On the generation of umbral flashes and running penumbral waves
From a review of the observed properties of umbral flashes and running penumbral waves it is proposed that the source of these periodic phenomena is the oscillatory convection which Danielson and Savage (1968) and Savage (1969) ave shown is likely to occur in the superadiabatic subphotospheric layers of sunspot umbras. Periods and growth rates are computed for oscillatory modes arising in a simple two-layer model umbra. Finally, the results suggest that umbral flashes result from disturbances produced by oscillatory convection occurring in the upper subphotospheric layer of the umbra where the superadiabatic temperature gradient is much enhanced over that in lower layers, while running penumbral waves are due to oscillations in a layer just below this upper layer.
- Research Organization:
- Hale Observatories, Pasadena, CA
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-29-001211
- OSTI ID:
- 4416507
- Journal Information:
- Solar Physics, Vol. 30, Issue 2; Other Information: Orig. Receipt Date: 30-JUN-74; ISSN 0038-0938
- Publisher:
- Springer
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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