Conclusions

A new automated wavelet analysis approach (based on an original idea in Ireland et al. 1999) to TRACE quiet-Sun UV data is presented. This permits the extension of previous Fourier analysis into the time-localised domain. The resulting occurrence rate at specific periods and lifetimes is directly comparable to the results of the classical Fourier approach. The important results are,

• The network is found to have a peak occurrence rate periodicity of log₁₀(P) = 2.451 ± 0.087 (P = 231-346 s) for a lifetime of 2-3 cycles, with a significant tail of higher-period oscillations, while the internetwork is found to have a well-defined peak occurrence rate periodicity of log₁₀(P) = 2.402 ± 0.090 (P = 205-309 s) for a lifetime of 2-3 cycles.
  
  
• Both the network and internetwork show a number of long-lifetime oscillations, however these do not seem to recur in the same location. Consequently the driver may have exhausted its energy in generating the LLO.
  
  
• On the other hand, oscillations at 230-280 s, and/or 2-3 cycles, show a tendency to recur at the same spatial position. These are considered good candidates for chromospheric heating.
  
  
• Network oscillations show an increase in occurrence rate and oscillatory power with increasing HOF from 1700 Å to 1216 Å, possibly as a result of the opening up of the canopy at higher altitudes. In the 1550 Å passband there is a marked decrease in both occurrence rate and oscillatory power, suggesting that any possible waves may have either dissipated, shocked, moved away from the network or changed in frequency. The network also contains more oscillations around 534 s in the lower HOF than upper HOF passbands, which agrees with the MHD model of Hasan & Kalkofen (1999).
  
  
• In the internetwork there is a decrease in occurrence rate from 1700 Å to 1600 Å. Hence, some oscillations seem unable to propagate past the low chromosphere. However, the increase at 1216 Å and subsequent decrease at 1550 Å suggests that some waves which do propagate through the low-chromosphere may once again excite further oscillations, before disappearing higher in the atmosphere.
  
  
• A comparison of the occurrence rate of oscillations in the network and internetwork shows that although the network generally dominates at periods greater than 300 s, for a small number of cycles and long periods the internetwork may dominate. Similarly, regions of network dominance may be found at very short periods (and low lifetimes) where Fourier analysis shows internetwork oscillations to dominate.