uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
The structure of an earthward propagating magnetic flux rope early in its evolution: comparison of methods
Show others and affiliations
2009 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, no 5, 2215-2224 p.Article in journal (Refereed) Published
Abstract [en]

We analyze a magnetic signature associated with the leading edge of a bursty bulk flow observed by Cluster at -19 R-E downtail on 22 August 2001. A distinct rotation of the magnetic field was seen by all four spacecraft. This event was previously examined by Slavin et al. (2003b) using both linear force-free modeling as well as a curlometer technique. Extending this work, we apply here single- and multi-spacecraft Grad-Shafranov (GS) reconstruction techniques to the Cluster observations and find good evidence that the structure encountered is indeed a magnetic flux rope and contains helical magnetic field lines. We find that the flux rope has a diameter of approximately 1 R-E, an axial field of 26.4 nT, a velocity of approximate to 650 km/s, a total axial current of 0.16 MA and magnetic fluxes of order 10(5) Wb. The field line twist is estimated as half a turn per RE. The invariant axis is inclined at 40 degrees to the ecliptic plane and 10 degrees to the GSM equatorial plane. The flux rope has a force-free core and non-force-free boundaries. When we compare and contrast our results with those obtained from minimum variance, single-spacecraft force-free fitting and curlometer techniques, we find in general fair agreement, but also clear differences such as a higher inclination of the axis to the ecliptic. We further conclude that single- spacecraft methods have limitations which should be kept in mind when applied to THEMIS observations, and that non-force-free GS and curlometer techniques are to be preferred in their analysis. Some properties we derived for this earthward - moving structure are similar to those inferred by Lui et al. (2007), using a different approach, for a tailward-moving flux rope observed during the expansion phase of the same substorm.

Place, publisher, year, edition, pages
2009. Vol. 27, no 5, 2215-2224 p.
Keyword [en]
Magnetospheric physics, Magnetotail, Storms and substorms, Space plasma physics, Magnetic reconnection
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-148331ISI: 000266406300038OAI: oai:DiVA.org:uu-148331DiVA: diva2:402104
Available from: 2011-03-07 Created: 2011-03-04 Last updated: 2011-03-07Bibliographically approved

Open Access in DiVA

No full text

By organisation
Swedish Institute of Space Physics, Uppsala Division
In the same journal
Annales Geophysicae
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 176 hits
ReferencesLink to record
Permanent link

Direct link