摘要:

During three balloon flights made in 1966 and 1967, cosmic electrons were investigated with the aid of a hodoscope detector that provided extensive and detailed information on each cosmic‐ray event triggering the apparatus. Similar information obtained during calibration exposures to protons and pions as well as to electrons was used to provide identification of cosmic electrons and to determine their energies. Differential primary electron intensities measured in the range from 1 to 25 Gev were substantially larger than some earlier measurements. In conjunction with existing measurements at energies above 100 Gev, this finding indicates that the energy spectrum of cosmic electrons is steeper than that of cosmic‐ray nuclei and consequently suggests that Compton/synchrotron energy loss plays a significant role in shaping the electron spect

ISSN:0148-0227    

DOI:10.1029/JA077i007p01087

年代:1972

数据来源: WILEY

摘要:

Low‐altitude dayside profiles of solar‐electron latitudes are examined as a function of magnetic activity. The solar‐electron measurements are compared both with outer‐zone electron measurements and with solar‐proton measurements in an attempt to determine the dayside limit of closed geomagnetic‐field lines. It is suggested that at magnetically quiet times the limit of closed field lines occurs at the position of the electron knee latitude (Λ ∼ 78°) and that, as magnetic activity increases, solar electrons scatter or diffuse across closed field lines. Thus the electron knee latitude at these times lies equatorward of the high‐latitude limi

ISSN:0148-0227    

DOI:10.1029/JA077i007p01103

年代:1972

数据来源: WILEY

摘要:

The interplanetary magnetic field is only slightly perturbed by the presence of the moon in the solar‐wind flow. A statistical study of the umbral increases and penumbral decreases and increases was conducted with variation of the solar‐wind plasma β value, the distance from the moon and the selenographic longitude of the limb regions of the lunar surface in the solar‐wind flow. All lunar‐wake anomalies show a strong positive correlation with the plasma β value, whereas only penumbral increases show a marked variation with distance from the moon. There is no clear correlation of occurrence of penumbral anomaly with selenographic longitude of the exposed lunar limb in the solar

ISSN:0148-0227    

DOI:10.1029/JA077i007p01109

年代:1972

数据来源: WILEY

摘要:

The earth's bow shock exhibited a clean laminar profile at low Mach number as it crossed and recrossed Ogo 5, Heos 1, and Explorer 33 on February 12, 1969. The approximate 120REdistance between Heos and Explorer during one set of crossings indicated the abrupt character of the laminar shock ‘front’ and the absence of magnetosheath turbulence both in the dayside hemisphere above the ecliptic and in the flank of the shock 75REbehind the earth and below the ecliptic. The abruptness of the shock and the coplanarity of the loci of Ogo and Heos with the local shock normal permit the most reliable estimates yet obtained of shock velocities along the normal. These mean velocities ranged from 11 to at least 100 km/sec over distances of 2

ISSN:0148-0227    

DOI:10.1029/JA077i007p01116

年代:1972

数据来源: WILEY

摘要:

In contrast with Haerendel's earlier analyses we point out that drift resonance due to electromagnetic perturbations does not result in violation of the second adiabatic invariantJ. A simple disturbance is chosen that suitably isolates the effects that have been suggested as important. When the classical adiabatic theory for motion within the disturbance is used, drifts appear that have been ignored in previous treatments. These drifts, however, reduce to such a form that it is clear they play no role in diffusive processes.

ISSN:0148-0227    

DOI:10.1029/JA077i007p01123

年代:1972

数据来源: WILEY

摘要:

A comparison of low‐energy charged‐particle intensities measured with the low‐altitude satellite Injun 5 and a ground‐based observation of an auroral arc at Fort Churchill on December 21, 1968, during late local evening has established that an intense precipitation band of electron intensities provides the primary energy influx for the auroral light. This precipitation event was located poleward of and adjacent to the trapping boundary for more energetic electron (E>45 kev) intensities. The peak energy fluxes were ∼10 ergs cm−2sec−1ster−1directed along the local magnetic‐field direction into the earth's atmosphere. Proton and electron intensities similar to those in the plasma sheet in the magnetotail were observed in a substantially less‐intense zone positioned equatorward of and adjacent to the trapping boundary. Angular distributions of these particle intensities from the plasma sheet were peaked at pitch angles perpendicular to the local magnetic field. The intense precipitation band of electron intensities poleward of the trapping boundary is interpreted as the signature of direct acceleration of magnetosheath electrons into the earth's atmosphere. The plasma‐sheet proton and electron intensities observed equatorward of the trapping boundary are identified as the ‘debris’ from this intense precipitation band located adjacent

ISSN:0148-0227    

DOI:10.1029/JA077i007p01128

年代:1972

数据来源: WILEY

摘要:

