Wednesday

Solar spicules, which can be observed when imaging the Sun using the Ca II H (396.9 nm) line, Mg II k(279.6 nm) line or the H Alpha (656.28 nm) spectral line filters, are thin cylindrical structures comprising of cold and dense plasma from the chromosphere making incursions -all the time- into the much hotter solar coronal plasma. Spicules seen in Ca II H filter are loosely classified by solar astronomers into two classes -- type-I and type-II, the latter being more energetic than the former. Our numerical magneto-hydrodynamic (MHD) experiments in two dimensions establishes that periodic forcing due to formation and destruction of convective granules on the visible solar surface is sufficient to form the forest of spicules with physical characteristics similar to the observed spicules. In our unified model of the spicule forest, the more energetic spicules are formed when this periodic forcing is further aided by magnetic reconnection. Therefore our simulations further contribute to unveiling the subtleties of spicule formation. We also study the characteristics of spicules formed in coronal holes versus in quiet sun or the active region. It is to be noted that spicules are not dependent on the 2-dimensionality of our model. We obtain spicules of similar characteristics in a 3-dimensional version of the same model. The behavior only gets richer because now the spicules can also have a torsional mode apart from the transverse kink and sausage modes also seen in the 2-dimensional model. New interesting features like short lived coronal swirls also appear in the 3-dimensional model alongside spicules but with a very small spatial overlap even though there exists striking temporal coincidence.