磁気圏対流の発達に伴う内部磁気圏プラズマ密度の異常増加

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(1) .

(2) . ☢ẼᅪᑐὶࡢⓎ㐩࡟క࠺ෆ㒊☢Ẽᅪࣉࣛࢬ࣐ᐦᗘࡢ␗ᖖቑຍ Steep increase in plasma mass density associated with growth of magnetospheric convection ᑿⰼ ⏤⣖*1, ᯇ⥴ ⩧ః*1, *2 Yuki Obana*1 , Shogo Matsuo*1, *2 Abstract Using the cross-phase analysis of geomagnetic data observed in Northern America, we determined the equatorial mass density at L = 2.6 and 2.9 during two geomagnetic storms in April 2001. On 25 April, in the late recovery phase of the first storm, the frequency of the field line resonances increased slightly in response to the reductions in the mass density of the plasma. From 25 to 27 April, the plasma mass density showed a clear diurnal variation associated with a linear increase in the plasma density in the daytime and a decrease in the plasma density at nighttime. The daytime increases in the plasma mass density were related to refilling rates ranging from 181 to 33 amu/cc/h over L = 2.6–2.9. This result is comparable with the results obtained in previous studies. On the other hand, on 28 April, the second storm commenced, and the plasma mass density increased very steeply. The increase rate reached 473 and 118 amu/cc/h at L = 2.6 and 2.9, respectively. These values are remarkably high in comparison with the refilling rate observed previously. Such an increase in the main phase of the storm can be qualitatively explained by the transfer of the plasma and/or the delay of the co-rotation due to the magnetic convection.. 㸬ࡣࡌࡵ࡟ ᆅ⌫☢ሙࡢໃຊᅪ࡛࠶ࡿᆅ⌫☢Ẽᅪࡢ୰࡟ࡣࠊࣉࣛࢬ࣐ࡢ ᗘ࣭ᅽຊ➼࡟ࡼࡗ࡚ศ㢮ࡉࢀࡿࡉ ࡲࡊࡲ࡞㡿ᇦࡀ࠶ࡿࠋࡑࡢ୰ࡢ୍ࡘ࡛࠶ࡿࣉࣛࢬ࣐ᅪࡣෆ㒊☢Ẽᅪ࡟఩⨨ࡋࠊ㟁㞳ᅪ㉳※࡜⪃࠼ ࡽࢀࡿ෭ࡓ࠸ࣉࣛࢬ࣐ࡀ㧗ᐦᗘ࡟⃰㞟ࡋ࡚࠸ࡿ㡿ᇦ࡛࠶ࡿࠋࣉࣛࢬ࣐ᅪࡢእഃࡢቃ⏺ࡣࣉࣛࢬ࣐ ᅪ⏺㠃࡜࿧ࡤࢀࠊࡋࡤࡋࡤᐦᗘࡢᛴ⃭࡞ኚ໬ࢆక࠺ࠊ᫂░࡞ቃ⏺࡜ࡋ࡚ほ ࡉࢀࡿ[1,2]ࠋࣉࣛࢬ ࣐ᅪ⏺㠃ࡣ୍⯡࡟ࠊඹᅇ㌿ࡍࡿ㛢ࡌࡓ☢ຊ⥺࡜ᑐὶࡍࡿ㛤࠸ࡓ☢ຊ⥺ࡢ㌶㐨ࡢቃ⏺࡛࠶ࡿ࡜ㄝ᫂ ࡉࢀ࡚࠾ࡾࠊ☢Ẽᅪᑐὶ㟁ሙࡢᾘ㛗࡟ᛂ⟅ࡋ࡚ࣉࣛࢬ࣐ᅪࡢ኱ࡁࡉࡸᙧ≧ࡶࢲ࢖ࢼ࣑ࢵࢡ࡟ኚ໬ ࡍࡿ[3]ࠋ☢Ẽᅪ࡟ᩘ᪥㛫㟼✜࡞≧ែࡀ⥆࠸ࡓᚋࡣࠊࣉࣛࢬ࣐ᅪࡣ㟁㞳ᅪ࠿ࡽࡢࣉࣛࢬ࣐౪⤥ࡢ⤖ ᯝ㣬࿴ࡋࠊL ~ 8 ⛬ᗘࡲ࡛ᣑ኱ࡋ࡚࠸ࡿࠋࡦ࡜ࡓࡧ☢Ẽᅪ࡟ᨐ஘ࡀⓎ⏕ࡋ࡚☢Ẽᅪᑐὶࡀᙉࡲࡿ࡜ࠊ ࣉࣛࢬ࣐ᅪࡣእഃ࠿ࡽᾐ㣗ࡉࢀࠊࣉࣛࢬ࣐ᅪ⏺㠃ࡣᆅᚰ㊥㞳 2 ~ 3 [Re]⛬ᗘࡲ࡛⦰ᑠࡋࠊ☢᮰⟶ෆ ࡢࣉࣛࢬ࣐ᐦᗘࡀ኱ࡁࡃῶᑡࡍࡿࠋᨐ஘ࡀ཰ࡲࡾࠊ☢Ẽᅪᑐὶࡀ཰ࡲࡿ࡜ࠊ෌ࡧඹᅇ㌿㡿ᇦࡀᣑ ኱ࡋࠊ㛢ࡌࡓ☢ຊ⥺࡬࡜㟁㞳ᅪ࠿ࡽᚎࠎ࡟ࣉࣛࢬ࣐ࡀ౪⤥ࡉࢀࠊࣉࣛࢬ࣐ᅪࡣᩘ᪥㛫࠿ࡅ࡚ᅇ᚟ ࡍࡿ[4,5]ࠋࡇࡢᅇ᚟ࣉࣟࢭࢫࢆࣉࣛࢬ࣐ᅪࡢ෌඘ሸ࡜࠸࠺ࠋ "#$%&'()*+',-./$012345" ࣉࣛࢬ࣐ᅪࡢᾐ㣗࡜෌඘ሸࡣ☢Ẽᅪࣉࣛࢬ࣐ࡢ㉳※ࡸᆅ⌫኱Ẽ࠿ࡽࡢ≀㉁ὶฟࠊᆅ⌫኱Ẽ⤌ᡂ *1 ኱㜰㟁Ẽ㏻ಙ኱Ꮫ ᕤᏛ㒊 ᇶ♏⌮ᕤᏛ⛉, *2 ᰴᘧ఍♫ ᪂࿴〇సᡤ !. .

