Next PPARC Seminar

************************************************************************   PPARC seminar news #11 in FY2017


2017/9/22(Fri.) 9:00-12:00 at S407 @ C building  chairperson: Sakanoi

Kyoko Mimura (M2)
Title:Magnetospheric response for the appearence of theta aurora inffered from the analyses of MHD simulation data
Abstract: The theta aurora sometimes appears in the polar cap region when IMF
(Interplanetary Magnetic Field) By polarity reversal under the northward IMF condition. This aurora is thought to be caused by the plasma sheet which penetrates in the lobe region by IMF By polarity reversal. The magnetic field structure change associated with the theta aurora has not been studied sufficiently yet. The present paper tries to elucidate the magnetospheric structure change by using the global MHD simulation. We perform MHD simulation by changing IMF By polarity from negative (-4.3nT) to positive (4.3nT) under the northward IMF condition (Bz=4.3nT) in this study. Simulation results seem to show there are three stages of the theta aurora evolution from the view of plasma disturbances in the magnetosphere. From the viewpoint of the magnetic field structure, it is revealed that the Movement of the magnetosphere when the change of the plasma sheet converges and the null points. In the future, we want reveal about deformation of the magnetic field structure associated with the By reversal and associated transformation of plasma sheet. And in this presentation, we will talk mainly about that the caractristics of plasma disterbanec and magnetic field structure respectively.
太陽風中の磁場,IMF(interplanetary magnetic field)のBzが正(北向き)で、Byの符号が変化するとき、極冠域内に棒状のアークが出現し、シータオーロラと呼ばれるオーロラが形成されることがある。このオーロラが出現する理由として、プラズマシートの変形があげられる。IMF Bzが北向きでByの符号が反転すると、プラズマシートがローブ領域に張り出す。この張り出したプラズマシート中のプラズマがシータオーロラの棒状のアークの起源となっていることがシミュレーション(Tanaka et al.,2004)からも観測(R.C.Fear et al., 2014)からも示唆されている。私たちは、このプラズマシートの変形がどうして起こるのか、MHD(Magnetohydro dinamics)シミュレーションを用いた立場から明らかにすることを目的として本研究を行っている。MHDシミュレーションによりシータオーロラが出現されるとするIMF条件(Bz=+4.3nT,By=-4.3nT→+4.3nT)で計算したデータを解析すると、大きくわけて2つの特徴をつかむことができた。まず、プラズマの圧力と対流の時間変化の特徴から、シータオーロラの成長過程を3つのフェーズに分けられる、というものである。そして、磁力線構造の変化から、本シュミレーション条件下でのnull点の動きと、プラズマシートの変化が収束するときの磁気圏の動きについて新たに傾向をつかむことができた。今後、圧力と対流、そして磁力線の変化を組み合わせて、シータオーロラ出現条件下での磁気圏の構造変化を議論することを本研究の最終目的としているが、今回の発表ではそれぞれのデータから得られた特徴について報告する。
Yu Endo (M2) Title: "N2+ resonant scattering light in the topside ionosphere observed with auroral spectrograph " Abstract: For several years it was believed that the solar wind was the major source of magnetospheric plasma, and that essentially all ionospheric plasma was gravitationally bound to low altitudes. However, the first polar orbit satellites such as 1971-89A and 1976-65B observed significant amounts of O+ ions originated from ionosphere [Shelley et al., 1972; Shelley et al., 1976; Sharp et al., 1977]. The important source of this ion outflow is ion upflow, upflowing ions in the ionosphere. It generally occurs below at altitudes of 1,000 km, and O+ ion is the main species of ion upflow. The mechanism of ion upflow can be divided into two types, strong ambipolar diffusion (type 1) [Moen et al., 2004; Lund et al., 2012] and ion frictional heating (type 2) [Wahlund et al., 1992]. While, the minor upflowing ions such as N2+ were observed in the topside ionosphere and higher altitude by some satellites [Hoffman et al., 1974; Yau et al., 1993; Romick et al., 1999; Peterson et al., 2004; Mizuno et al., 2005]. However, there are few observations of N2+ ion upflow and no observation from the ground, and the mechanism of molecular upflowing ions is uncertain. My research purpose is to resolve the mechanism N2+ ion upflow by the observation from the ground. The analysis method is to observe the N2+ resonant scattering light in the topside ionosphere by auroral spectrograph. This instrument was installed in 2000 at Longyearbyen in Svalbard, Norway (78.15N, 16.04 E). This has observed 427.8 nm emission (N2+ resonant scattering light) since 2004. We did the Data set according to preceding study, and we analyzed 75 days in this study. We resulted in detecting 13 events of N2+ resonant scattering light in the topside ionosphere. In brief our auroral emission height calculation, the N2+ emission in lower F-region is correlated with Kp index, and the N2+ emission height extends to high altitude as Kp index increases. On 22th January 2012, the auroral arc with N2+ resonant scattering light passed over EISCAT/ESR located in Longyearbyen around 15:30 UT, the O+ ion upflow was not observed then. On 21th December 2015, the large magnetic storm occurred (Dst index ~ -150 nT). We analyzed this event during the time between 7:00 UT and 8:20 UT, Kp index was 5 at this time and 7- in preceding 6 hours. We found that N2+ emission in lower F-region is correlated with 630 nm emission caused by precipitating soft electrons. The correlation coefficients between N2+ emission at altitudes of 300 km and 630 nm emission is 0.75. The N2+ emission in the topside ionosphere around altitudes of 800 km increases (100 R to 300 R) with time. In discussion, the N2+ ion in lower F-region seems to be created by the charge exchange reaction between N2 and O+ ion suggested by Feldman [1973]. O+ ion is created in lower F-region by precipitating soft electrons causing 630 nm emission. And, this created N2+ ion is the important source of N2+ ion upflow. N2+ ion usually exists in E-region, however, the charge exchange reaction is very active in F-region during the time of geomagnetic disturbed condition. It seems to occur N2+ ion upflow in F-region not in E-region. 以上


