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| Titel |
Measurement of electromotive force in the inner heliosphere |
| VerfasserIn |
Bernhard Hofer, Yasuhito Narita |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145790
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| Publikation (Nr.) |
 EGU/EGU2017-9761.pdf |
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| Zusammenfassung |
| Electromotive force plays an essential role in solar dynamo mechanism. We address the
question if the electromotive force ever operates in the inner heliosphere when a
magnetic cloud passes by, such as a coronal mass ejection (CME). In this work, we
use the magnetic field data and plasma data from the Helios-2 spacecraft in the
year 1978, where the spacecraft is at a radial distance of about 0.4 AU from the
Sun, to perform first-time measurements of the electromotive force in the inner
heliosphere.
We compare between two cases under which the electromotive force is likely in operation:
one in a quasi-stationary solar wind and the other in a transient solar wind with a magnetic
cloud. Our measurements show a short-time enhancement of the electromotive
force from roughly 10−4 V/m to several 10−3 V/m after the shock. These results
indicate that the electromotive force is in operation in the inner heliosphere and
is enhanced when a magnetic cloud or CME occurs. Our measurements open a
door to systematically investigate the electromotive force and its modeling with the
kinetic helicity effect (the so-called alpha term), the turbulent diffusion effect (beta
term), and the cross helicity effect (gamma term) in the mean-field dynamo theory. |
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