High latitude convection based on long-term incoherent scatter radar observations in North America

Zhang, Shun‐Rong; Holt, J. M.; McCready, M.

doi:10.1016/j.jastp.2006.08.017

Cited by 38 publications

(49 citation statements)

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“…The transpolar flow over the Magnetic Pole is usually not aligned with the noon-midnight meridian; it is "rotated" around the Pole to prenoon for B y > 0 and to postnoon for B y < 0. With the advance of season from winter to summer, the misalignment increases (Zhang et al, 2007). An important factor affecting the shape of the convection cells is the conductance at high latitudes and its global-scale distribution (e.g., Zhang et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal and solar cycle variations in the ionospheric convection reversal boundary location inferred from monthly SuperDARN data sets

Koustov

Fiori

2016

Ann. Geophys.

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Abstract. Multi-year (1995Multi-year ( -2013 velocity data collected by the Super Dual Auroral Network (SuperDARN) HF radars are considered to investigate seasonal and solar cycle variations of the convection reversal boundary (CRB) location for interplanetary magnetic field (IMF) B z < 0. By considering monthly data sets we show that the CRB is at higher latitudes in summer between 1995 and 2007. The poleward shifts are on the order of 2-5 • . After 2007, the seasonal effect weakens, and the highest latitudes for the CRB start to occur during the winter time. We show that the CRB latitudes decrease with an increase of the IMF transverse component at a rate of (1-2 • )/2 nT. Because of this effect, on average, the CRB latitudes are lower during high solar activity periods with stronger IMFs. We also confirm the effect of the CRB dawn-dusk shifts related to the IMF changes in the IMF B y sign.

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Section: Introductionmentioning

confidence: 99%

“…With the advance of season from winter to summer, the misalignment increases (Zhang et al, 2007). An important factor affecting the shape of the convection cells is the conductance at high latitudes and its global-scale distribution (e.g., Zhang et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Seasonal and solar cycle variations in the ionospheric convection reversal boundary location inferred from monthly SuperDARN data sets

Koustov

Fiori

2016

Ann. Geophys.

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“…[2] Various observational studies have found seasonal variations in the high-latitude ionospheric convection pattern and the cross-polar cap potential [de la Beaujardière et al, 1991;Weimer, 1995;Ruohoniemi and Greenwald, 2005;Zhang et al, 2007;Pettigrew et al, 2010]. In general, the ionospheric convection is stronger and the cross-polar cap potential is larger near the equinoxes than near either of the solstices.…”

Section: Introductionmentioning

confidence: 99%

The effects of seasonal and diurnal variations in the Earth's magnetic dipole orientation on solar wind–magnetosphere‐ionosphere coupling

2012

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.[1] The angle m between the geomagnetic dipole axis and the geocentric solar magnetospheric (GSM) z axis, sometimes called the "dipole tilt," varies as a function of UT and season. Observations have shown that the cross-polar cap potential tends to maximize near the equinoxes, when on average m = 0, with smaller values observed near the solstices. This is similar to the well-known semiannual variation in geomagnetic activity. We use numerical model simulations to investigate the role of two possible mechanisms that may be responsible for the influence of m on the magnetosphere-ionosphere system: variations in the coupling efficiency between the solar wind and the magnetosphere and variations in the ionospheric conductance over the polar caps. Under southward interplanetary magnetic field (IMF) conditions, variations in ionospheric conductance at high magnetic latitudes are responsible for 10-30% of the variations in the cross-polar cap potential associated with m, but variations in solar wind-magnetosphere coupling are more important and responsible for 70-90%. Variations in viscous processes contribute slightly to this, but variations in the reconnection rate with m are the dominant cause. The variation in the reconnection rate is primarily the result of a variation in the length of the section of the separator line along which relatively strong reconnection occurs. Changes in solar wind-magnetosphere coupling also affect the field-aligned currents, but these are influenced as well by variations in the conductance associated with variations in m, more so than the cross-polar cap potential. This may be the case for geomagnetic activity too.Citation: Cnossen, I., M. Wiltberger, and J. E. Ouellette (2012), The effects of seasonal and diurnal variations in the Earth's magnetic dipole orientation on solar wind-magnetosphere-ionosphere coupling,

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“…The ionospheric convection response to a change in the IMF as measured by the spacecraft is a sum of the following time intervals: (1) the propagation time for the IMF to reach the at the front side magnetopause (assumed to be typically located at X GSE = 10 Re), (2) the magnetosphere-ionosphere communication time, and (3) the ionospheric convection reconfiguration time (Zhang et al, 2007).…”

Section: Response Time Of Ionospheric Convection To Imf B Ymentioning

confidence: 99%

“…Such approach is used for construction of the statistical models with binning of both IMF and ionospheric data (e.g. Heppner and Maynard, 1987;Papitashvili and Rich, 2002;Zhang et al, 2007). In the frame of this approach the slow variations of the IMF may be accounted for.…”

Section: Response Time Of Ionospheric Convection To Imf B Ymentioning

confidence: 99%

IMF By effects in the plasma flow at the polar cap boundary

Lukianova

Kozlovsky

2011

Ann. Geophys.

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Abstract. We used the dataset obtained from the EISCAT Svalbard Radar during [2000][2001][2002][2003][2004][2005][2006][2007][2008] to study statistically the ionospheric convection in a vicinity of the polar cap boundary as related to IMF B y conditions separately for northward and southward IMF. The effect of IMF B y is manifested in the intensity and direction of the azimuthal component of ionospheric flow. The most significant effect is observed on the day and night sides whereas on dawn and dusk the effect is essentially less prominent. However, there is an asymmetry with respect to the noon-midnight meridian. On the day side the intensity of B y -related azimuthal flow is maximal exactly at noon, whereas on the night side the maximum is shifted toward the post-midnight hours (∼03:00 MLT). On the dusk side the relative reduction of the azimuthal flow is much larger than that on the dawn side. Overall, the magnetospheric response to IMF B y seems to be stronger in the 00:00-12:00 MLT sector compared to the 12:00-24:00 MLTs. Quantitative characteristics of the IMF B y effect are presented and partly explained by the magnetospheric electric fields generated due to the solar wind and also by the position of open-closed boundary for different IMF orientation.

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High latitude convection based on long-term incoherent scatter radar observations in North America

Cited by 38 publications

References 50 publications

Seasonal and solar cycle variations in the ionospheric convection reversal boundary location inferred from monthly SuperDARN data sets

Seasonal and solar cycle variations in the ionospheric convection reversal boundary location inferred from monthly SuperDARN data sets

The effects of seasonal and diurnal variations in the Earth's magnetic dipole orientation on solar wind–magnetosphere‐ionosphere coupling

IMF <i>B</i><sub><i>y</i></sub> effects in the plasma flow at the polar cap boundary

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High latitude convection based on long-term incoherent scatter radar observations in North America

Cited by 38 publications

References 50 publications

Seasonal and solar cycle variations in the ionospheric convection reversal boundary location inferred from monthly SuperDARN data sets

Seasonal and solar cycle variations in the ionospheric convection reversal boundary location inferred from monthly SuperDARN data sets

The effects of seasonal and diurnal variations in the Earth's magnetic dipole orientation on solar wind–magnetosphere‐ionosphere coupling

IMF &lt;i&gt;B&lt;/i&gt;&lt;sub&gt;&lt;i&gt;y&lt;/i&gt;&lt;/sub&gt; effects in the plasma flow at the polar cap boundary

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IMF <i>B</i><sub><i>y</i></sub> effects in the plasma flow at the polar cap boundary