(3) ࡢᡂࡾ❧ࡕࢆ⪃࠼ࡿ࠺࠼࡛㔜せ࡛࠶ࡿࡀࠊࡑࡢヲ⣽࡞ᥥീࡸ࣓࢝ࢽࢬ࣒࡟ࡣ࠸ࡲࡔ୙᫂࡞Ⅼࡀከ ࠸ࠋ౛࠼ࡤᴟᇦࡢ࢖࢜ࣥὶฟࡣ H+, He+, O+ࡢ⢏Ꮚ✀ࡈ࡜࡟ὶฟ㏿ᗘࡢ㧗ᗘࣉࣟࣇ࢓࢖ࣝࡶ᫂ࡽ࠿ ࡟ࡉࢀ࡚࠸ࡿࡀ[5]ࠊ୰ప⦋ᗘࡢ࢔࢘ࢺࣇ࣮ࣟほ ࡣὶ㔞ࡀᑡ࡞࠸࠺࠼ᨺᑕ⥺ᖏ⢏Ꮚࡢᙳ㡪࡛㞴ࡋ ࡃࠊ㐍ࢇ࡛࠸࡞࠸ࠋKrall et al. [6] ࡢ㟁㞳ᅪࣔࢹࣝᩘ್ィ⟬࡟ࡼࡿ࡜ࣉࣛࢬ࣐ᅪࡢ H+࡜ He+ࡢ෌඘ ሸ⋡ࡣኴ㝧άືᗘ࡟኱ࡁࡃ౫Ꮡࡋࠊࡑࢀࡒࢀ඲ࡃ␗࡞ࡿࡩࡿࡲ࠸ࢆぢࡏࡿ࡜ண᝿ࡉࢀ࡚࠸ࡿࡀࠊ ほ ࡛☜࠿ࡵࡓ౛ࡣ࡞࠸ࠋ ࡑࡇ࡛ᮏ◊✲࡛ࡣࠊᆅ☢ẼከⅬほ ࢹ࣮ࢱࢆ⏝࠸ࡓࣉࣛࢬ࣐ᐦᗘࡢ᥎ᐃἲࢆ⏝࠸࡚ࣉࣛࢬ࣐ᅪ ෌඘ሸࢆヲ⣽࡟ㄪ࡭ࡓࠋᆅ☢Ẽほ ࡟ࡼࡗ࡚㢖⦾࡟࡜ࡽ࠼ࡽࢀࡿ ULF ࿘Ἴᩘᖏࡢᆅ☢Ẽ⬦ືࡀ☢ ຊ⥺ඹ㬆᣺ື (field line resonance: FLR) ⓗ࡞ᛶ㉁ࢆᣢࡘࡇ࡜ࡣྂࡃ࠿ࡽ▱ࡽࢀ࡚࠾ࡾ[7]ࠊࡇࡢඹ 㬆᣺ືᩘࢆᆅ☢Ẽࢹ࣮ࢱ࠿ࡽᢳฟࡋࠊ☢Ẽᅪ㉥㐨㠃࡟࠾ࡅࡿࣉࣛࢬ࣐㉁㔞ᐦᗘࢆ᥎ᐃࡍࡿࠋᆅୖ ☢ሙほ ࡣேཱྀ⾨ᫍ࡟ࡼࡿᏱᐂࣉࣛࢬ࣐ࡢ┤᥋ほ ࡟ẚ࡭Ᏻ౯࡟ከⅬほ ⥙ࡀᒎ㛤࣭⥔ᣢ࡛ࡁࠊ 㛗ᮇほ ࡟ࡼࡗ࡚ኴ㝧άືᗘ࡜ࡢ㛵㐃࡞࡝ࢆㄪ࡭ࡿ㝿࡟᭷฼࡛࠶ࡿࠋᡃࠎࡣ 2010 ᖺᗘ࠿ࡽࢽ࣮ࣗ ࢪ࣮ࣛࣥࢻᆅ☢Ẽほ ⥙ࡢᩚഛࢆጞࡵ࡚࠾ࡾࠊᮏ◊✲ࡣࡑࡢࡓࡵࡢணഛゎᯒⓗ࡞ព⩏ࡶ࠶ࡿࠋ. 㸬ほ ᡭἲ ᆅ☢Ẽほ ࡟ࡼࡗ࡚ᚓࡽࢀࡓ ULF ࿘Ἴᩘᖏࡢᆅ☢Ẽ⬦ື࠿ࡽࣉࣛࢬ࣐㉁㔞ᐦᗘࢆぢ✚ࡶࡿࡓࡵ ࡟ࡣࠊᆅ☢Ẽほ Ⅼ࣌࢔ࢆ㑅ࡧࠊᆅ☢Ẽࢹ࣮ࢱ࠿ࡽ FLR ඹ㬆࿘Ἴᩘࢆྠᐃࡍࡿࠋḟ࡟Ἴື᪉⛬ᘧ ࢆゎࡃࡓࡵ࡟㐺ࡋࡓᆅ☢Ẽࣔࢹࣝ࡜ࣉࣛࢬ࣐ᐦᗘศᕸࣔࢹࣝࢆ㑅ᢥࡋࡓୖ࡛ࠊἼື᪉⛬ᘧࢆゎ࠸ ࡚ほ ࠿ࡽᚓࡓඹ㬆࿘Ἴᩘࢆㄝ᫂ࡍࡿࣉࣛࢬ࣐㉁㔞ᐦᗘࢆồࡵࡿࠋ௨ୗࠊྛᡭ㡰ࡢヲ⣽ࢆㄝ᫂ࡍ ࡿࠋ. ᆅ☢Ẽほ Ⅼ࣌࢔ࡢ㑅ᢥ ௒ᅇゎᯒ࡟⏝࠸ࡓᆅ☢Ẽࢹ࣮ࢱࡣ໭⡿࡟ᒎ㛤ࡉࢀࡓ the Magnetometers along the Eastern Atlantic Seaboard for Undergraduate Research and Education (MEASURE) ほ ⥙ࡢ Clarkson University (CLK, ⦋ᗘ 44.7°N, ⤒ᗘ 285.0°, L ್ 3.1Re)ࠊMillstone Hill (MSH, 42.6°N, 288.5°, 2.8Re)ࠊThe Johns Hopkins University Applied Physics Laboratory (APL, 39.2°N, 283.1°, 2.4Re)ࡢ 3 ほ Ⅼ࡛ᚓࡽࢀࡓࡶ ࡢ࡛࠶ࡿࠋ࠸ࡎࢀࡢほ Ⅼ࡛ࡶࣇࣛࢵࢡࢫࢤ࣮ࢺᆺ☢ຊィࢆ⏝࠸࡚ᆅ☢Ẽ 3 ᡂศࢆ㸯⛊ẖ࡟グ㘓 ࡋ࡚࠾ࡾࠊᮏ◊✲࡛ࡣ H㸦༡໭㸧ᡂศࢆ౑⏝ࡋࡓࠋL ್࡜ࡣ☢ຊ⥺ࡀ᭱ࡶ㐲᪉࡟㞳ࢀࡓⅬࡢᆅ⌫ ୰ᚰ࠿ࡽࡢ㊥㞳࡛ࠊ༢఩ࡢ Re ࡣᆅ⌫༙ᚄ࡛࠶ࡿࠋࡇࢀࡽࡢほ Ⅼ࠿ࡽ⾲㸯࡟♧ࡍほ Ⅼ࣌࢔ࢆస ⾲ 1 cross-phase ゎᯒ࡟⏝࠸ࡓᆅ☢Ẽほ Ⅼ࣌࢔ ほ Ⅼྡ. ⦋ᗘ. ⤒ᗘ. L್. CLK-MSH. 43.7±1.1 °N. 286.8±1.8 °. 2.9±0.2 Re. MSH-APL. 40.9±1.7 °N. 285.8±2.7 °. 2.6±0.2 Re. .

