dim ena emissions from 1-30 kev
DESCRIPTION
Dim ENA Emissions from 1-30 keV. D.J. McComas, P. Valek, J.L. Burch, and C.J. Pollock Southwest Research Institute San Antonio, TX H.O. Funsten, R.M. Skoug, M.F. Thomsen Los Alamos National Laboratory Los Alamos, NM Yosemite Meeting – 8 February 2002. Introduction/Outline. - PowerPoint PPT PresentationTRANSCRIPT
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Dim ENA Emissions from 1-30 keV
D.J. McComas, P. Valek, J.L. Burch, and C.J. PollockSouthwest Research Institute
San Antonio, TX
H.O. Funsten, R.M. Skoug, M.F. ThomsenLos Alamos National Laboratory
Los Alamos, NM
Yosemite Meeting – 8 February 2002
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Introduction/Outline
• Looking for dim ENA emissions requires careful attention to all MENA backgrounds
• Search for extended plasma sheet emissions• Find extended emissions associated w/ SDPSs• Find a remarkable background association w/ EPs• Examine low background emissions for annual
and directional asymmetries• Discuss possible implications for heliospheric
ENAs
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MENA Sensor Head Design
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Sources of Background Counts
• Coincident events– Energetic ions passing/scattering through collimator– Some penetrating radiation
• Non-coincident events– Solar and geocoronal UV (Ly- & shorter)– MCP dark counts (typically ~1 cm-2)– Most penetrating radiation
• Electronic noise• Electronic crosstalk
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Culling MENA Backgrounds
• Only possible with complete information (“statistics data” or direct events)
• Remove unphysical events– Too short and negative times-of-flight– Too small pulse heights– Illegal locations (stops in starts, gutters, etc.)
• Correct high fluxes for under sampling– Not required for dim events examined here
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Raw Culled
Head 1 MENA/Imm Stats: June 10, 2000; 11:01:37-11:21:38 (10 spins)
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Heads 1-3 MENA/Imm Stats: June 10, 2000; 11:01:37-11:21:38 (10 spins)
Raw Culled
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Studying Dim ENA emissions
• Achievable under locally quiet conditions– Not generally possible during storms– IMAGE at high altitude in Lobe
• Culling required to remove spurious points• Must view away from bright emissions
– Solar UV– Terrestrial scattered UV– Near-Earth ENA emissions
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40-min Averaged MENA Images
Typical Extended PS
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Borovsky et al., JGR, 103, 1998
0 5 10 15 20 25r [R ]E
The Near-EarthPlasma Sheet
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Borovsky et al., JGR, 103, 1998
“Superdense”Plasma Sheet
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Superdense Plasma Sheet Intervals• Identified in MPA data in Geosync• 31 days over 8 months (Oct-May 2001)• 13 intervals suitable for comparison
– Low enough backgrounds– Descent viewing (seasonal and orbital)
• 11 of 13 show extended ENA emissions• Several strong examples
– Very low background and excellent viewing• Extended PS ENA emissions clearly associated
with superdense intervals• SDPSs extend well beyond Geosync
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GOES-8 Background Data• GOES-8 --- NOAA Geosync satellite• Energetic Particle Sensor (EPS) data*• Differential proton flux channel• 700 keV – 4 MeV (penetrates collimator)• May be tail of lower energy distribution• May scatter in collimators and/or gratings• Enter MENA through aperture• Create correlated start/stop (“real”) events
* Thanks to Terry Onsager and NOAA/SEC
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April 2001
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May 2001
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MENA vs GOES
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Day of year
Cou
nts p
er S
pin
Black = 2000 Red = 2001
Annual Variation of ENAs away from Earth
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Coverage
Uncorrected
Corrected
Spatial Variationof ENAs away
from Earth
- GCI latitude vs longitude- 366 apogee spins (of 530)- GOES < 5 / cm2 s sr MeV- Holes at IMAGE Z-axis- Bright near solar apex
(~271 ra, 30 dec)
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Taken from Gruntman et al., JGR, 106, 2001
The Heliospheric interaction with the LISM
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Penetration of ENAs into Inner HSp
Gruntman et al., JGR, 106, 2001
McComas et al., GRL, 26, 1999
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Models of HSp Interaction ENAs near 1 AU
Gruntman et al., JGR, 106, 2001
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Czechowski et al., ICRC 2001, 2001
ACR generated ENAs
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Model Energy Distributions of ACR-ENAs
Czechowski et al., ICRC 2001, 2001
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Summary
• Able to examine dim ENA emissions by careful attention to various MENA backgrounds
• Found a remarkable background associated w/ GOES energetic protons
• Discovered quite distant plasma sheet emissions associated w/ “superdense plasma sheet” intervals– SDPSs extend well beyond Geosync
• Discovered annual and directional asymmetries in dim ENA emissions from ~1-30 kev that may be from heliospheric ENAs