摘要:

The photochemistry of CO2on Venus is discussed in the light of recent data obtained from Mariner 5 and Venus 4. It is suggested that preliminary data indicate that recombination of CO and O proceeds rapidly by formation of an unstable CO3complex. Models for the thermal structure of the Venus atmosphere are presented. These models are characterized by a remarkably small temperature lapse rate, about 2°K km−1, in the stratosphere. The scale height is approximately constant and equal to 5 km over an altitude range in excess of 50 km. The exospheric temperature is of the order of 700°K. It is suggested that dissociative recombination of CO2+could provide an important source of airglow emission in the fourth positive bands of CO. This emission system could account for the weak unidentified ultraviolet airglow detected by Mariner 5. The possibility of an important proton component of the Venus ionosphere is discussed. In particular, it is suggested that diffusion of proton from the sunlit hemisphere may provide an important nighttime source of ionization on Ve

ISSN:0148-0227    

DOI:10.1029/JA073i005p01513

年代:1968

数据来源: WILEY

摘要:

A number of models are considered for the electrical properties of the moon, and the interaction of each with the solar wind is described in detail for various angles of the interplanetary magnetic field. In general, a permanent shock will form ahead of the moon if its surface conductivity is high, a temporary shock will form if it has a very large conducting core, and no shock will form if there is a thick surface layer of poor conductivity. The rate at which the void behind the moon is filled depends on the orientation of the interplanetary field and its relative strength. The field depressions observed by Colburn et al. in the moon's plasma penumbra are explained qualitatively by the expansion of the plasma there.

ISSN:0148-0227    

DOI:10.1029/JA073i005p01523

年代:1968

数据来源: WILEY

摘要:

Details concerning the magnetic field structure expected on the basis of the author's model of solar wind interaction with the moon are discussed. A derivation is presented that supports the finding of Colburn et al. that the magnetic field in the plasma void region downstream of the moon (relative to the solar wind flow) is more intense than the ambient interplanetary magnetic field. In the expansion region surrounding the void, the field is less than ambient. These effects should be smallest when the magnetic field is perpendicular to the flow vector. A standing shock wave trailing several lunar radii behind the moon is expected regardless of the magnetic field orientation.

ISSN:0148-0227    

DOI:10.1029/JA073i005p01533

年代:1968

数据来源: WILEY

摘要:

A general technique is given for calculating the spectrum of plasma waves emitted upstream and downstream by a turbulent shock transition for a plane shock of arbitrary structure. The problem of identifying the waves of frequency ∼1 cps that sometimes appear to emanate from the earth's bow shock is discusse

ISSN:0148-0227    

DOI:10.1029/JA073i005p01543

年代:1968

数据来源: WILEY

摘要:

Pioneer 6 and 7 space probes carried charged‐particle telescopes that measured for the first time both the direction of arrival and differential energy spectra of protons and alpha particles over the energy range 0.6 to ∼100 Mev/nucleon. The background counting rate is reduced by using an anticoincidence shield around the telescope so that proton flux changes as small as ∼10−3particles/cm² sec ster are detected with a time resolution of ∼one hour. Near the beginning of the new solar activity cycle (no. 20) over the period December 1965‐September 1966, proton flux increases have been associated unambiguously with specific centers of solar activity. The origin and propagation of these protons in the corona and interplanetary space have been investigated for this period. Enhanced proton fluxes in the energy range 0.6–13 Mev have been observed to come from the sun continuously over heliocentric longitude ranges as great as 180° in association with specific active regions. The enhanced fluxes exhibit definite onsets, when the active centers reach ∼60–70° east of central meridian, and cutoffs, when the center reaches ∼100–130° west. The onset and cutoff, together with the modulation of galactic cosmic rays, point to the existence of a corotating magnetic region associated with the active center. Superposed on the 0.6‐Mev flux level are occasional large and discrete flare‐produced intensity increases from these centers extending in energy to more than 50 Mev for protons. The solar electrons that appear during the initial phase of some solar flare events have been excluded by energy loss versus range measurements. The protons from flares over a longitude range of>60° are observed initially to propagate rapidly through the corona to the interplanetary field. The short transit and rise times are not explained by isotropic diffusion from the flare site across coronal magnetic fields. From these observations, a quasi‐stationary model is proposed for the distribution of magnetic fields above the active center. In this model, some field lines rooted in or near the active center are spread out in the corona over a range of ∼100–180° longitude (possibly because of the presence of super‐heated coronal plasma) and then extended into interplanetary space by the solar wind. Observations prove that both the enhanced and discrete flare proton fluxes propagate along the spiral interplanetary magnetic field from the western hemisphere of the sun. Present evidence supports the view that the origin of the>0.6‐Mev proton flux is in flare‐like processes continually occurring in the solar active center. The existence of strong unidirectional anisotropies in the initial phases of discrete flare proton events implies that little scattering occurs in the magnetic fields between the sun and spacecraft. However, the gradual approach to an isotropic flux at late times indicates that the decay phase is controlled by the

ISSN:0148-0227    

DOI:10.1029/JA073i005p01555

年代:1968

数据来源: WILEY

摘要:

