Friday 24 February 2017
to 11:30 at
Sara Esteban (Stockholm University)
The penumbra is a strongly magnetized medium and, therefore, convection is expected to be inhibited if not completely suppressed. However, penumbrae are observed to harbor a plethora of bright filaments of different sizes that evolve in a few minutes. Since the discovery of the Evershed effect in 1909, theoretical models and observational studies have attempted to explain what it is happening in the penumbra, but none of them accounts for all observational facts. Therefore, we still have to understand how the gas moves in the presence of magnetic fields. Results from the latest published simulations support overturning convection as the responsible of penumbral flow motions, which reminds us of those observed in the quiet Sun at high-resolution observations. In addition, supersonic downflows in the penumbra are still a matter of debate. They were related to the Evershed flow sinks, but also to other structures such as the Evershed clouds. Thanks to improvements in instrumentation, they have been characterized in detail and more aspects are known.
During this talk I will review our current knowledge of how matter is transported in sunspot penumbrae. Specifically, I will shed light on the least known aspects of the velocity field in the penumbra, paying special attention to the smallest spatial scales and the temporal evolution of the flows.