Statistical detection of meteor showers using data from the Swedish infrasound network

Ludwik Liszka

Swedish Institute of Space Physics

SLU

901 83 Umea, Sweden

Swedish Infrasound Network

Present stations:

Kiruna

Jamton

Lycksele

Uppsala

Search for small and medium meteor events – objectives:

• To search for meteor events below the infrasonic background level

• To establish a set of indicators which can be used to discriminate a single event

• To develop techniques for extraction of events from combined multi-station data

Meteor on 2002-12-30 in Morjärv, Northern Sweden

Morjärv Meteor

Morjärv Meteor

Angle-of-arrival = 208º Vp = 350 m/s

Morjärv Meteor

How to optimize the indicators?

Principal Component Analysis (PCA) of multiple indicator data

Indicators are distributions of variables:

Angle-of-arrival

Phase velocity

Crosscorrelation

Spectral slope

Principal component analysis

• Purpose: to find a direction where maximum variance may be found in multivariate data

PCA

• Direction of maximum variance

Angle-of-arrival

Entropy = -1.18 (Emax=0, Emin=-2.42)

Phase velocity Vp

Cross-correlation

Spectral slope

Parameters of the analysis

• 1 window = 128 data points (7.11 sec)

• The window is moved in 32p steps (overlap)

• Distributions are created for each sample of 50 positions of the window

• 16 samples / 30 minutes

Discrimination of meteor impacts

Selection of data to find proper combination of indicators:

• Concorde vs. North Sea Meteor

Another approach is to apply PCA without pre-selecting transformation coefficients

Comparison of indicators

Plot of component loadings

High cross-correlation counts

Meteor discrimination

Bavarian Meteor 2002-04-065th principal component

Discriminant function based on 5th PC

Small meteors – meteor showersLeonids – 2002-11-18

  

Small meteors – meteor showersLeonids – 2001-11-18

Combination of information from 2 stations (North Sea Meteor) Lycksele - Jamton

Combination of information from 2 stations (North Sea Meteor) Lycksele - Kiruna

Combination of information from 2 stations (Leonids 2002-11-18)

Lycksele - Jamton

Conclusions

• PCA may be used to discriminate events with a specific signature, like meteor impacts

• The method may be applied to events below the noise level, for example, meteor showers