The problem of delineating the effects of the matter traversed by cosmic rays in the source region (which consists of matter in the ionized state) and in the interstellar medium (which is partially ionized) is investigated in great detail by studying the energy losses suffered by a charged particle in these two media. Expressions for the energy losses are derived from a consideration of the composition of neutral and ionized atoms in these media. The relative intensities of the nuclei of various energies and charges are then calculated for different path lengths traversed in such source regions and in space, taking both the effects of ionization loss and fragmentation in the media concerned. Three kinds of source spectra, namely power law spectra in total energy per nucleon, in kinetic energy per nucleon, and in rigidity are used for this purpose; the exponents and other constants involved in these spectra are deduced from the high‐energy data that are little affected by solar modulation. The implications of these calculations are discussed with reference to experimental results on the ratio of intensities (1) ΓH1αof H1nuclei (Z≥ 20) to α particles, (2) ΓHαof H nuclei (Z≥ 10) to α particles, and (3) ΓLSofLnuclei (Z= 3–5) toSnuclei (Z≥ 6) in the energy region 50–1000 Mev per nucleon. It is concluded that for similar source kinetic energy per nucleon and rigidity spectra, the effect of the matter traversed by particles in the source region is negligible compared to its value in the interstellar space. On the other hand, for a source spectrum that is a power law in total energy per nucleon, the experimental results would indicate an appreciable trapping of the particles in the so

ISSN:0148-0227    

DOI:10.1029/JA073i005p01583

年代:1968

数据来源: WILEY

摘要:

The role the external current responsible for the magnetospheric tail plays at quiet times in the penetration, motion, and arrival of low‐energy cosmic rays is deduced from the integration of 1‐ to 500‐Mev proton trajectories in a model magnetosphere. Using the Williams and Mead model, we show that protons can reach the midnight side at latitudes between 60° and 69° and the day side at latitudes between 60° and 80° by way of the tail. Protons have direct access to higher latitudes along open field lines. Thus, for latitudes above 60°, the cutoffs are lowered below the internal field cutoff values. No such lowering occurs for latitudes below 60° because the field lines in this region are not appreciably affected by the external current responsible for the tail. A daily cutoff variation, the minimum rigidity trajectories coming from the night side for any local time of arrival, is found. The directions of approach, along which the low‐energy cosmic rays cross the magnetopause en route to the station, show a variation with local time. The daily variation in cutoff and approach directions are induced by axial asymmetry of the geoma

ISSN:0148-0227    

DOI:10.1029/JA073i005p01593

年代:1968

数据来源: WILEY

摘要:

Observations of electron temperature and concentration at 1000 km carried out continuously since October 1964 by electrostatic probes on Explorer 22 have permitted certain ionospheric effects of increasing solar activity to be detected. Midday and midnight measurements throughout the latitude range of approximately 60°N to 60°S for one‐month periods in January 1965, 1966, and 1967 are presented. Comparison of these latitude profiles shows that the daytime electron concentration at 1000 km increases with solar activity at all latitudes, while the electron temperature increases initially (in the period from 1965 to 1966) but then decreases (1966 to 1967). The nighttime ionosphere is less affected by the increased solar activity, althoughNedecreases somewhat, andTeincreases slightly. This behavior of the 1000‐km ionosphere can be understood qualitatively in terms of the changing composition and density of the neutral atmosphere, which in turn is caused by the increase in neutral temperature during this period of increased solar activity. A factor of prime importance for the electron temperature is the escape of neutral hydrogen, which reduces the effective local cooling of electrons and permitsTeto rise initially. The higher gas temperatures associated with further increases in solar activity cause enhancement of the heavier neutral constituents (O, He), which again increases the local electron cooling and results in a return to lower electron tempera

ISSN:0148-0227    

DOI:10.1029/JA073i005p01607

年代:1968

数据来源: WILEY

摘要:

Six rocket measurements of theE‐region electron concentration distribution were conducted in the vicinity of the geomagnetic equator near the coast of Peru. The instrumentation consisted of the two‐frequency propagation experiment and a Langmuir probe. Four of the flights occurred near local noon on separate days. There is little variation between electron concentration profiles. No sporadicElayer was observed, althoughq‐type sporadicEwas visible on ionograms taken simultaneously with the flights. The remaining two flights were conducted on separate nights. The electron concentration height profiles suggest that on certain nights or, alternately, after midnight the equatorialEregion above 150 km is underF‐region control. The existence of a downward drift is supported by the measurements. Below 150 km, the existence of a layer at night has been established. The layer centered at 105 km had a peak density of 2 × 10³ cm−3on March 26, 1965, and 1.5 × 104cm−3on March 18, 1965. It is similar to that formed a

ISSN:0148-0227    

DOI:10.1029/JA073i005p01617

年代:1968

数据来源: WILEY

摘要:

This paper examines the relevance to the ionosphere of a certain plasma instability mechanism previously discussed by several authors. A linearized analysis of the mechanism is given that differs from earlier treatments in several respects and is more directly applicable to the ionosphere than to laboratory plasmas. It is found that the dynamo region of the ionosphere is likely to be unstable against the growth of irregularities in electron concentration with scale sizes in the range from a few tens of meters to a few kilometers, given the presence of steady electric fields comparable to those expected to be present from tidal dynamo action. It is further suggested that the space‐charge potentials associated with the growth of the dynamo‐region irregularities of larger scale size can be conducted up the magnetic field lines into theFregion, generating irregularities there in the presence of a vertical gradient in ionization near the equator and in the presence of horizontal gradients at high magnetic latitudes. It is shown that this theory appears to be capable of explaining many of the observed features ofF‐region irregularities, including their diurnal variation and their correlation with magnetic disturbance, which is in a positive sense at high latitudes and in a negative sense in the vicinity of the dip equator. The relationship of the mechanism to earlier theories of the growth of small‐scaleF‐region irregularities is

ISSN:0148-0227    

DOI:10.1029/JA073i005p01627

年代:1968

数据来源: WILEY