Modeling boot-shaped coronal holes using SOHO-MDI magnetic measurements

The boot-shaped coronal hole observed between the 22 and 30 August 1996, reproduced by rigidly rotating the data computed on 27 August with the rotation rate near the solar equator, is discussed. The data were acquired by the Michelson Doppler imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). The results suggest that change in size and shape of the holes observed during the period is caused by the projection effect. It was found that the whole solar observational synoptic chart may be used to approximately reproduce boot-shaped holes in solar minimum.