Results from the Mars Express Active Ionospheric Sounder

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Results from the Mars Express Active Ionospheric
Sounder

• D. D. Morgan1, D. A. Gurnett1, D. L. Kirchner1,
  F. Duru1, R. L. Huff1, D. A. Brain2, W. V.
  Boynton3, M. H. Acuña4, E. Nielsen5, A.
  Safaeinili6, J. J. Plaut6, G. Picardi7
• 1Department of Physics and Astronomy, University
  of Iowa, Iowa City, Iowa
• 2Space Physics Research Group, Space Sciences
  Laboratory, University of California, Berkeley,
  California
• 3Lunar and Planetary Laboratory, University of
  Arizona, Tucson, Arizona
• 4NASA Goddard Space Flight Center, Greenbelt,
  Maryland
• 5Max-Planck-Inst. For Solar System Research,
  Katlenburg-Lindau, Germany
• 6Jet Propulsion Laboratory, Pasadena, California
• 7Infocom Department, La Sapienza, University of
  Rome, Rome, Italy

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Mars Express Dec. 25, 2003
P-03-14
Dipole Antenna 2 x 20 m
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Mars Express Orbit
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Nominal Mars Express Orbital Parameters at
Insertion

• Orbital Inclination 86.3
• Apocenter 11,560 km (altitude)
• Pericenter 258 km (altitude)
• Orbital period 7.5 h
• Observing time about periapsis 1h

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Mars Express Radar Transmitter
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Mars Express Spacecraft
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Summary of Active Ionospheric Sounder sequence

• 160 frequencies sampled between 0.1 and 5.4 MHz
  (receive frequencies can be varied).
• 1 pulse every 7.857 ms, bandwidth 10 kHz
• 80 receive times per frequency , 91.4 µs/sample
• Complete cycle every 7.543 s (data rate limited).

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Timing of AIS data
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Radar Reflections from the Ionosphere
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Ionogram inversion

• Time delay equation

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Example Ionogram
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Topics of Interest

• Maximum electron density and total electron
  content
• Detection of magnetic fields
• Double and complex traces and oblique echoes
• Surface reflection and ionospheric absorption
• Ionogram inversion
• Spacecraft local electron density
• Total electron content

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Maximum electron density and total electron
content
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Maximum Electron Density Versus Solar Zenith Angle
From Gurnett et al.,2005
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Safaeinili et al. LPSC, 2006
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Spacecraft-local electron density
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Inbound Electron Density Orbit 2018
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Inbound Electron Density Orbit 2032
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Inbound Electron Density Orbit 1994
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Log10 ne
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Ionogram inversion

• Time delay equation

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Radar Reflections from the Ionosphere
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Corrected altitude
Apparent altitude
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Detection of magnetic fields
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Electron Cyclotron Echoes
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Comparison of the Measured and Model Magnetic
Field Strength
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Electron Cyclotron Echoes, Video/Audio
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Double and Complex Ionospheric Traces
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Oblique Echoes
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Comparison of Oblique Echoes to Crustal Magnetic
Fields
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Oblique Echoes and Crustal Magnetic Fields
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Best Fit Range to a Fixed Target
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Surface reflection and ionospheric absorption
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Surface reflection visibility statistic

• V 0 for not visible or 1 for visible,
  tabulated for each ionogram.
• We select ionograms at 850 km 10 km altitude
  (10 ionograms) and average v.

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Comparison with other data sets

1. Averaged surface reflection visibility.
2. Background of Mars Global Surveyor Electron
   Reflectometer (gt10 MeV) with two hour smoothing
   to remove orbit signature.
3. Background of Mars Odyssey Gamma Ray Spectrometer
   (gt 10 MeV).
4. GOES-12 Solar Environment Monitor soft x-ray flux
   (Earth).
5. NOAA daily X and M class flare counts.

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Overview of data
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Table 1 Absorption Events

• Event Start End
  ?T, days
• 1 20050710-0931 20050725-0833
  15.0
• 2 20050801-0633 20050808-1406
  7.3
• 3 20050823-0310 20050827-0751
  4.2
• 4 20050901-0223 20050904-1112
  3.4
• 5 20050905-1353 20050923-1816
  18.2 ?

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• Event 1
• Start 20050710-0931
• End 20050725-0833
• Duration 15.0 d

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Event 2 Start 20050801-0633 End
20050808-1406 Duration 7.3 d
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Event 3 Start 20050823-0310 End
20050827-0751 Duration 4.2 d
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Event 4 Start 20050901-0223 End
20050904-1112 Duration 3.4 d
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Event 5 Start 20050905-1353 End
20050923-1816 Duration 18.2 d (?)
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Surface reflection visibility variation with Mars
geodetic longitude and latitude

• Why? Wed like to see if the crustal fields
  affect the surface reflection.
• Bins are 10 in latitude and 20 in longitude.
• Altitudes lt 1000 km are selected.
• Absorption events are removed.

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Surface reflection visibility as a function of
Mars latitude and longitudeData from July 4
December 14, 2005
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Surface reflection visibility (absorption events
removed) as a function of solar zenith angle
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Appendix Electron-neutral collision damping at
Mars

• Full dispersion relation
  Imaginary part Thermal
  speed

Real part
Electron-neutral collision frequency
Imaginary part f fpe
eneutral cross section (Strangeway, 1996)
Group velocity
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Conclusion

• Absorption of the surface reflection corresponds
  extremely well and in detail with enhancements in
  solar energetic particle flux.
• Energetic ions can penetrate the night side of
  Mars due to their cyclotron radius gt 0.10 R?
• Surface reflection visibility is an increasing
  function of solar zenith angle, with near 100
  visibility on the night side.