HINODE SOT discovered a new type of chromospheric activities in sunspot penumbrae, which is called penumbral microjets. Their lifetime is shorter than 1min, and apparent rise velocity is faster than 50km/s, which is significantly faster than the sound speed in the chromosphere. These very dynamical nature of the penumbral microjets suggests that they are possibly driven by magnetic reconnection in uncombed magnetic field configuration of penumbral filaments.
So far, their temporal evolution and apparent velocity have been studied only using image sequences taken through the CaII-H filter. It is important to directly measure velocities of penumbral microjets with Dopplergrams of chromospheric spectral lines. For this purpose, SOT can provide limited use of H-alpha Dopplergram simultaneous with CaII-H imaging. Diagnostic by SP is also important to know magnetic configuration around the footpoints of penumbral microjets, and to validate the magnetic reconnection scenario.
Another important question is what the transition region and coronal response to the penumbral microjets is. It has been know that there are cool 1MK coronal loops emanating from a sunspot, and bright structures seen in transition region lines, which is called sunspot plumes, are associated with the footpoints of the coronal loops. EIS and XRT observations together with SOT are essential to know the coronal and transition region response.
ref. Katsukawa et al. 2007, Science 318 (5856), 1594-1597 |
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