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

Provan, G.; Yeoman, T. K.

doi:10.1007/s00585-999-0855-1

Cited by 45 publications

(35 citation statements)

References 41 publications

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“…Ridley et al, 1998). Our findings also support Lockwood (1997) and Provan and Yeoman (1999), who considered cusp particle precipitation observations and plasma flow data and concluded that the ionospheric projection of the magnetopause X-line was wider than that predicted solely by cusp particle precipitation data (Newell and Meng, 1992).…”

Section: The Longitudinal Extent Of the Magnetopause Reconnection X-linesupporting

confidence: 87%

The location and rate of dayside reconnection during an interval of southward interplanetary magnetic field

et al. 2003

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Abstract. Using ionospheric data from the SuperDARN radar network and a DMSP satellite we obtain a comprehensive description of the spatial and temporal pattern of dayside reconnection. During a period of southward interplanetary magnetic field (IMF), the data are used to determine the location of the ionospheric projection of the dayside magnetopause reconnection X-line. From the flow of plasma across the projected X-line, we derive the reconnection rate across 7 h of longitude and estimate it for the total length of the Xline footprint, which was found to be 10 h of longitude. Using the Tsyganenko 96 magnetic field model, the ionospheric data are mapped to the magnetopause, in order to provide an estimate of the extent of the reconnection X-line. This is found to be ∼38 R E in extent, spanning the whole dayside magnetopause from dawn to dusk flank. Our results are compared with previously reported encounters by the Equator-S and Geotail spacecraft with a reconnecting magnetopause, near the dawn flank, for the same period. The SuperDARN observations allow the satellite data to be set in the context of the whole magnetopause reconnection X-line. The total potential associated with dayside reconnection was ∼150 kV. The reconnection signatures detected by the Equator-S satellite mapped to a region in the ionosphere showing continuous flow across the polar cap boundary, but the reconnection rate was variable and showed a clear spatial variation, with a distinct minimum at 14:00 magnetic local time which was present throughout the 30-min study period.

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Section: The Longitudinal Extent Of the Magnetopause Reconnection X-linesupporting

confidence: 87%

The location and rate of dayside reconnection during an interval of southward interplanetary magnetic field

et al. 2003

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“…While the range of MLT included in this survey is very large, extending well away from noon, 75% of time series are taken between 0800 and 1600 MLT with a peak around 1000 MLT. Our range of MLT is larger than that of Provan and Yeoman [1999] who observed PIFs from 0250 to 1650 MLT with the CUTLASS Finland radar (also with a peak around 1000 MLT). This is probably due to our inclusion of all suitable time series within the radar field of view at the time of PIFs.…”

Section: Methodscontrasting

confidence: 67%

A statistical analysis of ionospheric velocity and magnetic field power spectra at the time of pulsed ionospheric flows

Abel

Freeman

2002

J. Geophys. Res.

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[1] We analyze the power spectrum of the line-of-sight ionospheric velocity measured by the SuperDARN CUTLASS Finland radar and of contemporaneous magnetic field perturbations measured by nearby IMAGE magnetometers. The measurements come from 69-87°AACGM latitude and 0415-2230 MLT during 58 intervals of pulsed ionospheric flow between March 1995 and September 1996. The median power spectrum of both the velocity and magnetic field is of power law form with a best fit exponent of À0.5 and À1.3, respectively. By simulating the effect of the finite sample window on the measured spectral exponent and on the structure seen in the power spectral density of individual spectra, we show that the measured spectral exponent actually corresponds to a true exponent of À0.95 for the velocity and À1.8 for the magnetic field. Furthermore, it is shown that the difference in the exponents of the velocity and magnetic field spectra is at least in part due to a spatial smoothing effect that causes the spectral exponent of the ground magnetic spectrum to be less than that of the ionospheric current spectrum producing it. The power law power spectrum implies that there is no preferred timescale for ionospheric velocity and current fluctuations in the observed frequency range. It is proposed that this scale-free nature may arise from the intermittent, turbulent nature of the interplanetary magnetic field causing magnetic reconnection to occur at the magnetopause on a wide range of spatial and temporal scales.

