English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

We report on the properties of halo coronal mass ejections (HCMEs) in solarcycles 23 and 24. We compare the HCMEs properties between the correspondingphases (rise, maximum, and declining) in cycles 23 and 24 in addition tocomparing those between the whole cycles. Despite the significant decline inthe sunspot number (SSN) in cycle 24, which dropped by 46% with respect tocycle 23, the abundance of HCMEs is similar in the two cycles. The HCME rateper SSN is 44% higher in cycle 24. In the maximum phase, cycle-24 ratenormalized to SSN increased by 127% while the SSN dropped by 43%. The sourcelongitudes of cycle-24 HCMEs are more uniformly distributed than those in cycle23. We found that the average sky-plane speed in cycle 23 is ~16% higher thanthat in cycle 24. The size distributions of the associated flares between thetwo cycles and the corresponding phases are similar. The average speed at acentral meridian distance (CMD) = 600 for cycle 23 is ~28% higher than that ofcycle 24. We discuss the unusual bump in HCME activity in the declining phaseof cycle 23 as due to exceptional active regions that produced many CMEs duringOctober 2003 to October 2005. The differing HCME properties in the two cyclescan be attributed to the anomalous expansion of cycle-24 CMEs. Considering theHCMEs in the rise, maximum and declining phases, we find that the maximum phaseshows the highest contrast between the two cycles.

Intercycle and intracycle variation of halo CME rate obtained from SOHO/LASCO observations