Cosmic-Ray Fluxes Present and Past Nathaniel Lifton, Marek Zreda, Darin Desilets, John Clem  Background  Objectives  Present-Day Fluxes  Instrumental Measurements  Modeling  Time-Integrated Fluxes  In Situ 14 C in Saturated Surfaces CRONUS-Earth

Background Production Rates Well-Established at Few Sites Production Rates Well-Established at Few Sites Scaling Models Predict Production Rates Elsewhere Scaling Models Predict Production Rates Elsewhere Current Scaling Models Based on Modern Cosmic-Ray Measurements Current Scaling Models Based on Modern Cosmic-Ray Measurements Lal, 1991; Stone, 2000; Dunai, 2000, 2001; Desilets & Zreda, 2003; Lifton et al., in prep Lal, 1991; Stone, 2000; Dunai, 2000, 2001; Desilets & Zreda, 2003; Lifton et al., in prep Neutron Monitors (NM) Neutron Monitors (NM) Other Instruments/Techniques Other Instruments/Techniques Problems Problems Need to Tie CR Measurements to CN Production in Rocks Need to Tie CR Measurements to CN Production in Rocks Limited Empirical Testing of Models Over Millenial Time Scales Limited Empirical Testing of Models Over Millenial Time Scales Scarcity of Samples of Well-Established Age Scarcity of Samples of Well-Established Age CRONUS-Earth

Objectives Relate NM Measurements to CN Production Rates Relate NM Measurements to CN Production Rates Global NM Network Data, Published Surveys Global NM Network Data, Published Surveys CRONUS-Earth

Global Neutron Monitor Network CRONUS-Earth

Global Neutron Monitor Network CRONUS-Earth

Objectives Relate NM Measurements to CN Production Rates Relate NM Measurements to CN Production Rates Global NM Network Data, Published Surveys Global NM Network Data, Published Surveys CRONUS-Earth Selected Low-Energy Neutron Detector Measurements Selected Low-Energy Neutron Detector Measurements Using NM Data as a Basis for CN Scaling Using NM Data as a Basis for CN Scaling Can a Single Scaling Model Apply to the Entire Neutron Energy Spectrum? Can a Single Scaling Model Apply to the Entire Neutron Energy Spectrum? Detailed NM Response to Secondary Cosmic Rays? Detailed NM Response to Secondary Cosmic Rays? NMs More Sensitive to High Energies NMs More Sensitive to High Energies Are Rocks as Well? Are Rocks as Well? Physically Relate NM Response and CN Production in Rock Physically Relate NM Response and CN Production in Rock Test Scaling Models over Millenial Time Scales Test Scaling Models over Millenial Time Scales In Situ 14 C in Saturated Surfaces In Situ 14 C in Saturated Surfaces

Present-Day Fluxes Measurements (Zreda, Desilets) Modeling (Zreda, Desilets, Clem) CRONUS-Earth

Time-Integrated Scaling From In Situ 14 C Production Rates Short Half-Life 5,730 yr Secular Equilibrium by About 25 kyr Insensitive to Moderate Erosion Rates Many Geomorphic Settings Suitable for Production Rate Determinations CRONUS-Earth

In Situ Cosmogenic 14 C (In Situ 14 C) Extract From Quartz Opportunity for Thorough Empirical Testing of Scaling Models Integrated Over Millenial Time Scales CRONUS-Earth

Existing Altitude Transects CRONUS-Earth

In Situ 14 C Production Rate Scaling Produced by Nucleons and Muons 83% spallation, 15% slow muon, 2% fast muon (Heisinger et al, 2002) Preliminary Antarctic Data Suggest Low Muogenic Production CRONUS-Earth

Antarctic Altitude Transect CRONUS-Earth

In Situ 14 C Production Rate Scaling Produced by Nucleons and Muons 83% spallation, 15% slow muon, 2% fast muon (Heisinger et al, 2002) Preliminary Antarctic Data Suggest Low Muogenic Production CRONUS-Earth Scale to SL, High Latitude Scale to SL, High Latitude Time-integrated production rate Time-integrated production rate Account for geomagnetic and solar variability Account for geomagnetic and solar variability Test atmospheric models Test atmospheric models Test For Bias With Sample Altitude and Latitude Test For Bias With Sample Altitude and Latitude

Identifying Scaling Model Biases CRONUS-Earth

Uncertainties Scatter in Preliminary Data Scatter in Preliminary Data CRONUS-Earth

Observed Scatter CRONUS-Earth

Uncertainties Scatter in Preliminary Data Scatter in Preliminary Data CRONUS-Earth Low Values = Geologic Factors Low Values = Geologic Factors Address with Many Analyses Address with Many Analyses High Values = Inadequate Pretreatment? High Values = Inadequate Pretreatment? Identify and Minimize Lab Sources of Scatter Identify and Minimize Lab Sources of Scatter Different Workers Different Workers Different Sample Prep Techniques Different Sample Prep Techniques Different Degrees of Etching? Different Degrees of Etching? Objective Indicator of Etching Amount Objective Indicator of Etching Amount Ba, Al, Zr? Ba, Al, Zr?

Stepwise Dissolution CRONUS-Earth

Uncertainties Scatter in Preliminary Data Scatter in Preliminary Data Low Values = Geologic Factors Low Values = Geologic Factors Address with Many Analyses Address with Many Analyses High Values = Inadequate Pretreatment? High Values = Inadequate Pretreatment? CRONUS-Earth Identify and Minimize Lab Sources of Scatter Identify and Minimize Lab Sources of Scatter Different Workers Different Workers Different Sample Prep Techniques Different Sample Prep Techniques Different Degrees of Etching? Different Degrees of Etching? Objective Indicator of Etching Amount Objective Indicator of Etching Amount Ba, Al, Zr? Ba, Al, Zr? Spallogenic/Muogenic Production Proportions Spallogenic/Muogenic Production Proportions Antarctic Altitude Transect Antarctic Altitude Transect 5-10 m Drill Cores from Geological Calibration 5-10 m Drill Cores from Geological Calibration

Timeline and Deliverables Year 1 Year 1 Identify Global Sample Set for Saturated 14 C Analysis Identify Global Sample Set for Saturated 14 C Analysis Already Collected by Other Investigators Already Collected by Other Investigators Evidence for 14 C Saturation Evidence for 14 C Saturation Stable/Long-Lived CN Data Stable/Long-Lived CN Data Geomorphic/Geologic Indicators Geomorphic/Geologic Indicators Years 1-5 Years 1-5 Analyses Analyses Year 5 Year 5 Results Compared with Other CRONUS Data Results Compared with Other CRONUS Data Geomagnetic & Solar Variation Effects Geomagnetic & Solar Variation Effects Atmospheric Effects Atmospheric Effects Spallogenic/Muogenic Production Spallogenic/Muogenic Production Incorporate into Parameter Estimation Model Incorporate into Parameter Estimation Model Write Papers Write Papers CRONUS-Earth

Geological Calibration Lake Bonneville Shorelines

Lake Bonneville, Utah

Tabernacle Hill

Bonneville & Provo Shorelines