite (Explorer 45) whose orbit is close to the magnetic equatorial plane where the wave-particle interaction is most efficient. These emissions are observed during the main phase of a geomagnetic storm in the nightside of the magnetosphere outside of the plasmasphere around L = 3–5. The emissions consist essentially of two frequency regimes, one below the equatorial electron gyro-frequency, ?H0, and the other above ?H0. The emissions below ?H0 are whistler mode and there is a sharp band of “missing emissions” along ?= ?H02. The emissions above ?H0 are electrostatic mode and the frequency ranges up to 3?H02. It is concluded that these emissions are generated by the enhanced relativity low energy (1–5 keV) ring current electrons, penetrating into the nightside magnetosphere during the main phase of a magneto storm. Although the high energy (50–350 keV) electrons showed remarkable changes of pitch angle distribution, their associations with VLF-emissions are not so significant as those of low energy electrons.  相似文献   

12.
The direction of motion of the auroral forms in several sectors of the auroral oval during substorms is studied. The creation phase is characterized by the equatorward displacement of the luminous region in evening (15–21 LT) and in day (09–15 LT) hours, while individual forms in the luminous region drift mainly poleward with a mean velocity of 230 m/sec in day hours and equatorward with the mean velocity of 230 m/sec in evening hours. The equatorial shift of the luminous region correlates well with the BZ-component of the interplanetary magnetic field. The onset of the displacement coincides with the southward BZ-rotation and is accompanied by auroral intensity increase for about 10–20 min.During the expansive and recovery phases the day auroras drift poleward with mean velocities of 330 and 300 m/sec, respectively. In the evening sector the individual auroral forms drift both poleward and equatorward during the expansive phase and drift mainly towards the pole during the recovery phase with a mean velocity of 200 m/sec. In the morning sector characteristics of the motion of the individual auroral forms are more complicated than in the other sectors. The well defined shifts of the luminous region are not discovered. The possible relation between the motions of individual auroral forms with the magnetosphere convection is discussed.  相似文献   

13.
The magnetopause, the boundary layer, or current sheath, which separates the magnetosphere from the solar wind, is the particular interaction considered in this paper.The collision free electron skin depth, ξe = cωpe, where c is the velocity of light and ωpe, is the plasma frequency, gives a classical measure of the penetration depth of a collisionless plasma by an electromagnetic field. This penetration depth is small compared with the dimensions of the magnetosphere and hence the boundary layer may be conveniently considered in one dimension.In General all one dimensional solutions lie within an order of magnitude of the value of ξe, the only exception being the important one, in which the electric field perpendicular to the current sheath plane is not present, either due to a particular trapped particle distribution or due to a short circuiting end effect. For this exception the thickness is increased by the factor (mii/me)12.The current sheath solutions discussed are equilibrium solutions but not necessarily stable equilibrium solutions.The extension of the models to three dimensions has a larger effect than might at first be expected. The effect may be intuitively understood as a consequence of flux conservation in the sheath. The one dimensional solutions then correspond to the current sheath profiles at the thinnest point of the three dimensional sheath.  相似文献   

14.
A method recently reported for measuring radial drifts in the equatorial plane and ionosphere-magnetosphere coupling fluxes from the Doppler shifts and group delays on whistler mode signals is applied to VLF transmissions from station NLK on 18.6 kHz. Data from 22 nights, primarily during the months November to February, are analysed. When averaged over a time of about 90 min, drifts found are accurate to ±20 ms?1, corresponding to an equatorial electric field accuracy of ±0.05 mVm?1 and fluxes, to ±1.5 × 1012 el m?2 s?1 (two hemisphere total). Given currently accepted values of coupling fluxes, the flux accuracy is of marginal value on individual nights, but useful information on average behaviour may be obtained.We find fluxes generally contribute less than 20% to the measured Doppler shift, most of which is therefore produced by cross-L drifts. To an accuracy of about 20% then, Doppler data alone may give information on these drifts. Doppler shift data previously accumulated over a number of years and relating to signals in ducts near L = 2.3 are re-examined. Dominating the nightly behaviour is an inward drift which reaches a maximum of ～ 100 ms?1 as the duct ends cross the dusk terminator and an outward drift at dawn of the same magnitude which is initiated when the duct end crosses the terminator in the E or lower F-region. In some months, separate effects can be seen corresponding to sunrise at each end of the duct.During the night, there are clear differences between December and June solstice drift behaviour which are as yet unexplained.Two-hemisphere-total coupling fluxes found from the 22 nights of data are ～ 1?2 × 1012 elm?2s?1. At the time of the evening maximum of inward drift the flow is to the ionosphere, but later in the night upfluxes were measured.  相似文献   

