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Trapped Proton Models: TPM1 and Beyond

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Title: Trapped Proton Models: TPM1 and Beyond


1
Trapped Proton ModelsTPM-1 and Beyond
  • Stuart L. Huston
  • Science Applications International Corporation
  • Working Group Meeting on New Standard Radiation
    Belt and Space Plasma Models for Spacecraft
    Engineering
  • College Park, MD
  • 2004 October 58

Work supported by NASA Space Environments and
Effects Program (SEE) and Living With a Star
Targeted Research and Technology Program
(LWS-TRT), and by Science Applications
International Corporation, McDonnell Douglas, and
Boeing
2
Outline
  • NOAAPRO/LATRM
  • TPM-1
  • Recent Work
  • Implications/Needs/etc.

3
The Basic Question
  • Q Why spend ? to get data and develop a
    radiation environment model?
  • A
  • Uncertainty in the environment can increase total
    life cycle costs by many G
  • Trading system lifetime, reliability,
    replenishment, performance, mass, numbers of s/c,
    etc.
  • Risk management/mitigation
  • Overdesign vs. underdesign
  • Uncertainty in the environment may limit or
    prohibit certain technologies and/or missions
  • Without good environment models, effects models
    are useless of limited value

xxxxxxx
4
NOAAPRO/LATRM
  • Objective
  • Develop solar-cycle dependent model of low
    altitude (lt1000 km) protons
  • Use NOAA/POES MEPED data (gt16, gt 36, gt 80 MeV)
  • Implementation
  • Empirical curve fit for solar cycle variation
  • Input is latitude/longitude/altitude/date
  • Model calculates magnetic coordinates
  • Output is simple integral flux

5
Proton Flux is Controlled by Atmospheric
Density/Solar Activity
6
Introduction of Phase Lag Gives Good Correlation
with Data
Simple exponential relationship between proton
flux and phase-lagged solar flux Note that there
is still factor of 2 uncertainty in flux
prediction Even larger errors during transient
events
7
Model/Data Comparison Magnetic Equator
8
TPM-1
  • Problems w/NOAAPRO
  • Poor energy resolution
  • Limited spatial coverage
  • Objective
  • Combine CRRESPRO and NOAAPRO
  • Model valid from low-altitude to near GEO
  • Challenges
  • Poor spatial resolution/biasing in CRRESPRO at
    low altitudes
  • Intercalibration of very different detectors
  • Combining integral flux data (POES) with
    differential data (CRRES)
  • Approach
  • Convert CRRESPRO from bins to grids
  • Scale spectra based on NOAAPRO
  • Use NOAAPRO solar cycle variation

9
CRRESPRO 16.9 MeV Quiet
Flux is defined in bins of L/l assumed constant
within bin Resolution is too coarse to capture
gradients near atmospheric cutoff Fluxes are
biased towards higher values due to gradients
within bins
10
TPM-0 16.9 MeV Quiet
TPM-0 was an interim model based on
CRRESPRO CRRESPRO fluxes converted to grids,
allowing interpolation within grid Fluxes
normalized so that average flux within bin equals
CRRESPRO flux
11
Calibration of POES Detectors
SEM-2 (NOAA-15 later) re-designed to reduce
contamination
12
Electron Contamination(calculations by T.
Cayton, LANL)
13
Comparison Low Altitude Models
14
TPM-1 Spectra (High-L)
15
Flux vs. AltitudeTPM-1 Quiet Model
16
Flux vs. AltitudeTPM-1 Quiet Model vs. AP-8
  • NOTE population is variable, TPM-1 represents a
    snapshot at solar maximum

17
TPM-1 Summary As Delivered
  • Energy Range 1 81.5 MeV
  • Regional coverage
  • 300 - 36,000 km
  • 1.2 lt L lt 5.5
  • 0 lt l lt 50
  • Inputs
  • Latitude, Longitude, Altitude (internal field
    model calculates magnetic coordinates
  • Can perform orbital integration
  • Date (i.e., phase of solar cycle)
  • F10.7 history
  • Time coverage
  • Data cover 1978 1995 (with special attention to
    1990-1991)
  • Valid for any point in solar cycle
  • Time scale (vs. resolution) 1 month

18
TPM-1 Summary (concluded)
  • Calibration/Intercalibration
  • Detector calibration issues as discussed
  • Very limited validation/characterization
    performed
  • Comparison with other models
  • Absolute magnitude within about a factor of 5 of
    AP-8 (depending on energy/region)
  • Spectra generally harder than AP-8
  • Radial profiles show that flux peaks at lower
    altitudes than AP-8
  • Low altitude fluxes are lower than CRRESPRO,
    higher than AP-8
  • Additional comments
  • Another solar cycle of POES data for
    incorporation into model
  • High altitude portion (CRRESPRO) based on a
    snapshot at solar max
  • Quiet and active models what do we do about
    active periods?

