IMF effect on the polar cap contraction and expansion during a period of substorms

Aikio, Anita; Pitkänen, Timo; Honkonen, Ilja; Palmroth, Minna; Amm, O.

doi:10.5194/angeo-31-1021-2013

Cited by 8 publications

(10 citation statements)

References 52 publications

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“…), Hubert, Palmroth, et al (2006), and Milan et al (2009 used auroral images to also infer the loss of open flux during substorm expansion phases, which also implies a relationship between −AL and Φ N . The variation of Φ N inferred from time-constants by Laundal et al (2020) shows a strong variation with −AL, as does the analysis of the polar cap boundary location by Aikio et al (2013).…”

Section: Variation Of φ Pc With Imf B Z and The Al Indexmentioning

confidence: 62%

A Survey of 25 Years' Transpolar Voltage Data From the SuperDARN Radar Network and the Expanding‐Contracting Polar Cap Model

Lockwood

McWilliams

2021

JGR Space Physics

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This paper studies the expanding-contracting polar cap (ECPC) model of ionospheric convection excitation ) using an unprecedentedly large data set of observations of the transpolar voltage Φ PC , also known as the cross-cap potential difference. The ECPC model predicts that Φ PC at any one instant depends on the reconnection voltage in the cross-tail current sheet Φ N as well as that at the dayside magnetopause Φ D .One specific aim is to recreate two scatter plots from surveys of Φ PC that have been of great importance to our understanding of the excitation of ionospheric polar convection by the solar wind flow, but here using a much larger data set of observations. The first of these scatter plots shows the dependence of Φ PC on the northward component B Z of the interplanetary magnetic field (IMF) in the geocentric solar magnetospheric (GSM) reference frame (

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Section: Variation Of φ Pc With Imf B Z and The Al Indexmentioning

confidence: 62%

A Survey of 25 Years' Transpolar Voltage Data From the SuperDARN Radar Network and the Expanding‐Contracting Polar Cap Model

Lockwood

McWilliams

2021

JGR Space Physics

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“…The evening maximum region expanded to earlier times and constituted of two local maxima, 14–15 MLT and 16–19 MLT. During southward IMF with increasing solar wind electric field, we expect to have a stronger coupling between the solar wind and the terrestrial magnetosphere increasing the polar cap size and expanding the auroral oval to lower latitudes [ Cowley and Lockwood , ; Aikio et al , ]. Hence, the oval expands to the latitude of TRO at an earlier MLT with increasing E SW .…”

Section: Discussionmentioning

confidence: 99%

Solar wind effect on Joule heating in the high‐latitude ionosphere

2014

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The effect of solar wind on several electrodynamic parameters, measured simultaneously by the European Incoherent Scatter (EISCAT) radars in Tromsø (TRO, 66.6° cgmLat) and on Svalbard (ESR, 75.4° cgmLat), has been evaluated statistically. The main emphasis is on Joule heating rate QJ, which has been estimated by taking into account the neutral wind. In addition, a generally used proxy QE, which is the Pedersen conductance times the electric field squared, has been calculated. The most important findings are as follows. (i) The decrease in Joule heating in the afternoon‐evening sector due to winds reported by Aikio et al. (2012) requires southward interplanetary magnetic field (IMF) conditions and a sufficiently high solar wind electric field. The increase in the morning sector takes place for all IMF directions within a region where the upper E neutral wind has a large equatorward component and the F region plasma flow is directed eastward. (ii) At ESR, an afternoon hot spot of Joule heating centered typically at 14–15 magnetic local time (MLT) is observed during all IMF conditions. Enhanced Pedersen conductances within the hot spot region are observed only for the IMF Bz + /By− conditions, and the corresponding convection electric field values within the hot spot are smaller than during the other IMF conditions. Hence, the hot spot represents a region of persistent magnetospheric electromagnetic energy input, and the median value is about 3 mW/m2. (iii) For the southward IMF conditions, the MLT‐integrated QE for By− is twice the value for By+ at TRO. This can plausibly be explained by the higher average solar wind electric field values for By−.

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“…They observed small time delays (only a few minutes); the delay was shortest in the ~1400 magnetic local time (MLT) sector. Aikio et al () used ACE solar wind data, Geotail data in the magnetosphere, and ground‐based data from the EISCAT radars and the Magnetometers ‐ Ionospheric Radars‐ Allsky Cameras Large Experiment (MIRACLE) magnetometers to study the variations of the magnetotail inclination angle, the location of the polar cap boundary, and the magnetic signature of the convection reversal boundary, with respect to variations in the IMF B Z component. They estimated a time lag of the response of about 17 min.…”

Section: Introductionmentioning

confidence: 99%

The Delayed Time Response of Geomagnetic Activity to the Solar Wind

et al. 2017

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We investigate the lagged correlation between a selection of geomagnetic indices and solar wind parameters for a complete solar cycle, from 2000 to 2011. We first discuss the mathematical assumptions required for such a correlation analysis. The solar wind parameters and geomagnetic indices have inherent timescales that smooth the variations of the correlation coefficients with time lag. Furthermore, the solar wind structure associated with corotating interaction regions and coronal mass ejections, and the compression regions ahead of them, strongly impacts the lagged correlation analysis results. This work shows that such bias must be taken into account in a correct interpretation of correlations. We then evidence that the magnetospheric response time to solar wind parameters involves multiple timescales. The simultaneous and quick response of the PC and AE indices to solar wind dynamic pressure with a delay of ~5 min suggests that magnetospheric compression by solar wind can trigger substorm activity. We find that the PC and AE indices respond to interplanetary magnetic field (IMF) BZ with a response time of respectively ~20 and ~35 min. The response of the SYM‐H index takes longer (~80 min) and is less sharp, SYM‐H being statistically significantly correlated to the IMF BZ observed up to more than ~10 h before. Our results suggest that the solar wind velocity's dominant impact on geomagnetic activity is caused by the compression regions at the interface of fast/slow solar wind regimes, which are very geo‐effective as they are associated with high solar wind pressure and strong interplanetary magnetic field.

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IMF effect on the polar cap contraction and expansion during a period of substorms

Cited by 8 publications

References 52 publications

A Survey of 25 Years' Transpolar Voltage Data From the SuperDARN Radar Network and the Expanding‐Contracting Polar Cap Model

A Survey of 25 Years' Transpolar Voltage Data From the SuperDARN Radar Network and the Expanding‐Contracting Polar Cap Model

Solar wind effect on Joule heating in the high‐latitude ionosphere

The Delayed Time Response of Geomagnetic Activity to the Solar Wind

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