Cosmic-Ray FluxesCosmic-Ray FluxesPresent and PastPresent and Past
Nathaniel Lifton, Marek Zreda, Darin Desilets, John ClemNathaniel Lifton, Marek Zreda, Darin Desilets, John Clem
BackgroundBackground ObjectivesObjectives Present-Day FluxesPresent-Day Fluxes
Instrumental MeasurementsInstrumental Measurements ModelingModeling
Time-Integrated FluxesTime-Integrated Fluxes In Situ In Situ 1414C in Saturated SurfacesC in Saturated Surfaces
CRONUS-Earth
BackgroundBackground
Production Rates Well-Established at Few SitesProduction Rates Well-Established at Few Sites Scaling Models Predict Production Rates ElsewhereScaling Models Predict Production Rates Elsewhere
Current Scaling Models Based on Modern Current Scaling Models Based on Modern Cosmic-Ray MeasurementsCosmic-Ray Measurements Lal, 1991; Stone, 2000; Dunai, 2000, 2001; Lal, 1991; Stone, 2000; Dunai, 2000, 2001;
Desilets & Zreda, 2003; Lifton et al., in prep Desilets & Zreda, 2003; Lifton et al., in prep Neutron Monitors (NM)Neutron Monitors (NM) Other Instruments/TechniquesOther Instruments/Techniques
ProblemsProblems Need to Tie CR Measurements to CN Production in RocksNeed to Tie CR Measurements to CN Production in Rocks
Limited Empirical Testing of Models Over Millenial Time ScalesLimited Empirical Testing of Models Over Millenial Time Scales Scarcity of Samples of Well-Established AgeScarcity of Samples of Well-Established Age
CRONUS-Earth
ObjectivesObjectives Relate NM Measurements to CN Production RatesRelate NM Measurements to CN Production Rates
Global NM Network Data, Published SurveysGlobal NM Network Data, Published Surveys
CRONUS-Earth
Global Neutron Monitor NetworkGlobal Neutron Monitor Network
CRONUS-Earth
Global Global Neutron Neutron Monitor Monitor NetworkNetwork
CRONUS-Earth
ObjectivesObjectives
Relate NM Measurements to CN Production RatesRelate NM Measurements to CN Production Rates Global NM Network Data, Published SurveysGlobal NM Network Data, Published Surveys
CRONUS-Earth
Selected Low-Energy Neutron Detector MeasurementsSelected Low-Energy Neutron Detector Measurements
Using NM Data as a Basis for CN ScalingUsing NM Data as a Basis for CN Scaling Can a Single Scaling Model Apply to the Entire Neutron Energy Can a Single Scaling Model Apply to the Entire Neutron Energy
Spectrum?Spectrum? Detailed NM Response to Secondary Cosmic Rays?Detailed NM Response to Secondary Cosmic Rays?
NMs More Sensitive to High EnergiesNMs More Sensitive to High Energies Are Rocks as Well?Are Rocks as Well?
Physically Relate NM Response and CN Production in RockPhysically Relate NM Response and CN Production in Rock
Test Scaling Models over Millenial Time ScalesTest Scaling Models over Millenial Time Scales In Situ In Situ 1414C in Saturated SurfacesC in Saturated Surfaces
Present-Day FluxesPresent-Day Fluxes Measurements Measurements (Zreda, Desilets)(Zreda, Desilets) Modeling Modeling (Zreda, Desilets, Clem)(Zreda, Desilets, Clem)
CRONUS-Earth
Time-Integrated Scaling From Time-Integrated Scaling From In Situ In Situ 1414C Production RatesC Production Rates
Short Half-LifeShort Half-Life 5,730 yr5,730 yr
Secular Equilibrium Secular Equilibrium by About 25 kyrby About 25 kyr
Insensitive to Insensitive to Moderate Erosion Moderate Erosion RatesRates
Many Geomorphic Many Geomorphic Settings Suitable Settings Suitable for Production Rate for Production Rate DeterminationsDeterminations
CRONUS-Earth
In Situ Cosmogenic In Situ Cosmogenic 1414CC(In Situ (In Situ 1414C)C)
Extract From QuartzExtract From Quartz Opportunity for Opportunity for
Thorough Empirical Thorough Empirical Testing of Scaling Testing of Scaling ModelsModels Integrated Over Integrated Over
Millenial Time ScalesMillenial Time Scales
CRONUS-Earth
Existing Altitude TransectsExisting Altitude Transects
CRONUS-Earth
In Situ In Situ 1414C Production Rate ScalingC Production Rate Scaling Produced by Nucleons and MuonsProduced by Nucleons and Muons
83% spallation, 15% slow muon, 2% fast muon83% spallation, 15% slow muon, 2% fast muon(Heisinger et al, 2002)(Heisinger et al, 2002)