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“…However, it is important here to attempt to clarify the nomenclature that has been used in previous publications for dayside transients observed by HF radars, and to justify the terminology adopted in this paper. As noted in the Introduction, three terms to describe such features are in current usage: flow channel events (FECs) (Pinnock et al, 1993Neudegg et al, 1999Neudegg et al, , 2000, pulsed ionospheric flows (PIFs) (Provan et al, 1998;Provan and Yeoman, 1999;McWilliams et al, 2000) and polewardmoving radar auroral forms (PMRAFs) (Wild et al, 2001). FCEs and PIFs, as their names suggest, describe bursts of enhanced flow in a background of slower-moving plasma.…”

Section: Cutlass Hf Observationsmentioning

confidence: 99%

“…These include many observations by the HF coherent scatter radars of the Super Dual Auroral Radar Network (SuperDARN) of dayside transients, which generally exhibit an antisunward motion. Dependant on their exact characteristics, and crucially, the parameter in which they are identified, these ionospheric transients have been termed flow channel events (FCEs) (Pinnock et al, 1993;1995;Neudegg et al, 1999;, pulsed ionospheric flows (PIFs) (Provan et al, 1998;Provan and Yeoman, 1999;McWilliams et al, 2000) or poleward-moving radar auroral forms (PMRAFs) (Wild et al, 2001). However, it has become increasingly evident that these three so-called forms of dayside transients are in fact very much related, and in some cases actually describe the same phenomena; this is discussed by Wild et al (2001) and in more detail later in the present paper.…”

Section: Introductionmentioning

confidence: 99%

Ground-based observations of the auroral zone and polar cap ionospheric responses to dayside transient reconnection

et al. 2002

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Abstract.Observations from the EISCAT VHF incoherent scatter radar system in northern Norway, during a run of the common programme CP-4, reveal a series of polewardpropagating F-region electron density enhancements in the pre-noon sector on 23 November 1999. These plasma density features, which are observed under conditions of a strongly southward interplanetary magnetic field, exhibit a recurrence rate of under 10 min and appear to emanate from the vicinity of the open/closed field-line boundary from where they travel into the polar cap; this is suggestive of their being an ionospheric response to transient reconnection at the dayside magnetopause (flux transfer events). Simultaneous with the density structures detected by the VHF radar, polewardmoving radar auroral forms (PMRAFs) are observed by the Finland HF coherent scatter radar. It is thought that PMRAFs, which are commonly observed near local noon by HF radars, are also related to flux transfer events, although the specific mechanism for the generation of the field-aligned irregularities within such features is not well understood. The HF observations suggest, that for much of their existence, the PMRAFs trace fossil signatures of transient reconnection rather than revealing the footprint of active reconnection itself; this is evidenced not least by the fact that the PMRAFs become narrower in spectral width as they evolve away from the region of more classical, broad cusp scatter in which they originate. Interpretation of the HF observations with reference to the plasma parameters diagnosed by the incoherent scatter radar suggests that as the PMRAFs migrate away from the reconnection site and across the polar cap, entrained in the ambient antisunward flow, the irregularities therein are generated by the presence of gradients in the electron density, with these gradients having been formed through structuring of the ionosphere in the cusp region in response to transient reconnection.

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

Cited by 45 publications

References 41 publications

The location and rate of dayside reconnection during an interval of southward interplanetary magnetic field

The location and rate of dayside reconnection during an interval of southward interplanetary magnetic field

A statistical analysis of ionospheric velocity and magnetic field power spectra at the time of pulsed ionospheric flows

Ground-based observations of the auroral zone and polar cap ionospheric responses to dayside transient reconnection

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