Solar Physics

, Volume 284, Issue 2, pp 297-314

First online:

The Intensity–Velocity Phase Spectra of Evanescent Oscillations and Acoustic Sources

  • G. SeverinoAffiliated withINAF-Osservatorio Astronomico di Capodimonte Email author 
  • , T. StrausAffiliated withINAF-Osservatorio Astronomico di Capodimonte
  • , M. OlivieroAffiliated withINAF-Osservatorio Astronomico di Capodimonte
  • , M. SteffenAffiliated withLeibniz-Institut für Astrophysik Potsdam (AIP)
  • , B. FleckAffiliated withESA Science Operations Dept., c/o NASA GSFC

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


There are three major issues in modeling solar evanescent oscillations: the variation of the intensity [I]–velocity [V] phase difference of p-modes close to the base of photosphere; the existence of a plateau of negative IV phase differences below and between the ridges of the low-frequency p-modes; the explanation of the IV cross-spectra of the evanescent oscillations. We present new interpretations for the first two issues, based on modeling intensity fluctuations taking steep temperature gradients, opacity, and non-adiabatic cooling into account.

We also discuss consequences of our model for the explanation of power spectra and cross-power spectra of p-modes. In particular, we present evidence that the acoustic sources that generate evanescent waves produce a coherent background that explains the plateau–interridge regime of negative IV phase difference.


Helioseismology, direct modeling Waves, modes Velocity fields, photosphere