19
New Directions
20
Recent Work (Sponsored by SEE LWS)
  • Statistical solar cycle variation (Xapsos, 2002)
  • Slot Dynamics Study (2003)
  • Investigated statistics of slot region
  • Long-Term Dynamics (2004 2005)
  • Extend energy range by combining w/SAMPEX data
    (collaboration with BIRA)
  • Extend high energy/low altitude data to equator
    with analytical model Salammbô (collaboration
    with ONERA)
  • Develop statistical model for low-altitude solar
    variation (collaboration with GSFC)

21
Statistical Solar Cycle Variation
Standard TPM-1 requires knowledge of solar flux
and its history at the time of interest Xapsos
combined historical solar cycle data to determine
flux history as a function of confidence level
22
Statistical Solar Cycle Variation
23
Transient Belts Problem
TPM-1 contains quiet and active models No
guidance as to how often the belts are
active Under LWS, we looked at these belts
using POES long-term data
24
NOAA-06/08 1986
(a) Survey plot showing color-coded intensity as
a function of time and L-shell.
(c) Probability of exceeding a given flux as a
function of L-shell.
(d) Time period from which data are taken in
relation to solar cycle.
(b) Flux vs. time at several discrete L-shells.
25
Variability vs. L
Proton fluxes at L 2.5 are quite dynamic Flux
is enhanced 25 of the time 90 confidence
level is 10X higher than mean Enhancements of
up to 150X, lasting up to 1.5 years March 1991
event was unique in its inward extent (as well as
magnitude) Electron contamination use SEM-2
data from NOAA-15, -16, -17
26
TPM-1 Summary 2
  • Attempt to provide successor to AP-8, but limited
    energy range limits usefulness
  • Can be used to assess uncertainty in AP-8
  • Very limited validation performed
  • No provision for maintenance/upgrades
  • Work done since initial release has not been
    incorporated into TPM-1

27
Modeling/Software Issues
  • ALL particles plasma, trapped protons/electrons,
    solar (protons, heavies), GCR
  • protons .01(?) lt E lt 400 MeV
  • electrons 1 keV(?) lt E lt 10 MeV
  • Average, worst-case, of time above threshold,
    maximum time continuously above threshold
  • Time scale of variations
  • Estimate of uncertainty ? safety margins
  • How much due to variability of environment
    statistical model
  • How much due to uncertainty in measurement,
  • How much due to modeling assumptions/simplificatio
    ns
  • Verification/Validation
  • What aspects of software implementation need to
    be considered in determining model architecture?
  • Elliptical orbits different regions of space
    with different time scales, phasing, etc.

28
Data Issues
  • Level of processing
  • time averaging
  • calibration, contamination, etc.
  • Intercalibration different detectors, different
    orbits, different epochs
  • Access to data treatment of sensitive/proprietar
    y data
  • operational/piggyback detectors on commercial
    s/c
  • classified s/c
  • High fidelity vs. low fidelity detectors
  • Is there any archival data worth using?

29
Programmatic Issues
  • Long-term commitment to model development and
    maintenance
  • e.g., IRI, original TREMP
  • Understanding of financial benefit
  • Current approach makes the job difficult
  • new proposals every few years ? small chunks of
    the total based on anticipated funding levels
  • development of ad hoc models for specific
    engineering applications
  • need a global roadmap and commitment to follow it
  • Inter-Agency, Inter-Program collaboration
  • Modeling is critical, but not a PI activity
    (Vette, 1991)
  • Need an impartial modeling center with access
    to data a la Aerospace/NSSDC activities
  • Can engineering modeling needs impact scientific
    missions?
  • Will there be an engineering mission to
    map/monitor the environment?
  • Export restrictions
  • collaboration, data sharing
  • model distribution
  • How to implement model
  • E.g., GEOSpace, SPENVIS
  • Stand-alone vs. web-based
  • Commercial tools (e.g., Space Radiation)
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