摘要:

Spectral measurements of solar X rays with photon energy greater than 20 kev were carried out in 1959 during portions of three class 2+solar flares. Two of the flares showed strong fluxes with spectra equivalent to that expected from a thermal plasma with temperature ∼108degrees. The emission spectra obtained on September 1, 1959, were indicative of a rapidly cooling plasma with initial temperature of about 285 million degrees. It is argued that a similar plasma could have explained the observations of Peterson and Winckler in 1958 and that there currently exists no definitive observational evidence for nonthermal solar X‐ray emission. Spectra in the 2‐ to 20‐kev spectral region during solar microflare activity are suggestive of the existence of a peaking in the solar X‐ray spectrum in the 8‐ to 15‐kev region, presumably caused by Fe line and recombination contin

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03611

年代:1966

数据来源: WILEY

摘要:

Dessler and Karplus have predicted that measurable changes in trapped particle fluxes should accompany the betatron acceleration and radial movement of the particles due to time‐dependent diamagnetic ring currents. The adiabatic deceleration and reacceleration of trapped protons have now been observed by a detector on the Explorer 26 satellite. The measured time dependence of the particle fluxes are shown to follow the variations expected theoreticall

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03623

年代:1966

数据来源: WILEY

摘要:

The aurora, as determined from the College HF multifrequency backscatter records, was present somewhere on the College geomagnetic meridian during 1965 a minimum of 65% of the time at any hour on the dayside of the earth, and 95% on the nightside. The southern boundary of the aurora (1) occurred at approximately 77° geomagnetic latitude during midday periods whenKp, the planetary magnetic activity index, was less than 4, (2) during mid‐night periods occurred at approximately 70° whenKpwas 0o, and 68° whenKpwas less than 2, and (3) in general extended farther south at any hour as magnetic activity increased. The midday aurora on magnetically quiet days (Kp<4) during the 1965 summer solstice was approximately 1.5° north of that during the winter solstice. The 1965 backscatter results agree closely with 1957 to 1959 optical results; thus, the position and the rate of occurrence of the dayside aurora for a given level of magnetic activity are almost independent of both season and solar act

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03629

年代:1966

数据来源: WILEY

摘要:

Attention is drawn to the importance of backscattered planetary radiation for resonantly scattered day airglow. A simple method for estimating the appropriate albedo by ground measurements is suggested.

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03635

年代:1966

数据来源: WILEY

摘要:

In this paper we discuss a method of determining ion temperature in the ionosphere from cyclotron damping of proton whistlers. These whistlers are dispersed forms of lightning impulses, observed by satellites as propagating left‐hand polarized (ion cyclotron) waves. It is found that the amplitude of the proton whistler decreases abruptly at a wave frequency slightly below the proton gyrofrequency at the satellite. Of several factors considered, it is found that only cyclotron damping can satisfactorily explain this abrupt cutoff. The theory of cyclotron damping of proton whistlers is developed, and the difference between the wave frequency at cutoff and the proton gyrofrequency at the satellite is related to the proton temperature. Sample proton temperatures in the ionosphere are determined, using proton whistlers observed by the Injun 3 and Alouette 1 satellites. The temperatures found are comparable to those obtained previously by other experimenters. The method of observing ion temperatures developed here has inherent advantages in that the parameters measured are independent of electron temperature and ion compositio

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03639

年代:1966

数据来源: WILEY

摘要:

The extent and frequency of occurrence of spreadF, as shown on 8400 ionograms taken by the Alouette satellite, have been investigated. These ionograms were taken during the solstice periods of December 1962 and June 1963. The spreadFobserved was found to be consistent with three proposed qualitative radio‐propagation models. These models involve: aspect‐sensitive scattering from thin magnetic‐field‐aligned irregularities, waveguide‐like action—called ducting—along wide irregularities, and refraction due to large‐scale reductions in electron density. The three types of spreadFwere found to exhibit markedly different occurrence patterns during the two obse

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03653

年代:1966

数据来源: WILEY

摘要:

Very steep latitudinal electron‐density gradients are found to occur in the topsideFlayer at high latitudes. They occur either associated with the trough (>6% km−1) or within the auroral zone (>60% km−1). The electron‐density scale height at 1000 km may be nearly constant across these gr

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03665

年代:1966

数据来源: WILEY

摘要:

Values of the vertical column electron content of the ionosphere at Huancayo, Peru, are presented for an 18‐month interval. These data were obtained from an analysis of Faraday rotation data from a radio beacon satellite (Transit 4A). The daytime electron content is found to vary with the 10.7‐cm solar radio flux, and, after normalization for this dependence, the average diurnal variation is found to be quite regular with a range of about 20:1. A biannual variation in the daytime electron content is found also, with maxima near the equinoxes and with a range of about

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03671

年代:1966

数据来源: WILEY

摘要:

It is now generally agreed that the maximum probability of observing the radio aurora with a backscatter radar is obtained when the line of sight is orthogonal to the earth's magnetic field in the echo region. Significant but small departures from this rule have generally been explained either by changes in height of the echo region or by radio absorption. An explanation invoking tropospheric and ionospheric refraction is offered that explains in a simple manner many of the observed anomalies. A straightforward method of calculating the effects is presented, and curves are included from which all the important parameters may be immediately obtained. It is shown that tropospheric refraction is relatively unimportant in influencing the aspect angle, but it leads to a significant depression of the ray from its position determined in the absence of refraction.

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03677

年代:1966

数据来源: WILEY

摘要:

The production and equilibrium spectra of secondary electrons (negatrons and positrons) resulting from cosmic‐ray interactions in the galaxy are calculated. These electrons arise from the decay of secondary pions and neutrons produced by nuclear interactions of cosmic‐ray protons and alpha particles with the interstellar gas. The equilibrium flux is determined by escape of electrons from the galaxy and by ionization, inverse Compton, and synchrotron energy losses. A comparison of the calculated secondary electron equilibrium spectrum with the measured electron intensity, positron‐negatron ratio, and nonthermal radio emission from the galactic halo suggests that an additional primary electron source of roughly the same magnitude is req

ISSN:0148-0227    

DOI:10.1029/JZ071i015p03687

年代:1966

数据来源: WILEY