The Peculiar Behavior of Halo Coronal Mass Ejections in Solar Cycle 24

Abstract

We report on a remarkable finding that the halo coronal mass ejections (CMEs) in cycle 24 are more abundant than in cycle 23, although the sunspot number in cycle 24 has dropped by about 40%. We also find that the distribution of halo-CME source locations is different in cycle 24: the longitude distribution of halos is much flatter with the number of halos originating at central meridian distance >/=60 degrees twice as large as that in cycle 23. On the other hand, the average speed and the associated soft X-ray flare size are the same in the two cycles, suggesting that the ambient medium into which the CMEs are ejected is significantly different. We suggest that both the higher abundance and larger central meridian longitudes of halo CMEs can be explained as a consequence of the diminished total pressure in the heliosphere in cycle 24 (Gopalswamy et al. 2014). The reduced total pressure allows CMEs expand more than usual making them appear as halos.

arXiv comment12 pages, 5 figures, accepted for publication in the Astrophysical Journal Letters, April 7, 2015

References in corpus (4)

• Anomalous Expansion of Coronal Mass Ejections during Solar Cycle 24 and its Space Weather Implications
• Spatial Relationship between Solar Flares and Coronal Mass Ejections
• Testing the Empirical Shock Arrival Model using Quadrature Observations
• Width of Radio-Loud and Radio-Quiet CMEs

Cited by in corpus (26)

• History and Development of Coronal Mass Ejections as a Key Player in Solar Terrestrial Relationship
• Properties and Geoeffectiveness of Magnetic Clouds during Solar Cycles 23 and 24
• Coronal Flux Ropes and their Interplanetary Counterparts
• A Statistical Study of CME Properties and of the Correlation Between Flares and CMEs over Solar Cycles 23 and 24
• The 2012 July 23 Backside Eruption: An Extreme Energetic Particle Event?
• The Sun and Space Weather
• Catalogue of >55 MeV Wide-longitude Solar Proton Events Observed by SOHO, ACE, and the STEREOs at $\approx$1 AU during 2009-2016
• Importance of CME Radial Expansion on the Ability of Slow CMEs to Drive Shocks
• Mass Loss via Solar Wind and Coronal Mass Ejections During Solar Cycle 23 and 24
• Sun-to-Earth Propagation of the 2015 June 21 Coronal Mass Ejection Revealed by Optical, EUV, and Radio Observations
• The State of the Heliosphere Revealed by Limb Halo Coronal Mass Ejections in Solar Cycles 23 and 24
• On the enhanced coronal mass ejection detection rate since the solar cycle 23 polar field reversal
• North-south asymmetry in small and large sunspot group activity and violation of even-odd solar cycle rule
• Active Longitude and Coronal Mass Ejection Occurrences
• Relativistic proton levels from region AR 12673 (GLE \#72) and the heliospheric current sheet as a Sun$-$Earth magnetic connection
• High-energy solar particle events in cycle 24
• What do halo CMEs tell us about solar cycle 25?
• The 2015 Summer Solstice Storm: one of the major geomagnetic storms of solar cycle 24 observed at ground level
• Effect of the Weakened Heliosphere in Solar Cycle 24 on the Properties of Coronal Mass Ejections
• Solar Activity and Space Weather
• Kinematics of coronal mass ejections in the LASCO field of view
• Quasi-periodic Variations of Coronal Mass Ejections with Different Angular Widths
• Comparing SSN Index to X-ray Flare and Coronal Mass Ejection Rates from Solar Cycles 22-24
• The Temporal and Spatial Behaviors of CME Occurrence Rate at Different Latitudes
• Iron-rich solar particle events measured by SOHO/ERNE during two solar cycles
• Kinematic study of radio-loud CMEs associated with solar flares and DH type II radio emissions during solar cycles 23 and 24