15.
Magnetic-field aligned currents driven by plasma pressure inhomogeneities (plasma clouds) in the distant magnetosphere are analyzed quantitatively. A parallel potential drop is found to be established in the upward current region whenever a spatial scale D0 for the pressure gradient in the equatorial magnetosphere is smaller than ≈ 3g0BiB0, where g0 is a hot electron gyroradius in the equatorial magnetic field B0 (Bi denotes the magnetic induction in the ionosphere). A theoretical derivation is given for the experimentally observed linear relation T = AEp + T0 between the characteristic energy T of precipitating magnetospheric electrons and the peak energy Ep in inverted-V electron spectra. Three-dimensional potential structures accelerating electrons earthward are shown to be established beneath some model clouds which could correspond to a large scale inverted-V structure and to a thin (~ 1 km) auroral arc.  相似文献   

16.
New characteristics of VLF chorus in the outer magnetosphere are reported. The study is based on more than 400 hours of broadband (0.3–12.5 kHz) data collected by the Stanford University/Stanford Research Institute VLF experiment on OGO 3 during 1966–1967. Bandlimited emissions constitute the dominant form of whistler-mode radiation in the region 4? L? 10. Magnetospheric chorus occurs mainly from 0300 to 1500 LT, at higher L at noon than at dawn, and moves to lower L during geomagnetic disturbance, in accord with ground observations of VLF chorus. Occurrence is moderate near the equator, lower near 15°, and maximum at high latitudes (far down the field lines). The centre frequency ? of the chorus band varies as L?3> and at low latitudes is closely related to the electron gyrofrequency on the dipole field line through the satellite. Based on the measured local gyrofrequency ?H, the normalized frequency distribution of chorus observed within 10° of the dipole equator shows two peaks, at ??H ? 0.53 and ??H ? 0.34. This bimodal distribution is a persistent statistical feature of near equatorial chorus, independent of L, LT and Kp. However there is considerable variability in individual events, with chorus often observed above, below, and between these statistical peaks; in particular, it is not unusual for single emissions to cross ??H = 0.50. When two bands are simultaneously present individual emission elements only rarely show one-to-one correlation between bands. For low Kp the median bandwidth of the upper band, gap and lower band are all ～16% of their centre frequencies, independent of L; for higher Kp the bandwidth of the lower band increases. Bandwidth also increases with latitude beyond ~10°. Starting frequencies of narrowband emissions range throughout the band. The majority of the emissions rise in frequency at a rate between 0.2 and 2.0 kHz/sec; this rate increases with Kp and decreases with L. Falling tones are rarely observed at dipole latitudes <2.5°. The observations are interpreted in terms of whistler-mode propagation theory and a gyroresonant feedback interaction model. An exact expression is derived for the critical frequency, ??H ? 0.5, at which the curvature of the refractive index surface vanishes at zero wave normal angle. Near this frequency rays with initial wave normal angles between 0° and ?20° are focused along the initial field line for thousands of km, enhancing the phase-bunching of incoming gyroresonant electrons. The upper peak in the bimodal normalized frequency distribution is attributed to this enhancement near the critical frequency, at latitudes of ~5°. Slightly below the critical frequency interference between modes with different ray velocities may contribute to the dip in the bimodal distribution. The lower peak may reflect a corresponding peak in the resonant electron distribution, or guiding in field-aligned density irregularities. The observations are consistent with gyroresonant generation of emissions near the equator, followed by spreading of the radiation over a range of L shells farther down the field lines.  相似文献   

