The thermospheric heating efficiency under electron precipitation conditions

in Planetary and Space Science (1982), 30

The results of a study of the altitude distribution of particle heating due to magnetospheric electron penetration into the atmosphere are presented. Updated chemical species data were used in the study ... [more ▼]

The results of a study of the altitude distribution of particle heating due to magnetospheric electron penetration into the atmosphere are presented. Updated chemical species data were used in the study, and attention was given to day- and night-side precipitation energy fluxes. The data base on chemical species was obtained from the Atmosphere Explorer C spacecraft and lower altitude observations. A system of 16 continuity equations was employed to formulate a time-dependent auroral model covering reactions and rate coefficients of electrons and O, O2, N2, NNO, and N ions. The heating efficiency of direct dissociation of atmospheric molecules, exothermic chemical reactions involving ions, ground state and metastable neutral species, and cooling of the thermal electrons was calculated. The calculations indicate that over 60 percent of the energy input is transferred to the neutral gas. Particle heating can exceed 1 erg/sq cm per sec. [less ▲]

MgII Airglow in the Atmosphere of Venus: Observations and Theory.

Conference (1982, June 01)

Not Available

The effect of particle precipitation events on the neutral and ion chemistry of the middle atmosphere. II - Odd hydrogen

in Planetary and Space Science (1981), 29

A one dimensional time-dependent model of the neutral and ion chemistry of the middle atmosphere has been used to examine the production of odd hydrogen (H, OH, and HO2) during charged particle ... [more ▼]

A one dimensional time-dependent model of the neutral and ion chemistry of the middle atmosphere has been used to examine the production of odd hydrogen (H, OH, and HO2) during charged particle precipitation. At altitudes above about 65 km, odd hydrogen production depends on the ionization rate, and the atomic oxygen and water vapor densities. Odd hydrogen production is shown to exhibit diurnal and other time dependent variations during such an event at these altitudes, and the assumption that two odd hydrogen particles are always produced per ionization is reexamined. [less ▲]

The altitude distribution of the Venus ultraviolet nightglow and implications on vertical transport

in Geophysical Research Letters (1981), 8

The altitude distribution of the nitric oxide nightglow was measured with an ultraviolet spectrometer on board Pioneer Venus, in order to study the effects of the distribution on the Venus nightside lower ... [more ▼]

The altitude distribution of the nitric oxide nightglow was measured with an ultraviolet spectrometer on board Pioneer Venus, in order to study the effects of the distribution on the Venus nightside lower thermosphere transport properties. Limb profiles were obtained with an 8 ms integration period on several orbits near periapsis. The observations were made between P minus 2 min and P plus 4 min, where altitude ranges between 150 and 350 km, and latitude varies from 24 degrees N to 9 degrees S. A method independent of the spacecraft attitude data was used to fit the observed limb profiles, and to find the altitude of the maximum of the layer (115 plus or minus 2 km), and the topside scale height (about 3 km). It is shown that downward transport by diffusion alone is not sufficient, and if vertical motion is parameterized by eddy diffusion, an eddy diffusion coefficient is deduced from the altitude of the layer. [less ▲]

Morphology of the Venus ultraviolet night airglow

in Journal of Geophysical Research (1980), 85

Images of the nightside of Venus in the (0,1)delta band of nitric oxide have been obtained by the Pioneer Venus orbiter ultraviolet spectrometer (OUVS). The emission, which is produced by radiative ... [more ▼]

Images of the nightside of Venus in the (0,1)delta band of nitric oxide have been obtained by the Pioneer Venus orbiter ultraviolet spectrometer (OUVS). The emission, which is produced by radiative association of N and O, shows a bright spot reaching 5 kR and located at 2 a.m. local solar time just south of the equator. The emitting layer is at 111 + or - 7-km altitude. A one dimensional vertical transport model shows that the hemispheric average brightness of 0.8 kR is consistent with the orbiter neutral mass spectrometer (ONMS) measurements of N and O near 167 km, and that the altitude of the emitting layer is consistent with the eddy mixing model proposed to explain the dayside helium profile measured by the bus neutral mass spectrometer. In the model, N reaches a peak of 7 x 10 to the 8th per cu cm at 114 km, and O reaches a peak of 2.6 x 10 to the 11th per cu cm at 106 km. There is a fair degree of consistency between the ONMS, OUVS, and other airglow measurements, except as regards the local time dependence. [less ▲]

