Coronal Mass Ejections Associated with Slow Long Duration Flares

TL;DR

This study investigates the relationship between slow long duration flares and associated CMEs, revealing that these CMEs are characterized by high velocities and prolonged acceleration phases, which are crucial for space weather prediction.

Contribution

It provides detailed analysis of CMEs linked to slow long duration flares, highlighting their high velocities and extended acceleration phases, advancing understanding of their role in space weather.

Findings

CMEs associated with slow LDEs have median velocity of 1423 km/s.

Half of these CMEs have low main acceleration (<300 m/s^2).

Prolonged acceleration phases up to 7 solar radii are common.

Abstract

It is well known that there is temporal relationship between coronal mass ejections (CMEs) and associated flares. The duration of the acceleration phase is related to the duration of the rise phase of a flare. We investigate CMEs associated with slow long duration events (LDEs), i.e. flares with the long rising phase. We determined the relationships between flares and CMEs and analyzed the CME kinematics in detail. The parameters of the flares (GOES flux, duration of the rising phase) show strong correlations with the CME parameters (velocity, acceleration during main acceleration phase and duration of the CME acceleration phase). These correlations confirm the strong relation between slow LDEs and CMEs. We also analyzed the relation between the parameters of the CMEs, i.e. a velocity, an acceleration during the main acceleration phase, a duration of the acceleration phase, and a height of a CME at the end of the acceleration phase. The CMEs associated with the slow LDEs are characterized by high velocity during the propagation phase, with the median equal 1423 km/s. In half of the analyzed cases, the main acceleration was low (a<300 m/s^2), which suggests that the high velocity is caused by the prolongated acceleration phase (the median for the duration of the acceleration phase is equal 90 minutes). The CMEs were accelerated up to several solar radii (with the median 7 Rsun), which is much higher than in typical impulsive CMEs. Therefore, slow LDEs may potentially precede extremely strong geomagnetic storms. The analysis of slow LDEs and associated CMEs may give important information for developing more accurate space weather forecasts, especially for extreme events.