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Relationship between three-dimensional velocity of filament eruptions and CME association  

Daikichi SEKI   Submitted: 2021-02-09 18:52

It is widely recognised that filament disappearances or eruptions are frequently associated with Coronal Mass Ejections (CMEs). Since CMEs are a major source of disturbances of the space environment surrounding the Earth, it is important to investigate these associations in detail for the better prediction of CME occurrence. However, the proportion of filament disappearances associated with CMEs is under debate. The estimates range from ∼10% to ∼90% and could be affected by the manners to select the events. In this study, we aim to reveal what parameters control the association between filament eruptions and CMEs. We analysed the relationships between CME associations and the physical parameters of filaments including their length, maximum ascending velocity, and direction of eruptions using 28 events of filament eruptions observed in Hα. We found that the product of the maximum radial velocity and the filament length is well correlated with the CME occurrence. If the product is larger than 8.0106 km2 s-1, the filament will become a CME with a probability of 93%, and if the product is smaller than this value, it will not become a CME with a probability of 100%. We suggest a kinetic-energy threshold above which filament eruptions are associated with CMEs. Our findings also suggest the importance of measuring the velocity vector of filament eruption in three-dimensional space for the better prediction of CME occurrence.

Authors: Daikichi Seki, Kenichi Otsuji, Takako T. Ishii, Ayumi Asai, Kiyoshi Ichimoto
Projects: None

Publication Status: Accepted for publication in Earth, Planets and Space
Last Modified: 2021-02-10 08:19
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Small-scale motions in solar filaments as the precursors of eruptions  

Daikichi SEKI   Submitted: 2019-02-25 19:44

Filaments, the dense cooler plasma floating in the solar corona supported by magnetic fields, generally exhibit certain activations before they erupt. In our previous study (Seki et al. 2017 ), we observed that the standard deviation of the line-of-sight (LOS) velocities of the small- scale motions in a filament increased prior to its eruption. However, because that study only analyzed one event, it is unclear whether such an increase in the standard deviation of LOS velocities is common in filament eruptions. In this study, 12 filaments that vanished in Hα line center images were analyzed in a manner similar to the one in our previous work; these included two quiescent filaments, four active region filaments, and six intermediate filaments. We verified that in all the 12 events, the standard deviation of the LOS velocities increased before the filaments vanished. Moreover, we observed that the quiescent filaments had approximately 10 times longer duration of an increase in the standard deviation than the other types of filaments. We concluded that the standard deviation of the LOS velocities of the small-scale motions in a filament can potentially be used as the precursor of a filament eruption.

Authors: Daikichi SEKI, Kenichi OTSUJI, Hiroaki ISOBE, Takako T. ISHII, Kiyoshi ICHIMOTO and Kazunari SHIBATA
Projects: Other

Publication Status: Accepted for publication in PASJ on 2019 Feb 22
Last Modified: 2019-02-27 12:13
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Increase in the amplitude of line-of-sight velocities of the small-scale motions in a solar filament before eruption  

Daikichi SEKI   Submitted: 2017-05-25 18:44

We present a study on the evolution of the small scale velocity field in a solar filament as it approaches to the eruption. The observation was carried out by the Solar Dynamics Doppler Imager (SDDI) that was newly installed on the Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory. The SDDI obtains a narrow-band full disk image of the sun at 73 channels from Hα - 9.0 Å to Hα + 9.0 Å, allowing us to study the line-of-sight (LOS) velocity of the filament before and during the eruption. The observed filament is a quiescent filament that erupted on 2016 November 5. We derived the LOS velocity at each pixel in the filament using the Becker's cloud model, and made the histograms of the LOS velocity at each time. The standard deviation of the LOS velocity distribution can be regarded as a measure for the amplitude of the small scale motion in the filament. We found that the standard deviation on the previous day of the eruption was mostly constant around 2-3 km s-1, and it slightly increased to 3-4 km s-1 on the day of the eruption. It shows further increase with a rate of 1.1 m s-2 about three hours before eruption and again with a rate of 2.8 m s-2 about an hour before eruption. From this result we suggest the increase in the amplitude of the small scale motions in a filament can be regarded as a precursor of the eruption.

Authors: Daikichi Seki, Kenichi Otsuji, Hiroaki Isobe, Takako T. Ishii, Takahito Sakaue, Kumi Hirose
Projects: None

Publication Status: Accepted for publication in ApJL on May 25, 2017
Last Modified: 2017-05-31 13:50
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Relationship between three-dimensional velocity of filament eruptions and CME association
Small-scale motions in solar filaments as the precursors of eruptions
Increase in the amplitude of line-of-sight velocities of the small-scale motions in a solar filament before eruption

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