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Дата изменения: Thu Jan 13 19:37:25 2000
Дата индексирования: Mon Oct 1 23:59:14 2012
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We examine spectral time series of coronal line Mg IX 368 Å and transition region line O V 629 Å, observed with the Coronal Diagnostic Spectrometer (CDS) onboard the SOHO spacecraft. Primarily we were looking for intensity and velocity oscillations in polar plumes, however by chance we detected a giant macro-spicule at the limb and were able to follow its dynamical structure. We observe blue and red-shifted emission in O V from the macro-spicule structure, which indicates that it is probably a rotating twisted magnetic jet. The emission is also detected from the macro-spicule in the Mg IX 368 Å line, at a temperature of 1 million K.

Both Fourier and wavelet transforms have been applied independently to the analysis of the oscillations in order to find the most reliable periods. We report here on the existence of long period oscillations in the polar plumes as observed in the O V 629 Å line. The counts for Mg IX were too low and so this line was not used in the power analysis. Our observations indicate the presence of compressional waves with periods of 20-25 minutes. Our observation will be compared with MHD numerical simulations for the propagation of Alfven waves. <