tracing a meteoric trajectory with infrasound

Tracing a meteoric trajectory with infrasound

Läslo Evers and Hein Haak

evers@knmi.nlhttp://www.knmi.nl/~evers

Royal Netherlands Meteorological Institute (KNMI)Seismology Division

The presented work is under review with Geoph. Res. Lett.

Dutch Infrasound Arrays

Meteoric Infrasound in DBN

2003 February 1918h18m24.08s GMT

Detections at DBN

Meteoric Infrasound in DIA

2003 February 1918h17m59.31s GMT

Detections at DIA

Resolution I: Fisher ratio response

Resolution II: best beams at DIABest beam 1st arrival: 1.0 deg and 359.9 m/s

Best beam 2nd arrival: 359.0 deg and 335.6 m/s

Summary of the observations

2003.02.1918h17m57.28s

1.0o

359.9 m/s359.0o

335.6 m/s

32.3o

341.5 m/s 35.8o

373.5 m/s

Localization through cross bearing

What can be used for validation?• Reported time of occurrence of 18h13m05s• Observed approximate direction from S to N

What is known?• Arrival times of the different phases at DBN and DIA• Bearing and range from cross bearing

How?• Least squares optimization of observed and modeled differential traveltimes for different heights

• 4D source characteristics: location and time. Is the source moving (bolide) or static (nuclear test)?

What might be derived and why?

Atmospheric models

Raytracing for the 1st arrival DIA

Differential traveltime modeling

Observed Δt: 2.94±0.01 sMinimum at 0.03 s: 32, 56 km

Observed Δt: 3.37±0.15 sfound at 0.22 s: 27, 57 km

Trajectory reconstruction

Conclusions and discussion

The source is identified as moving, this bolide could be located in 4D by two nearby arrays.

Reported time of occurrence and path confirmed. Only convergent solutions found for ECMWF

models. snr of 17 in DBN and 2 in DIA: spatial coherence

lost in larger aperture array, resp. 60 and 1500 m. Average of DBN and DIA origin time correct, but an

absolute difference of ~8 sec caused by uncertainties in model and bearings.