(4) ࡗࡓࠋᕥ࠿ࡽほ Ⅼྡࡢ 3 ᩥᏐࢥ࣮ࢻࠊ࣌࢔ࡢ୰㛫ᆅⅬ࡟࠾ࡅࡿ⦋ᗘࠊ⤒ᗘࠊL ್ࢆ♧ࡋ࡚࠸ࡿࠋ ᮏ◊✲࡛⾜ࡗࡓゎᯒ࡛ࡣ☢Ẽᅪ㉥㐨㠃࡟࠾ࡅࡿࣉࣛࢬ࣐㉁㔞ᐦᗘࡀᚓࡽࢀࡿࡢ࡛ࠊࡇࡢࢹ࣮ࢱ ࢭࢵࢺ࠿ࡽࡣ☢Ẽᅪࡢ L=2.6, 2.9 Re ࡟࠾ࡅࡿࣉࣛࢬ࣐ᐦᗘࡀồࡵࡽࢀࡿࡇ࡜࡟࡞ࡿࠋ. )/5 ࿘Ἴᩘࡢྠᐃ ULF ⬦ື࠿ࡽ FLR ࿘Ἴᩘࢆྠᐃࡍࡿ࡟ࡣࠊほ Ⅼ࣌࢔㛫࡛᣺ᖜࡲࡓࡣ఩┦ྠኈࢆẚ㍑ࡍࡿࠋ FLR ᣺ᖜࡣඹ㬆Ⅼ࡛ᴟ኱࡜࡞ࡿᛶ㉁ࡀ࠶ࡿࠋࡲࡓࠊඹ㬆࿘Ἴᩘࡣ☢ຊ⥺ࡢ㛗ࡉ࡟౫Ꮡࡍࡿࡢ࡛ࠊ୍⯡ ⓗ࡟⦋ᗘࡢ␗࡞ࡿほ Ⅼ࡛ࡣ㧗⦋ᗘഃࡢほ Ⅼࡢ࡯࠺ࡀప࠸ඹ㬆࿘Ἴᩘࢆᣢࡘࠋࡑࡢࡓࡵほ Ⅼ ࣌࢔㛫ࡢ᣺ᖜẚࢫ࣌ࢡࢺࣝࡣ཮ᴟᏊᆺࡢ᭤⥺ࢆᥥࡁࠊ཮ᴟᏊࡢ୰㛫ࡲࡓࡣ㸯ࢆ㏻ࡿⅬࡀ࣌࢔ࡢ୰ 㛫ᆅⅬ࡟࠾ࡅࡿඹ㬆᣺ືᩘ࡜ࡋ࡚ᢳฟࡉࢀࡿࠋࡇࢀࡀ᣺ᖜẚἲࡲࡓࡣ gradient ἲ➼࡜࿧ࡤࢀࡿ᪉ ἲ࡛࠶ࡿ[8]ࠋࡲࡓࠊFLR ࡢ఩┦ࡣඹ㬆Ⅼࡢ๓ᚋ࡛኱ࡁࡃኚ໬ࡍࡿᛶ㉁ࡀ࠶ࡿࡢ࡛ࠊ㸰Ⅼ㛫ࡢ఩┦ ᕪࢫ࣌ࢡࢺࣝࡣ୰㛫ᆅⅬࡢඹ㬆᣺ືᩘࢆ୰ᚰ࡟ᴟ኱ࡲࡓࡣᴟᑠࢆ♧ࡍࠋࡇࢀࡀ cross-phase ἲࡢཎ ⌮࡛࠶ࡿ[9]ࠋ ᮏ◊✲࡛ࡣࠊgradient ἲࠊcross-phase ἲ୧᪉ࢆ౑ࡗ࡚ FLR ࿘Ἴᩘࢆྠᐃࡋࠊࡑࡢᕪࢆ࿘ἼᩘỴ ᐃୖࡢㄗᕪ⠊ᅖ࡜ࡋࡓࠋᅗ㸯ࡣ 2001 ᖺ 4 ᭶ 27 ᪥ 17:30-18:30 UT ࡟ CLK-MSH ࡛ほ ࡉࢀࡓᆅ☢ Ẽ H ᡂศࢹ࣮ࢱࢆ౑ࡗࡓゎᯒ౛࡛࠶ࡿࠋほ Ⅼࡢᆅ᪉᫬ࡣ LT = UT – 5 ᫬㛫࡞ࡢ࡛ṇ༗㐣ࡂࡢほ ࢹ࣮ࢱ࡛࠶ࡿࠋୖ࠿ࡽ CLK ࡢࣃ࣮࣡ࢫ࣌ࢡࢺࣝ(a)ࠊMSH ࡢࣃ࣮࣡ࢫ࣌ࢡࢺࣝ(b)ࠊCLK-MSH 㛫ࡢࢥࣄ࣮ࣞࣥࢫ(c)ࠊ఩┦ᕪ(d)ࠊࣃ࣮࣡ẚ(e) ࢆ♧ࡋ࡚࠾ࡾࠊᶓ㍈ࡣࡍ࡭࡚࿘Ἴᩘ࡛࠶ࡿࠋ0-23 mHz ࡢ⠊ᅖ࡛ࡣࢥࣄ࣮ࣞࣥࢫࡀ୍㈏ࡋ࡚ 0.9 ௨ୖࢆಖࡗ࡚࠾ࡾࠊCLK ࡜ MSH ࡟ඹ㏻ࡢಙྕࡀධᑕࡋ࡚ ࠸ࡿࡇ࡜ࡀఛ࠼ࡿࠋࡲࡓ఩┦ᕪ࡜ࣃ࣮࣡ẚ࡟ࡣ~14mHz ࿘㎶࡟≉ᚩⓗ࡞ᵓ㐀ࡀぢࡽࢀࡿࠋ఩┦ᕪ ࡣᴟᑠࢆ♧ࡋࠊࣃ࣮࣡ẚࡣప࿘Ἴᩘഃ࡛ᴟ኱ࠊ㧗࿘Ἴᩘഃ࡛ᴟᑠ࡜࡞ࡿ཮ᴟᏊᆺࡢኚ໬ࢆぢࡏ࡚ ࠸ࡿࡇ࡜࠿ࡽ CLK-MSH ୰㛫Ⅼࡢඹ㬆࿘Ἴᩘࢆ 14.5±0.2 mHz ࡜ྠᐃࡋࡓࠋ. ᆅ☢Ẽࣔࢹࣝࡢ㑅ᢥ ୖࡢᡭ㡰࡛☢ຊ⥺ඹ㬆࿘Ἴᩘࡀᚓࡽࢀࡓࡢ࡛ࠊḟ࡟Ἴື᪉⛬ᘧࢆゎ࠸࡚ほ ࡜୍⮴ࡍࡿඹ㬆࿘ Ἴᩘࢆ୚࠼ࡿࣉࣛࢬ࣐ᐦᗘࢆィ⟬ࡍࡿࠋFLR Ἴື᪉⛬ᘧࢆゎࡃࡓࡵ࡟ࡣ☢ຊ⥺ࡢᙧ≧࡜☢ሙᙉᗘ ࡢ᝟ሗࡀᚲせ࡛࠶ࡾࠊࡇࢀࡣࣔࢹࣝ࠿ࡽ୚࠼ࡿࠋᮏ◊✲࡛ࡣࠊẚ㍑ⓗ L ್ࡢప࠸(<3㸧ほ Ⅼ࣌࢔ ࢆ౑ࡗ࡚࠸ࡿࡓࡵࠊ཮ᴟᏊ☢ሙࣔࢹࣝࢆ฼⏝ࡋ࡚࠸ࡿࠋSinger et al. [10] ࡟ࡼࡿ࡜ࠊL<5 ࡛ࡣࠊ཮ ᴟᏊࡣẚ㍑ⓗⰋ࠸㏆ఝ࡛࠶ࡾࠊࢺࣟ࢖ࢲ࣮ࣝࣔࢻࡢඹ㬆࿘Ἴᩘ࡟࠾ࡅࡿㄗᕪࡣ 10 %௨ୗ࡛࠶ࡿࠋ. ࣉࣛࢬ࣐ᐦᗘศᕸࣔࢹࣝࡢ㑅ᢥ FLR Ἴື᪉⛬ᘧࢆゎࡃ࡟ࡣ☢ຊ⥺ἢ࠸ࡢࣉࣛࢬ࣐ᐦᗘศᕸࣉࣟࣇ࢓࢖ࣝࡶᚲせ࡛࠶ࡾࠊࡇࢀࡶ ࣔࢹࣝ࠿ࡽ୚࠼ࡿࠋᮏ◊✲࡛ࡣᆅ⌫୰ᚰ࠿ࡽࡢ㊥㞳㸸r ࡟ࡘ࠸࡚ᐦᗘࡀɏ ൌ ɏ௘௤ ‫ି ݎ‬௠ ࡛ኚ໬ࡍࡿᣦᩘ 㛵ᩘࣔࢹࣝࢆ⏝࠸ࡓࠋɏࡣ௵ពࡢⅬ࡟࠾ࡅࡿࣉࣛࢬ࣐㉁㔞ᐦᗘࠊɏ௘௤ ࡣ☢Ẽᅪ㉥㐨㠃࡟࠾ࡅࡿࣉࣛ ࢬ࣐㉁㔞ᐦᗘ࡛࠶ࡿࠋᣦᩘ m ࡣ Takahashi et al. [11] ࡢᥦ᱌ࡍࡿ-1㹼0 ࡟ᇶ࡙ࡁࠊm=-1 ࢆ᥇⏝ࡋࡓࠋ. .

