An Interpretation of the Large Scale Ionospheric Magnetic Fields and The Altitude Distribution Of The Ionospheric Plasma on The Dayside Of Venus And Mars

  1. Janet G. Luhmann,
  2. Mariella Tatrallyay and
  3. Robert O. Pepin
  1. A. M. Krymskii

Published Online: 18 MAR 2013

DOI: 10.1029/GM066p0289

Venus and Mars: Atntospheres, Ionospheres, and Solar Wind Interactions

Venus and Mars: Atntospheres, Ionospheres, and Solar Wind Interactions

How to Cite

Krymskii, A. M. (1992) An Interpretation of the Large Scale Ionospheric Magnetic Fields and The Altitude Distribution Of The Ionospheric Plasma on The Dayside Of Venus And Mars, in Venus and Mars: Atntospheres, Ionospheres, and Solar Wind Interactions (eds J. G. Luhmann, M. Tatrallyay and R. O. Pepin), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM066p0289

Author Information

  1. Rostov State University, Rostov on the Don, USSR

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1992

ISBN Information

Print ISBN: 9780875900322

Online ISBN: 9781118663844

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Keywords:

  • Venus (Planet)—Atmosphere—Congresses;
  • Mars (Planet)—Atmosphere—Congresses;
  • Solar wind—Congresses

Summary

The altitude distributions of electron density obtained from the radio occultation of spacecraft provide a unique opportunity to study the evolution of the ionosphere at Venus and Mars through the solar cycle. It has been shown that the plasma scale height is sensitive to the ability of the ionosphere (magnetosphere) of the planet to stand off the solar wind flow and to the details of the ionospheric plasma convection. The MHD theory predicts significant effects of the large scale magnetic field on plasma convection. The features of the magnetic field can manifest themselves in the plasma scale height. The scenario of the solar wind interaction with Mars described by Breus et al. [1989], under the assumption that there is an intrinsic magnetic field of 45–50 nT at the surface of the planet, seems to be in reasonable agreement with the data obtained by Martian missions. This scenario predicts that there should be an intrinsic magnetosphere when the solar wind dynamic pressure is low during solar minimum. Mass-loading is the dominant effect in the solar wind/Mars interaction during solar maximum. The plasma scale height is analyzed to determine its dependence on the ratio of the thermal pressure of the plasma to the pressure of the magnetic field β, and on the ratio of the vertical magnetic field component to the horizontal component. It is demonstrated that the scale height of the plasma is proportional to the neutral atmosphere scale height if β is low and the vertical magnetic field is small. This is typical for the “overpressure” region where the solar wind pressure exceeds ionospheric thermal pressure, or near the magnetic equator of the intrinsic magnetosphere. In other cases diffusive equilibrium exists. The variations of the plasma scale height in response to the evolution of the Martian magnetosphere within the solar cycle are discussed. In-situ observations of the Martian ionosphere revealed high ion temperatures while a small plasma scale height of ∼29 km is observed throughout the topside ionosphere [Hanson et al., 1977]. This seems to be evidence of a horizontal magnetic field and low β conditions within the Martian ionosphere. Predictions for Mars are compared with the situation at Venus.