摘要:

Whistler mode noise leads to electron pitch angle diffusion. Similarly, ion cyclotron noise couples to ions. This diffusion results in particle precipitation into the ionosphere and creates a pitch angle distributon of trapped particles that is unstable to further wave growth. Since excessive wave growth leads to rapid diffusion and particle loss, the requirement that the growth rate be limited to the rate at which wave energy is depleted by wave propagation permits an estimate of an upper limit to the trapped equatorial particle flux. Electron fluxes>40 kev and proton fluxes>120 kev observed on Explorers 14 and 12, respectively, obey this limit with occasional exceptions. BeyondL= 4, the fluxes are just below their limit, indicating that an unspecified acceleration source, sufficient to keep the trapped particles near their precipitation limit, exists. Limiting proton and electron fluxes are roughly equal, suggesting a partial explanation for the existence of larger densities of high‐energy protons than of electrons. Observed electron pitch angle profiles correspond to a diffusion coefficient in agreement with observed lifetimes. The required equatorial whistler mode wide band noise intensity, 10−2γ, is not obviously inconsistent with observations and is consistent with the lifetime and with limiting trapped particle inten

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00001

年代:1966

数据来源: WILEY

摘要:

A new VLF phenomenon named a proton whistler has been identified in the VLF data from Alouette 1 and Injun 3 satellites. Two independent analyses on 12% of the proton whistler Injun 3 data were conducted: a semimonthly sample of data for Injun 3's 10‐month lifetime to determine the gross features of proton whistlers; and a local nighttime and local daytime study of proton whistlers. Six assertions are made from these experimental observations: (1) Proton whistlers are observed only after the reception of an upward‐propagating electron whistler. (2) At a frequency termed the crossover frequency (ω12), the initial electron whistler frequency‐time trace and the proton whistler trace are coincident in time. (3) Proton whistler traces show initially a rapid rise in frequency which starts at ω12and which asymptotically approaches the proton gyrofrequency Ω1(200–650 cps for altitudes of 2700–400 km). (4) Proton whistlers occur more frequently during local nighttime than during local daytime, and they have not been observed to occur below 442 km during local nighttime or below 640 km during local daytime. (5) The ratio of the crossover frequency to the proton gyrofrequency increases with decreasing altitude and approaches unity at an altitude of approximately 440 km around local midnight and approximately 640 km around local noon. (6) There is an apparent northern hemisphere‐southern hemisphere asymmetry in the occurrence of proton whistlers; they occur 3 times more frequently in the northern than in the southern hemisphere. Also, there is a high‐latitude boundary in the occurrence of proton whistlers that seems to correspond with the auroral zone. The theory describing proton whistlers due to Gurne

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00029

年代:1966

数据来源: WILEY

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00046

年代:1966

数据来源: WILEY

摘要:

The derivation and the accuracy of an expression relating the fractional concentration of H+, α1=n(H+)/ne, to the crossover frequency ω12for a VLF proton whistler are discussed. To an accuracy of ±3½% it is found that α1= (264/255) (1 ‐ Λ122), where Λ12= ω12/Ω1and Ω1is the proton gyrofrequency. Values of α1have been deduced from measurement of proton whistler spectrograms for some of the satellite Injun 3 VLF data and plotted against altitude (400–2600 km) and against invariant latitude (20°–63°) for summer daytime and winter nighttime of 1963. The fractional concentration of H+is found to be higher for winter nighttime than for summer daytime at all altitudes and latitudes; the ratio was approximately 3:1 at 1000 km. At 1000 km the value of α1dropped from 0.43 in the 20°–30° invariant latitude range to 0.27 in the 40°–45° range for summer daytime. For winter nighttime α1was nearly constant at 0.82 for 1000 km from 30° to 50° latitude, but dropped to 0.75 in the 50°–63° latitude range. Near 2400 km for summer daytime, α1drops from 0.65 at 46° latitude to 0.20 at 56° latitude. This same tendency is observed for winter nighttime, apparently being due to auroral‐zone heating. These observations are consistent with the assumption that the heavier ions tend to predominate with increasing latitude for a given altitude. Comparison of these VLF proton whistler results for α1is made with reasonably good agreement to rocket ion mass spectrometer results of NASA 8.23 and to Alouette 1 VLF results deduced from lower hybrid resonance frequency. This general agreement establishes the VLF radio technique as an independent method for determining ion concentrations in the ionosphere. The general equations for uniquely determining the concentration of O+, He+, and H+from observation of the critical frequencies (crossovers, hybrid resonances, and cutoffs) due to the presence of ions are