Preliminary AntarcticPreliminary Antarctic Data Suggest Low Muogenic Data Suggest Low Muogenic ProductionProduction
CRONUS-Earth
Antarctic Altitude TransectAntarctic Altitude Transect
CRONUS-Earth
In Situ In Situ 1414C Production Rate ScalingC Production Rate Scaling Produced by Nucleons and MuonsProduced by Nucleons and Muons
83% spallation, 15% slow muon, 2% fast muon83% spallation, 15% slow muon, 2% fast muon(Heisinger et al, 2002)(Heisinger et al, 2002)
Preliminary AntarcticPreliminary Antarctic Data Suggest Low Muogenic Data Suggest Low Muogenic ProductionProduction
CRONUS-Earth
Scale to SL, High LatitudeScale to SL, High Latitude Time-integrated production rateTime-integrated production rate Account for geomagnetic and solar variabilityAccount for geomagnetic and solar variability Test atmospheric modelsTest atmospheric models
Test For Bias With Sample Altitude and LatitudeTest For Bias With Sample Altitude and Latitude
Identifying Identifying Scaling Scaling Model Model BiasesBiases
CRONUS-Earth
UncertaintiesUncertainties Scatter in Preliminary DataScatter in Preliminary Data
CRONUS-Earth
Observed ScatterObserved Scatter
CRONUS-Earth
UncertaintiesUncertainties Scatter in Preliminary DataScatter in Preliminary Data
CRONUS-Earth
Low Values = Geologic FactorsLow Values = Geologic Factors Address with Many AnalysesAddress with Many Analyses
High Values = Inadequate Pretreatment?High Values = Inadequate Pretreatment?
Identify and Minimize Lab Sources of ScatterIdentify and Minimize Lab Sources of Scatter Different WorkersDifferent Workers Different Sample Prep TechniquesDifferent Sample Prep Techniques Different Degrees of Etching?Different Degrees of Etching? Objective Indicator of Etching AmountObjective Indicator of Etching Amount
BaBa, Al, Zr?, Al, Zr?
Stepwise DissolutionStepwise Dissolution
6.8E+05
7.0E+05
7.2E+05
7.4E+05
7.6E+05
7.8E+05
8.0E+05
8.2E+05
8.4E+05
8.6E+05
8.8E+05
BNR3-1 BNR3-2 BNR3-3 BNR3-4 BNR3-5
Sample Number
In Situ
14C (at/g SiO
2)
0
5
10
15
20
25
30
35
40
45
50
Ba (ppm)
In Situ 14CBa
CRONUS-Earth
UncertaintiesUncertainties Scatter in Preliminary DataScatter in Preliminary Data
Low Values = Geologic FactorsLow Values = Geologic Factors Address with Many AnalysesAddress with Many Analyses
High Values = Inadequate Pretreatment?High Values = Inadequate Pretreatment?
CRONUS-Earth
Identify and Minimize Lab Sources of ScatterIdentify and Minimize Lab Sources of Scatter Different WorkersDifferent Workers Different Sample Prep TechniquesDifferent Sample Prep Techniques Different Degrees of Etching?Different Degrees of Etching? Objective Indicator of Etching AmountObjective Indicator of Etching Amount
BaBa, Al, Zr?, Al, Zr?
Spallogenic/Muogenic Production ProportionsSpallogenic/Muogenic Production Proportions Antarctic Altitude TransectAntarctic Altitude Transect 5-10 m Drill Cores from Geological Calibration5-10 m Drill Cores from Geological Calibration
Timeline and DeliverablesTimeline and Deliverables Year 1Year 1
Identify Global Sample Set for Saturated Identify Global Sample Set for Saturated 1414C AnalysisC Analysis Already Collected by Other InvestigatorsAlready Collected by Other Investigators Evidence for Evidence for 1414C SaturationC Saturation
Stable/Long-Lived CN DataStable/Long-Lived CN Data Geomorphic/Geologic IndicatorsGeomorphic/Geologic Indicators
Years 1-5Years 1-5 AnalysesAnalyses
Year 5Year 5 Results Compared with Other CRONUS DataResults Compared with Other CRONUS Data
Geomagnetic & Solar Variation EffectsGeomagnetic & Solar Variation Effects Atmospheric EffectsAtmospheric Effects Spallogenic/Muogenic ProductionSpallogenic/Muogenic Production Incorporate into Parameter Estimation ModelIncorporate into Parameter Estimation Model
Write PapersWrite Papers
CRONUS-Earth
Geological CalibrationGeological CalibrationLake Bonneville ShorelinesLake Bonneville Shorelines
Lake Bonneville, UtahLake Bonneville, Utah
Tabernacle HillTabernacle Hill
Bonneville & Provo ShorelinesBonneville & Provo Shorelines