Study of Sun-Earth Couplings using MAGDAS/CPMN Data

第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月15日（火） 国立極地研究所 2階大会議

On the energy of the poloidal magnetic field near the ionosphere

The role of the ionospheric Hall effect on the energy balance in the magnetosphere-ionosphere (MI) system coupled through the field-aligned current (FAC) is discussed. FACs lose their stored electromagnetic energy in the ionosphere through Joule dissipation; this process is caused by the closure of the FAC via the ionospheric Pedersen current carried by ions. On the other hand, the ionospheric rotational Hall current carried by electrons cannot be dissipated. However, the ionospheric rotational Hall current can also be excited by an incident FAC, causing it to radiate Poynting fluxes that lead to the growth of a poloidal-type magnetic field in the magnetosphere and atmosphere. From the viewpoint of energy conservation, a few ambiguities in the above statements may be recognized. In this paper, we clarify the energy balance of the electromagnetic disturbances between the magnetosphere, ionosphere and atmosphere. The generation of the Hall current (together with the associated poloidal magnetic field) will be shown to occur during the growth stage, when the electromagnetic energy is pumped through the divergent Hall current, regardless of how slow the growth may have been

Anomalous ULF Emissions and Their Possible Association with the Strong Earthquakes in Sumatra, Indonesia, during 2007-2012

Eleven strong Sumatran earthquakes, with their epicenter less than 550 km away from the Kototabang (KTB) geomagnetic station (2007-2012), were studied to examine the occurrence of anomalous ultra-low frequency emissions (ULF-EM). Anomalous ULF signals, possibly associated with the earthquake's precursors, were determined by the Welch ratio SZ/SH at 0.06 Hz at the KTB station. These ULF anomalies were then compared with geomagnetic data observed from two reference stations in Darwin and Davao, to prevent misinterpretation of global geomagnetic disturbances as precursors. This study aims to analyze the relationship between earthquake magnitude and hypocenter radius, and seismic index against lead time during ULF-EM anomalies. We used the polarization ratio Welch method in terms of power spectrum density to evaluate the geomagnetic data by overlapping windows and applying fast Fourier transform (FFT). The results showed anomalous variations in onset and lead time, determined using the standard deviation controlling the SZ/SH power pattern. Our positive correlation between lead time of ULF emission and earthquake magnitude as well as between lead time and seismic index. It shows a negative correlation between hypocenter distances to KTB station against lead time

KARAKTERISTIK TINGKAT GANGGUAN GEOMAGNET REGIONAL INDONESIA [CHARACTERISTIC OF GEOMAGNETIC DISTURBANCE LEVEL OVER INDONESIAN REGION]

Tingkat gangguan geomagnet merupakan besaran yang menggambarkan aktivitas geomagnet, yang mencakup informasi tentang fenomena yang terjadi di magnetosfer. Gangguan geomagnet ini diperoleh dari pengukuran variasi harian geomagnet yang sudah bebas dari variasi hari tenangnya. Data variasi harian geomagnet yang digunakan dalam penelitian ini diperoleh dari pengukuran magnetometer yang dilakukan Lembaga Penerbangan dan Antariksa Nasional (Lapan) bekerjasama dengan Universitas Kyushu dan Badan Meteorologi, Klimatologi dan Geofisika (BMKG) pada stasiun-stasiun pengamatan geomagnet di Kototabang, Pontianak, Parepare, Manado, dan Kupang. Untuk mengetahui karakteristik gangguan geomagnet regional Indonesia dari kelima stasiun tersebut digunakan suatu metode yang dikenal dengan analisis komponen utama (Principal Component Analysis/PCA). Dengan penelitian ini diharapkan dapat mengetahui tingkat gangguan geomagnet regional Indonesia. Hasil perhitungan tingkat gangguan geomagnet dari 5 stasiun secara visual menunjukkan hasil gangguan yang hampir sama. Dari hasil analisis komponen utama kelima stasiun memiliki korelasi data yang kuat antara stasiun satu dengan lainnya. Disamping itu gangguan geomagnet dari stasiun Manado merupakan gangguan geomagnet paling dominan yang ditunjukkan dengan nilai eigen tertinggi 2,81.Kata Kunci: Gangguan geomagnet, Variasi harian geomagnet, Analisis komponen utam

