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A Modeling Analysis of the Apparent Linear Relation Between Mesospheric Temperatures and Meteor Height Distributions Measured by a Meteor Radar

2022-01-01T00:00:00Z

Title: A Modeling Analysis of the Apparent Linear Relation Between Mesospheric Temperatures and Meteor Height Distributions Measured by a Meteor Radar Authors: Lee, Wonseok; Lee, Changsup; Kim, Jeong-Han; Kam, Hosik; Kim, Yong Ha Abstract: A new method of estimating mesospheric temperature has recently been proposed by utilizing an apparent linear relation between atmospheric temperatures and full widths at half maximum (FWHMs) of meteor height distributions measured by a meteor radar (MR). However, the new method assumes that the meteor height distribution is dominantly dependent on the atmospheric conditions, rather than on meteoroid characteristics (mass and velocity). In order to verify this assumption, we have developed a meteor ablation model and applied it to the observed parameters by a MR at King Sejong Station (62.2 degrees S, 58.8 degrees W). The simulation results show that the FWHM of meteor height distribution increases linearly with the mesospheric temperature and its linear relation matches well with the observed relation. We found that the seasonal variation of meteor velocity distributions is significant but has only little effect on the variation of the height distribution. We also found that the observed characteristics of meteors are consistent with a Gaussian distribution of logarithmic masses, and this distribution is nearly invariable throughout the year with the average peak value of 10-6.2kg ${10}<^>{-6.2}\hspace*{.5em}\text{kg}$. Thus, we conclude that observed meteor height distributions are mainly dependent on the mesospheric temperature, and can be used as a mesospheric temperature indicator.

Mesospheric short-period gravity waves in the Antarctic Peninsula observed in all-sky airglow images and their possible source locations

2021-12-27T00:00:00Z

Title: Mesospheric short-period gravity waves in the Antarctic Peninsula observed in all-sky airglow images and their possible source locations Authors: Kam, Hosik; Song, In-Sun; Kim, Jeong-Han; Kim, Yong Ha; Song, Byeong-Gwon; Nakamura, Takuji; Tomikawa, Yoshihiro; Kogure, Masaru; Ejiri, Mitsumu K.; Perwitasari, Septi; Tsutsumi, Masaki; Kwak, Young-Sil Abstract: This study presents an analysis of OH airglow images observed from an all-sky camera (ASC) at King Sejong Station (KSS), Antarctic for the 2012？2016 period. The two- dimensional power spectra of short-period gravity waves (< 1 h) as a function of phase velocities are obtained using the M-transform method that employs the time sequence of ASC images. The amplitudes of the power spectral densities show that the mesospheric wave activity is the largest during winter (May, June, and July) and is the smallest in fall (February, March, and April). Wind-blocking diagrams are constructed on the same two-dimensional domain as in the two-dimensional spectra using horizontal winds obtained from MERRA-2 reanalysis at z = 0？80 km and from KSS meteor radar data at z = 80？90 km. Climatologically, the spectral regions of slowly propagating gravity waves (< 30 m s-1) are overlaid by the wind-blocking areas, which suggests the filtering of gravity waves with small phase speeds by winds below the upper stratosphere. Eastward propagating gravity waves in winter and intense south- eastward waves in spring (October) are found to be unfiltered by the stratospheric winds. It is also found from the spectral analysis that these unfiltered gravity waves can originate from the upper stratosphere or the lower mesosphere, and not from the troposphere, which suggests the possibility of ASC observation of the secondary gravity waves generated near the stratopause.

Observations of the Aurora by Visible All-Sky Camera at Jang Bogo Station, Antarctica

2021-09-30T00:00:00Z

Title: Observations of the Aurora by Visible All-Sky Camera at Jang Bogo Station, Antarctica Authors: Jee, Geonhwa; Ham, Young-Bae; Choi, Yoonseung; Kim, Eunsol; Lee, Changsup; Kwon, Hyuck-Jin; Trondsen, Trond S.; Kim, Jieun; Kim, Jeong-Han Abstract: The auroral observation has been started at Jang Bogo Station (JBS), Antarctica by using a visible All-sky camera (v-ASC) in 2018 to routinely monitor the aurora in association with the simultaneous observations of the ionosphere, thermosphere and magnetosphere at the station. In this article, the auroral observations are introduced with the analysis procedure to recognize the aurora from the v-ASC image data and to compute the auroral occurrences and the initial results on their spatial and temporal distributions are presented. The auroral occurrences are mostly confined to the northern horizon in the evening sector and extend to the zenith from the northwest to cover almost the entire sky disk over JBS at around 08 MLT (magnetic local time; 03 LT) and then retract to the northeast in the morning sector. At near the magnetic local noon, the occurrences are horizontally distributed in the northern sky disk, which shows the auroral occurrences in the cusp region. The results of the auroral occurrences indicate that JBS is located most of the time in the polar cap near the poleward boundary of the auroral oval in the nightside and approaches closer to the oval in the morning sector. At around 08 MLT (03 LT), JBS is located within the auroral oval and then moves away from it, finally being located in the cusp region at the magnetic local noon, which indicates that the location of JBS turns out to be ideal to investigate the variabilities of the poleward boundary of the auroral oval from long-term observations of the auroral occurrences. The future plan for the ground auroral observations near JBS is presented.

Isolated Proton Aurora Driven by EMIC Pc1 Wave: PWING, Swarm, and NOAA POES Multi-Instrument Observations

2021-09-28T00:00:00Z

Title: Isolated Proton Aurora Driven by EMIC Pc1 Wave: PWING, Swarm, and NOAA POES Multi-Instrument Observations Authors: Kim, Hyangpyo; Shiokawa, Kazuo; Park, Jaeheung; Miyoshi, Yoshizumi; Miyashita, Yukinaga; Stolle, Claudia; Connor, Hyunju Kim; Hwang, Junga; Buchert, Stephan; Kwon, Hyuck-Jin; Nakamura, Satoko; Nakamura, Kohki; Oyama, Shin-Ichiro; Otsuka, Yuichi; Nagatsuma, Tsutomu; Sakaguchi, Kaori Abstract: We report the concurrent observations of F-region plasma changes and field-aligned currents (FACs) above isolated proton auroras (IPAs) associated with electromagnetic ion cyclotron Pc1 waves. Key events on 19 March 2020 and 12 September 2018 show that ground magnetometers and all-sky imagers detected concurrent Pc1 wave and IPA, during which NOAA POES observed precipitating energetic protons. In the ionospheric F-layer above the IPA zone, the Swarm satellites observed transverse Pc1 waves, which span wider latitudes than IPA. Around IPA, Swarm also detected the bipolar FAC and localized plasma density enhancement, which is occasionally surrounded by wide/shallow depletion. This indicates that wave-induced proton precipitation contributes to the energy transfer from the magnetosphere to the ionosphere. Plain Language Summary Electromagnetic ion cyclotron (EMIC) wave is known to precipitate energetic protons into the energy transfer from the magnetosphere to the ionosphere.