(5) )/5 Ἴື᪉⛬ᘧࢆゎࡃ ᭱ᚋ࡟ FLR Ἴື᪉⛬ᘧࢆゎࡁࠊほ ࡜୍⮴ࡍࡿඹ㬆࿘Ἴᩘࢆ୚࠼ࡿࣉࣛࢬ࣐ᐦᗘࢆィ⟬ࡍࡿࠋ ᮏ◊✲࡛ࡣἼື᪉⛬ᘧࢆゎࡃ௦ࢃࡾ࡟ࠊࢺࣟ࢖ࢲ࣮ࣝࣔࢻᅛ᭷࿘ᮇࡢ㏆ఝᘧࢆ⏝࠸ࡓ[12]ࠋࡇࡢ㏆ ఝᘧ࡟ࡼࡿㄗᕪࡣࠊL = 2.66 ࡛ 0.9 %࡜ぢ✚ࡶࡽࢀ࡚࠸ࡿ[12]ࠋ2001 ᖺ 4 ᭶ 27 ᪥ 17:30-18:30 UT ࡟ ࠾ࡅࡿ CLK-MSH ࡢඹ㬆࿘Ἴᩘ 14.5±0.2 mHz ࡟ᑐᛂࡍࡿ㉥㐨㠃ࣉࣛࢬ࣐㉁㔞ᐦᗘࡣ 1360±40 amu/cc ࡛࠶ࡗࡓࠋ. 㸬ゎᯒ⤖ᯝ ゎᯒᮇ㛫ࡢᏱᐂኳẼᴫἣ ᮏ◊✲࡛ࡣ 2001 ᖺ 4 ᭶࡟Ⓨ⏕ࡋࡓ஧ࡘࡢ☢Ẽᔒ࡟క࠺ࣉࣛࢬ࣐ᐦᗘኚ໬ࢆㄪ࡭ࡿࡓࡵ࡟ࠊ4 ᭶ 20 ᪥࠿ࡽ 5 ᭶ 6 ᪥ࡢ 17 ᪥㛫࡟໭⡿኱㝣ࡢ୰⦋ᗘᖏ࡛ほ ࡉࢀࡓᆅ☢Ẽࢹ࣮ࢱࢆゎᯒࡋࡓࠋᅗ 2 ࡣヱᙜᮇ㛫ࡢᏱᐂኳẼᴫἣࢆ♧ࡍࢹ࣮ࢱ࡛࠶ࡿࠋୖ࠿ࡽኴ㝧㢼ࡢࣉࣟࢺࣥᐦᗘ(a)ࠊኴ㝧㢼㏿ᗘ(b)ࠊ ᝨᫍ㛫✵㛫☢ሙ (Interplanetary Magnetic Field: IMF) ᙉᗘ(c)ࠊᝨᫍ㛫✵㛫☢ሙ༡໭ᡂศ (IMF_Bzࠊ ໭ྥࡁࡀṇ) (d)ࠊDst ᣦᩘ(e)ࢆ♧ࡍࠋᶓ㍈ࡣ᪥௜࡛┠┒ࡣ UT ࡢ 0 ᫬ࢆ♧ࡍࠋ 4 ᭶ 21 ᪥ᚋ༙ࠊኴ㝧㢼ࣉࣟࢺࣥᐦᗘ࡜ IMF ᙉᗘࡀᛴ⃭࡟ୖ᪼ࡋࠊ⥆࠸࡚ IMF_Bz ࡣ኱ࡁࡃ㈇᪉ ྥ࡟᣺ࢀࠊ30 ᫬㛫࡯࡝<-10~-5 nT ࢆಖᣢࡋࡓࠋࡇࡢࡼ࠺࡞ኚ໬ࡣ㧗㏿ኴ㝧㢼ࡢ๓㠃࡟⏕ࡌࡿᅽ⦰ 㡿ᇦ࡟඾ᆺⓗࡔࡀࡇࡢ࢖࣋ࣥࢺ࡛ࡣኴ㝧㢼㏿ᗘࡣ 400~300 km/s ࡛⤊ጞࡋ࡚࠾ࡾࠊ㧗㏿ኴ㝧㢼ࡢ฿ 㐩ࡣ☜ㄆࡉࢀ࡞࠿ࡗࡓࠋኴ㝧㢼ࡣప㏿࡛࠶ࡗࡓࡀࠊIMF_Bz ࡀ༡ྥࡁ࡜࡞ࡗࡓࡇ࡜࡛☢Ẽᅪෆࡢᑐ ὶࢆᘬࡁ㉳ࡇࡋࡓࡢ࡛࠶ࢁ࠺ࠋ☢Ẽᔒࡢᣦᶆ࡛࠶ࡿ Dst ᣦᩘࡀ 21 ᪥ 23 ᫬௨㝆ᛴ⃭࡟ୗࡀࡾጞࡵࠊ. ᅗ 1 2001 ᖺ 4 ᭶ 27 ᪥ 17㸸30 -18㸸30 UT ࡟ CLK – MSH ࡛ほ ࡉࢀࡓ ᆅ☢Ẽኚື༡໭ᡂศࡢࢫ࣌ࢡࢺࣝゎᯒ⤖ᯝ. .

(6) 22 ᪥ 16 ᫬࡟ࡣ-102 nT ࡟㐩ࡋࡓࠋࡇࡢࡇ࡜࠿ࡽ 21 ᪥ 23 ᫬࠿ࡽ☢ẼᔒࡀⓎ⏕ࡋ࡚࠾ࡾ 22 ᪥ 16 ᫬ ࡲ࡛ࡀ୺┦ࠊࡑࢀ௨㝆ࡢᩘ᪥㛫ࡀᅇ᚟┦࡜ㄞࡳྲྀࢀࡿࠋࡇࡢ☢Ẽᔒࢆ౽ᐅୖࠕ☢Ẽᔒ㸯ࠖ࡜ࡋࡓࠋ 23 ᪥ᚋ༙࠿ࡽ 27 ᪥ࡲ࡛ࡢ㛫ࠊIMF_Bz ࡣᴫࡡ 0~5nT ࡢ㛫࡛᥎⛣ࡋ࡚࠾ࡾࠊ☢Ẽᔒ㸯ࡣ✜ࡸ࠿࡟ᅇ ᚟ࡋ࡚࠸ࡗࡓࠋ 28 ᪥࡟ධࡿ࡜෌ࡧኴ㝧㢼ࡢᨐ஘ࡀ฿㐩ࡍࡿࠋࡇࡢ࡜ࡁࡣኴ㝧㢼ࣉࣟࢺࣥᐦᗘࠊIMF ᙉᗘࠊኴ㝧㢼㏿ᗘࡍ࡭࡚ࡀᛴቑࡋࠊ඾ᆺⓗ࡞㧗㏿ኴ㝧㢼࡟ࡼࡿᅽ⦰ᵓ㐀ࡢ≉ᚩࢆ♧ࡋ࡚࠸ࡿࠋ୍᪉ IMF_Bz ࡣࡣࡌࡵ໭ྥࡁᡂศࢆ♧ࡋࠊࡢࡕ࡟༡ྥࡁ࡟㌿ࡌࡓࠋࡑࡢࡓࡵ Dst ᣦᩘࡣ 28 ᪥ 2 ᫬௨㝆୍᫬ⓗ࡟ ୖ᪼ࡋ࡚ 28 ᪥ 6 ᫬࡟ 41nT ࡟㐩ࡋࠊࡑࡢᚋᛴῶࡋ࡚ 29 ᪥ 4 ᫬࡟-47nT ࡟㐩ࡋࡓࠋࡇࡢࡇ࡜࠿ࡽࡲ ࡎኴ㝧㢼ືᅽࡢ㧗ࡲࡾ࡟ࡼࡗ࡚☢Ẽᅪ๓㠃ࡀᅽ⦰ࡉࢀࠊ28 ᪥ 6 ᫬࠿ࡽ 29 ᪥ 4 ᫬ࡀ☢Ẽᔒࡢ୺┦ࠊ ࡑࡢ࠶࡜ࢆᅇ᚟┦࡜ㄞࡳྲྀࡿࡇ࡜ࡀ࡛ࡁࡿࠋࡇࡢ☢Ẽᔒࢆࠕ☢Ẽᔒ 2ࠖ࡜ࡋࡓࠋ. ᅗ 2 4 ᭶ 20 ᪥࠿ࡽ 5 ᭶ 6 ᪥ࡢኴ㝧㢼ࣉࣟࢺࣥᐦᗘ(a), ኴ㝧㢼㏿ᗘ(b), IMF ᙉᗘ(c), IMF ༡໭ᡂศ(d), Dst ᣦᩘ(e). .

