SOHO/CDS observations of waves above the network
Gömöry P.1, Rybák J.1, Kucera A.1, Curdt W.2, Wöhl H.3
1 Astronomical Institute of the Slovak Academy of Sciences,
SK-05960 Tatranská Lomnica, Slovakia
2 Max-Planck-Institut für Sonnensystemforschung, D-37191 Katlenburg-Lindau, Germany
3 Kiepenheuer-Institut für Sonnenphysik, D-79104 Freiburg, Germany
Abstract:
We analyze temporal variations in the intensities and the
Doppler shifts of He I 584.33 A (chromosphere), O V 629.73 A (transition region), and Mg IX 368.07 A (corona)
measured in and above chromospheric network near disk center with the Coronal Diagnostic Spectrometer (CDS)
onboard the Solar and Heliospheric Observatory (SOHO). There is significant correlation between the He I and
O V modulations, with O V intensity leading He I intensity by 27.3s +- 4.6s but no significant time shift in
the Doppler shift. Cross-correlation between the O V and Mg IX intensities reveals multiple maxima without
correlation between their Doppler shifts. Wavelet power analysis gives evidence of intermittent chromospheric
and transition-region oscillations with periodicities in the 250 - 450s range and of coronal oscillations in the
110 - 300s range. Wavelet phase difference analysis shows that the determined time shift between variations of
the He I and O V intensities is dominated by waves with about 300s periodicity. We interpret these results as
giving evidence of compressive waves that propagate downward from the transition region to the chromosphere in
the particular chromospheric network. We discuss different scenarios regarding origin and source localization
of waves, and we speculate on their role in coronal heating above chromospheric network.