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Astron. Astrophys. 360, 1126-1138 (2000)


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Linear and nonlinear statistical analysis of narrow-band dm-spikes observed during the June 15, 1991 flare

H. Mészárosová 1, M. Karlický 1, A. Veronig 2, P. Zlobec 3 and M. Messerotti 3

1 Astronomical Institute of the Academy of Sciences of the Czech Republic, 25165 Ondejov, Czech Republic (hana@asu.cas.cz)
2 Institute of Astronomy, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
3 Trieste Astronomical Observatory, Via G.B. Tiepolo 11, 34131 Trieste, Italy

Received 25 October 1999 / Accepted 6 April 2000

Abstract

Narrow-band dm-spikes observed during the June 15, 1991 flare are statistically analysed. The character of their frequency distributions at 237, 327, 408 and 610 MHz in both L- and R-handed circular polarizations is studied. While for the complete time intervals no simple distributions of spikes (either exponential or power-law) are recognized, for shorter intervals both exponential and power-law distributions are observed. No significant difference is found in the distributions for L- and R-polarized data. Further analysis reveals that spikes appearing in dense groups and with high intensities preferentially have exponential distributions, while the sparse spikes with lower intensities are rather characterized by power-law distribution functions with high exponents. Groups of independent spikes (cases with low rates and low intensities) have power-law distributions trend in agreement with the coherent spike mechanisms. Tests are provided regarding statistical analyses. The nonlinear analysis reveals that the degree of complexity of the system varies. It decreases when the attractor dimensions and the Lyapunov exponents assume smaller values, which happens when very strong spikes are present. The changing characteristics of the statistical parameters are probably the result of a mutual interaction in the source environment or a product of propagation conditions.

Key words: acceleration of particles – methods: data analysis – methods: statistical – Sun: flares – Sun: magnetic fields – Sun: radio radiation

Send offprint requests to: H. Mészárosová (hana@asu.cas.cz)

© European Southern Observatory (ESO) 2000

Online publication: August 23, 2000

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