(7) ࣉࣛࢬ࣐ᐦᗘࡢ᪥᪥ኚ໬ ᅗ 3 ࡣ MSH-ALPࠊCLK-MSH ࡢࢹ࣮ࢱ࠿ࡽồࡵࡓ 2001 ᖺ 4 ᭶ 20 ᪥࠿ࡽ 5 ᭶ 6 ᪥ࡢࣉࣛࢬ࣐㉁㔞ᐦᗘ࡛࠶ࡿࠋࡑࢀࡒࢀ L=2.6 (a) ࡜ L=2.9 (b) ࡢ☢Ẽᅪ㉥㐨㠃࡟࠾ࡅࡿ್࡟┦ᙜࡍࡿࠋࢹ࣮ࢱࡢ ศᕸ࡟೫ࡾࡀ࠶ࡿࡢࡣ᫬ᢡࠊ☢ຊ⥺ඹ㬆᣺ືࡢ᳨ฟࡀᅔ㞴࡟࡞ࡿࡓࡵ࡛࠶ࡿࠋࡓ࡜࠼ࡤ㟁㞳ᒙ㟁 ᑟᗘࡀప࠸ኪ㛫ࡣ☢ຊ⥺ඹ㬆᣺ືࡢῶ⾶ࡀᙉࡃࠊ᳨ฟࡀᅔ㞴࡟࡞ࡿࠋࡲࡓࠊᆅ☢Ẽኚື࡟☢Ẽᅪ ᨐ஘ᡂศࡀ༟㉺ࡋࡓሙྜࠊ㏫࡟☢Ẽᅪ⎔ቃࡀ㟼✜㐣ࡂ࡚⬦ືࡢ࢚ࢿࣝࢠ࣮※ࡀᙅࡍࡂࡿሙྜࠊ☢ ຊ⥺ඹ㬆㡿ᇦࡢᖜࡀほ Ⅼ࣌࢔㛫ࡢ㊥㞳࡜኱ᖜ࡟␗࡞ࡿሙྜ࡞࡝࡟ࡣࠊ᫨ഃ࡛ࡶ᳨ฟࡀᅔ㞴࡜࡞ ࡿࠋ ࡣࡌࡵࡢᩘ᪥㛫ࠊࣉࣛࢬ࣐ᐦᗘࡣ⣙ 2000~2500 amu/cc (L=2.6)ࠊ1000~1300 amu/cc (L=2.9) ࡛୙ つ๎࡟᥎⛣ࡋ࡚࠸ࡿࠋ25 ᪥࡟ධࡿ࡜☢Ẽᔒ 1 ࡢ㛤ጞ࡟క࠸ࣉࣛࢬ࣐ᐦᗘࡀࢃࡎ࠿࡟ୗࡀࡿࡀࠊ L=2.9 ࡛ࡶ 800amu/cc ࢆୗᅇࡿࡇ࡜ࡣ࡞ࡃࠊ᏶඲࡞ᾐ㣗ࡣ㉳ࡇࡽ࡞࠿ࡗࡓ࡜ࡳࡽࢀࡿࠋ25 ᪥࠿ࡽ 27 ᪥ࡲ࡛ࡣ᪥୰ࡢᐦᗘୖ᪼࡜ࠊኪ㛫ほ ࡀ୙ྍ⬟࡞᫬㛫ᖏࡢᐦᗘపୗࢆ⧞ࡾ㏉ࡍࠋࡑࡋ࡚ 28 ᪥ ࡢ᪥୰ࣉࣛࢬ࣐ᐦᗘࡣᛴ⃭࡟ୖ᪼ࡋࠊࡑࢀ௨㝆ᐦᗘࡢ㧗࠸≧ែࡀಖࡓࢀࡿࠋࡍ࡞ࢃࡕ☢Ẽᔒ㸯ࡢ ᅇ᚟┦ᚋᮇ࠿ࡽ㐃⥆ⓗ࡞ᐦᗘୖ᪼ࡀ⾲ࢀጞࡵࠊ☢Ẽᔒ㸰ࡢ୺┦࡟ྜࢃࡏ࡚ᛴ⃭࡞ᐦᗘୖ᪼ࡀ㉳ࡇ ࡗ࡚࠸ࡓࠋࡇࡢ࢖࣋ࣥࢺ࡛ࡣ☢Ẽᔒ࡟క࠺୍⯡ⓗ࡞ࣉࣛࢬ࣐ᐦᗘࡢኚື࡜ࡣ඲ࡃ␗࡞ࡿኚ໬ࡀほ ࡉࢀࡓ࡜ゝ࠼ࡿࠋ. ᅗ 3 4 ᭶ 20 ᪥࠿ࡽ 5 ᭶ 6 ᪥ࡢ L=2.6 (a)࡜ L=2.9 (b)࡟࠾ࡅࡿࣉࣛࢬ࣐㉁㔞ᐦᗘ. .

(8) (a)MSHͲ APL(L=2.6). plasmamassdensity(amu/cc). 6000 5000 4000 3000 2000. y=473.3xͲ 5276.2 R²=0.954. 1000 0. 10. 14. 18. 22. UT (hour) (b)CLKͲ MSH(L=2.9). plasmamassdensity(amu/cc). 2500 2000 1500 1000. y=118.4xͲ 8.1 R²=0.870. 500 0. 10. 14. 18 UT (hour). 22. ᅗ 4 4 ᭶ 28 ᪥ࡢ L=2.6 (a)࡜ L=2.9 (b)࡟࠾ࡅࡿࣉࣛࢬ࣐㉁㔞ᐦᗘࡢ᫬㛫ኚ໬. .

(9) ࣉࣛࢬ࣐ᐦᗘࡢ༢఩᫬㛫ᙜࡓࡾኚ໬㔞 ḟ࡟ 4 ᭶ 25㸫28 ᪥ࡢ༢఩᫬㛫ᙜࡓࡾࡢࣉࣛࢬ࣐ᐦᗘୖ᪼⋡ࢆィ⟬ࡋࡓࠋᅗ 4 ࡣ 4 ᭶ 28 ᪥ࡢ L=2.6 (a) ࡜ L=2.9 (b) ࡟࠾ࡅࡿࣉࣛࢬ࣐ᐦᗘࡢ᫬㛫ኚ໬ࢆ♧ࡋ࡚࠸ࡿࠋᅗ୰ࡢ┤⥺ࡣࢹ࣮ࢱ࡟᭱ࡶࡼࡃ ୍⮴ࡍࡿ┤⥺ࢆ᭱ᑠ஧஌ἲ࡟ࡼࡾồࡵࡓࡶࡢ࡛ࠊࡑࡢഴࡁ࠿ࡽ 1 ᫬㛫࠶ࡓࡾࡢࣉࣛࢬ࣐ᐦᗘቑຍ 㔞ࡣ L=2.6 ࡛ 473 amu/cc/hourࠊL=2.9 ࡛ 118 amu/cc/hour ࡜⟬ฟࡉࢀࡓࠋྠᵝࡢゎᯒࢆ 4 ᭶ 25 ᪥~27 ᪥ࡢྛࢹ࣮ࢱ࡟ࡘ࠸࡚ࡶ⾜ࡗࡓ⤖ᯝࢆ⾲ 2 ࡟♧ࡍࠋẚ㍑ࡢࡓࡵࠊ㐣ཤࡢࢹ࣮ࢱゎᯒ◊✲ࡢ⤖ᯝࡶ ྜࢃࡏ࡚ᥖ㍕ࡋ࡚࠸ࡿࠋᮏ◊✲࡟ࡼࡿ 2001 ᖺ 4 ᭶ 28 ᪥ࡢほ ௨እࡣ࠸ࡎࢀࡶ☢Ẽᔒࡀᅇ᚟┦࡟ ධࡗࡓ┤ᚋ 1~3 ᪥ࡢᐦᗘୖ᪼ࢆㄪ࡭ࡓࡶࡢ࡛࠶ࡿࠋᡃࠎࡢ⤖ᯝࡶྵࡵࠊ࡯࡜ࢇ࡝ࡢゎᯒ⤖ᯝ࡛ྠ ୍࢖࣋ࣥࢺෆ࡛ࡣ L ್ࡢᑠࡉ࠸࡯࠺ࡀ༢఩᫬㛫ᙜࡓࡾࡢᐦᗘୖ᪼⋡ࡀ኱ࡁ࠸ࠋࡇࢀࡣ L ್ࡀ኱ࡁ ࠸☢᮰⟶࡯࡝㛗ࡃࠊ㟁㞳ᅪ࡟࠾ࡅࡿ༢఩㠃✚ᙜࡓࡾࡢయ✚ࡶ኱ࡁࡃ࡞ࡿࡓࡵ࡜⪃࠼ࡽࢀࡿ[14]ࠋ ࡲࡓࠊ௒ᅇゎᯒࡋࡓ⤖ᯝࡢ࠺ࡕ 4 ᭶ 25 ᪥㹼27 ᪥ࡢᐦᗘୖ᪼⋡ࡣ㐣ཤࡢゎᯒ⤖ᯝ࡜ྠ⛬ᗘࡢ኱ ࡁࡉ࡛࠶ࡗࡓࡢ࡟ᑐࡋࠊ4 ᭶ 28 ᪥ࡢᐦᗘୖ᪼⋡ࡣ✺ฟࡋ࡚኱ࡁ࠿ࡗࡓࠋ2001 ᖺ 6 ᭶ 19 ᪥ࡢᐦᗘ ኚ໬ࡶྠ⛬ᗘ࡟኱ࡁ࠸ࡀࡇࡢ࢖࣋ࣥࢺ࡛ࡣ L ್ࡢ኱ࡁ࠸ほ Ⅼ࡛ࡼࡾ㧗࠸ୖ᪼⋡ࡀぢࡽࢀࠊ㏻ᖖ ࡜ࡣ㐪ࡗࡓᐦᗘୖ࣓᪼࢝ࢽࢬ࣒ࡀാ࠸࡚࠸ࡓࡢ࠿ࡶࡋࢀ࡞࠸ࠋ. ⾲ 2 ࣉࣛࢬ࣐ᐦᗘࡢ༢఩᫬㛫ᙜࡓࡾኚ໬㔞 Source and Date. Increasing Rate of Plasma Mass Density. [amu/cc/hour]. L=2.0. L=2.3. L=2.6. L=3.1. L=3.3. L=3.8. 25 Apr 2001. -. -. 181. 40. -. -. -. 26 Apr 2001. -. -. 52. 33. -. -. -. 27 Apr 2001. -. -. 79. 58. -. -. -. 28 Apr 2001. -. -. 473. 118. -. -. -. 200. -. -. -. -. -. -. 11 Mar 2004. -. 248. 110. -. -. 25 Apr 2001. -. -. -. 27. 19. -. -. 26 Apr 2001. -. -. -. 32. 23. -. -. 18 Jun 2001. -. -. -. 46. 70. -. -. 19 Jun 2001. -. -. -. 98. 106. -. -. L=2.9. Our Observation. Chi et al., 2000 25 Sep 1998 Obana et al., 2010. . 39. 13.