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00047

年代:1966

数据来源: WILEY

摘要:

A number of observations on satellite data are presented which pertain to low energy (∼100 key) electrons in the dark magnetosphere and which were obtained with a scintillation counter aboard Explorer 14. It is shown that the trapping region near the magnetic midnight meridian and at low magnetic latitudes extends on quiet days to distances in excess of 12 Re. The extent of this region and the morphology of electrons near its outer boundary are shown to have a pronounced dependence on geomagnetic activity. Electrons trapped in the distant geomagnetic field are shown to have a pitch‐angle distribution whose maximum is along the field lines and which undergoes a 90° change through a region of near Isotropic electron fluxes, generally located at about 7 to 8 Re, near the equatorial plane. Evidence is presented to the effect that the distant field as deduced from the anisotropic features of trapped electrons is highly distorted, having an almost radial appearance and showing a tendency to align itself along the earth‐sun direction. A case has been found in which trapped electrons in this region displayed a net flow away from the earth over a 3‐minute interval. Finally, it is shown that electron fluxes outside the trapping region and specifically in the tail of the magnetosphere are essentially isotropic, that they appear in pulse‐like events clustered around the geomagnetic equatorial plane (at least up to 16 Re), and that the frequency of their occurrence decreases with geocentri

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00061

年代:1966

数据来源: WILEY

摘要:

An analysis of the occurrence frequency of midlatitude geomagnetic bays gives strong support to the polar electrojet configuration of Akasofu, Chapman, and Meng. Modifications of that current system, combined with an emphasis on the importance of differential movement of the overhead current system with respect to an observer, result in consistent explanations of the form of most geomagnetic bay phenomena. A study is made of phenomena that we term ‘transition bays,’ and the dependence of the form of geomagnetic bays on latitude is investigated. It is shown thatDbays show a drop in occurrence frequency around local midnight relative to the number of events before and after. This dip is shown to identify the ‘demarcation line’ for the average current system for the bay. Subauroral and polar‐cap stations may lie in a ‘cancellation zone’ so that theHcomponent of the disturbance will have its contribution from the electrojet almost canceled by the contribution from the overhead return current. It is shown that there are two separate causes of geomagnetic bays, and their manifestations are discus

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00079

年代:1966

数据来源: WILEY

摘要:

Satellite Relay 1 has performed a thorough mapping of the energy spectrum and spatial distribution of protons in the inner zone. New intensity maps are presented in this paper for six energy ranges between 1.1 and 63 Mev as of January 1, 1963. With these six distributions and previously published intensities in two more ranges accurate energy spectrums can be constructed at arbitrarily selected locations throughout most of the inner zone. The Relay 1 data compare favorably with those of other experiments and unify our knowledge of the proton distributions. In any energy range the maximum intensity is found at the equator, and varies along a line of force near the equator as the third or fourth power of 1/B.There are fewer high‐energy than low‐energy protons, and they are found closer to the earth. Sample intensites arej= 3.7 × 106cm−2sec−1ster−1from 1.1 to 14 Mev atL= 2.2 on the equator andj= 1.6 × 104cm−2sec−1ster−1from 18.2 to 25 Mev atL= 1.6 on the equator. Neutron albedo sources, both cosmic ray and solar proton sources, are weaker than required by as much as four orders of magnitude at 1 Mev. Adiabatic breakdown theories are in disagreement with the spatial dependence of the energy spectrum and cannot be controlling factors. Injection and diffusion of solar wind particles is a possible source, but more theoretical work is needed to clarify the

