Seonghwan Choi

AO-308: the high-order adaptive optics system at Big Bear Solar Observatory

In this paper we present Big Bear Solar Observatory’s (BBSO) newest adaptive optics system – AO-308. AO-308 is a result of collaboration between BBSO and National Solar Observatory (NSO). AO-308 uses a 357 actuators deformable mirror (DM) from Xinetics and its wave front sensor (WFS) has 308 sub-apertures. The WFS uses a Phantom V7.3 camera which runs at 2000 Hz with the region of interest of 416×400 pixels. AO-308 utilizes digital signal processors (DSPs) for image processing. AO-308 has been successfully used during the 2013 observing season. The system can correct up to 310 modes providing diffraction limited images at all wavelengths of interest.

COMPONENT-BASED DEVELOPMENT OF OBSERVATIONAL SOFTWARE FOR KASI SOLAR IMAGING SPECTROGRAPH

In this paper, we have made the component-based development of observational software for KASI solar imaging spectrograph (KSIS) that is able to obtain three-dimensional imaging spectrograms by using a scanning mirror in front of the spectrograph slit. Since 2002, the KASI solar spectrograph has been successfully operated to observe solar spectra for a given slit region as well as to inspect the response functions of narrow band filters. To improve its capability, we have developed the KSIS that can perform sequential observations of solar spectra by simultaneously controlling the scanning mirror and the CCD camera via Visual C++. Main task of this paper is to introduce the development of the component-based software for KSIS. Each component of the software is reusable on the level of executable file instead of source code because the software was developed by using CBD (component-based development) methodology. The main advantage of such a component-based software is that key components such as image processing component and display component can be applied to other similar observational software without any modifications. Using this software, we have successfully obtained solar imaging spectra of an active region (AR 10708) including a small sunspot. Finally, we present solar spectra () that were obtained at an active region and a quiet region in order to confirm the validity of the developed KSIS and its software.

Characteristics of the E- and F-region field-aligned irregularities in middle latitudes: Initial results obtained from the Daejeon 40.8 MHz VHF radar in South Korea

Copyright

CONSTRUCTION OF AN E-CALLISTO STATION IN KOREA

The e- CALLISTO is a global network of frequency-agile solar radio spectrometers that was constructed in a collaboration between Swiss Federal Institute of Technology Zurich (ETH Zurich) and local host institutes. It is intended to monitor solar radio bursts 24 hours a day in frequency range between 45 MHz and 870 MHz. One of e- CALLISTO spectrometer was installed at Korea Astronomy and Space Science Institute (KASI) in 2007 October. The spectrometer gets signals from a horizontally polarized log-periodic antenna mounted on an automatic Sun-tracking system. Tracking status and data are monitored in Space Weather Monitoring Laboratory (SWML) of KASI in real time, and flare time data are transferred to ETH Zurich data archive daily. Using this spectrometer we obtained a couple of type II solar radio bursts on 2007 December 31, and found that these bursts are associated with a CME which occurred on the east limb.

APPLICATION OF SUPPORT VECTOR MACHINE TO THE PREDICTION OF GEO-EFFECTIVE HALO CMES

In this study we apply Support Vector Machine (SVM) to the prediction of geo-effective halo coronal mass ejections (CMEs). The SVM, which is one of machine learning algorithms, is used for the purpose of classification and regression analysis. We use halo and partial halo CMEs from January 1996 to April 2010 in the SOHO/LASCO CME Catalog for training and prediction. And we also use their associated X-ray flare classes to identify front-side halo CMEs (stronger than B1 class), and the Dst index to determine geo-effective halo CMEs (stronger than -50 nT). The combinations of the speed and the angular width of CMEs, and their associated X-ray classes are used for input features of the SVM. We make an attempt to find the best model by using cross-validation which is processed by changing kernel functions of the SVM and their parameters. As a result we obtain statistical parameters for the best model by using the speed of CME and its associated X-ray flare class as input features of the SVM: Accuracy=0.66, PODy=0.76, PODn=0.49, FAR=0.72, Bias=1.06, CSI=0.59, TSS=0.25. The performance of the statistical parameters by applying the SVM is much better than those from the simple classifications based on constant classifiers.

