Multi-instrument observations of nightside plasma patches under conditions of IMF &amp;lt;I&amp;gt;B&amp;lt;sub&amp;gt;z&amp;lt;/sub&amp;gt;&amp;lt;/I&amp;gt; positive

Wood, Alan; Pryse, S. E.; Middleton, H. R.; Howells, V. S. C.

doi:10.5194/angeo-26-2203-2008

Cited by 6 publications

(6 citation statements)

References 37 publications

(38 reference statements)

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“…It was therefore suggested that the patches associated with IMF B z positive had entered the polar cap during conditions of IMF B z negative. This result was supported by observations of plasma in the nightside ionosphere using the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR), where plasma observed during IMF B z positive was shown to have crossed the solar terminator in the polar region when IMF B z was negative [ Wood et al , 2008]. This study also illustrated cross‐polar transport under IMF B z positive when IMF ∣ B y ∣ ≫ ∣ B z ∣.…”

Section: Introductionsupporting

confidence: 74%

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Seasonal influence on polar cap patches in the high‐latitude nightside ionosphere

Wood

Pryse

2010

J. Geophys. Res.

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[1] The influence of the season on the patch-to-background density ratio of polar cap patches in the nightside ionosphere was observed above northern Scandinavia around solar maximum (1999)(2000)(2001). This is the first study of the seasonal effect in the nightside polar ionosphere. The observations were conducted by the European Incoherent Scatter Svalbard Radar under conditions favorable for patches based on the high-latitude plasma convection pattern, the interplanetary magnetic field, and an absence of in situ precipitation. Patch-to-background ratios of up to 9.4 ± 2.9 were observed between midwinter and equinox, with values of up to 1.9 ± 0.2 in summer. As the patch-to-background ratios in summer were <2, the enhancements could not formally be called patches; however, these were significant density enhancements within the antisunward cross-polar flow. Aberystwyth University's PLASLIFE (PLASma LIFEtime) computer simulation was used to model the observed seasonal trend in the patch-to-background ratio and to establish reasons for the difference between winter and summer values. This difference was primarily attributed to variation in the chemical composition of the atmosphere, which, in summer, both reduced the electron densities of the plasma drawn into the polar cap on the dayside and enhanced plasma loss by recombination. A secondary factor was the maintenance of the background polar ionosphere by photoionization in summer.

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Section: Introductionsupporting

confidence: 74%

“…The modeled and observed values at the final location were compared and agreed within experimental uncertainties. PLASLIFE had also been used previously to assist in the interpretation of observations in the nightside ionosphere [ Pryse et al , 2006; Wood et al , 2008].…”

Section: Instrumentation and Simulationmentioning

confidence: 99%

Seasonal influence on polar cap patches in the high‐latitude nightside ionosphere

Wood

Pryse

2010

J. Geophys. Res.

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“…The results of the superposed epoch analysis (Figure ) for IMF Bz follow the reasoning of Sojka et al [] and Coley and Heelis [] that a majority of polar patch detections coincides with a southward IMF. However, the large IMF Bz standard deviation suggests the development of polar patches also during positive IMF Bz conditions which has been shown by Wood et al [] and Hosokawa et al []. The results of the IMF By analysis indicate that IMF By is mainly positive in the SH and negative in the NH.…”

Section: Discussionmentioning

confidence: 58%

Long‐term analysis of ionospheric polar patches based on CHAMP TEC data

et al. 2013

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[1] Total electron content (TEC) from LEO satellites offers great possibility to sound the upper ionosphere and plasmasphere. This paper describes a method to derive absolute TEC observations aboard CHAMP considering multipath effects and receiver differential code bias. The long-term data set of 9 years GPS observations is used to investigate the climatological behavior of high-latitude plasma patches in both hemispheres. The occurrence of polar patches has a clear correlation with the solar cycle, which is less pronounced in the Southern Hemisphere (SH). Summed over all years, we observed a higher number of patches in the SH. The maximum occurrence rate of patches has been found at the dayside polar cusp during 12:00-18:00 MLT (magnetic local time) supporting the mechanisms for patch creation by local particle precipitation and by intrusion of subauroral plasma into the polar cap through tongues of ionization (TOIs). The latter mechanism seems to be even more important in the SH. Investigating the patches in comparison with interplanetary magnetic field (IMF) conditions, we found that decreased IMF Bz and enhanced merging electric field preceded the patch observation; hence, patch creation follows a period of enhanced solar wind input into the magnetosphere/ionosphere. We further found an annual cycle in patch occurrence with maxima at equinox and December solstice and a June solstice minimum which reflects the global ionospheric seasonal asymmetry in electron density. We suggest that enhanced TEC at midlatitudes and low latitudes during December solstice provides a greater possibility to transport high-density plasma to the polar region through the buildup of TOIs.Citation: Noja, M., C. Stolle, J. Park, and H. Lühr (2013), Long-term analysis of ionospheric polar patches based on CHAMP TEC data, Radio Sci., 48,[289][290][291][292][293][294][295][296][297][298][299][300][301]

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“…Traditionally, the polar cap has been thought to be dominated by Sun‐aligned arc structures for positive IMF Bz, and polar cap patches for negative IMF Bz [ Crowley , 1996]. Most reports of polar cap patches are for negative IMF Bz conditions [e.g., Buchau et al , 1983; Rodger et al , 1994a; McEwen and Harris , 1996], but Oksavik et al [2006a] reported a special case where a patch formed inside a northward IMF lobe cell due to an extended period of local particle precipitation poleward of the dayside open/closed boundary (OCB), and Wood et al [2008] observed plasma of dayside origin in the midnight sector during northward IMF.…”

Section: Introductionmentioning

confidence: 99%

On the entry and transit of high‐density plasma across the polar cap

Oksavik¹,

et al. 2010

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Observations are presented from SuperDARN and the EISCAT Svalbard Radar of two intense polar cap patch events on 6 February 2001. The interplanetary magnetic field (IMF) was dominated by a large positive By component, and for both events the electron density exceeded 1012 m−3 in the F region. With SuperDARN we tracked the events all the way across the polar cap, from the dayside Svalbard sector to the nightside Alaska sector. The flow speed was highly dynamic and pulsed, and both patches underwent substantial rotation in the polar cap. On the nightside the leading edge had become the trailing edge. It suggests that the first patch to enter the polar cap on the dayside may not always be the first patch to reach the nightside; plasma might be stagnant in the polar cap or even overtaken. The study also provides evidence that momentum transfer in the dayside polar cap can last significantly longer than 10 min after reconnection, especially for extremely long field lines where IMF By is dominating, i.e., on “old open field lines.” Knowledge of the solar wind driver and the coupling processes is therefore extremely important for predicting the motion of a polar cap patch event across the polar cap. Gradients in the plasma flow associated with the rotation of the extreme density may in itself lead to a stronger growth of ionospheric irregularities. These irregularities may continue to grow all the way across the polar cap. The result is more efficient creation of ionospheric irregularities.

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Multi-instrument observations of nightside plasma patches under conditions of IMF <I>B<sub>z</sub></I> positive

Cited by 6 publications

References 37 publications

Seasonal influence on polar cap patches in the high‐latitude nightside ionosphere

Seasonal influence on polar cap patches in the high‐latitude nightside ionosphere

Long‐term analysis of ionospheric polar patches based on CHAMP TEC data

On the entry and transit of high‐density plasma across the polar cap

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