Coronal Hole and Solar Global Magnetic Field Evolution in 1976 – 2012

Abstract

Coronal hole spatial-temporal evolution is studied and comparison made with that of the solar global magnetic field in cycles 21 -23 (1976 -2012). The latitude-longitude distribution dynamics of coronal holes and the regularities in the global magnetic field associated with the solar polar field reversal are analyzed. Polar and non-polar coronal hole populations are considered. The investigation reveals some temporal and spatial regularities in coronal hole distributions that match well the global magnetic-field cycle evolution. The results show that the non-polar coronal hole longitudinal distribution follows all configuration changes in the global magnetic-field structure. Reorganizations of the global magnetic-field and coronal hole distributions occur simultaneously during a time interval of a few solar rotations. The cycle evolution of the non-polar coronal holes reflects the transition of the solar global magnetic field from the zonal structure to sectorial and vice versa. Two different type waves of nonpolar coronal holes are revealed from their latitudinal distribution. The first one is short poleward waves. They trace the poleward motion of the unipolar photospheric magnetic fields from approximately 35 • to the associated pole in each hemisphere and the redevelopment of a new-polarity polar CH. Although they start the poleward movement before the change of the polar magnetic field in the associated hemisphere, they reach the pole after the polar reversal. The other type of non-polar CH wave forms two sinusoidal branches associated with the positive-and negative-polarity magnetic fields. The complete period of the wave was equal to ≈268 CRs (22 years). These wave CHs arrive at high latitudes during declining phases when the new polarity polar CHs are already completely formed.

Solar Open Flux Migration from Pole to Pole: Magnetic Field Reversal

“…By including the effects of differential rotation, magnetic diffusion, and meridional flow for the formation of polar open fluxes, the model demonstrated that part of the leading-polarity fluxes of the active regions diffuse to the other hemisphere, while the remaining fluxes are carried pole-ward by the meridional flow. A different model based on observational results was proposed by Ikhsanov & Tavastsherna 31 and Bilenko & Tavastsherna 13 . They suggested that the polar open fluxes are generated by the poleward transportation of the open fluxes at around 35° latitude.…”

“…Ikhsanov & Ivanov 8 analyzed different properties of equatorial and polar coronal holes from 1970 to 1995, including numbers, locations, areas and polarities, and reported that both types of coronal holes can be further divided into multiple sub-classes based on the temporal variation of their properties. A recent study by Bilenko & Tavastsherna 13 examined the evolution of coronal holes and solar global magnetic fields over three solar cycles from 1976 to 2012. By analyzing the temporal variation of coronal hole location, they reported that non-polar coronal holes exhibit a poleward motion and a sinusoidal motion.…”

Space Weather Quarterly Volume 14, Issue 4, 2017

“…For the McA maps we can plot the latitude-longitude locations of specific colored (numbered) regions on each map and concatenate them together to form butterfly plots of specific features over SC time scales (see examples in Gibson et al, 2017). (Figure 2b) with sunspots and CH centers, have recently been made (e.g., Bilenko & Tavastsherna, 2016;Karna et al, 2015;. The activity bands of these features emerge around 55° north and south latitudes and take 18-19 years to reach the equator.…”

Formation and Evolutionary Changes of Coronal Holes During the Rising Phase of Cycle 23

“…CHs are known to be good tracers of cyclic variations of solar GMF (Ikhsanov, Ivanov, 1999;Mogilevsky, Obridko, Shilova, 1997;Obridko, Shelting, 1989;Bilenko, 2002;Bilenko and Tavastsherna, 2016;Bilenko, Tavastsherna, 2017). During the solar activity minimum when the zonal structure of the GMF was dominated, the CHs followed GMF structure.…”

“…Dynamics of the latitudinal distribution of non-polar CHs traced changes in the structure of the GMF from the zonal to the sectorial. The CHs of one polarity occupied the regions extended in latitude and longitude (Bilenko, 2002;Bilenko and Tavastsherna, 2016). Figure 3 shows some examples of different GMF topologies on the source surface at different states of the sectorial structure for CRs 1943CRs , 1948CRs , 1951CRs , and 1958 (Figure 3, a5, b5, c5, d5) and daily CH images in EUV 195 Å (a1, a2, b1, b2, c1, c2, d1, d2) and line HeI 10830 Å, combined with photospheric magnetic fields (a3, a4, b3, b4, c3, c4, d3, d4).…”