Development of a correlation tracker system for the New Solar Telescope

In this paper, we report on the development of a correlation tracker system for the New Solar Telescope (NST). It consists of three sub-systems: a tip-tilt mirror unit, a camera unit, and a control unit. Its software has been developed via Microsoft Visual C++, which enables us to take images from the high-speed CMOS camera in order to measure the image motions induced by atmospheric turbulence by using SAD algorithm and 2-D FFT cross-correlation, and to control the high-dynamics Piezo tip-tilt mirror for tip-tilt correction. We adopted the SIMD technology and parallel programming technology based on the Intel Core 2 Quad processor without any additional processing system (FPGA or DSP) for high-speed performance. As a result, we can make a tip-tilt correction with about seven hundreds of Hz in a closed loop mode. The prototype system has been successfully developed in a laboratory and will be installed on the NST.

Development of the camera lens system for total solar eclipse observation (Conference Presentation)

Korea Astronomy and Space Science Institute (KASI) has been developing the Camera Lens System (CLS) for the Total Solar Eclipse (TSE) observation. In 2016 we have assembled a simple camera system including a camera lens, a polarizer, bandpass filters, and CCD to observe the solar corona during the Total Solar Eclipse in Indonesia. Even we could not obtain the satisfactory result in the observation due to poor environment, we obtained some lessons such as poor image quality due to ghost effect from the lens system. For 2017 TSE observation, we have studied and adapted the compact coronagraph design proposed by NASA. The compact coronagraph design dramatically reduces the volume and weight and can be used for TSE observation without an external occulter which blocks the solar disk. We are in developing another camera system using the compact coronagraph design to test and verify key components including bandpass filter, polarizer, and CCD, and it will be used for the Total Solar Eclipse (TSE) in 2017. We plan to adapt this design for a coronagraph mission in the future. In this report we introduce the progress and current status of the project and focus on optical engineering works including designing, analyzing, testing, and building for the TSE observation.

Real Time Monitoring of Extracellular Glutamate Release in Rat Ischemia Model Treated by Nimodipine

It is well known that cerebral ischemia is associated with extracellular concentrations of the excitatory amino acids. Real time quantitative measurement of glutamate which is the most abundant excitatory neurotransmitter would be very helpful parameter, in order to evaluate brain injury during or after surgery, as well as validation of the instantaneous effect of drug. In order to define the effect of nimodipine on glutamate release and neuronal cell damage, we monitored real-time extracellular glutamate release and cerebral blood flow (CBF) in an eleven vessel occlusion global ischemia rat model. Changes in glutamate release and CBF were monitored by laser-Doppler flowmetry and amperometric biosensor, respectively. A ten minute 11VO cerebral ischemia was initiated by pulling the snares on the common carotid arteries (CCAs) and the external carotid arteries (ECAs). Nimodipine was infused during the ischemic period (0.025 μg/100gm/min: diluted 20 times by normal saline). The infusion site for nimodipine was located lateral to the probe of cerebral blood flowmeter. Three days after occlusion, histological analysis was performed by Nissel staining, in order to assessment of neuronal cell damage. In comparison with the ischemia and nimodipine group, the maximum changes in glutamate concentration showed statistically significant difference between two groups, resulting in neuronal cell death. It is considered that nimodipine may reduce glutamate release with brain damage during a global ischemic episode in the eleven vessel occlusion rat model.

Real-Time Monitoring of Extracellular Glutamate Release on Repetitive Ischemic Injury in Global Ischemia Model

During the operation, neurosurgeons usually perform the multiple temporary occlusions of parental artery which may induce the neuronal damage. It is generally thought that neuronal damage by cerebral ischemia is associated with extracellular concentrations of the excitatory amino acids. In this experiment, we measured the dynamics of extracellular glutamate release in 11 vessel occlusion (VO) model during repeated occlusion within short interval. Changes in cerebral blood flow were monitored by laser-Doppler flowmetry simultaneously with cortical glutamate level measured by amperometric biosensor. During ischemic episode, the maximum change of glutamate release was gradually decreased as 112.38 ± 26.21 μM in first period, 82.63 ± 18.50 μM in second period, and 48.58 ± 11.89 μM in third period. The time interval be tween the ischemia induction and the beginning of glutamate release was increased as 106.7 ± 10.89 (sec) at first attack, 139.11 ± 3.87 (sec) in second attack, 169.00 ± 14.56 (sec) in third ischemic period. From the results of real-time monitoring about glutamate release in 11 VO model during repetitive ischemic episode, it was demonstrated that repetitive ischemia induced less glutamate release from neuronal cell than single ischemia due to endogeneous protective mechanism which delayed glutamate release time in later ischemic injury.