Objectives: To find a chromospheric counter part of the transient horizontal magnetic fields (THMFs) seen on the photosphere.
Scientific Background: Our science objective is to find a chromospheric counterpart of the transient horizontal magnetic fields (THMFs) discovered in the photosphere. The horizontal magnetic fields with high time variation were observed all over the Sun in the photsphere with the SOLIS and GONG instruments (Harvey et al. 2007). Unprecedented high spatial resolution observation with Spectro-polarimeter (SP) aboard Hinode has extended the studies considerably; granular-sized THMFs are indeed ubiquitous in the photosphere (Lites et al. 2008, Orozco Suarez et al. 2007, Centeno et al. 2007, and Ishikawa et al. 2008). Ishikawa & Tsuneta (2009) points out that the magnetic energy flux, with which THMFs potentially provide the quiet Sun (2~106 erg cm-2 sec-1) is comparable to total chromospheric energy loss of 4~106 erg cm-2 sec-1(Withbroe & Noyes 1977), and that THMFs could contribute to the chromospheric and coronal heating (see also Trujillo Bueno et al. 2004; Abbett 2007; Isobe et al. 2008). Thus, whether THMFs reaches the chromosphere (or not) should be observationally pursued to understand the possible role of THMFs for the chromospheric and coronal heating. In broader context, any transient magnetic phenomena in the chromosphere is our observing target. Here we would like to request spectro-polarimetric observation of the Fe I 630.1/630.2nm line. Simultaneously, Tenerife Infrared Polarimeter (TIP) with Vacuum Tower Telescope (VTT) will perform spectro-polarimetric observation of the He I 1083 nm line to detect chromospheric magnetic signals with the joint action of Hanle and Zeeman effects, and we plan to find any transient magnetic phenomena including THMFs both in the chromosphere and in the photosphere simultaneously. Hinode observes the photosphere with SP (630.1/630.2 nm) and with NFI magnetograms (525.02 nm). SP has a very skinny field of view to have ultra high cadence of 1 min or so, and Shutter-less NFI magnetograms provide wide-field context Stokes IQUV images at the blue wing with time cadence of about 30 sec. TIP performs the spectro-polarimetric observation for the He I line also with very skinny FOV of ~3h~80h to have high time cadence between 1 and 3 min. This is an ideal arrangement for the detection of THMF counter part, which has mean lifetime of only 4 min. Uniqueness of our investigation is that we perform simultaneous spectro-polarimetric observations with unprecedented high time cadence combined with very deep exposure for both the chromopshere and the photosphere. This research is a part of Ph. D. thesis topics of R. Ishikawa.
Former projects We already carried out the joint observation campaign between VTT/TIP and Hinode/SOT from April 29, 2008 to May 12, 2008 (HOP 71). In this campaign, the internetwork region with a narrow FOV (∼15h~80h) was observed by SP and TIP simultaneously with moderate time cadence of 7.5 min, and we found that some of chromospheric magnetic fields drastically changes with the time scale less than 7.5 min (Ishikawa et al. in preparation). However, the time cadence of 7.5 min was too low to see the time evolution of THMFs, and the exposure time for each slit position for VTT/TIP was not enough to obtain good signal-to-noise ratio. Thus, we would like to improve our observation program. |
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