2013 Russian Fireball Largest Ever Detected by CTBTO Infrasound - - PowerPoint PPT Presentation

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2013 Russian Fireball Largest Ever Detected by CTBTO Infrasound - - PowerPoint PPT Presentation

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2013 Russian Fireball Largest Ever Detected by CTBTO Infrasound Sensors A. Le Pichon, N. Brachet, J. Vergoz - CEA, DAM, DIF, France P. Mialle, D. Brown - PTS/CTBTO, Vienna, Austria L. Ceranna, C. Pilger - BGR, Hannover, Germany M. Garcs -

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SLIDE 1

Science and Technology Conference

June 17-21 2013, Vienna, Austria

2013 Russian Fireball Largest Ever Detected by CTBTO Infrasound Sensors

  • A. Le Pichon, N. Brachet, J. Vergoz - CEA, DAM, DIF, France
  • P. Mialle, D. Brown - PTS/CTBTO, Vienna, Austria
  • L. Ceranna, C. Pilger - BGR, Hannover, Germany
  • M. Garcés - ISLA, Univ. Hawaii, USA
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SLIDE 2

Science and Technology Conference

June 17-21 2013, Vienna, Austria

Chelyabinsk fireball, 15/02/2013

Largest ever detected by CTBTO infrasound sensors

  • On 15 February, 2013, a large Earth‐impacting

fireball entered the Earth's atmosphere over the Kazakh/Russia border

  • Maximum brightness south of Chelyabinsk

(54.80°N 61.10°E) near 30 km altitude

  • A small asteroid at high speed (~20 km/s)

Effective diameter: ~20 m Mass: ~10,000 t Source: Univ. Western Ontario, Canada http://www.nasa.gov/mission_pages/asteroids/new s/asteroid20130215.html

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Science and Technology Conference

June 17-21 2013, Vienna, Austria

Chelyabinsk fireball, 15/02/2013

Largest ever detected by CTBTO infrasound sensors

20 IMS stations 30 arrivals Period: 20-80 s Duration: 10 min – 3 h Max distance: 86,600 km Most energetic event being instrumentally recorded

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Science and Technology Conference

June 17-21 2013, Vienna, Austria

Shock wave: Meteors generate infrasound during their entry in the Earth's atmosphere. Mach cones become cylinders and generate shock waves (ReVelle D.O., 1976, 1997) Fragmentation: The high speed combined with an increasing atmospheric density, lead to thermal bursts. Energy of the explosions may reach several kilotons TNT equivalent (e.g. Edwards W.N., 2010) Propagation: Infrasound signals are refracted and channeled over long distances by the temperature gradient and the wind structure of the atmosphere

Infrasound from meteoroids

Different source mechanisms

Generation of hypersonic shockwaves perpendicular to the meteor trail Adapted from Ens et al., JASTP, 2012 Explosive fragmentation event generating a point source

  • f infrasonic

wave Occasionally an impact with the Earth

  • ccurs
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Science and Technology Conference

June 17-21 2013, Vienna, Austria

Distance [km] Altitude [km]

IS24 Tahiti [1-4] Hz, 2003/12/01

Infrasound from meteoroids

Example of full-wave modeling

Ceranna et al., 2005

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Science and Technology Conference

June 17-21 2013, Vienna, Austria

Frequency 9:30 10:00 23:00 00:00 01:00 Frequency 13:00 14:00 15:00 16:00 Frequency Ig1 - 2013/02/15 – first arrival (6,500 km) Back-azimuth [°] Ig3 – 2013/02/16 - first full circumnavigation (46,600 km) Ig5 – 2013/02/18 - second full circumnavigation (86,600 km)

Chelyabinsk fireball, 15/02/2013

Detection at IS53 (Fairbanks, Alaska) @ 0.05-4 Hz

Decrease of signal frequency with distance Almost no attenuation between Ig3 and Ig5 Limitation of the standard frequency band

5 Pa 0.1 Pa 0.1 Pa

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Science and Technology Conference

June 17-21 2013, Vienna, Austria

Ig5 - IS53 Alaska (Ig5, 86600 km) 0.01-4 Hz, T=40 s

Chelyabinsk fireball, 15/02/2013

Detection by IS53 (Fairbanks, Alaska)

2 hours

1 km

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Science and Technology Conference

