High spatial and temporal resolution observations of the ionospheric cusp

Pinnock, M.; Rodger, A. S.; Dudeney, J. R.; Rich, F. J.; Baker, K. B.

doi:10.1007/s00585-995-0919-9

Cited by 132 publications

(122 citation statements)

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“…A key and unique prediction of this model is that patches of newly opened flux, produced by successive reconnection pulses, are appended to each other in a contiguous manner, causing discontinuous steps in the cusp ion dispersion on the boundaries between poleward moving events. The observation of these "cusp ion steps" in association with poleward moving events [Lockwood et al, 1993b;Pinnock et al, 1995] The two-dimensional reconnection pulse is similar in many ways to the flux rope model from which it evolved. Indeed, if the reconnection X line is short, this model can re-produce the "elbow" of newly opened field lines of the fossil flux tube model [Seinenov et al, 1995].…”

Section: Two-dimensional (2-d) Reconnection Pulse Modelmentioning

confidence: 82%

On the cause of a magnetospheric flux transfer event

Lockwood¹,

Hapgood²

1998

J. Geophys. Res.

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Abstract. We present a detailed investigation of a magnetospheric flux transfer event (FFE) seen by the Active Magnetospheric Tracer Explorer (AMPTE) UKS and IRM satellites around 1046 UT on October 28, 1984. This event has been discussed many times previously in the literature and has been cited as support for a variety of theories of FTE formation. We make use of a model developed to reproduce ion precipitations seen in the cusp ionosphere. The analysis confirms that the FTE is well explained as a brief excursion into an open low-latitude boundary layer (LLBL), as predicted by two theories of magnetospheric FTEs, namely, that they are bulges in the open LLBL due to reconnection rate enhancements or that they are indentations of the magnetopause by magnetosheath pressure increases (but in the presence of ongoing steady reconnection). The indentation of the inner edge of the open LLBL that these two models seek to explain is found to be shallow for this event. The ion model reproduces the continuous evolution of the ion distribution function between the sheath-like population at the event center and the surrounding magnetospheric populations; it also provides an explanation of the high-pressure core of the event as comprising field lines that were reconnected considerably earlier than those that are draped over it to give the event boundary layer. The magnetopause transition parameter is used to isolate a field rotation on the boundaries of the core, which is subjected to the tangential stress balance test. The test identifies this to be a convecting structure, which is neither a rotational discontinuity (Pal)) nor a contact discontinuity, but could possibly be a slow shock. In addition, evidence for ion reflection off a weak RD on the magnetospheric side of this structure is found. The event structure is consistent in many ways with features predicted for the open LLBL by analytic MHD theories and by MHD and hybrid simulations. The de HoffinanTeller velocity of the structure is significantly different from that of the magnetosheath flow, indicating that it is not an indentation caused by a high-pressure pulse in the sheath but is consistent with the motion of newly opened field lines (different from the sheath flow because of the magnetic tension force) deduced from the best fit to the ion data. However, we cannot here role out the possibility that the sheath flow pattern has changed in the long interval between the two satellites observing the FTE and subsequently emerging into the magnetosheath; thus this test is not conclusive in this particular case. Analysis of the fitted elapsed time since reconnection shows that the core of the event was reconnected in one pulse and the event boundary layer was reconnected in a subsequent pulse. Between these two pulses is a period of very low (but nonzero) reconnection rate, which lasts about 14 rains. Thus the analysis supports, but does not definitively verify, the concept that the FTE is a partial passage into an open LLBL caused by a traveling bulge in that layer pr...

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Section: Two-dimensional (2-d) Reconnection Pulse Modelmentioning

confidence: 82%

On the cause of a magnetospheric flux transfer event

Lockwood¹,

Hapgood²

1998

J. Geophys. Res.

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“…The identi®cation of high-speed¯ow bursts such as these has been the most commonly used method to identify pulsed cusp footprint signatures in the radar data in previous studies of the ionospheric footprint of the magnetospheric cusp (e.g. Pinnock et al, 1995;Rodger and Pinnock, 1997;Provan et al, 1998;Neudegg et al, 1999).…”

Section: Selecting the Pif Intervalsmentioning

confidence: 99%

A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HF radar

2000

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Abstract. Nearly two years of 2-min resolution data and 7-to 21-s resolution data from the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and repetition frequencies of pulsed ionospheric¯ows in the noon-sector high-latitude ionosphere. Pulsed ionospheric¯ow bursts are believed to be the ionospheric footprint of newly reconnected geomagnetic ®eld lines, which occur during episodes of magnetic¯ux transfer to the terrestrial magnetosphere ±¯ux transfer events or FTEs. The distribution of pulsed ionospheric¯ows were found to be well grouped in the radar ®eld of view, and to be in the vicinity of the radar signature of the cusp footprint. Two thirds of the pulsed ionospheric¯ow intervals included in the statistical study occurred when the interplanetary magnetic ®eld had a southward component, supporting the hypothesis that pulsed ionospheric¯ows are a reconnection-related phenomenon. The occurrence rate of the pulsed ionospheric¯ow¯uctuation period was independent of the radar scan mode. The statistical results obtained from the radar data are compared to occurrence rates and repetition frequencies of FTEs derived from spacecraft data near the magnetopause reconnection region, and to ground-based optical measurements of poleward moving auroral forms. The distributions obtained by the various instruments in di erent regions of the magnetosphere were remarkably similar. The radar, therefore, appears to give an unbiased sample of magnetopause activity in its routine observations of the cusp footprint.

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“…The e ect of the IMF B y component on this average distribution is discussed in Provan et al (1998). They showed that the statistical location of PIFs is strongly dependent on IMF conditions, moving to the pre-noon sector during intervals of positive IMF B y and into the post-noon sector during intervals of negative IMF B y .…”

Section: Statistical Characteristics Of Pifsmentioning

confidence: 99%

Statistical observations of the MLT, latitude and size of pulsed ionospheric flows with the CUTLASS Finland radar

Provan

Yeoman

1999

Ann. Geophys.

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Abstract. A study has been performed on the occurrence of pulsed ionospheric¯ows as detected by the CUTLASS Finland HF radar. These¯ows have been suggested as being created at the ionospheric footprint of newly-reconnected ®eld lines, during episodes of magnetic¯ux transfer into the terrestrial magnetosphere (¯ux transfer events or FTEs). Two years of both hightime resolution and normal scan data from the CUT-LASS Finland radar have been analysed in order to perform a statistical study of the extent and location of the pulsed ionospheric¯ows. We note a great similarity between the statistical pattern of the coherent radar observations of pulsed ionospheric¯ows and the traditional low-altitude satellite identi®cation of the particle signature associated with the cusp/cleft region. However, the coherent scatter radar observations suggest that the merging gap is far wider than that proposed by the Newell and Meng model. The new model for cusp low-altitude particle signatures, proposed by Lockwood and Onsager and Lockwood provides a uni®ed framework to explain the dayside precipitation regimes observed both by the low-altitude satellites and by coherent scatter radar detection.

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High spatial and temporal resolution observations of the ionospheric cusp

Cited by 132 publications

References 0 publications

On the cause of a magnetospheric flux transfer event

On the cause of a magnetospheric flux transfer event

A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HF radar

Statistical observations of the MLT, latitude and size of pulsed ionospheric flows with the CUTLASS Finland radar

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