DOUBLE STAR IMAGE CONJUNCTIONS: OPPORTUNITY FOR NEW SCIENCE

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DOUBLE STAR IMAGE CONJUNCTIONSOPPORTUNITY FOR
NEW SCIENCE

• Pontus Cson Brandt, D. G. Mitchell, S. Ohtani,
  E. C. Roelof, R. Demajistre JHUAPL, MD
• R. A. Wolf Rice, TX
• M. C. Fok NASA GSFC, MD

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OUTLINE

• WHY ENA IMAGING?
• WHAT HAVE WE LEARNED?
• MI-coupling at work
• WHY gt2 VANTAGE POINTS?
• CONJUNCTIONS

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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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THE IMAGE MISSION

• Lifetime 2000-2005
• 800 x 8 Re solar inertial orbit (more later on
  orbit)
• LENA 50 eV-10 keV
• MENA 1-50 keV
• HENA 10-200 keV (hydrogen) 50-180 keV (oxygen)
• FUV auroral imager (proton and electron aurora)
• EUV plasmaspheric imager. Images light
  resonantly scattered sunlight scattered on He.

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High-Energy Neutral Atom (HENA) Imager
Lead Investigator D. Mitchell, Applied Physics
Lab
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STORM AS SEEN BY HENA March 31 2001 (60-119 keV
protons)
-40 nT
21 nT
26 nT
0730 UT
0830 UT
0930 UT
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WHY ENA IMAGING?

• The only way to image proton plasma.
• The hot plasma (ring current/plasma sheet) in the
  Terrestrial magnetosphere has proven to be more
  dynamic than anticipated.
• Need to measure global pressure on timescales lt
  10-20 min.
• All of the region 2 and probably a large portion
  of the nightside region 1 current system is
  PRESSURE DRIVEN.

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MEASURED/COMPUTED QUANTITIES
SCIENTIFIC UNDERSTANDING
ENA
STORM, SUBSTORM DYNAMICS
PRESSURE
CURRENTS
MI-COUPLING
B-FIELD TOPOLOGY
DB (Biot-Savarts)
ADIABATIC EFFECTS ON RADIATION BELTS
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WHAT HAVE WE LEARNED SO FAR?

• The morphology of the storm-time ring current
  depends heavily on the ionospheric conductivity.
• Storm main phase ring current peaks around
  midnight.
• Storm-time ring current penetrates always deeper
  than geosynchronous.
• Heavy ions (O) are energized dramatically during
  storm-time substorms.
• Storm-time substorm injections can have an
  extreme local time extent (to noon).

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MI-COUPLING AT WORK

• Old picture storm-time ring current peaks at
  dusk, because thats where the Alfven layer comes
  closest to the Earth in a dawn-dusk E-field.
• New picture Wolf, 1980 Fok et al., 2001
  storm-time ring current peaks at midnight.
  Consistent with IMAGE results Cson Brandt et
  al., 2002.
• Mechanism
• The convectional E-field (dawn-dusk) try to force
  Hall currents to flow across the terminators
  (conductivity jump)?positive charge
  build-up?skewing of potential pattern.
• Probably some additional intricate effects.

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SubAuroral Polarization Stream (SAPS) (Foster et
al., EOS and JGR, 2002)
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WHY gt2 VANTAGE POINTS?

• ANSWER one polar vantage point and on at the
  equator can resolve large-scale pitch-angle
  distributions (PAD) for the first time! ? Effects
  on all results discussed above.
• Specifically is there a high-energy (100 keV)
  component of trapped ions during storm main
  phase?
• Perigee passes with IMAGE and simultaneous apogee
  passes with DSP will give essential information
  on upper atmosphere interactions during different
  phases of the storm/substorm.
• Note tomography requires far more vantage points
  than just a couple.

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CONJUNCTIONS
JAN 2001
JAN 2002
JAN 2003
JAN 2004 Mostly equatorial vantage point
JAN 2005 Mostly polar
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PAD AND VANTAGE POINTS60-119 keV hydrogen ENA
EQUATORIAL VANTAGE POINT Dst-54 nT
POLAR VANTAGE POINT Dst-71 nT
Note a factor of 2 stronger flux for equatorial
vantage point?Anisotropy2.
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3rd (and 4th) CONJUNCTION ?

• NASA S/C TWINS launch in mid 2003.
• 2 ENA imagers in 2 opposing Molnyia orbits.
  1000km x 7.2 Re. 64 deg incl.
• Based on IMAGE/MENA design.
• H and O
• 1-70 keV

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CONCLUSIONS

• At mid-2004 IMAGE apocenter will be at 30-40 deg
  lat (southern hemi)?PAD resolved for first time!!
• Later in 2005 IMAGE apocenter towards southern
  pole.
• Perigee-Apogee combinations essential for
  detailed information on upper atmospheric
  interactions.
• Ring current see effects of magnetospheric
  E-fields? in-situ measurements (E-fields and
  particles) essential. Also for intercalibrating
  DSP/NUADU and IMAGE/HENA.
• Third (and fourth) conjunction with TWINS. Launch
  in 2003.

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LAUNCH END OF 2003?
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R1 HIGH CONDUCTIVITY R2 LOW CONDUCTIVITY Sp
HIGH, SH LOW ? NORTHWARD E-FIELDS WE THINK.