Small-scale Turbulent Motion of the Plasma in a Solar Filament as the Precursor of Eruption |
|
Daikichi SEKI Submitted: 2021-06-22 19:57
A filament, a dense cool plasma supported by the magnetic fields in the solar corona, often becomes unstable and erupts. It is empirically known that the filament often demonstrates some activations such as a turbulent motion prior to eruption. In our previous study (Seki et al. 2017), we analysed the Doppler velocity of an Hα filament and found that the standard deviation of the line-of-sight-velocity (LOSV) distribution in a filament, which indicates the increasing amplitude of the small-scale motions, increased prior to the onset of the eruption. Here, we present a further analysis on this filament eruption, which initiated approximately at 03:40UT on 2016 November 5 in the vicinity of NOAA AR 12605. It includes a coronal line observation and the extrapolation of the surrounding magnetic fields. We found that both the spatially averaged micro-turbulence inside the filament and the nearby coronal line emission increased 6 and 10 hours prior to eruption, respectively. In this event, we did not find any significant changes in the global potential-field configuration preceding the eruption for the past 2 days, which indicates that there is a case in which it is difficult to predict the eruption only by tracking the extrapolated global magnetic fields. In terms of space weather prediction, our result on the turbulent motions in a filament could be used as the useful precursor of a filament eruption.
Authors: Daikichi Seki, Kenichi Otsuji, Hiroaki Isobe, Giulio Del Zanna, Takako T. Ishii, Takahito Sakaue, Kiyoshi Ichimoto, Kazunari Shibata
Projects: None
|
Publication Status: accepted for publication in ApJ
Last Modified: 2021-06-23 03:08
|
 
 
|
|
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 8.0×106 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
|
 
 
|
|
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
|
 
 
|
|
|
Key
|
 | Go to main E-Print page. |
 | Download Preprint. |
 | Submitters Homepage. |
 | Edit Entry. |
 | Delete abstract. |
|
|
|