The University of Southampton
University of Southampton Institutional Repository

IMF control of cusp proton emission intensity and dayside convection: implications for component and anti-parallel reconnection

Lockwood, M., Lanchester, B.S., Frey, H.U., Throp, K., Morley, S.K., Milan, S.E. and Lester, M. (2003) IMF control of cusp proton emission intensity and dayside convection: implications for component and anti-parallel reconnection Annales Geophysicae, 21, (4), 955 -982.

Record type: Article


We study a brightening of the Lyman-? emission in the cusp which occurred in response to a short-lived southward turning of the interplanetary magnetic field (IMF) during a period of strongly enhanced solar wind plasma concentration. The cusp proton emission is detected using the SI-12 channel of the FUV imager on the IMAGE spacecraft. Analysis of the IMF observations recorded by the ACE and Wind spacecraft reveals that the assumption of a constant propagation lag from the upstream spacecraft to the Earth is not adequate for these high time-resolution studies. The variations of the southward IMF component observed by ACE and Wind allow for the calculation of the ACE-to-Earth lag as a function of time. Application of the derived propagation delays reveals that the intensity of the cusp emission varied systematically with the IMF clock angle, the relationship being particularly striking when the intensity is normalised to allow for the variation in the upstream solar wind proton concentration. The latitude of the cusp migrated equatorward while the lagged IMF pointed southward, confirming the lag calculation and indicating ongoing magnetopause reconnection. Dayside convection, as monitored by the SuperDARN network of radars, responded rapidly to the IMF changes but lagged behind the cusp proton emission response: this is shown to be as predicted by the model of flow excitation by Cowley and Lockwood (1992). We use the numerical cusp ion precipitation model of Lockwood and Davis (1996), along with modelled Lyman-? emission efficiency and the SI-12 instrument response, to investigate the effect of the sheath field clock angle on the acceleration of ions on crossing the dayside magnetopause. This modelling reveals that the emission commences on each reconnected field line 2–2.5min after it is opened and peaks 3–5 min after it is opened. We discuss how comparison of the Lyman-? intensities with oxygen emissions observed simultaneously by the SI-13 channel of the FUV instrument offers an opportunity to test whether or not the clock angle dependence is consistent with the “component” or the “anti-parallel” reconnection hypothesis.

PDF ang-21-955.pdf - Version of Record
Restricted to Repository staff only
Download (7MB)

More information

Published date: 2003
Keywords: magnetospheric physics, magnetopause, cusp and boundary layers, solar wind-magnetosphere interactions, space plasma physics, magnetic reconnection


Local EPrints ID: 37646
ISSN: 0992-7689
PURE UUID: dca990b7-edd6-4b0b-9625-26a7eb035b37

Catalogue record

Date deposited: 24 May 2006
Last modified: 17 Jul 2017 15:41

Export record


Author: M. Lockwood
Author: B.S. Lanchester
Author: H.U. Frey
Author: K. Throp
Author: S.K. Morley
Author: S.E. Milan
Author: M. Lester

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton:

ePrints Soton supports OAI 2.0 with a base URL of

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.