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| Titel |
An analysis of the accuracy of magnetopause reconnection rate variations deduced from cusp ion dispersion characteristics |
| VerfasserIn |
M. Lockwood, C. J. Davis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 14, no. 2 ; Nr. 14, no. 2, S.149-161 |
| Datensatznummer |
250012165
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| Publikation (Nr.) |
 copernicus.org/angeo-14-149-1996.pdf |
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| Zusammenfassung |
| We present an analysis of the accuracy of the
method introduced by Lockwood et al. (1994) for the determination of the
magnetopause reconnection rate from the dispersion of precipitating ions in the
ionospheric cusp region. Tests are made by applying the method to synthesised
data. The simulated cusp ion precipitation data are produced by an analytic
model of the evolution of newly-opened field lines, along which magnetosheath
ions are firstly injected across the magnetopause and then dispersed as they
propagate into the ionosphere. The rate at which these newly opened field lines
are generated by reconnection can be varied. The derived reconnection rate
estimates are then compared with the input variation to the model and the
accuracy of the method assessed. Results are presented for steady-state
reconnection, for continuous reconnection showing a sine-wave variation in rate
and for reconnection which only occurs in square wave pulses. It is found that
the method always yields the total flux reconnected (per unit length of the
open-closed field-line boundary) to within an accuracy of better than 5%, but
that pulses tend to be smoothed so that the peak reconnection rate within the
pulse is underestimated and the pulse length is overestimated. This smoothing is
reduced if the separation between energy channels of the instrument is reduced;
however this also acts to increase the experimental uncertainty in the
estimates, an effect which can be countered by improving the time resolution of
the observations. The limited time resolution of the data is shown to set a
minimum reconnection rate below which the method gives spurious short-period
oscillations about the true value. Various examples of reconnection rate
variations derived from cusp observations are discussed in the light of this
analysis. |
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