E-Print Archive

There are 4488 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
Global and local expansion of magnetic clouds in the inner heliosphere  

Adriana Maria Gulisano   Submitted: 2009-09-29 02:55

Observations of magnetic clouds (MCs) are consistent with the presence of flux ropes detected in the solar wind (SW) a few days after their expulsion from the Sun as Coronal Mass Ejections (CMEs). Both, the in situ observations of plasma velocity profiles and the increase of their size with solar distance show that MCs are typically expanding structures. The aim of this work is to derive the expansion properties of MCs in the inner heliosphere from 0.3 to 1 AU. We analyze MCs observed by the two Helios spacecraft using in situ magnetic field and velocity measurements. We split the sample in two subsets: those MCs with a velocity profile that are significantly perturbed from the expected linear profile and those which are not. From the slope of the in situ measured bulk velocity along the Sun-Earth direction, we compute an expansion speed with respect to the cloud center for each of the analyzed MCs. We analyze how the expansion speed depends on the MC size, the translation velocity, and the heliocentric distance, finding that all MCs in the subset of non-perturbed MCs expand with almost the same non-dimensional expansion rate (zeta).We find departures from this general rule for zeta only for perturbed MCs, and we interpret the departures as the consequence of a local and strong SW perturbation by SW fast streams, affecting the MC even inside its interior in addition to the direct interaction region between the SW and the MC. We also compute the dependence of the mean total SW pressure on the solar distance and we confirm that the decrease of the total SW pressure with distance is the main origin of the observed MC expansion rate. We found that zeta was 0.91 +-0.23 for non-perturbed MCs while zeta was 0.48 +- 0.79 for perturbed MCs, being the larger spread in the last ones due to the influence of solar wind local environment conditions on the expansion.

Authors: A. M. Gulisano, P. Démoulin, S. Dasso, M. E. Ruiz, and E. Marsch
Projects: None

Publication Status: Astronomy & Astrophysics, In press
Last Modified: 2009-09-30 08:09
Go to main E-Print page  Edit Entry  Download Preprint  Delete Entry 

Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
Global and local expansion of magnetic clouds in the inner heliosphere

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey

© 2000-2020 Solar Physics Group - Montana State University