Variations in the polar cap area during two substorm cycles
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...It is now realized that many echoes from the E region have more than one spectral peak (known as two-peaked E-region echoes or TWOPEEs), and contain backscatter contributions from two or more of the echo types listed above (e.g. Milan et al. 2003a; Danskin et al. 2004)....
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...…which allow estimates of changes in polar cap area (such as those made by spacecraft auroral imagers), it is possible to estimate the magnetopause reconnection rate during the substorm growth phase, assuming there is little or no magnetotail reconnection (Lewis et al. 1998; Milan et al. 2003b)....
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...These echoes are characterized by particularly high backscatter power but appear to be sensitive to the radar operating frequency, being seen predominantly near 10–12 MHz (Milan et al. 2003a) • Like population ii, population iv echoes have ulos values which appear proportional to vlos, but with a constant of proportionality close to *0.8 (Uspensky et al. 2001; Milan et al. 2003a)....
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...STARE comprised two radars that each transmitted radio signals in the very high frequency (VHF) range (at 400 MHz), simultaneously along 8 beams....
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...The radar is still operational today and comprises a main array of 16 log-periodic antennae which transmit and receive radio signals in the HF frequency range from 8 MHz to 20 MHz....
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204 citations
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...…the polar cap increases, as indicated by an increase of the magnetic flux content in the tail lobes (McPherron 1972; McPherron et al. 1973a,b; Caan et al. 1973, 1978; Hsu and McPherron 2004) and an increase in the polar cap area (Frank and Craven 1988; Milan et al. 2003, 2008; Taylor et al. 1996)....
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References
1,060 citations
"Variations in the polar cap area du..." refers background or result in this paper
...(2000b), who showed ionospheric reconnection signatures extending from noon to 18 MLT for By > 0 nT, and the observations of Kawano and Russell (1996) which show magnetopause reconnection signatures as far tailwards asX = −10RE . Much of the flow crossing the OCB has a large sunward component, especially in the post-noon sector, placing the convection reversal boundaries (or focii of the twin-cell potential pattern) within the polar cap, possibly contrary to expectations. However, this picture is consistent with the paradigm of Lockwood (1997), in which the merging gap is suggested to be located at lower latitude and to be much broader in MLT extent than previous estimates based on “traditional” interpretations of low altitude particle precipitation cusp signatures (e....
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...(2000b), who showed ionospheric reconnection signatures extending from noon to 18 MLT for By > 0 nT, and the observations of Kawano and Russell (1996) which show magnetopause reconnection signatures as far tailwards asX = −10RE ....
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...(2000b), who showed ionospheric reconnection signatures extending from noon to 18 MLT for By > 0 nT, and the observations of Kawano and Russell (1996) which show magnetopause reconnection signatures as far tailwards asX = −10RE . Much of the flow crossing the OCB has a large sunward component, especially in the post-noon sector, placing the convection reversal boundaries (or focii of the twin-cell potential pattern) within the polar cap, possibly contrary to expectations. However, this picture is consistent with the paradigm of Lockwood (1997), in which the merging gap is suggested to be located at lower latitude and to be much broader in MLT extent than previous estimates based on “traditional” interpretations of low altitude particle precipitation cusp signatures (e.g. Newell and Meng, 1992). Indeed, there is considerable similarity between our Fig. 8 and Fig. 1b of Lockwood (1997). If anything, the paradigm of Lockwood would suggest that the true location of the OCB might lie a small distance equatorwards of our estimate, as no signatures of the coupling taking place at the magnetopause can reach the ionosphere in less than one Alfv én travel-time, of the order of 1 or 2 min, in which time magnetic field lines threading this region have convected some distance polewards (see, also, Rodger and Pinnock, 1997; Oksavik et al....
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...To achieve this redistribution of the flux and to return the OCB to its circular equilibrium state, these plasma flows will have the familiar twin-cell pattern of the convection flow (e.g. Heppner and Maynard, 1987; Ruohoniemi and Greenwald, 1996)....
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1,051 citations
985 citations
"Variations in the polar cap area du..." refers background in this paper
...…now supports there being a significant bursty component to reconnection, from observations of flux transfer events (FTEs) at the magnetopause (e.g. Russell and Elphic, 1978, 1979; Haerendel et al., 1978; Kawano and Russell, 1996), to transient auroral and convection signatures in the dayside…...
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934 citations
709 citations
"Variations in the polar cap area du..." refers background or result in this paper
...Our estimate of the dayside reconnection rate, determined from the rate of polar cap expansion, is found to be consistent with the reconnection voltage determined along the dayside OCB by radar plasma drift measurements, lending credence to the convection excitation paradigm of Siscoe and Huang (1985), Cowley and Lockwood (1992), Cowley et al....
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...…now supports there being a significant bursty component to reconnection, from observations of flux transfer events (FTEs) at the magnetopause (e.g. Russell and Elphic, 1978, 1979; Haerendel et al., 1978; Kawano and Russell, 1996), to transient auroral and convection signatures in the dayside…...
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