Broad Band Imager

1. Visible wavelength broad band imager

The broad band imager is used to observe the solar photosphere and low chromosphere. The wavelenths will be chosen such that the observation can be carried out from photosphere to the chromosphere. A list of possible filters along with the observation level in the solar atmosphere and their scientific purpose is presented in Table 1.

Table 1 Details of broad band imaging filters, the height covered in the soalr atmosphere and objects of scientific interests

Ca II K 3934 filter of about 2-3Å band pass will be used to observe the low chromosphere. The large band pass will allow higher amount of flux that can be useful to study the oscillations. Since the cadence will be very high one can use the speckle reconstruction technique to get high contrast images.

G-band images are obtained in the band of CH molecule. The images have very good contrast for the magnetic features. The pass band of the filter is about 10Å. Blue and red continuum filters will have a band pass of 5\AA. The images taken from these filters will have a better contrast to the granulation than the G-band images. These images can be used to align the different types of images obtained from various telescopes across the world. These images are also useful to find the horizontal velocity in the granulation and pores.

The Hα filter will have a band pass of about 0.25Å. The Hα images have very good contrast for the higher chromosphere. This is the only line that shows the fibril nature of the chromosphere and hence also shows the direction of the magnetic fields, chirality etc.

CN molecular band images are similar to the G-band images and have very good contrast for the magnetic elements. The band width of the filter is about 5-10Å. Further, there will be some options to include filters like TiO (7058\AA), Ca II 8542 Å, Na I 5896 etc. to observe the sunspot umbra, upper chromosphere and lower chromosphere.

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