Abstract Details
| Name: Varsha K R Affiliation: Bangalore University Conference ID: ASI2018_1447 Title : Yearly variation of rotation rate of coronal holes. Authors and Co-Authors : Varsha,K. R, Hiremath, K. M and Manjunath Hegde Indian Institute of Astrophysics, Bengaluru-560034, India Abstract Type : Poster Abstract Category : Sun and the Solar System Abstract : Coronal holes are one of sun's important activity phenomena which can easily be observed in the sun's corona, especially in the x-ray or uv wavelengths. Coronal holes appear to be darker, cooler, and have low density plasma compared to the ambient medium. Genesis of their origin, thermal and dynamical properties and of their feeble magnetic field structure remain a mystery. Aim of present study is to examine whether coronal holes that occur at higher latitudes rotate rigidly or differentially. In order to achieve this goal, nearly one cycle (1997–2006), SOHO/EIT 195 Å calibrated images are used. Using basic morphological operations like erosion and dilation coronal holes are accurately detected from the images. Individual pixel information enclosing coronal holes is obtained. After fixing the heliographic coordinates for these individual pixels, average heliographic coordinates (latitude and longitude) for each coronal hole are computed and rotation rates of coronal holes are estimated. The important results are as follows: For different latitude zones, between 80◦ north and 75◦ south, irrespective of their area, the number of days observed on the solar disk, coronal holes rotate rigidly. |