ENA IMAGING AT EARTH: UPDATES FROM THE IMAGE MISSION

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ENA IMAGING AT EARTH UPDATES FROM THE IMAGE
MISSION

• P. Cson Brandt, D. G. Mitchell, E. C. Roelof, R.
  DeMajistre, K. Jonsson, M. Collier, M. C. Fok

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OUTLINE

• Comparative planetary ENA imaging. Earth-Mars
  differences.
• IMAGE introduction. Regions imaged by IMAGE.
• Ring current - plasma sheet imaging. Clues to MI
  coupling.
• Outflow and magnetosheath imaging.
• Whats APLs involvement?

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MARS MAGNETOSPHERE
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Charge Exchange
A magnetically trapped ion captures an electron
from a neutral hydrogen atom...
creating an energetic neutral atom (ENA) that is
no longer trapped.
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ENA Detection Techniques
RING CURRENT/PLASMA SHEET
RING CURRENT/PLASMA SHEET
POLAR OUTFLOW ISN SOLAR WIND INTERACTIONS
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High-Energy Neutral Atom (HENA) Imager
Lead Investigator D. Mitchell, Applied Physics
Lab
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Medium-Energy Neutral Atom (HENA) Imager
Lead Investigator C. Pollock, SwRI
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Low-Energy Neutral Atom (HENA) Imager
Lead Investigator T. Moore, NASA/GSFC
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The IMAGE Science Payload
HENA APL
MENA, CIDP SwRI
LENA GSFC
EUV Univ. of Arizona
FUV UC Berkeley
RPI U. Mass/Lowell
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HENA IMAGE (Hydrogen ENA 10-198 keV)

• NOT ONLY PRETTY PICTURES!
• General storm circulation and dynamics.
• Plasma sheet dynamics during substorms.
• Storm-substorm relationship.
• Source and losses of the storm-time ring current.
• Electrical current systems
• MI-coupling
• ENAs from the Heliospheric termination shock

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CONSTRAINED LINEAR INVERSION
ENA-cts in pixel i
MEASUREMENT EQUATION
Ion flux in equatorial plane
Quadrature weights geometry, mapping, etc.
STANDARD CONSTRAINED LINEAR SOLUTION Twomey,
1977
Constraint matrix
Constraint strength
BAD (WEAK) g
GOOD g
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NEW PICTURE(Wolf et al. already in the
70sRCM runs)
Enhanced pressure
No significant ring current pressure
Sub-Auroral Polarization Streams (SAPS)
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PRESSURE DRIVEN CURRENTS
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PLASMASPHERE
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MID-LATITUDE IONOSPHERIC ELECTRIC FIELDS
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Modeling II 26-27 June 2000
Volland-Stern
Volland-Stern SAPS
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Plume Evolution
Plume
Quiet Psphere
Onset Sunward surge
Plume Narrowing
Plume Wrapping
Stages of Plasmaspheric Erosion Above is an
implementation of the Grebowsky model. At the
start, the quiet plasmasphere. After the
convection is increased, the LCE moves inward,
creating a sunward surge of eroded plasma that
forms a dayside plume. Over the course of
several hours, this plume narrows in MLT. After
convection decreases again, the plume is suddenly
in the corotation zone again, and plume wrapping
ensues.
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LENA Solar Wind Neutrals Polar Ion Outflow
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MODELING
Using the most recent data available from ACE,
the CCMC has perform MHD simulations of the
Earth's environment during the March 31, 2001
event. These results have been incorporated into
Fok's neutral atom imaging model. Note that a
spacecraft doing remote sensing at about the
IMAGE position will observe two signals a narrow
high Mach number signal from the solar wind
direction and a diffuse sheath signal falling
between the Earth and Sun.
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ASTRID/PIPPI-MCP
ASTRID/PIPPI-MCP observations (left) and
simulations (right). NPI is similar to the
PIPPI-MCP. The NPI has been modified to eliminate
stray light, but ghost reflections can still be
seen in the NPI data. Suggests that it may not be
internal reflections.
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NPI - PIPPI

• IMAGE/LENA observes magnetosheath/solar wind ENAs
  in the range of lt1e7 (cm2 sr s keV)-1.
• ASTRID/PIPPI-MCP could observe gt1e4 (cm2 sr s
  keV)-1.
• Modeled Mars flux lt1e11 (m2 sr s)-1 1e7 (cm2
  sr s keV) Gunell, 2003.
• NPI is sensitive enough to detect solar wind ENAs
  at Mars.
• Biggest challenge is sun light (direct and
  reflected).

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ASPERA/NPI
1. DIRECT SUNLIGHT
BLOCKED SECTOR!?
3. SATURATION EFFECT
2. GHOST REFLECTION
ASPERA-3/NPI data from the slew manouvre
2003-07-09. Note that the sun pulse moves as
expected from sectors 18-19 to 23-25.
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ASPERA/NPI

1. Specify solar contamination
2. Direct sun
3. Saturation effects
4. Ghost signal from internal reflections or
   electronic phenomenon
5. HIGH PRIOTITY ON UV calibrations in Arizona in
   Oct-Nov.
6. Lessons from Astrid/PIPPI-MCP instrument
7. Develop data display software in IDL
8. Try to predict where solar contamination will
   appear in relation to ENA emissions
9. Simulate viewing geometry and solar response for
   realistic orbit to establish best vantage points
   for ENA imaging

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PRESENTATION AT sd-www.jhuapl.edu/IMAGE/ (look
under meetings)
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MAINPHASE?RECOVERY(24 NOV 2001)