Young-Deuk Park

A STATISTICAL STUDY OF TWO CLASSES OF CORONAL MASS EJECTIONS

A comprehensive statistical study is performed to address the question of whether two classes of coronal mass ejections (CMEs) exist. A total of 3217 CME events observed by SOHO/LASCO in 1996-2000 have been analyzed. We have examined the distributions of CMEs according to speed and acceleration, respectively, and investigated the correlation between speed and acceleration of CMEs. This statistical analysis is conducted for two subsets containing those CMEs that show a temporal and spatial association either with GOES X-ray solar flares or with eruptive filaments. We have found that CMEs associated with flares have a higher median speed than those associated with eruptive filaments and that the median speed of CMEs associated with strong flares is higher than that of weak-flare-associated CMEs. The distribution of CME acceleration shows a conspicuous peak near zero, not only for the whole data set, but also for the two subsets associated either with solar flares or with eruptive filaments. However, we have confirmed that the CMEs associated with major flares tend to be more decelerated than the CMEs related to eruptive filaments. The fraction of flare-associated CMEs has a tendency to increase with the CME speed, whereas the fraction of eruptive-filament-associated CMEs tends to decrease with the CME speed. This result supports the concept of two CME classes. We have found a possibility of two components in the CME speed distribution for both the CME data associated with flares larger than M1 class and the CME data related with limb flares. Our results suggest that the apparent single-peak distribution of CME speed can be attributed to the projection effect and possibly to abundance of small flares too. We also note that there is a possible correlation between the speed of CMEs and the time-integrated X-ray flux of the CME-associated limb flares.

ESTIMATION OF SPICULE MAGNETIC FIELD USING OBSERVED MHD WAVES BY THE HINODE SOT

Using the MHD coronal seismology technique, we estimated the magnetic field for three spicules observed in 2008 June. For this study, we used the high resolution Ca II H line (3968.5 ˚A) images observed by the Hinode SOT and considered a vertical thin flux tube as a spicule model. To our knowledge, this is the first attempt to estimate the spicule magnetic field using the Hinode observation. From the observed oscillation properties, we determined the periods, amplitudes, minimum wavelengths, and wave speeds. We interpreted the observed oscillations as MHD kink waves propagating through a vertical thin flux tube embedded in a uniform field environment. Then we estimated spicule magnetic field assuming spicule densities. Major results from this study are as follows : (1) we observed three oscillating spicules having durations of 5-7 minutes, oscillating periods of 2-3 minutes, and transverse displacements of 700-1000 km. (2) The estimated magnetic field in spicules is about 10-18 G for lower density limit and about 43-76 G for upper density limit. (3) In this analysis, we can estimate the minimum wavelength of the oscillations, such as 60000 km, 56000 km, and 45000 km. This may be due to the much longer wavelength comparing with the height of spicules. (4) In the first event occurred on 2008 June 03, the oscillation existed during limited time (about 250 s). This means that the oscillation may be triggered by an impulsive mechanism (like low atmospheric reconnection), not continuous. Being compared with the ground-based observations of spicule oscillations, our observation indicates quite different one, i.e., more than one order longer in wavelength, a factor of 3-4 larger in wave speed, and 2-3 times longer in period.

SIMULTANEOUS OBSERVATION OF A HOT EXPLOSION BY NST AND IRIS

We present the first simultaneous observations of so-called “hot explosions” in the cool atmosphere of the Sun made by the New Solar Telescope (NST) of Big Bear Solar Observatory and the Interface Region Imaging Spectrograph (IRIS) in space. The data were obtained during the joint IRIS-NST observations on 2014 July 30. The explosion of interest started around 19:20 UT and lasted for about 10 minutes. Our findings are as follows: (1) the IRIS brightening was observed in three channels of slit-jaw images, which cover the temperature range from 4000 to 80,000 K; (2) during the brightening, the Si iv emission profile showed a double-peaked shape with highly blue and redshifted components ( and 80 km s−1); (3) wing brightening occurred in Hα and Ca ii 8542 Å bands and related surges were observed in both bands of the NST Fast Imaging Solar Spectrograph (FISS) instrument; (4) the elongated granule, seen in NST TiO data, is clear evidence of the emergence of positive flux to trigger the hot explosion; (5) the brightening in Solar Dynamics Observatory/Atmospheric Imaging Assembly 1600 Å images is quite consistent with the IRIS brightening. These observations suggest that our event is a hot explosion that occurred in the cool atmosphere of the Sun. In addition, our event appeared as an Ellerman bomb (EB) in the wing of Hα, although its intensity is weak and the vertical extent of the brightening seems to be relatively high compared with the typical EBs.

Intensity and Doppler velocity oscillations in pore atmospheres

We have investigated chromospheric traveling features running across two merged pores from their centers at speeds of about 55 km s−1, in the active region AR 11828. The pores were observed on 2013 August 24 by using high-time, spatial, and spectral resolution data from the Fast Imaging Solar Spectrograph of the 1.6 m New Solar Telescope. We infer a line-of-sight (LOS) velocity by applying the lambdameter method to the Ca ii 8542 A band and Hα band, and investigate intensity and LOS velocity changes at different wavelengths and different positions at the pores. We find that they have three-minute oscillations, and the intensity oscillation from the line center (0.0

STUDY OF MAGNETIC HELICITY INJECTION IN THE ACTIVE REGION NOAA 9236 PRODUCING MULTIPLE FLARE-ASSOCIATED CORONAL MASS EJECTION EVENTS

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Spectral observations of FUV auroral arcs and comparison with inverted-V precipitating electrons

) is preceded by that from the core (−0.3

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

\overset{\circ}{\rm A}

Hα SPECTRAL PROPERTIES OF VELOCITY THREADS CONSTITUTING A QUIESCENT SOLAR FILAMENT

) of the bands. There is no phase difference between the intensity and the LOS velocity oscillations at a given wavelength. The amplitude of LOS velocity from the near core spectra (

Ionospheric F2-Layer Semi-Annual Variation in Middle Latitude by Solar Activity

{\Delta }\lambda =0.10-0.21\;\overset{\circ}{\rm A}

CAPABILITY OF THE FAST IMAGING SOLAR SPECTROGRAPH ON NST/BBSO FOR OBSERVING FILAMENTS/PROMINENCES AT THE SPECTRAL LINES Hα, Ca II 8542, AND Ca II K

) is greater than that from the far core spectra (