Regular and Oscillatory Motion of Coronal Bright Points
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REGULAR AND OSCILLATORY MOTION OF CORONAL BRIGHT POINTS
T. Tsinamdzgvrishvili,1 B. Shergelashvili,1,2,3 B. Chargeishvili,1 I. Mghebrishvili,1 T. Mdzinarishvili,1 and D. Japaridze1
Long-term automatic tracking of coronal bright points has made it possible to study their proper motions using data from the AIA 193 Å channel of SDO/AIA. Fits files for 95 visually long-lived bright points uniformly distributed in latitude have been chosen for processing. A specially developed program automatically fixes the heliographic coordinates of the centroid of the chosen coronal bright points in a series of Fits files. It was found that the proper motions of all the coronal bright points studied here have a distinct oscillatory character. The periods of the oscillations range from 5 to 60 h with an average of 20 h. Some tendencies in the latitudinal dependence of the oscillatory characteristics have been found. A possible explanation of these oscillations in terms of the propagation of helical waves along the magnetic loops that form the structure of the coronal bright points is pointed out. Linear trends in the latitudinal and longitudinal components of the motion of the coronal points are used to determine the rotational velocity and meridional migration of the coronal bright points. An analysis of the rotational velocities confirms the differential character of the latitudinal dependence. The problem of determining the direction and magnitude of the meridional migration is discussed. Keywords: coronal bright points: proper motion: oscillations
(1) Abastumani Astrophysical Observatory, Iliya State University, Tbilisi, Georgia; e-mail: [email protected] (2) Institute of Space Studies, Austrian Academy of Sciences, Austria (3) Combinatorics Optimization and Support for Taking Solutions, KU Leuven Campus, Leuven, Kortrijk, Belgium
Original article submitted October 26, 2019; accepted for publication June 24, 2020. Translated from Astrofizika, Vol. 63, No. 3, pp. 489-499 (August 2020) 430
0571-7256/19/6303-0430 ©2020 Springer Science+Business Media, LLC
1. Introduction
Coronal bright points (CBP) are small active regions associated with small magnetic formations in the solar corona. They are bright dynamic formations, visible on the quiescent sun and coronal holes and consist of loops, locally coupled with photospheric bipolar magnetic fields [1,2]. CBP usually last from a few hours to several days and have sizes less than 50". About half of all CBP have lifetimes of less than 20 min, while the average lifetime of the other half is 6 h. Less than 5% of CBP have lifetimes greater than 20 h [3,4]. Because they are numerous and almost uniformly distributed, CBP are a convenient instrument for studying the differential rotation of the sun and meridional flows on the sun. Sunspots are the most often used and oldest tracers for studying the differential rotation of the sun [5-8]. Although they have many advantages, there are limits to the use of sunspots as tracers, since their latitudinal distribution is
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