It is time to begin the discussion on how best to formulate a Reference Ionosphere for Mars. Preliminary sponsorship for such an effort is being sought from COSPAR, and hopefully an international group can meet on this topic during the next COSPAR meeting in Moscow in 2014. At the time, a true Mars International Reference Ionosphere (MIRI) effort can commence. As part of the COSPAR meeting in Paris in 2004, a small group met to discuss reference atmospheres and ionospheres in the Solar System. At that time, the consensus was that insufficient data existed for Mars and thus theoretical models of the martian upper atmosphere and ionosphere offered the only practical solution at that time . In the decade since that meeting, a remarkable amount of new observations became available from the Mars Global Surveyor (MGS) and Mars Express (MEX) satellites.
This website summarizes the first attempt to created an initial version of a reference ionosphere—one we call the Mars Initial Reference Ionosphere (MIRI Mark-1). It is a semi-empirical model that links the photo-chemical-equilibrium equation to observations of maximum electron density (Nmax) obtained from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard the MEX spacecraft. Over 100,000 values of peak electron density from the years 2005-2019 were used to create parameterizations for a semi-empirical MIRI Mark-1. A full description of the approach taken is available . The model gives a single output parameter: the maximum electron density (Nmax) of the martian ionosphere versus solar zenith angle (SZA).
To obtain a run of MIRI, the user selects a date from an interactive calendar. If a specific solar zenith angle (SZA) is desired, the user inputs that value. If not, MIRI uses its archive of Mars' distances from the Sun and solar radio fluxes (F10.7) spanning the years 1965-2019 to compute Nmax vs. SZAs (between 0o and 90o) at Mars for that date. Uncertainty levels are given for the model values based on the variability patterns in the data used in its formulation. A graphical output shows the date requested, the distance of Mars from the Sun, its orbital longitude, the solar radio flux measured at 1 AU that is applied at Mars (together with its contextual 3-month mean). The assumption is made that solar rotation effects determine the date to use for F10.7 measured at Earth to be applied at Mars' orbital longitude. The model can be used for dates in the past (back to 1965) and well as for the future (to 2019). Forecasts involve use of predicted solar flux conditions. A table of Nmax vs. SZA is also provided.
Give it a try! We welcome comments and suggestions.
--The Boston University - University of Iowa MIRI Team
Michael Mendillo, Angela Marusiak, Gerard Lawler, and Paul Withers
Center for Space Physics, Boston University
David Morgan and Donald Gurnett
Department of Physics and Astronomy, The University of Iowa