Solar Physics

, Volume 284, Issue 2, pp 297–314 | Cite as

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

  • G. Severino
  • T. Straus
  • M. Oliviero
  • M. Steffen
  • B. Fleck


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 



This work is dedicated to F.-L. Deubner, a pioneer of helioseismology and our master in this field. We thank the anonymous referee for making a number of very useful comments. One of the authors (GS) acknowledges financial support from the Italian Space Agency (ASI) and from the PRIN-INAF 2010 Asteroseismology: looking inside the stars with space- and ground-based observations. SDO/HMI data courtesy of NASA/SDO and the HMI science team.


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Copyright information

© Springer Science+Business Media Dordrecht 2012

Authors and Affiliations

  • G. Severino
    • 1
  • T. Straus
    • 1
  • M. Oliviero
    • 1
  • M. Steffen
    • 2
  • B. Fleck
    • 3
  1. 1.INAF-Osservatorio Astronomico di CapodimonteNapoliItaly
  2. 2.Leibniz-Institut für Astrophysik Potsdam (AIP)PotsdamGermany
  3. 3.ESA Science Operations Dept.c/o NASA GSFCGreenbeltUSA

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