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Observational Overview of the May 2024 G5-Level Geomagnetic Storm: From Solar Eruptions to Terrestrial Consequences
Park, Sung-Hong; Lim, Eun-Kyung; Kim, Sujin +25 more
This study reports comprehensive observations for the G5-level geomagnetic storm that occurred from May 10 to 12, 2024, the most intense event since the 2003 Halloween storm. The storm was triggered by a series of coronal mass ejections (CMEs) originating from the merging of two active regions 13664/13668, which formed a large and complex photosph…
Development of Forecast Algorithm for Coronal Mass Ejection Speed and Arrival Time Based on Propagation Tracking by Interplanetary Scintillation g-Value
Jang, Soojeong; Park, Sa-Rah; Jeon, Ho-Cheol +4 more
We have developed an algorithm for tracking coronal mass ejection (CME) propagation that allows us to estimate CME speed and its arrival time at Earth. The algorithm may be used either to forecast the CME's arrival on the day of the forecast or to update the CME tracking information for the next day's forecast. In our case study, we successfully t…
Analysis of Field-Aligned Currents in the High-Altitude Nightside Auroral Region: Cluster Observation
Shin, Youra; Lee, Ensang; Lee, Jae-Jin
In this paper we present analysis of current density when the Cluster spacecraft pass the nightside auroral region at about 4-5 RE from the center of Earth. The analysis is made when the inter-spacecraft separation is within 200 km, which allows all four spacecraft to be situated inside the same current sheet. On 22 February 2002, two field-aligne…
Exploring the Diffuse X-ray Emission of Supernova Remnant Kesteven 69 with XMM-Newton
Hui, Chung Yue; Seo, Kyoung-Ae
We have investigated the X-ray emission from the shock-heated plasma of the Galactic supernova remnant Kesteven 69 with XMM-Newton. Assuming the plasma is at collisional ionization equilibrium, a plasma temperature and a column absorption are found to be kT ~ 0.62 keV and NH ~ 2.85 ×10^22 cm-2 respectively by imaging spectroscopy. Together with th…
X-Ray, UV and Optical Observations of Classical Cepheids: New Insights into Cepheid Evolution, and the Heating and Dynamics of Their Atmospheres
Guinan, Edward F.; Engle, Scott G.
To broaden the understanding of classical Cepheid structure, evolution and atmospheres, we have extended our continuing secret lives of Cepheids program by obtaining XMM/Chandra X-ray observations, and Hubble space telescope (HST) / cosmic origins spectrograph (COS) FUV-UV spectra of the bright, nearby Cepheids Polaris, δ Cep and β Dor. Previous s…
IUE Spectra of Seyvert 1 Galaxy NGC 7469- BLR Characteristics of NGC 7469
Hyung, Siek; Son, Dong-Hoon
From the line ratios of Si III] 1892 to C III] 1909 (Feibelman & Aller 1987), we estimated the BLR electron densities and their changes of Seyfert 1 galaxy NGC 7469 using IUE spectra observed from June 11 to July 29, 1996 (Wanders et al. 1997). We separated blended Si III] and C III] lines using the STARLINK/DIPSO and measured their fluxes wit…
Starspot Model of RS CVn Type Binary SZ PSC
Kang, Young-Woon
The emission lines of the ultraviolet region and the light curves of the optical region have been analyzed to investigate the distorted light curves of SZ Psc. The Mg II emission lines of the IUE spectra confirmed that the chromospheric activity of SZ Psc occurs on the K1 IV star. The distorted light curves in the optical region have been analyzed…
Determination of Stellar Surface Temperature Using Ultraviolet Spectra
Choi, Young-Jun; Han, Wonyong; Kang, Young Woon +3 more
Color indexes and effective temperatures for 25 standard stars have been determined as a pilot project which show a relationship between color index and effective temperature in ultraviolet region. The effective temperature was determined by comparing energy distribution curves derived from the IUE low dispersion spectra with Kurucz atmosphere mod…
The Chromospheric Activity on V711 Tau
Kang, Young-Woon
The relationship between Mg ¥± emission line and light variation of V711 Tau has been derived to investigate the chromospheric activity on V711 Tau. First, a shape of an optical light curve was compared with that of ultraviolet constructed from the IUE low resolution spectra. Second, the intensities of Mg ¥± k emission lines have been reduced from…
SS Lac in Open Cluster NGC 7209
Kang, Young Woon
We present IUE observations in far ultraviolet region for SS Lac in open cluster NGC 7209. The IUE short wavelength spectrum and long wavelength spectrum were merged to produce an energy distribution curve between 1200A and 3200A. The curve has been unreddened to take out reddening effect. Then the surface temperature, gravity and abundance of SS …