Is the Solar Chromosphere Heated by Acoustic Waves?
Abstract
Space observations with TRACE have measured only 10% of the energy flux required to heat the nonmagnetic part of the solar chromosphere and have thereby called into question the theory of chromospheric heating by acoustic waves. To explain the deficit in the measured flux, heating by processes related to the magnetic field and the limited spatial resolution of the space observations have been invoked. This paper argues that radiation emerging from the nonmagnetic chromosphere shows that the heating mechanism is dissipation of acoustic waves. The full energy flux required for acoustic heating of the chromosphere must therefore pass through the photosphere. The explanation of the missing flux by the limited spatial resolution of TRACE confirms the principle of the effect, but the test is preliminary since the hydrodynamic model on which the test is based has temperature fluctuations that far exceed those of the Sun. The shape of the acoustic spectrum observed with TRACE appears to support the theory of wave generation in the solar convection zone. But the low energy flux and the limited acoustic frequency range of the observations prevent a definitive conclusion.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2007
- DOI:
- 10.1086/523259
- Bibcode:
- 2007ApJ...671.2154K
- Keywords:
-
- Hydrodynamics;
- Shock Waves;
- Sun: Chromosphere;
- Sun: Oscillations