| Project/Area Number |
14540416
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | Tohoku Intsitute of Technology |
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Principal Investigator |
NAKAGAWA Tomoko Tohoku Institute of Technology, Communication Engineering, Associate Professor, 工学部・通信工学科, 助教授 (40222161)
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| Project Period (FY) |
2002 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2003: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2002: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Keywords | CME / acceleration of solar wind / solar wind plasma / IMF / interplanetary space / non-spiral field / NOZOMI / SOHO / LASCO / 「SOHO」衛星 / 太陽風 / 惑星空間磁場 / ICME / 太陽風の加速 / 平面状磁場構造 / 宇宙天気予報 |
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| Research Abstract |
The speeds of propagation of CMEs in interplanetary space are less distributed than their initial speeds measured on their departure from the limb of the Sun. Gopalswamy et al.(2000, 2001) presented a linear relationship between initial speeds of limb CMEs and their average acceleration during their travel time in interplanetary space. The linear relationship suggests that some dragging force is acting on CMEs. If similar relationship holds within 20 solar radii from the Sun, it would give information on the initial speed of 'ambient' solar wind in the vicinity of the Sun. The relationship between the initial acceleration and the initial speeds of limb CMEs was examined by using SOHO/LASCO CME Catalogue. For the cases for which correlation coefficient was fairly good (from -0.6 to -I), the 'ambient' solar wind speed within 20 solar radii was estimated to be 150 -570 km/s. It is somewhat slower than but close to the speeds of real solar wind measured in interplanetary space.
Interplanetary counterparts of a halo CME which occurred on April 13, 1999, were observed by NOZOMI and ACE on April 16-18, when the two spacecraft were within 3 degrees in heliocentric longitude and 0.2 AU in heliocentric distance. The interplanetary magnetic fields had filamentary structures with large Bz components, and the Bz component was positive at NOZOMI while negative at ACE. Both magnetic fields were different from a magnetic cloud. It implies that the CME had a number of filamentary structures of magetic field lines with various directions. An interplanetary magnetic field of this kind can be used for detection of candidates of interplanetary counterparts of CMEs.
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