FLR analysis of MAGDAS data in North America

第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月15日（火） 国立極地研究所 2階大会議室前フロ

トウナン アジア チイキ ニオケル セキドウ ジェット デンリュウ ノ タイヨウ カツドウ イゾンセイ

赤道ジェット電流(equatorial electrojet: EEJ)は,昼側磁気赤道直下における電離層電気伝導度の局所的増強に起因する電流系である.我々は,波長10.7 cmの太陽電波強度(F10.7)を太陽活動度の指標として用いて,EEJ強度の太陽活動度依存性を調査した.本研究で我々は,MAGDAS/CPMN 観測網のデータを用いて新しく構築されたEEJ指数の一つの成分であるEUEL指数のうち,2011 年の東南アジア地域のデータから算出されたEUEL 指数を解析に用いた.磁気赤道から±3°の狭い緯度帯に集中して流れるEEJ 帯の内側と外側にそれぞれ位置する2 観測点で得られたEUEL 指数の差からEEJ 強度を算出し(2 観測点法),F10.7 強度とEEJ強度に関してパワースペクトル解析と相関解析を行った.その結果,F10.7変動と正相で同期した約24 日と28 日周期を持つEEJ 強度の変動成分の存在を見いだした.一方でEEJ強度の日変化は,解析を行った期間,F10.7 の日変化と,低い相関を示していたことが明らかとなった.A:The equatorial electrojet (EEJ) is a current system caused by the enhanced ionospheric conductivity near the dayside magnetic dip equator. We examined the dependence of the EEJ on solar activity, represented by the 10.7 cm solar radio flux (F10.7). For this analysis, we used a new equatorial electrojet index, EUEL, provided by the MAGDAS/CPMN network in the Southeast Asia sector for the year 2011. Using a two-station method, the EEJ strength was calculated as the difference between the EUEL index of the dip equator station and the EUEL index of the off-dip equator station located outside the narrow channel (±3°in latitudinal range) of the EEJ band. The relationship between the EEJ component and the F10.7 index was then examined using power spectrum and correlation analyses. We found approximate 24-day and 28-day periodicities in the EEJ component, which are in phase with F10.7 variations. On the other hand, the daily values of EEJ showed low correlation with the daily F10.7 variations during the study period

Use of single-component wind speed in Rankine-Hugoniot analysis of interplanetary shocks

We have extended and deployed a routine designed to run independently on the Web providing real-time analysis of interplanetary shock observations from L_1. The program accesses real-time magnetic field, solar wind speed, and proton density data from the Advanced Composition Explorer (ACE) spacecraft, searches for interplanetary shocks, analyzes shocks according to the Rankine-Hugoniot (R-H) jump conditions, and provides shock solutions on the Web for space weather applications. Because the ACE real-time data stream contains the wind speed but not the three-component wind velocity, we describe modifications to the R-H analysis that use the scalar wind speed and show successful results for analyses of strong interplanetary shocks at 1 AU. We compare the three-component and one-component solutions and find the greatest disagreement between the two rests in estimations of the shock speed rather than the shock propagation direction. Uncertainties in magnetic quantities such as magnetic compression and shock normal angle relative to the upstream magnetic field show large uncertainties in both analyses when performed using an automated routine whereas analyses of the shock normal alone do not. The automated data point selection scheme, together with the natural variability of the magnetic field, is inferred to be a problem in a few instances for this and other reasons. For a broad range of interplanetary shocks that arrive 30 to 60 min after passing L_1, this method will provide 15 to 45 min of advanced warning prior to the shock's collision with the Earth's magnetopause. The shock, in turn, provides advance warning of the approaching driver gas

Development of the Virtual Earth\u27s Magnetosphere System (VEMS)

We have constructed a new research environment for geo-space science based on 3-D visualization tool and network database; Virtual Earth\u27s Magnetosphere System (VEMS). With an interactive research environment researchers can visually understand structures of the Earth\u27s magnetosphere using VEMS. On the VEMS, computer simulation results and observation data are simultaneously visualized, having a potential to data assimilation for geo-space studies in the future. Since the VEMS deals with time-dependent data, it also helps researchers to study dynamics of the Earth\u27s magnetosphere. We found that immersive data analyses are possible using the VEMS on a virtual reality system

Relation between Pi 2 magnetic pulsations at L=1.3-2.1 and dipolarizations at AMPTE/CCE

In order to investigate relations between low-latitude Pi 1-2 pulsations on the ground and substorm-associated variations in space, we analyzed magnetic data from the conjugate area of L=1.3-2.1 and λ～140°E, and from AMPTE/CCE in the midnight sector during August 9 to September 4,1986. From the correlation analysis, most of low-latitude Pi pulsations are found to occur within +1 to -2 min of the onsets of substorm-associated dipolarizations at geocentric distances of 8-9 R_E in the magnetotail. The dipolarizations appear to be localized in the magnetotail, because the orbiting spacecraft often cannot detect a dipolarization corresponding to an obvious Pi 2 on the grouud