(10) 㸬⪃ᐹ. ᮏ◊✲ࡢゎᯒ⤖ᯝ࠿ࡽࠊ☢Ẽᔒ㸰ࡢ୺┦ᮇ㛫࡟࠶ࡓࡿ 4 ᭶ 28 ᪥࡟✺ฟࡋ࡚኱ࡁ࡞ࣉࣛࢬ࣐ᐦᗘ ୖ᪼⋡ࡀほ ࡉࢀࡓࠋࡋ࠿ࡋࡣࡌࡵ࡟㏙࡭ࡓࡼ࠺࡟ࠊ☢Ẽᅪᑐὶࡢᾘ㛗࡜㐃ືࡋ࡚㉳ࡇࡿࣉࣛࢬ ࣐ᅪࡢᐦᗘኚືࡣ㏻ᖖࠊᑐὶࡢⓎ㐩࡜࡜ࡶ࡟ᐦᗘపୗࢆ㉳ࡇࡍࠋᮏ◊✲ࡢゎᯒᮇ㛫࡟ᖖ࡜ࡣ㏫ࡢ ᐦᗘኚ໬ࡀ㉳ࡇࡗ࡚࠸ࡓ⌮⏤ࢆ⪃ᐹࡍࡿࠋ. ኴ㝧㢼ືᅽࡢᛴቑ࡟ࡼࡿ☢Ẽᅪ๓㠃ࡢᅽ⦰ ᅗ 2 ࡛♧ࡋࡓࡼ࠺࡟ 28 ᪥ࡢࡣࡌࡵࠊኴ㝧㢼ࡢᐦᗘ࣭㏿ᗘࡀᛴ⃭࡟ୖ᪼ࡋ࡚࠸ࡿࠋࡇࢀ࡟ࡼࡾື ᅽࡀᛴቑࡋ☢Ẽᅪ๓㠃ࡀᅽ⦰ࡉࢀࡓ࡜⪃࠼ࡽࢀࡿࠋᐇ㝿 Dst ᣦᩘ࡟ࡶ 40 nT ࡢᛴ⃭࡞ୖ᪼ࡀほ ࡉࢀ࡚࠾ࡾࠊࡇࡢᅽ⦰ࡢᙳ㡪࡛᫨ഃࣉࣛࢬ࣐ᅪࡶᅽ⦰ࡉࢀᐦᗘࡢᛴୖ᪼ࡀ㉳ࡇࡗࡓࡢ࠿ࡶࡋࢀ࡞ ࠸ࠋࡋ࠿ࡋኴ㝧㢼ືᅽኚ໬ࡀ L=2~3 ࡯࡝ࡢ῝ෆ㒊☢Ẽᅪࡲ࡛ᅽ⦰ࡋࡓ࡜⪃࠼ࡿࡢࡣ㞴ࡋ࠸ࠋࡲࡓ ᅽ⦰㐣⛬ࡢ⤊஢ᚋࡣࣉࣛࢬ࣐ᐦᗘࡣ㧗Ṇࡲࡾࡍࡿ࡜⪃࠼ࡽࢀࡿࡀࠊᐇ㝿࡟ࡣ Dst ᣦᩘࡢ❧ࡕୖࡀ ࡾᚋ 20 ᫬㛫௨ୖ࡟ࢃࡓࡗ࡚⥅⥆ⓗ࡟ᐦᗘୖ᪼ࡀほ ࡉࢀ࡚࠾ࡾࠊࡇࢀࢆㄝ᫂ࡍࡿࡢࡣ㞴ࡋ࠸࠿ࡶ ࡋࢀ࡞࠸ࠋ. ᑐὶ࡟ࡼࡿኪഃ࠿ࡽࡢࣉࣛࢬ࣐ὶධ ☢Ẽᅪᑐὶࡣ☢Ẽᅪᑿ㒊࠿ࡽ᫨ഃ࡬ྥࡅ࡚኱つᶍ࡞ࣉࣛࢬ࣐࡜☢᮰⟶ࡢ㐠ືࢆᘬࡁ㉳ࡇࡍࡢ࡛ࠊ ࣉࣛࢬ࣐ᅪᾐ㣗ࡢึᮇẁ㝵࡛ኪഃࡢࣉࣛࢬ࣐ᅪ⏺㠃ࡀෆഃ࡬ධࡾ㎸ࡴࠋࡇࡢࡇ࡜ࡣほ ࠿ࡽࡶ☜ ࠿ࡵࡽࢀ࡚࠸ࡿࡀ[15]ࠊ᫨ഃ᪉ྥ࡬⛣㏦ࡉࢀࡓࣉࣛࢬ࣐ࡀࡑࡢᚋ࡝ࡇ࠿ࡽ࡝ࡢࡼ࠺࡟ᾘ㈝ࡉࢀࡿࡢ ࠿ࠊ࠸ࡲࡔ᫂ࡽ࠿࡟ࡣ࡞ࡗ࡚࠸࡞࠸ࠋᮏ◊✲࡛ほ ࡉࢀࡓ 4 ᭶ 28 ᪥ࡢࣉࣛࢬ࣐ᐦᗘୖ᪼ࡣࠊኪഃ ࠿ࡽࡢࣉࣛࢬ࣐ࡢ㍺㏦࡟ࡼࡿࡶࡢ࠿ࡶࡋࢀ࡞࠸ࠋIMF ࡢ༡ྥࡁᡂศ࡜ Dst ᣦᩘࠊ࡝ࡕࡽࡢᣦᶆࡶ ☢Ẽᅪᑐὶࡀᑡ࡞ࡃ࡜ࡶ 29 ᪥ࡢึࡵࡈࢁࡲ࡛ࡣ⥅⥆ࡋ࡚࠸ࡓࡇ࡜ࢆ♧ࡋ࡚࠾ࡾࠊ⥅⥆ⓗ࡞ࣉࣛࢬ ࣐౪⤥ࡀྍ⬟࡛࠶ࡗࡓࡇ࡜ࢆ♧၀ࡋ࡚࠸ࡿࠋࡋ࠿ࡋ࡞ࡀࡽࠊࡇࡢࣔࢹ࡛ࣝࡣᮅ᪉ࡸኤ᪉㡿ᇦ࡬ࡢ ࣉࣛࢬ࣐౪⤥ࡣᐜ࡛᫆࠶ࡿࡀࠊṇ༗௜㏆ࡢ㡿ᇦ࡬౪⤥ࡍࡿࡢࡣ㞴ࡋ࠸࠿ࡶࡋࢀ࡞࠸ࠋ௒ᚋࣔࢹࣝ ィ⟬➼ࢆ⾜ࡗ࡚☜ㄆࡍࡿᚲせࡀ࠶ࡿࡔࢁ࠺ࠋ. ᑐὶ࡟ࡼࡿඹᅇ㌿㏿ᗘࡢ㐜ᘏ ☢Ẽᅪᑐὶࡢቑ኱࡟ࡼࡿࡶ࠺ࡦ࡜ࡘࡢᙳ㡪࡜ࡋ࡚ࠊ༗ᚋഃ࡟࠾ࡅࡿ☢᮰⟶ࡢඹᅇ㌿ࡢ㐜ᘏࢆ⪃ ࠼ࡿࠋ☢Ẽᅪෆࡢ☢᮰⟶ࡢ㐠ືࡣ☢Ẽᅪᑐὶ㟁ሙ࡜ඹᅇ㌿㟁ሙࡢ㔜ࡡྜࢃࡏ࡛⏕ࡲࢀࡿ㟁ሙ࡟ᨭ 㓄ࡉࢀࠊඹᅇ㌿ࡀᨭ㓄ⓗ࡞ࣉࣛࢬ࣐ᅪෆ࡟࠾࠸࡚ࡶ☢᮰⟶ࡢᅇ㌿㏿ᗘࡣ 10㸣⛬ᗘඹᅇ㌿࠿ࡽ㐜ࢀ ࡚࠸ࡿ[16]ࠋ☢Ẽᅪᑐὶࡣ༗ᚋഃࡢඹᅇ㌿ࢆጉࡆࡿ᪉ྥ࡟ാࡃࡢ࡛ࠊᑐὶࡀᙉࡲࢀࡤࡇࡢ㐜ᘏࡣࡉ. .

