On the enhanced coronal mass ejection detection rate since the solar cycle 23 polar field reversal

TL;DR

This study shows an increased rate of large coronal mass ejections during solar cycle 24, starting after the polar field reversal in 2004, supported by multiple independent data sources and linked to heliospheric pressure changes.

Contribution

It provides new evidence of an enhanced CME detection rate post-polar field reversal, using three independent databases and automated detection methods.

Findings

CME rate increased during solar cycle 24 compared to cycle 23.

Enhanced CME rate began shortly after the polar field reversal in 2004.

The increase correlates with weakened polar magnetic fields and heliospheric pressure.

Abstract

Coronal mass ejections (CMEs) with angular width $> 30^{\circ}$ have been observed to occur at a higher rate during solar cycle 24 compared to cycle 23, per sunspot number. This result is supported by data from three independent databases constructed using Large Angle and Spectrometric Coronagraph Experiment (LASCO) coronagraph images, two employing automated detection techniques and one compiled manually by human observers. According to the two databases that cover a larger field of view, the enhanced CME rate actually began shortly after the cycle 23 polar field reversal, in 2004, when the polar fields returned with a 40\% reduction in strength and interplanetary radial magnetic field became $\approx 30\%$ weaker. This result is consistent with the link between anomalous CME expansion and heliospheric total pressure decrease recently reported by Gopalswamy et al.