Response of an optically thin,isothermal atmosphere to a convective overshoot |
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| Authors: | Chen Cheng-Jen |
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| Institution: | (1) Advanced Study Program, National Center for Atmospheric Research, Boulder, Colo., U.S.A.;(2) Convair Aerospace Division, General Dynamics, 92138 San Diego, Calif., U.S.A. |
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| Abstract: | Radiation is believed to be hostile to the generation of gravity waves by granulation at the base of photosphere where the radiation is effective. A convective overshoot from subphotosphere seems able to penetrate to a height where the solar temperature is minimum and to excite the gravity waves in a stable region there.The response of the solar atmosphere to a Gaussian disturbance characterizing such a convective overshoot is studied in an unbounded isothermal atmosphere. Radiative effects are included, but only in regions which are optically thin. The response is measured in terms of mean vertical kinetic energy density (E
z) and mean vertical external energy flux (Q
z).
E
z and Q
z were calculated for a wide range of frequencies centered at the observed 5-min velocity oscillation period. The computed sharp and broad power spectra at the lower chromosphere and the upper photosphere, respectively, are attributed to the combined effects of space damping and source function. Low-frequency waves (2000 s or longer) are found to be not responsible for depositing energy in the upper solar atmosphere.The National Center for Atmospheric Research is sponsored by the National Science Foundation. |
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