Airborne Magnetic Measurements Associated with SW06 Experiment

Will AveraPat Gallacher, Wayne KinneyNaval Research Laboratory

And

Brad NelsonDefence 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 lines @ 300’ (Lines 1,2,3,4)– 4 lines @ 500’ (Lines 5,6,11,12)– 2 lines @ 1000’ (Lines 7,8)– 2 lines @ 2000’ (Lines 9,10)– each line was ~ 10 minutes in length (~ 60 km) + 3 minutes per

corner– All lines were along the same track

• 39.5317 N , 73.6478 W to 38.9560 N , 73.0213 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 navigation @ 4 Hz

500’ Results: Track Reproducibility : Lines 5,6,11,12

• Excellent reproducibility => Good geologic noise removal

All 4 Lines OverlyLine 11

Unfiltered

So

uth

No

rth

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 DataModel : 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 DataModel : 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