Collados, M.
Referencia bibliográfica
Astronomische Nachrichten, vol. 323, no. 3/4, p. 254-256
Advertised on:
7
2002
Número de citas
5
Número de citas referidas
4
Descripción
Recently a number of works have given interesting results on the
penumbral fine structure of sunpots (del Toro Iniesta, Bellot Rubio
& Collados 2001; Schlichenmaier & Collados 2002), where, for
instance, cold supersonic Evershed downflows were observed. In addition,
there are recent results that show the existence of shock wave trains
propagating in umbral chromospheres with a 3-min period, where the
photospheric driving signal has also been detected. The phase difference
between the photospheric and chromospheric signals in the 5.5-6.5 mHz
band (3 minute) allows to infer that an upward propagation of the slow
magnetoacoustic mode, with an increasing velocity amplitude (due to the
rapid decrease of density) and reaching the non-linear regime, is giving
rise to shock fronts. All these results show that the umbra and the
penumbra have a dynamical behaviour which is far from being near an
equilibrium situation.