Velocities and Temperatures of an Ellerman Bomb and Its Associated Features     

Heesu Yang  Jongchul Chae  Eun-Kyung Lim  Hyungmin Park  Kyuhyoun Cho  Ram Ajor Maurya  Donguk Song  Yeon-Han Kim  Philip R. Goode 《Solar physics》2013,288(1):39-53

We investigated the velocity and temperature characteristics of an Ellerman bomb (EB) and its associated features based on observations made with the Fast Imaging Solar Spectrograph (FISS) and a broadband TiO filter of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. In the TiO images of the photospheric level, we found a granular cell expanding in two opposite directions near the site of the EB. When one end of this granule reached the EB site, the transverse speed of the tip of the expanding granule rapidly decreased and the EB brightened. The wings of the Hα profile of the EB indicated that the EB was blueshifted up to 7 km?s^?1. About 260 s after the EB brightening, a surge was seen in absorption and varied from a blueshift of 20 km?s^?1 to a redshift of 40 km?s^?1 seen in the Hα and Ca ii 8542 Å lines. From the Doppler absorption width of the two lines determined by applying the cloud model, we estimated the mean temperature of the surge material to be about 29000 K and the mean speed of nonthermal motion to be about 11 km?s^?1. We discuss the physical implications of our results in terms of magnetic reconnection and processes related to it.  相似文献   

Connection Between Chromospheric Events and Photospheric Dynamics     

A. Anđić  J. Chae  H. Park  H. Yang  K. Ahn  W. Cao  Y. D. Park 《Solar physics》2013,288(1):55-71

We analyzed chromospheric events and their connection to oscillation phenomena and photospheric dynamics. The observations were done with the New Solar Telescope of Big Bear Solar Observatory using a broad-band imager at the wavelength of a TiO band and FISS spectrograph scanning Ca?ii and Hα spectral lines. The event in Ca?ii showed strong plasma flows and propagating waves in the chromosphere. The movement of the footpoints of flux tubes in the photosphere indicated flux tube entanglement and magnetic reconnection as a possible cause of the observed brightening and waves propagating in the chromosphere. An upward propagating train of waves was observed at the site of the downflow event in Hα. There was no clear relationship between photospheric waves and the Ca?ii and Hα events. Our observations indicate that chromospheric waves that were previously thought to originate from the photosphere may be generated by some events in the chromosphere as well.  相似文献   

Chromospheric Sunspot Oscillations in Hα and Ca ii 8542 Å     

Ram Ajor Maurya  Jongchul Chae  Hyungmin Park  Heesu Yang  Donguk Song  Kyuhyoun Cho 《Solar physics》2013,288(1):73-88

We study chromospheric oscillations including umbral flashes and running penumbral waves in a sunspot of active region NOAA 11242 using scanning spectroscopy in Hα and Ca?ii 8542 Å with the Fast Imaging Solar Spectrograph (FISS) at the 1.6 meter New Solar Telescope at the Big Bear Solar Observatory. A bisector method is applied to spectral observations to construct chromospheric Doppler-velocity maps. Temporal-sequence analysis of these shows enhanced high-frequency oscillations inside the sunspot umbra in both lines. Their peak frequency gradually decreases outward from the umbra. The oscillation power is found to be associated with magnetic-field strength and inclination, with different relationships in different frequency bands.  相似文献   

The Angstrom Project: a microlensing survey of the structure and composition of the bulge of the Andromeda galaxy     

E. Kerins  M. J. Darnley  J. P. Duke  A. Gould  C. Han  Y.-B. Jeon  A. Newsam  B.-G. Park 《Monthly notices of the Royal Astronomical Society》2006,365(4):1099-1108

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Preparation and Charaterization of Self-assembled Nanoparticles Based on Linolenic-acid Modified Chitosan     