June 17-21 2013, Vienna, Austria

Chelyabinsk fireball, 15/02/2013

Observations of global multiple paths

Barograms of phase aligned recordings at 20 IMS stations Band-passed filter: 15-80 s

Ig1 Ig2

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SLIDE 9

Science and Technology Conference

June 17-21 2013, Vienna, Austria

Chelyabinsk fireball, 15/02/2013

USArray observations

280 m/s 270 m/s 260 m/s Courtesy of C. Degroot-Hedlin UCSD, USA

Time after event [min] Distance to source [degrees]

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Science and Technology Conference

June 17-21 2013, Vienna, Austria

Chelyabinsk fireball, 15/02/2013

Global stratospheric wind circulation @ 50 km altitude

  • ECMWF-91 profiles,

0.5°x0.5° resolution, 91 altitude levels, http://www.ecmwf.int

  • Dominant eastward winds

at mid-latitude in NH

  • Weather conditions

remained relatively stable

  • ver three days
  • Detecting stations are

uniformly distributed

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Science and Technology Conference

June 17-21 2013, Vienna, Austria

Is It

Courtesy of C. Degroot-Hedlin UCSD, USA

North Pole

Duct height [km]

Predicted refracting height Range-dependent ray- tracing ECMWF-91

Phase identification globally consistent with the measured celerity values Brown D. et al., 2002

Is > 285 m/s It < 285 m/s

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SLIDE 12

Science and Technology Conference

June 17-21 2013, Vienna, Austria

Source altitude: 0 km Source altitude: 30 km

Chelyabinsk fireball, 15/02/2013

Attenuation vs. frequency and source altitude

Upwind - It Downwind - Is Upwind - It Downwind - Is

At low frequency, the attenuation is less sensitive to stratospheric winds Elevated source favored long propagation range

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SLIDE 13

Science and Technology Conference

June 17-21 2013, Vienna, Austria

Chelyabinsk fireball, 15/02/2013

Example of range-dependent simulated ray paths (Ig1 and Ig2)

Ig1 Ig2

Towards IS27 - Antarctica

Ig1 Ig2

Energy trapped in elevated stratospheric duct Returned acoustic energy to the surface through diffraction

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SLIDE 14

Science and Technology Conference

June 17-21 2013, Vienna, Austria

Chelyabinsk fireball, 15/02/2013

Example of range-dependent simulated ray paths (Ig1 and Ig3)

Towards IS26 - Germany

Ig3 Ig1

Returned energy from elevated thermospheric ducts (upwind) Phase conversion from thermospheric in NH to stratospheric in SH Negligible absorption in the thermosphere at period near 50 s

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SLIDE 15

Science and Technology Conference

June 17-21 2013, Vienna, Austria

Ig1

  • Mean period: 39 s
  • Explosive yield: ~450 kt of TNT
  • Energy consistent with measured
  • ptical radiant energy

(U.S. Government sensors) http://neo.jpl.nasa.gov/fireballs

  • Expected to occur once every 100

years

Flux rate of NEO From Brown et al., Nature, 2002

Tunguska 1908 ~10 Mt Chelyabinsk 2013 ~450 kt

U.S. Air Force Technical Center (AFTAC)

Chelyabinsk fireball, 15/02/2013

Estimated yield as a function of period

log W/2 = 4.14 log T - 3.61

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SLIDE 16

Science and Technology Conference

June 17-21 2013, Vienna, Austria

Signals produced by the 2013 Russian fireball observed at extreme

ranges by 20 IMS stations

Explosive energy estimated at ~450 kt Provide a prominent milestone for studying in detail infrasound

propagation around the globe as well as for calibrating the performance of the IMS network

Provide benchmark with additional constraints on source

characteristic estimates for assessing meteor impact hazard

Summary

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SLIDE 17

Science and Technology Conference

June 17-21 2013, Vienna, Austria

Acknowledgments

  • P. Brown, Dpt. of Physics and Astronomy, Univ. of Western Ontario, Canada
  • W. Edwards, Natural Resources Canada, Ottawa, Canada
  • C. Degroot-Hedlin, Univ. of California San Diego, USA
  • L. Evers, KNMI, The Netherlands

Le Pichon et al. (2013), Geophys. Res. Lett., doi:10.1002/grl.50619