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