HR: 0800h
AN: SH11A-0238    [Abstracts]
TI: Projection Effects and Other Position Angle Motions in White Light Coronal Brightness Structures - LASCO in 2002
AU: * Parker, G D
EM: parker@norwich.edu
AF: Norwich University, 158 Harmon Drive, Northfield, VT 05663 United States
AB: Two previous, published studies of the rotation of the white light corona each investigated one year of LASCO observations early in the current sunspot cycle. This paper presents preliminary results of an effort to extend the study of rotation to other years, concentrating on LASCO observations for 2002. The procedure is autocorrelation of brightness measured in daily images in annular arcs at fixed position angle and radial distance. In 2002, correlation functions show distinctive shapes as a function of solar latitude. The causes of this diversity and their implications regarding coronal rotation are discussed. The mid-latitude rotational signal is strong and relatively uncomplicated. As in earlier epochs, the rotation observed at polar latitudes is dominated by projection effects. The distinctive shapes of correlation functions near the poles and equator are very similar and differ markedly from those at mid-latitudes. At both poles and equator, brightness structures drift in position angle because of rotation. The equatorial drifts and correlation function pattern relate to the positions of multiple brightness structures and to the tilt of the heliomagnetic equator.
SOHO is a joint project of NASA and ESA. I am grateful to the Naval Research Laboratory and the LASCO team for access to coronal images. Development of procedures for image analysis has received support from NASA under Vermont-EPSCoR Grant Ncc5-581 and from the Eppley Foundation for Research.
DE: 7509 Corona
DE: 7524 Magnetic fields
DE: 7536 Solar activity cycle (2162)
DE: 7537 Solar and stellar variability (1650)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005