Desai Kashappa Goud H.  Park Hyun-Jin 《中国海洋大学学报(英文版)》2005,4(3):234-239

1 IntroductionHydrophobically modified water-soluble polymers,also known as hydrophobized polymers, are thosemodified by hydrophobic groups such as alkyl,arolkyl, and deoxycholic acid. In water, they canself-aggregate due to their intro- and/or intermolecularhydrophobic interaction. By this process, unique hy-drogel nanoparticles with hydrophobic core and hy-drophilic shell can be prepared, which is a new ap-proach to preparing the monodispersed hydrogelnanoparticles (Whitesides et al., 1991; …  相似文献   

Time-domain geoacoustic inversion of high-frequency chirp signal from a simple towed system     

Cheolsoo Park Woojae Seong Gerstoft  P. Siderius  M. 《Oceanic Engineering, IEEE Journal of》2003,28(3):468-478

An inversion method using a towed system consisting of a source and two receivers is presented. High-frequency chirp signals that have been emitted from the source are received after multiple penetrations and reflections from the shallow water sub-bottom structure and are processed for geoacoustical parameter estimation. The data are processed such that a good resolution and robustness is achieved via matched filtering, which requires information about the source signal. The inversion is formulated as an optimization problem, which maximizes the cost function defined as a normalized correlation between the measured and modeled signals directly in the time domain. The very fast simulated reannealing optimization method is applied to the global search problem. The modeled time signal is obtained using a ray approach. An experiment was carried out in the Mediterranean Sea using a towed source and receiver system. The inversion method is applied to the experimental data and results are found to be consistent with previous frequency-domain analyses using measurements from a towed horizontal array of receivers and measurements on a vertical array.  相似文献   

Detrital zircon ages from the Loch Maree Group, Lewisian Complex, NW Scotland: confirmation of a Palaeoproterozoic Laurentia—Fennoscandia connection     

M. J. Whitehouse  D. Bridgwater  R. G. Park 《地学学报》1997,9(5-6):260-263

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Korean Global Data Assimilation and Prediction System     

Song-You Hong  Seon Ki Park  Rokjin Park  Jimy Dudhia 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):265-265

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GPS observations of the ionospheric F2-layer behavior during the 20th November 2003 geomagnetic storm over South Korea   总被引：4，自引：1，他引：3  

Shuanggen Jin  O. F. Luo  P. Park 《Journal of Geodesy》2008,82(12):883-892

The ionospheric F2-layer peak density (NmF2) and its height (hmF2) are of great influence on the shape of the ionospheric electron density profile Ne (h) and may be indicative of other physical processes within the ionosphere, especially those due to geomagnetic storms. Such parameters are often estimated using models such as the semiempirical international reference ionosphere (IRI) models or are measured using moderately priced to expensive instrumentation, such as ionosondes or incoherent scatter radars. Global positioning system (GPS) observations have become a powerful tool for mapping high-resolution ionospheric structures, which can be used to study the ionospheric response to geomagnetic storms. In this paper, we describe how 3-D ionospheric electron density profiles were produced from data of the dense permanent Korean GPS network using the tomography reconstruction technique. These profiles are verified by independent ionosonde data. The responses of GPS-derived parameters at the ionospheric F2-layer to the 20th November 2003 geomagnetic storm over South Korea are investigated. A fairly large increase in the electron density at the F2-layer peak (the NmF2) (positive storm) has been observed during this storm, which is accompanied by a significant uplift in the height of the F2 layer peak (the hmF2). This is confirmed by independent ionosonde observations. We suggest that the F2-layer peak height uplift and NmF2 increase are mainly associated with a strong eastward electric field, and are not associated with the increase of the O/N₂ ratio obtained from the GUVI instruments aboard the TIMED satellite. It is also inferred that the increase in NmF2 is not caused by the changes in neutral composition, but is related to other nonchemical effects, such as dynamical changes of vertical ion motions induced by winds and E × B drifts, tides and waves in the mesosphere/lower thermosphere region, which can be dynamically coupled upward to generate ionospheric perturbations and oscillations.  相似文献   

Estimating the Texas Windstorm Insurance Association claim payout of commercial buildings from Hurricane Ike     

J. M. Kim  P. K. Woods  Y. J. Park  K. Son 《Natural Hazards》2016,81(1):405-421

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