Statistical detection of meteor showers using data from the Swedish infrasound network Ludwik Liszka Swedish Institute of Space Physics SLU 901 83 Umea,

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