(11) ࡽ࡟ቑ኱ࡍࡿࠋࡑࡢ⤖ᯝࠊ༗ᚋഃ࡛ࡣᆅୖࡢࠕᐃⅬほ ࡛ࠖᮾഃ࠿ࡽࡎࢀ࡚ࡁࡓ☢᮰⟶ࢆほ ࡋ ࡚࠸ࡿࡇ࡜࡟࡞ࡾࠊ㟁㞳ᅪ࠿ࡽࡢࣉࣛࢬ࣐౪⤥㔞ࡀ୍ᐃ࡛ࡶࣉࣛࢬ࣐ᐦᗘୖ᪼⋡ࡀぢ࠿ࡅୖࠊୖ ᪼ࡍࡿ࡜⪃࠼ࡽࢀࡿࠋ. ௒ᚋࡢㄢ㢟 4 ᭶ 28 ᪥ࡢࣉࣛࢬ࣐ᐦᗘ␗ᖖୖ᪼ࢆᐃᛶⓗ࡟ㄝ᫂ࡍࡿ࠸ࡃࡘ࠿ࡢࣔࢹࣝࢆ⪃ᐹࡋࡓࠋࡍ࡛࡟㏙ ࡭ࡓࡼ࠺࡟ࠊ࠸ࡎࢀ࠿୍ࡘࡢࣔࢹ࡛ࣝ༑ᩘ᫬㛫࡟ࢃࡓࡗ࡚⥅⥆ࡉࢀࡓᐦᗘୖ᪼ࢆㄝ᫂ࡍࡿࡢࡣ㞴 ࡋࡃࠊ࠸ࡃࡘ࠿ࡢ࣓࢝ࢽࢬ࣒ࡢ」ྜ࡜⪃࠼ࡓ࡯࠺ࡀࡼ࠸࠿ࡶࡋࢀ࡞࠸ࠋ௒ᚋ࡯࠿ࡢ⤒ᗘ⥺ࡢほ ࢹ࣮ࢱࡸ㟁Ꮚᐦᗘኚ໬➼࡜ẚ㍑ࡋ࡚඲⌫ⓗ࡞ᐦᗘኚ໬ࢆㄪ࡭ࡿᚲせࡀ࠶ࢁ࠺ࠋ ࡲࡓࠊኪഃࣉࣛࢬ࣐ᅪ⏺㠃ࡢ⛣ືࡸ༗ᚋഃ࡛ࡢඹᅇ㌿㐜ᘏࡣࠊࣉࣛࢬ࣐ᅪᾐ㣗ᮇ࡟࠾ࡅࡿࣉࣛ ࢬ࣐ὶኻ㐣⛬ࢆ⪃࠼ࡿୖ࡛㔜せ࡛ࠊኪഃࡢࣉࣛࢬ࣐ࡀ࡝ࡇࡲ࡛㐩ࡋࠊࡑࡢᚋ࡝ࡇ࠿ࡽ࡝ࡢࡼ࠺࡟ ὶฟࡍࡿࡢ࠿࠸ࡲࡔ᫂ࡽ࠿࡟࡞ࡗ࡚࠸࡞࠸ࠋᡃࠎࡢゎᯒ⤖ᯝࡣኪഃࡢࣉࣛࢬ࣐ࡀ᫨ഃ࡟୍᪦྿ࡁ ᐤࡏࡽࢀ࡚࠸ࡿࡇ࡜ࢆ♧၀ࡋ࡚࠸ࡿࠋࡉࡽ࡟ 29 ᪥௨㝆ࣉࣛࢬ࣐ᐦᗘࡀ㧗Ṇࡲࡾࡋ࡚࠸ࡿࡇ࡜࠿ࡽࠊ ὶฟ࣓࢝ࢽࢬ࣒ࡀసືࡍࡿࡓࡵ࡟ࡣఱࡽ࠿ࡢ᮲௳ࡸ㜈್ࡀ࠶ࡾࠊࡇࡢ࢖࣋ࣥࢺ࡛ࡣసືࡋ࡞࠿ࡗ ࡓྍ⬟ᛶࡶ♧၀ࡋ࡚࠸ࡿࠋ☢Ẽᔒ㸰ࡣ Dst ᣦᩘࡢ᭱ᑠ್ࡀ ̺47nT ࡟‶ࡓ࡞࠸ᑠつᶍ࡞☢Ẽᔒ࡛ ࠶ࡿࡇ࡜ࡀ㛵ಀࡋ࡚࠸ࡓࡢ࠿ࡶࡋࢀ࡞࠸ࠋ௒ᚋࡉࡽ࡟ゎᯒ౛ࢆቑࡸࡋࠊ᫂ࡽ࠿࡟ࡍࡿ࡭ࡁㄢ㢟࡛ ࠶ࡿࠋ. 㸬ࡲ࡜ࡵ 2001 ᖺ 4 ᭶ 20 ᪥࠿ࡽ 5 ᭶ 6 ᪥࡟໭⡿኱㝣ࡢ୰⦋ᗘᖏ࡛ほ ࡉࢀࡓᆅ☢Ẽࢹ࣮ࢱࢆゎᯒࡋ L=2.6, 2.9 ࡢ☢᮰⟶࡟࠾ࡅࡿ 17 ᪥㛫ࡢࣉࣛࢬ࣐ᐦᗘኚ໬ࢆㄪ࡭ࡓࠋࡇࡢᮇ㛫࡟ࡣ 4 ᭶ 21 ᪥࡜ 28 ᪥࡟஧ ࡘࡢ☢ẼᔒࡀⓎ⏕ࡋ࡚࠸ࡿࠋ୍ࡘ┠ࡢ☢Ẽᔒ࡛ࡣࣉࣛࢬ࣐ᐦᗘࡣࢃࡎ࠿࡟ῶᑡࡋࠊᅇ᚟┦㛤ጞ 4 ᪥┠࠿ࡽ෌඘ሸ࡜ࡳࡽࢀࡿ㐃⥆ⓗ࡞ᐦᗘୖ᪼ࡀぢࡽࢀࡓࠋᖹᆒⓗ࡞ᐦᗘୖ᪼⋡ࡣ L=2.6 ࡛ 50~180 amu/cc/hࠊL=2.9 ࡛ 30~60 amu/cc/h ࡛࠶ࡗࡓࠋࡇࢀࡣ㐣ཤ࡟ほ ࡉࢀࡓ☢Ẽᅪᅇ᚟┦࡟࠾ࡅࡿࣉࣛ ࢬ࣐ᅪ෌඘ሸ⋡࡜࡯ࡰ୍⮴ࡍࡿࠋ୍᪉ 4 ᭶ 28 ᪥࡟ጞࡲࡗࡓ☢Ẽᔒ࡛ࡣࣉࣛࢬ࣐ᐦᗘࡢῶᑡࡣぢࡽ ࢀࡎࠊ㏫࡟ 28 ᪥࡟ᛴ⃭࡞ࣉࣛࢬ࣐ᐦᗘࡢୖ᪼ࡀほ ࡉࢀࡓࠋࣉࣛࢬ࣐ᐦᗘୖ᪼⋡ࡣ L=2.6 ࡛ 473 amu/cc/hࠊL=2.9 ࡛ 118 amu/cc/h ࡟㐩ࡋ࡚࠾ࡾࠊ㐣ཤࡢ◊✲࡜ẚ㍑ࡋ࡚ࡶ✺ฟࡋ࡚㧗࠸ୖ᪼⋡࡛࠶ ࡗࡓࠋ ☢Ẽᔒ㛤ጞᚋ࡟␗ᖖ࡟㧗࠸ࣉࣛࢬ࣐ᐦᗘୖ᪼ࡀ⏕ࡌࡓ⌮⏤ࢆ⪃࠼ࡿࡓࡵ࡟ࠊኴ㝧㢼ືᅽࡢᛴቑ ࡟ࡼࡿ☢Ẽᅪ๓㠃ࡢᅽ⦰ࠊᑐὶ࡟ࡼࡿኪഃ࠿ࡽࡢࣉࣛࢬ࣐ὶධࠊᑐὶ࡟ࡼࡿඹᅇ㌿㏿ᗘࡢ㐜ᘏࡢ 3 ࡘࡢࣔࢹࣝࢆ⪃ᐹࡋࡓࠋኪഃ࠿ࡽࡢࣉࣛࢬ࣐ὶධ࡜ඹᅇ㌿㏿ᗘࡢ㐜ᘏࡣࠊᐦᗘୖ᪼ࡀ༑ᩘ᫬㛫 ⥅⥆ⓗ࡟⥆࠸ࡓࡇ࡜ࢆᐃᛶⓗ࡟ࡼࡃㄝ࡛᫂ࡁࡿࠋ௒ᅇᚓࡽࢀࡓ⤖ᯝࡣ☢Ẽᔒ㛤ጞᚋࠊኪഃ࠿ࡽ᫨ ഃ࡬ࣉࣛࢬ࣐ࡀ⛣㏦ࡉࢀࠊ༗ᚋഃ࡛ࡼ࡝ࡳࢆᙧᡂࡋࡓࡇ࡜ࢆ♧ࡋ࡚࠸ࡿࡢ࠿ࡶࡋࢀ࡞࠸ࠋࡉࡽ࡟. .