Satellite studies of N/D-2/ emission and ion chemistry in aurorae

in Journal of Geophysical Research (1980), 85

The incident particle flux ion and neutral composition data taken on the AE-D satellite have been used to investigate the quantal emission of N2(plus) at 4278 A, N(D-2) at 5200 A, and the ion chemistry in ... [more ▼]

The incident particle flux ion and neutral composition data taken on the AE-D satellite have been used to investigate the quantal emission of N2(plus) at 4278 A, N(D-2) at 5200 A, and the ion chemistry in aurorae. The results of a time dependent auroral model have been compared to the data. The calculated 4278 A emission of N2(plus), the 5200 A emission of N(D-2), the densities of O2(plus), NO(plus), N2(plus), O(plus), and the electron density are generally in agreement with the measured values. These results are consistent with the branching ratios and quenching rates deduced from previous studies of the N(D-2) densities in the day-time, mid-latitude ionosphere. It is found that in an auroral arc, the measured atomic oxygen density is lower than predicted by the MSIS model. [less ▲]

La face cachée de Venus

in Recherche (La) (1980), 11

The morphology of equatorial Mg/plus/ ion distribution deduced from 2800-A airglow observations

in Journal of Geophysical Research (1979), 84

The Visible Airglow Experiment on the Atmosphere Explorer E satellite has observed the resonantly scattered emission from Mg II at 2800 A in the equatorial ionosphere. Altitude profiles of the Mg(plus ... [more ▼]

The Visible Airglow Experiment on the Atmosphere Explorer E satellite has observed the resonantly scattered emission from Mg II at 2800 A in the equatorial ionosphere. Altitude profiles of the Mg(plus) ion distribution have been obtained from the inversion of the surface brightness measurements made on spinning orbits. These data show a daytime metallic ion layer between 150 and 200 km developing in the early morning and reaching about 100 ions/cu cm in the afternoon. Mg(plus) ions are also seen in the F 2 region mostly in the late afternoon hours within a few degrees of the dip equator. The study of the vertical column density measured in the despun mode indicates that the amount of Mg(plus) in the F region is most variable in the afternoon hours at low dip latitudes. These results can be explained in part by the diurnal variation of the E x B drift velocity which lifts the metallic ions up into the F region. The observations suggest that the vertical polarization electric field is not the primary transport mechanism extracting the Mg(plus) ions from the low-altitude source layer. [less ▲]

The latitudinal gradient of nitric oxide in the thermosphere

in Journal of Geophysical Research (1979), 84

Theoretical calculations of nitric oxide altitude profiles are made at five different latitudes by using neutral temperatures and composition primarily from the MSIS (mass spectrometer and incoherent ... [more ▼]

Theoretical calculations of nitric oxide altitude profiles are made at five different latitudes by using neutral temperatures and composition primarily from the MSIS (mass spectrometer and incoherent scatter) model. The nitric oxide calculated for an altitude of 105 km remains nearly constant with increasing latitude. Observations made by the ultraviolet nitric oxide instrument on the Atmosphere Explorer C satellite show that at low magnetic activity (Ap value of approximately 4), the NO density at 105 km agrees with the theory; however, at moderate levels of activity it increases with latitude. This discrepancy between the theoretical and observed latitudinal gradients of nitric oxide suggests the transport of NO from a high latitude source to lower latitudes. At 200 km the theoretical and observed latitudinal gradients are in reasonable agreement, an indication that the knowledge of the local composition and temperature is sufficient to model nitric oxide at this altitude. [less ▲]

Des catastrophes cosmiques ont-elles perturbé l'évolution de la vie ?

in Recherche (La) (1979), 10