Ion Measurements during Pioneer Venus Reen'i•y: Implications for Solar Cycle Variation of Ion Composition and Dynamics
نویسندگان
چکیده
During the final, low solar activity phase of the Pioneer Venus mission, the Orbiter Ion Mass Spectrometer measurements found all ion species, in the midnight-dusk sector, reduced in concentration relative to that observed at solar maximum. Molecular ion species comprised a greater part of the total ion concentration as O + and H + had the greatest depletions. The nightside ionospheric states were strikingly similar to the isolated solar maximum "disappearing" ionospheres. Both are very dynamic states characterized by a rapidly drifting plasma nd 30-100 eV superthermal O + ions.
منابع مشابه
Ionosphere of venus: first observations of the dayside ion composition near dawn and dusk.
The first in situ measurements of the composition of the ionosphere of Venus are provided by independent Bennett radio-frequency ion mass spectrometers on the Pioneer Venus bits and orbiter spacecraft, exploring the dawn and duskside regions, respectively. An extensive composition of ion species, rich in oxygen, nitrogen, and carbon chemistry is idenitified. The dominant topside ion is O(+), wi...
متن کاملThe nightside ionosphere of Venus under varying levels of solar Euv flux
Solar activity varied widely over the 14 year lifetime of the Pioneer Venus Orbiter, and these variations directly affected the properties of the nightside ionosphere. At solar maximum, when solar EUV was largest, the Venus ionosphere was found to extend to highest altitudes and nightward ion transport was the main source of the nightside ionosphere. At solar minimum, nightward ion transport wa...
متن کاملModel Calculations of the Dayside Ionosphere of Venus Energetics
A model of the energy balance of the dayside ionosphere of Venus is presented. Calculations of the dayside electron and ion temperature profiles are carried out and compared with data from experiments on the Pioneer Venus orbiter. The coupled heat conduction equations for electrons and ions are solved for several values of the solar zenith angle. It is shown that thermal conductivities are inhi...
متن کاملPLASMA TRANSPORT IN THE TOPSIDE VENUS IONOSPHERE R.w.scHuNK
Abeiraet-We have studied the extent to which certain transport processes affect ion composition and heat flow in the daytime, topside Venus ionosphere. Particular attention is given to the conditions that prevailed during the Mariner 5 measurements, at which time the topside Venus ionosphere appeared to be in a state of diffusive equilibrium. We have found that the ion composition is sensitive ...
متن کاملGiant flux ropes observed in the magnetized ionosphere at Venus
[1] The Venus ionospheric response to solar and solar wind variations is most evident in its magnetic field properties. Early Pioneer Venus observations during the solar maximum revealed that the Venus ionosphere exhibits two magnetic states depending on the solar wind dynamic pressure conditions: magnetized ionosphere with large-scale horizontal magnetic field; or unmagnetized ionosphere with ...
متن کامل