Examining Periodic Solar Wind Density Structures Observed in the SECCHI Heliospheric Imagers - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




Examining Periodic Solar Wind Density Structures Observed in the SECCHI Heliospheric Imagers - Astrophysics > Solar and Stellar Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: We present an analysis of small-scale, periodic, solar-wind densityenhancements length-scales as small as \approx 1000 Mm observed in imagesfrom the Heliospheric Imager HI aboard STEREO A. We discuss their possiblerelationship to periodic fluctuations of the proton density that have beenidentified at 1 AU using in-situ plasma measurements. Specifically, Viall,Kepko, and Spence 2008 examined 11 years of in-situ solar-wind densitymeasurements at 1 AU and demonstrated that not only turbulent structures, butalso non-turbulent periodic density structures exist in the solar wind withscale sizes of hundreds to one thousand Mm. In a subsequent paper, Viall,Spence, and Kasper 2009 analyzed the {\alpha} to proton solar-wind abundanceratio measured during one such event of periodic density structures,demonstrating that the plasma behavior was highly suggestive that eithertemporally or spatially varying coronal source plasma created those densitystructures. Large periodic density structures observed at 1 AU, which weregenerated in the corona, can be observable in coronal and heliosphericwhite-light images if they possess sufficiently high density contrast. Indeed,we identify such periodic density structures as they enter the HI field of viewand follow them as they advect with the solar wind through the images. Thesmaller periodic density structures that we identify in the images arecomparable in size to the larger structures analyzed in-situ at 1 AU, yieldingfurther evidence that periodic density enhancements are a consequence ofcoronal activity as the solar wind is formed.



Autor: Nicholeen M. Viall, Harlan E. Spence, Angelos Vourlidas, Russell Howard

Fuente: https://arxiv.org/







Documentos relacionados