(12) ௚ࡢ⤒ᗘ⥺ୖ࡛ࡶゎᯒࢆ㐍ࡵࠊ඲⌫ⓗ࡞ᐦᗘኚືࢆ᫂ࡽ࠿࡟ࡍࡿ࡜࡜ࡶ࡟ࠊࣔࢹࣝィ⟬ࢆ⾜࠸ᩘ 㔞ⓗẚ㍑◊✲ࢆ⾜ࡗ࡚ࣉࣛࢬ࣐ᅪࡢᾐ㣗㐣⛬࡟࠾ࡅࡿࣉࣛࢬ࣐ὶฟ⤒㊰ࢆゎ᫂ࡍࡿࡇ࡜ࡀ௒ᚋࡢ ㄢ㢟࡛࠶ࡿࠋ. ㅰ㎡ ᮏ◊✲䛷౑⏝䛧䛯ᆅ☢Ẽ䝕䞊䝍䛿㻹㻱㻭㻿㼁㻾㻱 ᆅ☢Ẽほ ⥙䛷ほ䛥䜜䚸㼁㻯㻸㻭 ᆅ☢Ẽ䝕䞊䝍䝉䞁䝍䞊䜢㏻䛨䛶౪⤥䛥䜜䜎䛧䛯䚹䝕䞊䝍䜢ᥦ౪䛔䛯䛰䛝䜎䛧䛯㻹㼍㼞㼗㻌㻹㼛㼘㼐㼣㼕㼚 ༤ኈ䛸䜹䝸䝣䜷䝹䝙䜰኱Ꮫ䝻䝃䞁䝊

(13) 䝹䝇ᰯᆅ⌫ᝨᫍ≀⌮Ꮫ◊✲ᡤ䛚䜘䜃ᆅ⌫Ᏹᐂ⛉Ꮫ⛉䛻ឤㅰ䛔䛯䛧䜎䛩䚹. ཧ⪃ᩥ⊩ [1] Park, C.G., “Whistler observation of the interchange of ionization between the ionosphere and the protonosphere”, J. of Geophys. Res., 75 (22), 4249-4260 (1970). [2] Chappell, C. R., K. K. Harris, and G. W. Sharp, “A Study of the Influence of Magnetic Activity on the Location of the Plasmapause as Measured by OGO 5”, J. of Geophys. Res., 75 (1), 50-56 (1970). [3] Nishida, A., “Formation of plasmapause, or magnetospheric plasma knee, by the combined action of magnetospheric convection and plasma escape from the tail”, J. Geophys. Res., 71, 5,669 (1966). [4] Park, C.G., “Some Features of Plasma Distribution in Plasmasphere Deduced from Antarctic Whistlers”, J. of Geophys. Res., 79 (1), 169-173 (1974). [5] Abe, T., B. A. Whalen, A. W. Yau, S. Watanabe, E. Sagawa, and K. I. Oyama, “Altitude profile of the polar wind velocity and its relationship to ionospheric conditions”, Geophysical Research Letters, 20(24), 2825-2828 (1993). [6] Krall, J., J. D. Huba, and J. A. Fedder, “Simulation of field-aligned H(+) and He(+) dynamics during late-stage plasmasphere refilling”, Annales Geophysicae, 26(6), 1507-1516 (2008). [7] Sugiura, M., and C. R. Wilson, “Oscillation of the Geomagnetic Field Lines and Associated Magnetic Perturbations at Conjugate Points”, J. of Geophys. Res., Vol. 69, pp.1211 (1964). [8] Baransky, L.N., Y.E. Borovkov, M.B. Gokhberg, and S.M. Krylov, “The Gradient-Method of Measuring the Resonance Frequencies of Magnetic-Field Lines”, Izvestiya Akademii Nauk Sssr Fizika Zemli (8), 74-91 (1985). [9] Waters, C.L., F.W. Menk, B.J. Fraser, and P.M. Ostwald, “Phase-Structure of Low-Latitude Pc3-4 Pulsations”, Planetary and Space Science, 39 (4), 569 (1991). [10] Singer, H.J., D.J. Southwood, R.J. Walker, and M.G. Kivelson, “Alfven wave resonances in a realistic magnetospheric magnetic field geometry”, J. of Geophys. Res., 86, 4589-4596 (1981). [11] Takahashi, K., R.E. Denton, R.R. Anderson, and W.J. Hughes, “Frequencies of standing Alfven wave harmonics and their implication for plasma mass distribution along geomagnetic field lines: Statistical analysis of CRRES data”, J. of Geophys. Res.-Space Physics, 109 (A8) (2004). [12] Vellante, M., and M. Forster, “Inference of the magnetospheric plasma mass density from field line. .

(14) resonances: A test using a plasmasphere model”, J. of Geophys. Res.-Space Physics, 111 (A11) (2006). [13] Chi, P.J., C.T. Russell, S. Musman, W.K. Peterson, G. Le, V. Angelopoulos, G.D. Reeves, M.B. Moldwin, and F.K. Chun, “Plasmaspheric depletion and refilling associated with the September 25, 1998 magnetic storm observed by ground magnetometers at L=2”, Geophysical Research Letters, 27 (5), 633-636 (2000). [14] Obana, Y., F. W. Menk, and I. Yoshikawa, “Plasma refilling rates for L=2.3-3.8 flux tubes”, J. of Geophys. Res.-Space Physics, 115, A03204, doi:10.1029/2009JAA014191 (2010). [15] Murakami, G., M. Hirai, and I. Yoshikawa, “The plasmapause response to the southward turning of the IMF derived from sequential EUV images”, J. of Geophys. Res.-Space Physics, 112(A6), 7 (2007). [16] Sandel, B. R., J. Goldstein, D. L. Gallagher, and M. Spasojevic, “Extreme Ultraviolet Imager observations of the structure and dynamics of the plasmasphere”, Space Science Reviews, 109(1-4), 25-46 (2003).. .

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