----- PPARC seminar schedule (v1.4, 2017-09-20) ---
17/09/15(Fri)  13:00-17:00 Kaneda @N307
17/09/22(Fri)  9:00-12:00 Endo, Mimura
17/09/29(Fri) 9:00-12:00 Arakawa
17/10/02(Mon) 9:00-12:00 Okada, Yoshizawa, Yagi
17/10/06(Fri)   13:00-16:00  Hino, Koizumi @N307
17/10/09(Mon)  holiday
17/10/15-19  SGEPSS(Kyoto)
17/10/23(Mon) 研究発表会
17/10/30(Mon) 9:00-12:00 Obara, Ishikawa
17/11/06(Mon) 9:00-12:00 Sakanoi, Fukizawa
17/11/13(Mon) 9:00-12:00 Misawa, Hirai
17/11/20(Mon) 9:00-12:00 Tsuchiya, Watanabe
17/11/27(Mon) 9:00-12:00 Kagitani, Koga
17/12/04(Mon) 9:00-12:00 - an optional day --
17/12/11(Mon) 9:00-12:00 Okada, Yagi
17/12/18(Mon) 9:00-12:00 Hino, Yoshizawa
18/01/08(Mon) holiday
18/01/15(Mon) - no seminar-
18/01/16(Tue) 研究発表会
18/01/19(Fri) D論締切
18/01/22(Mon) - no seminar -
18/01/26(Fri) M論締切
18/01/29(Mon) 9:00-12:00 Kaneda, Mizuguchi
18/01/30(Tue) 9:00-12:00 Arakawa, Endo
18/01/31(Wed) 13:00-16:00 Koizumi, Mimura
18/02/05-02/08 D/M審査会
18/02/12(Mon) holiday
18/02/15(Thu)  13:00-16:00 Watanabe, Hirai (review)
18/02/19(Mon) 9:00-12:00 Fukizawa, Ishikawa (review)
18/02/27-3/1 惑星圏研究会
----- 発表者 -----
D/1回: Mizuguchi, Kaneda, Kodama
M2/1回: Endo, Koizumi, Arakawa, Mimura
M1/2回: Ishikawa, Hirai, Fukizawa, Watanabe, うち1回はreview
B4/2回: Yoshizawa, Hino, Okada, Yagi

----- C-group seminar schedule (v1.3, 2017-09-12) ---
17/09/25(Mon)  13:00-17:30 D thesis preliminary oral exam. (Kaneda, K. Endo)
17/09/28(Thu)  13:00-16:30 M thesis preliminary oral exam. (Mimura, Y. Endo)
17/10/05(Thu)  09:00-16:00 SGEPSS reherasal
17/10/12(Thu)  13:00-16:30 M thesis preliminary oral exam. (Nishida, Terada)
17/10/15-19    (SGEPSS in Kyoto)
17/10/26(Thu)  13:00-16:30 M thesis preliminary oral exam. (Kamada, Arakawa)
17/11/02(Thu)  13:00-16:30 M thesis preliminary oral exam. (Ishigaya, Koizumi)
17/11/09(Thu)  (Geophys. Joint Seminar)
17/11/16(Thu)  13:00-   D2 interim report (Ooki)
17/11/23(Thu)  (holiday)
18/02/22(Thu)  13:00-   D2 interim report (Aizawa)


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  • C-Group - Seminar

    **  C-Group Seminar News '17 No.7  **

      ** Poster #4, and D-Report #4 **

        ** Poster #4 **

    Date & Time : Starting at 13:00 on Thursday, June 22
    Place : Lecture Room #N404

    T. Akiba

    A. Kamada

    Y. Koizumi
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    K. Mimura
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        ** D-Report #4 **

    Date & Time : Starting at 14:40 on Thursday, June 22
    Place : Lecture Room #N404

    K. Arao
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    *** C-group seminar 2017 schedule (v1.4, 2017-03-31) ***
    17/06/22(Thu) 13:00- Poster#4(Akiba, Kamada, Koizumi, Mimura), D-presen (Arao)
    17/06/29(Thu) 13:00- D-presen (K.Endo, Mizuguchi)
    17/07/13(Thu) Guest speaker (Prof.Tanaka from astronomical Institute)
    #May-June Bepi-SWT
    #Aug 20-31 IAU
    Poster presen: M1, M2 & D3
    D-presen: Mizuguchi, Koga

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