, M. Karlicky, J. Rybak
, F. Farnik,
K. Jiricka
H. Meszarosova, M. Karlicky, J. Rybak, F. Farnik,
K. Jiricka
Astronomical Institute of the Academy of Sciences of the Czech
Republic, 25165 Ondrejov, Czech Republic
Slovak Academy of Sciences, 05960 Tatranska Lomnica, Slovak Republic
Long period (
60 s) variations of the radio (0.8-4.5 GHz)
and X-ray fluxes observed during the July 14, 2000, April 12, 2001,
and April 15, 2001 flares by the Ondrejov radiospectrograph and Yohkoh
spacecraft are studied and the characteristic periods are searched for
by the Fourier and wavelet methods. The global statistical study of
these flares revealed characteristic periods in the interval of 60-513
s in the radio (0.8-4.5 GHz) and 60-330 s in the X-ray Yohkoh
fluxes. Cross-correlations between the radio fluxes at different
frequencies helped us to determine the bursts generated by plasma or
gyro-synchrotron mechanisms. In the April 12, 2001 flare, soft X-ray
fluxes of the sources located at the loop-top and footpoints of a
flare loop vary with the period of 60-320 s, and they are highly
correlated. But their relation to the radio (1.1 GHz - plasma emission
and 4.0 GHz - gyro-synchrotron emission) is complex. At the beginning
of the April 15, 2001 flare, in the 0.8-4.5 GHz range, a broadband
drifting radio burst with the time variation of 61-320 s was observed
at times of flare loop ejection. Its detailed statistical analysis
shows that this burst consists of two parts, and, that first part is
generated by the plasma emission mechanism and the second, probably,
by the gyro-synchrotron one. The characteristic period of about 300 s
found in three X-class flares in their dm-radio and X-ray emissions is
discussed.