**4. Emerging flux characterization**

Ilonidis et al. [13] found (from MDI data) some strong acoustic anomalies of 12–16 seconds as deep as 65 Mm, which became sunspots 1–2 days after detection with deep focus time-distance helioseismology (**Figure 6**). They ensured that measurements were made when magnetism was <300 G, otherwise masked out. They also found an emergence velocity of about 60 Mm in about 2 days, consistent with previously modeled velocities.

Shibata et al. [14] used the Solar Optical Telescope (SOT: hinode.nao.ac.jp/sot\_e/) on-board Hinode [15] in the Ca II H band (396.85 nm) of the Broadband Filter Imager (BFI) corresponding to chromospheric heating. They studied upper chromosphere and lower corona magnetic reconnection producing high-speed jets being involved in lower coronal X-ray jets and Hα surges. They found that solar nanoflares (spicule jets) events happen and propagate further than gravity-bound expectations by slow-mode magneto-acoustic shocks or fast-mode nonlinear Alfvèn waves shocks. They argue that their actual findings are one order of magnitude less than the necessary energy to heat the corona. To add some energy, they suggest a multiscale presence of nanoflares in the upper atmosphere, which are not all visible with Hinode instruments.

Karoff and Kjeldsen [16] found that the background noise from granulation correlates with flare activity, and that increase in the background noise transfers more power into high-frequency modes via stochastic excitation, as observed in their experiment.
