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Characteristics of Pc5 activity at high latitudes stations in Antarctica
Kwon, Hyuck-Jin,Kim, Khan-Hyuk,Jee, Geonhwa,Jin, Ho,Kim, Hyomin,Shin, Jehyuck,Lee, Seungah,Kwon, Jong-Woo,Kim, Jeong-Han,Lee, Changsup,Lessard, Marc Elsevier 2019 Journal of Atmospheric and Solar-Terrestrial Physi Vol.193 No.-
<P><B>Abstract</B></P> <P>We examined wave activities in the Pc5 frequency band (~2–7 mHz) using the magnetic field data from five Antarctic stations, which are AGO3 (72.5° S Altitude-Adjusted Corrected Geomagnetic latitude), South Pole (SPA, 74.6° S), McMurdo (MCM) and Jang Bogo Station (JBS, 80° S), and Dome C (DMC, 89.1° S), during 2017. Pc5 waves at AGO3 and SPA show characteristics associated with Kelvin-Helmohltz instability on the magnetopause and substorm activities, under closed field lines conditions. The local time and seasonal dependence of Pc5 wave activities at polar cap stations (MCM, JBS, and DMC) are significantly different from those at AGO3 and SPA. These indicate that the generation mechanism of Pc5 activities in the open field line region at polar cap is different from that in the closed field lines. We suggest that polar-cap Pc5 is generated by ionospheric current variations produced by solar dynamo between solar wind plasma and geomagnetic field.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pc5 pulsations observed at high latitude ground stations located in Antarctica in 2017. </LI> <LI> Latitudinal dependence of diurnal seasonal variations of Pc5 activities. </LI> <LI> The comparison of Pc5 and solar wind speed. </LI> <LI> Difference generation mechanism of Pc5 waves at auroral latitudes and polar-cap region. </LI> </UL> </P>
THEMIS Pi2 observations near dawn and dusk sectors in the inner magnetosphere
Kwon, Hyuck-Jin,Kim, Khan-Hyuk,Lee, Dong-Hun,Takahashi, K.,Park, Young-Deuk,Bonnell, J.W. 한국우주과학회 2010 한국우주과학회보 Vol.19 No.1
The most frequently suggested source for Pi2 pulsations in the inner magnetosphere (L < 4) is standing fast-mode waves trapped in the plasmasphere (i.e., plasmaspheric resonances). They have been considered as the source of low-latitude Pi2 pulsations. Th
Statistical Analysis of Low-latitude Pi2 Pulsations Observed at Bohyun Station in Korea
Jun, Chae-Woo,Kim, Khan-Huk,Kwon, Hyuck-Jin,Lee, Dong-Hun,Lee, Ensang,Park, Young-Deuk,Hwang, Junga 한국우주과학회 2013 Journal of Astronomy and Space Sciences Vol.30 No.1
We statistically investigated the properties of low-latitude Pi2 pulsations using Bohyun (BOH, Mlat = 29.8º, L = 1.35) ground magnetometer data in 2008. For this 1-year interval, 582 Pi2 events were identified when BOH was in the nightside from 1800 to 0600 local times. We found the following Pi2 characteristics. (1) The occurrence distribution of Pi2s is relatively constant in local times. (2) The Pi2 frequency varies in local times. That is, Pi2 pulsations in postmidnight sector had higher frequency than in premidnight sector. (3) Pi2 power in premidnight sector is stronger than in postmidnight sector. (4) Pi2 frequency has positive correlation with solar wind speed and AE index. (5) Pi2 power has not a clear correlation with solar wind parameters. This indicates that Pi2 power is not controlled by external sources. (6) It is found that the most probable-time between Pi2 onsets is Δt ~ 37.5 min: This is interpreted to be the period between Pi2 pulsations when they occur cyclically. We suggest that Δt ~ 37.5 min is the occurrence rate of reconnection of open field lines in the tail lobe.
Pc1/EMIC waves observed at subauroral latitude during sudden magnetospheric compressions
김관혁,이동훈,권혁진,이은상,Kim, Khan-Hyuk,Shiokawa, Kazuo,Lee, Dong-Hun,Kwon, Hyuck-Jin,Lee, Ensang 한국천문학회 2012 天文學會報 Vol.37 No.2
It is generally accepted that sudden compressions of the magnetosphere cause electromagnetic ion cyclotron (EMIC) wave growth by increasing the proton temperature anisotropy. These compression-associated EMIC waves are expected to be on higher latitudes (i.e., higher-L regions close to the magnetopause). In this study we examine Pc1 pulsations, which are believed to be generated by the EMIC instability, observed at subauroral latitude near the nominal plasmapause when the magnetosphere is suddenly compressed by solar wind dynamic pressure variations, using induction magnetometer data obtained from Athabasca, Canada (geomagnetic latitude = 61.7 N, L ~ 4.5). We identified 9 compression-associated Pc1 waves with frequencies of ~0.5-2.0 Hz. The wave activity appears in the horizontal H (positive north) and D (positive eastward) components. All of events show low coherence between H and D components. This indicates that the Pc1 pulsations in H and D oscillate with a different frequency. Thus, we cannot determine the polarization state of the waves. We will discuss the occurrence location of compression-associated Pc1 pulsations, their spectral structure, and wave properties.
Relation between Earthward magnetotail flow and low-latitude Pi2 pulsations
권혁진,김관혁,이동훈,이은상,Kwon, Hyuck-Jin,Kim, Khan-Hyuk,Lee, Dong-Hun,Takahashi, Kazue,Lee, Ensang,Angelopoulos, Vassilis,Park, Young-Deuk 한국천문학회 2012 天文學會報 Vol.37 No.2
It has been suggested that oscillatory earthward bursty bulk flows (BBFs) in the magnetotail are driving Pi2 oscillations on the ground. However, only a few studies examined the BBF-driven Pi2 model. The goal of this study is to establish the relation between BBFs and Pi2s. In order to examine BBF-drive model, we will conduct the timing analysis between BBFs and Pi2s for the intervals during which both Pi2 and BBF are present. In our study BBFs are identified with earthward flow speeds up to 200 km/s from THEMIS probes with a geocentric distance between 7 and 12 RE in the nightside magnetosphere for the interval from January 2008 to March 2008. Pi2 pulsations are identified at three low/mid-latitude ground stations having different local times; Bohyun (L = 1.35, LT ~ UT +9 hr), Hermanus (L = 1.83, LT ~ UT +2 hr) and Carson city (L = 2.00, LT ~ UT -2 hr). It is found that ~28% of BBFs have onset timing nearly identical to Pi2 onset. To investigate whether there is high similarity in the waveform between BBF and Pi2 oscillations, the coherence analysis is applied to the time series of BBF and Pi2 events. We found that there is no high coherence between BBF and Pi2 oscillations. Thus our observations suggest that low-latitude Pi2 oscillations are not directly driven by earthward flow bursts.