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Dayside reconnection under interplanetary magnetic field B y ‐dominated conditions: The formation and movement of bending arcs
Author(s) -
Carter J. A.,
Milan S. E.,
Fear R. C.,
Kullen A.,
Hairston M. R.
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020809
Subject(s) - physics , interplanetary magnetic field , polar , convection , arc (geometry) , flux (metallurgy) , interplanetary spaceflight , astrophysics , geophysics , ionosphere , magnetic field , solar wind , mechanics , geometry , astronomy , mathematics , materials science , quantum mechanics , metallurgy
Based upon a survey of global auroral images collected by the Polar Ultraviolet Imager, Kullen et al. (2002) subdivided polar cap auroral arcs into a number of categories, including that of “bending” arcs. We are concerned with those bending arcs that appear as a bifurcation of the dayside auroral oval and which subsequently form a spur intruding into the polar cap. Once formed, the spur moves poleward and antisunward over the lifetime of the arc. We propose that dayside bending arcs are ionospheric signatures of pulses of dayside reconnection and are therefore part of a group of transient phenomena associated with flux transfer events. We observe the formation and subsequent motion of a bending arc across the polar cap during a 30 min interval on 8 January 1999, and we show that this example is consistent with the proposed model. We quantify the motion of the arc and find it to be commensurate with the convection flows observed by both ground‐based radar observations and space‐based particle flow measurements. In addition, precipitating particles coincident with the arc appear to occur along open field lines, lending further support to the model.