17.
An intense, localized auroral disturbance observed by Intercosmos-Bulgaria-1300 satellite in the morning sector at the altitude 850 km is analyzed in detail. The disturbance is characterized by strong “jumps” of electric and magnetic fields reaching ～ 80 mV/m and ～ 100 nT, fluctuations of ion density (Δn/n ～ 70%) and bursts of downward and upward energetic electron fluxes. Electric and magnetic disturbances display a distinct spatial-temporal relationship typical for the standing quasi-monochromatic wave (? ～ 1 Hz, λx ～ 10 km). The ratio of amplitudes of electric and magnetic fluctuations is equal to Alfvén velocity (ΔE/ΔB ～ vA/c). However, a strong parallel component of the electric field (～ 30 mV/m) and large ion density fluctuations indicate significant changes of plasma properties (the effects of anomalous resistivity are possible).  相似文献   

18.
We examine time variations of the total magnetospheric output UT and the two geomagnetic indices AE and Dst during the magnetospheric storm of 31 December 1967–1 January 1968. A unique feature of this particular storm is that the solar-wind magnetosphere dynamo power ε was nearly constant for about 24 h by maintaining a high value of ～1019 erg s?1. It is found that UT was also nearly constant during that period, indicating that the magnetosphere is primarily a directly driven system. However, during an early epoch of the storm, the electrojet intensity levelled off, while the ring current began to grow during the same epoch. Subsequently, there occurred a sudden surge of the electrojet intensity, while the growth of the ring-current levelled off. Later variations of both the AE and Dst indices were very complex. After the surge, the AE index continued to decline and became as low as ~250 nT during the maximum epoch of this major storm (when the Dst decrease attained the maximum values). This trend can also be seen in many other major storms, but is often masked by changes of ε. One possible cause for such features for ε ? 1019erg/s?1 is that the neutral wind is generated by the (E × B) motion in the lower ionosphere, reducing the electrojet intensity and enhancing the ring-current particle-injection rate.  相似文献   

19.
VLF whistler mode signals have previously been used to infer radial plasma drifts in the equatorial plane of the plasmasphere and the field-aligned ionosphere-protonosphere coupling fluxes. Physical models of the plasmasphere consisting of O+ and H+ ions along dipole magnetic field lines, and including radial Ez × B drifts, are applied to a mid-latitude flux tube appropriate to whistler mode signals received at Wellington, New Zealand, from the fixed frequency VLF transmitter NLK (18.6 kHz) in Seattle, U.S.A. These models are first shown to provide a good representation of the recorded Doppler shift and group delay data. They are then used to simulate the process of deducing the drifts and fluxes from the recorded data. Provided the initial whistler mode duct latitude and the ionospheric contributions are known, the drifts at the equatorial plane can be estimated to about ± 20 ms?1 (～10–15%), and the two hemisphere ionosphere-protonosphere coupling fluxes to about ± 1012 m?2 s?1 (～40%).  相似文献   

20.
During very intense geomagnetic storm of November 7–8, 2004 simultaneous presence of storm time disturbance dynamo and eastward and westward directed prompt penetration electric fields inferred from the ground based magnetometer data in the 75° E sector is presented. Magnetometer observations show that, on the whole, average ΔH variation on 8 November remains below the night time level compared to its quiet day variation. A number of upward and downward excursions have been observed between 0130 UT and 0800 UT in the ΔH variation on 8 November. These excursions in ΔH have been attributed to the episodes of eastward and westward prompt penetrating electric fields. Ionospheric response in the equatorial ionization anomaly region along 75° E has also been studied using the total electron content data recorded at five GPS stations, namely Udaipur, Bengaluru (IISC), Hyderabad (HYDE), Maldives (MALD) and Diego Garcia (DGAR). Observation of markedly suppressed EIA, in conjunction with ΔH variation which was m negative during the daytime on 8 November, indicates the presence of an external field of opposite polarity (the disturbance dynamo electric field) that either undermined, or overshadowed the daytime ambient (eastward) electric field to the extent that the equatorial plasma fountain could not become effective.  相似文献   

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