D. Banerjee J.G. Doyle and E. O'Shea
Armagh Observatory, Armagh, BT61 9DG, N. Ireland
Dept. of Pure & Applied Phys., Queens University Belfast, Belfast BT7 1NN, N. Ireland
The power spectra for line intensities of lower chromospheric lines N I 1319 Å\ and C II 1335 Å are presented. On a number of occasions, intensity oscillations were seen to occur in N I at 3.7 mHz while C II over the same spatial location showed oscillations close to 2.7 mHz. In a network region, the C II line intensity was time-delayed by 1 min., compared to the N I line intensity. For network regions, the 5 min. intensity oscillations observed in N I are often accompanied with a blue-shifted line profile of 2--3 km s. These oscillations can be interpreted in terms of kink and sausage waves propagating upwards along thin magnetic flux tubes. These waves can be generated by random foot-point motions driven by exploding granules at the photospheric level.
Key words: Sun; chromospheric oscillations; SOHO; waves.