Comparison of the sidereal angular velocity of subphotospheric layers and small bright coronal structures during the declining phase of solar cycle 23

Abstract

Context. We compare solar differential rotation of subphotospheric layers derived from local helioseismology analysis of GONG++ dopplergrams and the one derived from tracing small bright coronal structures (SBCS) using EIT/SOHO images for the period August 2001 - December 2006, which correspond to the declining phase of solar cycle 23. Aims. The study aims to find a relationship between the rotation of the SBCS and the subphotospheric angular velocity. The northsouth asymmetries of both rotation velocity measurements are also investigated. Methods. Subphotospheric differential rotation was derived using ring-diagram analysis of GONG++ full-disk dopplergrams of 1 min cadence. The coronal rotation was derived by using an automatic method to identify and track the small bright coronal structures in EIT full-disk images of 6 hours cadence. Results. We find that the SBCS rotate faster than the considered upper subphotospheric layer (3Mm) by about 0.5 deg/day at the equator. This result joins the results of several other magnetic features (sunspots, plages, faculae, etc.) with a higher rotation than the solar plasma. The rotation rate latitudinal gradients of the SBCS and the subphotospheric layers are very similar. The SBCS motion shows an acceleration of about 0.005 deg/day/month during the declining phase of solar cycle 23, whereas the angular velocity of subsurface layers does not display any evident variation with time, except for the well known torsional oscillation pattern. Finally, both subphotospheric and coronal rotations of the southern hemisphere are predominantly larger than those of the northern hemisphere. At latitudes where the north-south asymmetry of the angular velocity increases (decreases) with activity for the SBCS, it decreases (increases) for subphotospheric layers.

6pages, 8 figures, Accepted for publication in Astronomy and Astrophysics

Cited by in corpus (8)

• Differential coronal rotation using radio images at 17 GHz
• Periodicities in the coronal rotation and sunspot numbers
• Steps toward a high precision solar rotation profile: Results from SDO/AIA coronal bright point data
• Why Does the Solar Corona Abnormally Rotate Faster Than the Photosphere?
• Investigation of the Differential Rotation by H-Alpha Filaments and Long-Lived Magnetic Features for Solar Activity Cycles 20 and 21
• Differential rotation of the solar corona: A new data-adaptive multiwavelength approach
• Internal-cycle variation of solar differential rotation
• Magnetic field as a tracer for studying the differential rotation of the solar corona