Thanks - a very nice fireball.
I see from the
URSA web site that the fireball was also widely observed from across Finland. They've put a
map together with preliminary track and potential fall zone for any resulting meteorites. I think they are indicating accuracy of 100km for the location of the potential fall zone. It looks to be a remote and largely wooded area. They've also provided links to the local infrasound network with some good prospects for infrasound detection of the meteoroid's passage through the atmosphere.
Infrasound is sound of a frequency below normal human hearing range. The sound is generated by the meteoroid traveling at hypersonic speeds through the atmosphere and associated fragmentation events.
Notes on times. The video suggests a 4 - 5 second visible flight ending around 02:14 MSK in the early hours of the 19th April 2014. MSK is UTC +4 hours, so the fireball occurred at 22:14 UTC on the 18th April 2014. Finland is on EEST (UTC +3 hours), so the reported times of 01:15 EEST on the 19th April 2014, roughly agree. The infrasound data is referenced to UTC.
There look to be probable infrasound detections from
Swedish-Finnish Infrasound Network stations at:
Sodankylä (64° 25' 14.2" N 26° 23' 24.7" E) approx 22:27 UTC 18/04/14. Infrasound propagation time 13 minutes onwards.
Kiruna (67° 35' 10.0" N 20° 25' 14.2" E) approx 22:38 UTC 18/4/14. Infrasound propagation time 24 minutes onwards.
Jämtön (65° 51' 46.4" N 26° 23' 24.7" E) approx 22:41 UTC 18/04/14. Infrasound propagation time 27 minutes onwards.
With an end-of-visible-flight close to Zapolyarny, the propagation velocity of the infrasound is roughly:
Sodankylä 1337 km/hr, 371 m/s
Kiruna 1152 km/hr, 320 m/s
Jämtön 1182 km/hr, 328 m/s
Given that the propagation speed will be affected by stratospheric winds, these seem reasonable. In each case the infrasound rumbles on for several minutes.
- Map generated by Infrasound source locator, Swedish Institute of Space Physics, Umeå