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00097

年代:1966

数据来源: WILEY

摘要:

Fast pulsations, characterized by half‐widths of 2–10 seconds and temporal spacings of 4–30 seconds, in the intensity of auroral‐zone X rays have been investigated using simultaneous pairs of balloon‐borne detectors with spatial separations of approximately 100–200 km. Such events, usually of an hour's duration, occur almost exclusively in the midnight to dawn sector (0200–0800 local hours) and appear preferentially on the equatorward side of the auroral zone. Spectral analysis shows the phenomena to be nonstationary but suggests that quasi‐periods of 5–10 seconds ought to be considered a significant feature of the process responsible for such variations. Cross‐correlation studies confirm the limited spatial extent of individual pulsations, on the average, and further indicate the possibility of longitudinal motions. Microburst events, characterized by scores of transient bursts each of about 200‐msec half‐width, occur most frequently around local noon, favoring the late morning and early afternoon. There appears to be little average latitude dependence across the auroral zone. Individual events, however, may be quite restricted in latitude. On one occasion, microbursts were observed for the better part of 3 hours atL= 5.5 in the absence of similar activity atL= 6.5, suggesting a rather localize

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00125

年代:1966

数据来源: WILEY

摘要:

Observations of the intensity of the nucleonic component have been obtained with an airborne neutron monitor aboard the U.S. Naval Oceanographic Office Project Magnet aircraft in a worldwide survey extending from the equator to the north and south geomagnetic poles. The data were reduced to a standard pressure altitude (500 mm of Hg), and the effects of temporal variations were removed by a normalization procedure involving four ground‐based neutron monitor stations distributed over a wide range of latitude. Representation of the results in the form of an isocosm map revealed general agreement with the Quenby and Wenk calculations of threshold rigidities. Discrepancies are attributable to the inexactness of the approximation adopted for taking into account the effects of the penumbra. The location of the cosmic‐ray equator, determined at seven points, was in accordance with calculations using the sixth‐order expansion of the geomagnetic potential. The variation in intensity along the equator was in agreement with earlier results obtained during a different phase of the solar cycle. Measurements in the arctic and antarctic regions reveal that, during a period of extreme solar cycle modulation, the intensities in the northern and southern polar caps were equal within less than 0.5%. The latitude dependence of the atmospheric attenuation length of the nucleonic component,L, was determined from observations of the dependence of intensity upon altitude. In the plateau region, the mean value ofLwas 136.1±0.3 g/cm2.Lincreased by about 11% over the range of threshold rigidity from 2.5 to 16 Gv. The absorption mean free path, λa,deduced fromL, was 160 g/cm2in the plateau region. Calculations based on currently accepted models of nuclear collision and of the process of nucleon propagation through the atmosphere yielded a value for the interaction length, λa, of about 80 g/cm2. This increased to 85 g/cm2when the effects of charge exchange were co

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00143

年代:1966

数据来源: WILEY

摘要:

The Explorer 12 measurements of the magnetic field outside the magnetosphere are compared with ground magnetograms from arctic observatories. Results indicate that an exterior field with a southerly component tends to be associated with ground disturbance, whereas a northward field is associated with quiet conditions. Examples are presented showing how a north‐to‐south field‐direction change accompanies an increase in ground activity, and also how south‐to‐north changes may produce quiet intervals between substorms. Results are discussed in terms of breaking and reconnection of the interplanetary field to the dipole field as the solar wind carries the variously directed interplanetary fields past

ISSN:0148-0227    

DOI:10.1029/JZ071i001p00155

年代:1966

数据来源: WILEY