The θBn problem: Determination of local magnetic parameters of interplanetary shocks from in situ IMF data
The angle θBn is the angle between the upstream magnetic field and the shock normal direction and is important for manyphenomena in interplanetary physics. We show that for most shock observations, θBn cannot be determined without addressing itsassociated uncertainty. We propose a...
| Autores: | , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2001 |
| País: | México |
| Institución: | Universidad Nacional Autónoma de México |
| Repositorio: | Redalyc-UNAM |
| OAI Identifier: | oai:redalyc.org:56840105 |
| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=56840105 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias de la Tierra MHD discontinuities interplanetary shocks Interplanetary physics |
| Sumario: | The angle θBn is the angle between the upstream magnetic field and the shock normal direction and is important for manyphenomena in interplanetary physics. We show that for most shock observations, θBn cannot be determined without addressing itsassociated uncertainty. We propose a simple computational technique to infer a more reliable value for θBn and its associateduncertainty. This technique is based on magnetic field data only, and can be useful when we cannot apply the iterative techniquesinvolving magnetic and plasma parameters. This method also can be applied to study other MHD discontinuities. To infer theshock local parameters, it is necessary to define upstream and downstream regions in the Rankine-Hugoniot relations. Fluctuationsof the interplanetary magnetic field, particularly its direction, restrict the duration of these regions to just a few minutesbefore and after the shock. Quasi-parallel shocks have larger associated uncertainties than quasi-perpendicular shocks. When θBnhas a large uncertainty, this angle becomes time dependent, i.e., does not have a well-defined value but varies within an angularrange. |
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