This paper presents a series of simultaneous observations of very‐low‐frequency radio noise by the Injun 5 satellite and of visual aurora along the same geomagnetic‐field line by the Fort Churchill Auroral Observatory. Seven observations from the period of August 29, 1968, to March 4, 1969, are discussed. In 5 of the 7 events studied VLF hiss is observed in association with auroral‐light emissions. These observations typically show the occurrence of VLF hiss in the general region of the auroral arc, with significant changes in the VLF spectrum sometimes observed in the immediate vicinity of the auroral arc. One event for which the associated charged‐particle fluxes have been analyzed is investigated in detail. The VLF radio noise intensity for this event is among the largest observed with Injun 5 and is much greater than can presently be explained by an incoherent Cerenkov radiation

ISSN:0148-0227    

DOI:10.1029/JA077i007p01137

年代:1972

数据来源: WILEY

摘要:

The 1963 and 1964 Alouette 1 records from the Ottawa station were studied to determine the statistical characteristics of VLF hiss exhibiting a sharp lower‐cutoff frequency associated with the lower‐hybrid resonance (LHR). A particular class of midlatitude hiss events were emphasized and designated ‘S‐type hiss.’ These events have lower‐cutoff frequencies that vary smoothly with time, have limited bandwidths, and do not appear to be associated with other VLF phenomena. Their diurnal time of peak occurrence provides evidence that their sources may be connected with the type of magnetospheric activity usually associated with auroral‐zone phenomena; yet, they are definitely midlatitude events. A likely means for transporting the electromagnetic energy is a horizontal duct that occurs as a result of the presence of more than one ion species in the topside ionosphere. Nonducted whistler‐mode signals may be trapped in the duct, and satellites within the region observe signals with characteristics determined by this guiding structure. Other forms of LHR hiss, such as whistler‐triggered events, may also be associated with these ducts. The characteristics of noise at altitudes above such ducts, or in the absence of ducts, may be different from that ofS‐type hiss. Some of the observed Alouette 1 events may be suc

ISSN:0148-0227    

DOI:10.1029/JA077i007p01146

年代:1972

数据来源: WILEY

摘要:

An ELF hiss band with characteristics not previously identified has been observed in data from the Stanford University VLF experiment on Ogo 4. The band exhibits the typical low‐frequency cutoff characteristic of downward‐propagating hiss and also a peculiar upper cutoff in the vicinity of 600 Hz, which is nearly independent of the satellite altitude (∼430 to 900 km) and latitude above ∼15°. This band‐limited ELF hiss (BLH) is observed from ∼10° up to 55° dipole latitude, where the nearly constant upper cutoff and the increasing (with latitude) lower cutoff merge. Around ∼10° dipole latitude, the BLH exhibits a sloping upper cutoff decreasing in frequency toward the equator (equatorial erosion). The BLH is seen most frequently from ∼0600 to ∼2200 LT, although some examples have been found between 0200 and 0500 LT, with less intensity. In the range 0 to 3 kHz and up to ∼55° dipole latitude, the BLH is the strongest signal observed. Its peak amplitude may reach 2 × 10−4γ²sol;Hz between 40° and 50° dipole latitude during daytime (∼1000 LT). After prolonged periods of low magnetic activity (Kp≤ 2), the upper cutoff may decrease to as low as 420 Hz but recovers about one day after a sharp increase in magnetic activity, such as a sudden commencement. The decrease and smearing of the lower cutoff of the background hiss, observed at latitudes greater than about 58°, is an indication of the light ion trough. A source location in the equatorial region nearL= 4 was found adequate to explain the characteristics of the BLH, as well as some of the observations of ELF hiss previously reported. Two possible generation mechanisms are briefly examined (Cerenkov and Doppler‐shifted cyclotron), but for either a certain amount of emission coherency or amplification is necessa

ISSN:0148-0227    

DOI:10.1029/JA077i007p01157

年代:1972

数据来源: WILEY

摘要:

With the use of a power integral formulation, a study is made of the VLF/ELF radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma. Expressions for the ray patterns are initially developed that apply for arbitrary values of driving frequencyf, static magnetic‐field strength , plasma density, and composition. These expressions are subsequently specialized to VLF/ELF radiation in a plasma modeled on the magnetosphere. A series of representative pattern plots are presented for frequencies between the proton (fpH) and electron (feH) gyrofrequencies. These patterns illustrate the fact that focusing effects that arise from the geometrical properties of the refractive index surface tend to dominate the radiation distribution over the entire rangefeH≥f≥ 4.6fpH. Focusing effects are particularly strong in the range ½feH≥f≥fLHR, where the major lobe of the pattern lies along and the lobe intensity varies inversely as the first power of the distance between source and observer rather than as the square of this distance. It is concluded that focusing effects should be of significant importance in the design of a VLF/ELF satellite transmitting system in the mag

ISSN:0148-0227    

DOI:10.1029/JA077i007p01174

年代:1972

数据来源: WILEY