Airborne Magnetic Measurements Associated with SW06 Experiment Will Avera Pat Gallacher, Wayne Kinney Naval Research Laboratory And Brad Nelson Defence Research and Development Canada SW06 Post-Experiment Meeting

Objective / Purpose Measure magnetic fields in the vicinity of NLIW’s Test theoretical predictions –Internal waves can produce measurable magnetic signatures

Plan / Measurements 12 flight lines were collected over NLIWs on August 2, 2006 –4 300’ (Lines 1,2,3,4) –4 500’ (Lines 5,6,11,12) –2 1000’ (Lines 7,8) –2 2000’ (Lines 9,10) –each line was ~ 10 minutes in length (~ 60 km) + 3 minutes per corner –All lines were along the same track N, W to N, W Start point and bearing for this line were given to us by Jim Moum who was on the OCEANUS OCEANUS was in the middle of one NLIW packet

SW06 NRC Convair flight line Simulations and Analysis -Very high resolution -MITgcm nonhydrostatic simulation -Forced with nested NCOM -Focus on nonlinear internal wave -Based on previous work including -MITgcm simulations of Hudson Canyon generation area -Nested NCOM simulations of high amplitude internal waves on shelf and slope in SW06 SW_06_new Domain (0.5km) current simulations LBSF Domain (0.5km) future simulations SW06 Moorings

The NRC Convair Convair data acquisition system –3 Cesium total-field magnetometers –2 vector magnetometers for compensation –Attitude and noise sensors –Post-processed DGPS 4 Hz

500’ Results: Track Reproducibility : Lines 5,6,11,12 Excellent reproducibility => Good geologic noise removal All 4 Lines Overly Line 11 Unfiltered South North

Magnetic Results: 500’ Alt - Lines 5, 6, 11, 12 OCEANUS located near the internal wave activity OCEANUS location sufficiently distant not to be disturbing measurements NLIW ? OCEANUS Lt. Blue = Line 11 Ships > 1 mile off line Black = Line 5 Blue = Line 6 Green =Line 12 Magnetic Data Model : U Velocity 1700 UT 1600 UT 1500 UT

Magnetic Results: 500’ Alt - Lines 5, 6, 11, 12 OCEANUS located near the internal wave activity OCEANUS location sufficiently distant not to be disturbing measurements NLIW ? OCEANUS Lt. Blue = Line 11 Ships > 1 mile off line Black = Line 5 Blue = Line 6 Green =Line 12 Magnetic Data Model : W Velocity 1700 UT 1600 UT 1500 UT

Conclusions (So Far) Data processing techniques –Appear to work for external magnetic noise reduction Anomalous residual noise on east side of the line is good candidate for NLIW –Jim Moum claimed the ship was in the middle of the NLIW –Residual noise correlated with OCEANUS position