Spectro-polarimeter (SP) aboard Hinode found that granular-sized horizontal magnetic fields are ubiquitous all over the solar photosphere (Lites et al. 2008, Orozco Suarez et al. 2007, Centeno et al. 2007, and Ishikawa et al. 2008). Such horizontal fields are highly transient with short lifetimes (1 to 10 minutes), and are called gtransient horizontal magnetic fieldsh(THMFs, Ishikawa et al. 2008). The properties of THMFs (e.g., lifetime and size) were studied (Ishikawa & Tsuneta 2009a). These horizontal magnetic fields are observed in the quiet Sun, a weak plage region (Ishikawa et al. 2008), and the polar regions (Tsuneta et al.2008; Ito et al. 2010), and the properties (e.g., the occurrence rate and magnetic field strength distribution) are the same among these regions. (Ishikawa et al. 2009a; Ito et al. 2010).
I will analyze larger number of events, and obtain the statistical properties of THMFs for my doctoral dissertation. One of important topics for my study is to reveal the relationship of THMFs with the solar activity by monitoring the long-term variation of their properties. Until now, every year from 2007 to 2010, we have carried out SP observations to see the temporal evolution of THMFs in the quiet Sun, during my repeated SOT-CO periods without submitting a proposal to HOP.
The Sun has been increasing the activity, and we would like to continue and extend the same observations with this HOP proposal. The proposed observation programs are the same as the one used for the comparison between quiet and plage regions in the solar minimum of February 2007 (Ishikawa & Tsuneta 2009b). The data sets so far obtained with the same observation programs should be a baseline to represent the solar minimum period for the new observations of THMFs in the rising phase of the solar activity. |
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