• 천문학회보
• /
• 제46권1호
• /
• pp.42.1-42.1
• /
• 2021

In this study, we present a visual explanation of a deep learning solar flare forecast model and its relationship to physical parameters of solar active regions (ARs). For this, we use full-disk magnetograms at 00:00 UT from the Solar and Heliospheric Observatory/Michelson Doppler Imager and the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, physical parameters from the Space-weather HMI Active Region Patch (SHARP), and Geostationary Operational Environmental Satellite X-ray flare data. Our deep learning flare forecast model based on the Convolutional Neural Network (CNN) predicts "Yes" or "No" for the daily occurrence of C-, M-, and X-class flares. We interpret the model using two CNN attribution methods (guided backpropagation and Gradient-weighted Class Activation Mapping [Grad-CAM]) that provide quantitative information on explaining the model. We find that our deep learning flare forecasting model is intimately related to AR physical properties that have also been distinguished in previous studies as holding significant predictive ability. Major results of this study are as follows. First, we successfully apply our deep learning models to the forecast of daily solar flare occurrence with TSS = 0.65, without any preprocessing to extract features from data. Second, using the attribution methods, we find that the polarity inversion line is an important feature for the deep learning flare forecasting model. Third, the ARs with high Grad-CAM values produce more flares than those with low Grad-CAM values. Fourth, nine SHARP parameters such as total unsigned vertical current, total unsigned current helicity, total unsigned flux, and total photospheric magnetic free energy density are well correlated with Grad-CAM values.

• 센서학회지
• /
• 제9권3호
• /
• pp.163-170
• /
• 2000

광주파수 변조 광섬유 간섭형 센서가 변위, 변형률 및 힘 등의 물리량을 측정하기 위하여 개발되어졌다. 일반적인 광섬유 간섭형 센서는 물리량에 따라 단지 정현파 형태의 신호를 보이기 때문에 물리량의 증감을 구별하는 것이 매우 어렵다. 본 연구에서는 물리량의 증감 방향을 구별하면서 물리량을 측정하기 위하여 단지 톱니파형으로 변조시킨 광원만을 사용하는 광섬유 마이켈슨 센서를 성하였다. 센서 출력은 일정한 정현파가 출력되도록 조절되어졌다. 출력신호는 일정 시간 간격동안 파형의 개수를 계수함에 의하여 처리되어졌다. 변형률은 파형 개수 변화량에 변형률을 구하기 위한 게이지 상수만을 곱함에 의하여 계산되었다. 이 센서의 변형률 측정 성능을 검토하기 위하여 광섬유 센서와 전기저항형 변형률 게이지가 부착된 알루미늄 시험편을 사용하여 만능시험기로 반복하중을 가하여 변형률의 증감을 측정하는 실험을 수행하였다. 이 실험으로부터 광섬유 센서에 의하여 측정된 변형률 변화량이 전기저항형 변형률 게이지의 변화량과 잘 일치하고 있음을 확인할 수 있었다.

• 천문학회지
• /
• 제37권1호
• /
• pp.41-53
• /
• 2004

It has been a big mystery what drives filament eruptions and flares. We have studied in detail an X1.8 flare and its associated filament eruption that occurred in NOAA Active Region 9236 on November 24,2000. For this work we have analyzed high temporal (about 1 minute) and spatial (about 1 arcsec) resolution images taken by Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory, Hoc centerline and blue wing ($-0.6{\AA}$) images from Big Bear Solar Observatory, and 1600 ${\AA}$ UV images by the Transition Region and Corona Explorer (TRACE). We have found that there were several transient brightenings seen in H$\alpha$ and, more noticeably in TRACE 1600 ${\AA}$ images around the preflare phase. A closer look at the UV brightenings in 1600 ${\AA}$ images reveals that they took place near one end of the erupting filament, and are a kind of jets supplying mass into the transient loops seen in 1600 ${\AA}$. These brightenings were also associated with canceling magnetic features (CMFs) as seen in the MDI magnetograms. The flux variations of these CMFs suggest that the flux cancellation may have been driven by the emergence of the new flux. For this event, we have estimated the ejection speeds of the filament ranging from 10 to 160 km $s^{-1}$ for the first twenty minutes. It is noted that the initiation of the filament eruption (as defined by the rise speed less than 20 km $s^{-1}$) coincided with the preflare activity characterized by UV brightenings and CMFs. The speed of the associated LASCO CME can be well extrapolated from the observed filament speed and its direction is consistent with those of the disturbed UV loops associated with the preflare activity. Supposing the H$\alpha$/UV transient brightenings and the canceling magnetic features are due to magnetic reconnect ion in the low atmosphere, our results may be strong observational evidence supporting that the initiation of the filament eruption and the preflare phase of the associated flare may be physically related to low-atmosphere magnetic reconnection.