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Intersite Environmental Correlations: E3 and E4 Investigations
Part 2: Bursts

Robert Schofield (Oregon) Janice Hester (SERF) N. Christensen (Carleton), P. Fritschel (MIT) M. Ito (Oregon), S. Klimenko (Florida) M. Landry (LHO), S. Marka (CIT) S. Mohanty (AEI), A. Ottewill (Wisconsin-Milwaukee) R Rahkola (Oregon)

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A search for coincident intersite environmental bursts

· Searched for threshold-exceeding events that occur at both Hanford and Livingston within a time window (about 30ms).

· Demanded that there be within-site as well as between-site coincidences in order to lower thresholds and maintain managable numbers of events.

· Modified Masahiro Ito's glitchMon to input multiple channels and output time series for events that met the threshold and coincidence criteria.

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E4 voltage channels; coincidence level: 6; : 3.5
Apparent event at Livingston, but the 1 event at Hanford may be coincident by chance. Top 5: Livingston; bottom 5: Hanford
Output from 560-580 Hz band: timing good to about 50 ms.
fourth order butterworth filter 100.0 80.0 60.0 40.0

Relative Units

20.0 0.0 -20.0 -40.0 -60.0 -80.0

coincidence level H0:PEM-MX_V1 H0:PEM-MX_V2 H0:PEM-LVEA2_V1 H0:PEM-LVEA2_V2 H0:PEM-LVEA2_V3 L0:PEM-EX_V1 L0:PEM-EX_V2 L0:PEM-LVEA_V1 L0:PEM-LVEA_V2 L0:PEM-LVEA_V3

-100.0 0.0

200.0

400.0

600.0

800.0

1000.0

Milliseconds after 673695511

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E4 voltage channels; coincidence level: 8; : 2.5

Top 5: Livingston; bottom 5: Hanford
Output from 560-580 Hz band: timing good to about 50 ms.
fourth order butterworth filter 100.0 80.0 60.0 40.0

Relative Units

20.0 0.0 -20.0 -40.0 -60.0 -80.0

coincidence level H0:PEM-MX_V1 H0:PEM-MX_V2 H0:PEM-LVEA2_V1 H0:PEM-LVEA2_V2 H0:PEM-LVEA2_V3 L0:PEM-EX_V1 L0:PEM-EX_V2 L0:PEM-LVEA_V1 L0:PEM-LVEA_V2 L0:PEM-LVEA_V3

-100.0 0.0

1000.0

Milliseconds after 673795274

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Signal vs. Distance

Number of observations Correlation coefficient Regression coefficient (SLOPE) Standard error of coefficient

= = = =

12 -0.65 -1.3 0.5


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The largest tabulated I/r during E4 (129kA, 20km)
Lightning strike appears on fluxgate magnetometer but not other channels.
Output from 560-580 Hz band: timing good to about 50 ms.
fourth order butterworth filter 400.0
L0:PEM-EX_MAG1X L0:PEM-EX_V1 L1:IOO-MC_F H0:PEM-COIL_MAGZ

200.0

Relative Units

0.0

-200.0

-400.0 0.0

200.0

400.0

600.0

800.0

1000.0

Milliseconds after 673744623

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S. Chatterji's coil magnetometers
Location at Hanford for E4 and E5;

Blue: E4 Hanford; Red: E4 Livingston
Power spectrum
10
3

H0:PEM-COIL_MAGZ L1:SUS-ETMY_COIL_LR

10

2

Magnitude

10

1
-1

10

10

-2

0

100

200

300

400

500

600

700

800

900

Frequency (Hz)
T0=14/05/2001 02:29:14 Avg=10 BW=0.187499

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Lightning (112 km, 180 kA) appears on coil and fluxgate magnetometers,
but is not evident on voltage or mode cleaner channels.

Output from 560-580 Hz band: timing good to about 50 ms.
fourth order butterworth filter 100.0
H0:PEM-COIL_MAGZ H0:PEM-MY_V1 H0:PEM-MY_MAGZ H0:PEM-LVEA2_V3 H1:IOO-MC_F

50.0

Relative Units

0.0

-50.0

-100.0 0.0

200.0

400.0

600.0

800.0

1000.0

Milliseconds after 673767497

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Intersite coincident events on coil magnetometers (E4)
Possible lightning strikes; red: Livingston; blue: Hanford.
Output from 560-580 Hz band: timing good to about 50 ms.
fourth order butterworth filter 100.0
L1:SUS-ETMY_COIL_LR H0:PEM-COIL_MAGZ

50.0

Relative Units

0.0

-50.0

-100.0 0.0

200.0

400.0

600.0

800.0

1000.0

Milliseconds after (top to bottom) 673826586, 673827832, 673828154, 673847365

Only Z-axis was available.

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545-595 Hz band-pass on 673827832

Output from 545-595 Hz band: timing good to about 20 ms.
fourth order elliptical filter 100.0
H0:PEM-COIL_MAGZ L1:SUS-ETMY_COIL_LR

50.0

Relative Units

0.0

-50.0

-100.0 0.0

200.0

400.0

600.0

800.0

1000.0

Milliseconds after 673827832

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Mere coincidence?
If the coil magnetometer coincidences were by chance, widening the coincidence window by a factor of 10 should increase the number of events by a factor of 10 (low event rate approximation). Time window of 25 bins gives 83 five sigma events in 10 hours. Time window of 250 bins gives 295 events instead of about 830. Better than 99% confidence that excess coincidences occur in the narrow time window.

BUT this result is only a couple of days old and programs need to be checked and supporting evidence accumulated.

So I am not yet completely convinced that we are detecting certain lightning strikes at both sites.

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Summary

· Stand alone code to search for intersite coincidences has been developed.

· No convincing examples of power line glitches that propagated between sites were found.

· No evidence yet of lightning strikes on other channels

· Fairly convincing evidence of greater than chance coincidences in magnetometer signals that could be lightning.

· Continue developing code to check for coincidences in signals that are offset in time from eachother.

· Upper thresholds as well as lower thresholds (windows)?

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