Bibliography

The Northward IMF Magnetosphere

The manner in which the Earth s magnetosphere responds to the solar wind is highly dependent upon the orientation of the interplanetary magnetic field (IMF), particularly the north–south (B Z ) component. As most auroral and geomagnetic activity occurs when the IMF is southward (or weakly northward, but dominated by the dawn–dusk [B Y ] component), it is perhaps unsurprising that these conditions have received the most attention. However, when the IMF is more strongly northward (B Z \textgreater 0 and B Z \textgreater \textbarB Y \textbar), magnetospheric dynamics (e.g. magnetic reconnection and auroral activity) move to higher latitudes; certain aspects of this activity are much more poorly understood than their southward IMF counterparts. In this chapter, we provide a review of the historical context and current understanding of the behavior of the Earth s magnetosphere during periods of northward IMF, and outline some current controversies and future directions of research.

Fear, Robert;

Published by:       Published on:

YEAR: 2021     DOI: 10.1002/9781119815624.ch19

auroral response; Earth s magnetosphere; geomagnetic activity; interplanetary magnetic field; magnetospheric dynamics; solar wind-magnetosphere coupling

Influence of interplanetary solar wind sector polarity on the ionosphere

Knowledge of solar sector polarity effects on the ionosphere may provide some clues in understanding of the ionospheric day-to-day variability and \textquotedbllefthysteresis\textquotedblright effect on foF2. Ionospheric response to changes in solar sector polarity has not been fully documented previously, partly due to the limitation of observations. In this study, a solar-terrestrial connection ranging from solar sector boundary (SB) crossings, geomagnetic disturbances and ionospheric perturbations has been demonstrated. The increases in interplanetary solar wind speed within three days are seen after SB crossings, while the decreases in solar wind dynamic pressure and magnetic field intensity immediately after SB crossings are confirmed by the superposed epoch analysis results. Furthermore, the interplanetary magnetic field (IMF) Bz component turns from northward to southward in March equinox and June solstice as the Earth passes from a solar sector of outward to inward directed magnetic fields, whereas the reverse situation occurs for the transition from toward to away sectors. The IMF Bz component for the same solar sector polarity has opposite signs between March equinox and September equinox, and also between June solstice and December solstice. In order to know how the ionosphere reacts to the interplanetary solar wind variations linkage of SB crossings, the F2 region critical frequency (foF2) covering about four solar cycles and total electron content (TEC) during 1998\textendash2011 are utilized to extract the related information, revealing that they are not modified significantly and vary within the range of \textpm15\% on average. The responses of the ionospheric TEC to SB crossings exhibit complex temporal and spatial variations and have strong dependencies on season, latitude, and solar cycle. This effect is more appreciable in equinoctial months than in solstitial months, which is mainly caused by larger southwardBzcomponents in equinox. In September equinox, latitudinal profile of relative variations of foF2 at noon is featured by depressions at high latitudes and enhancements in low-equatorial latitudes during IMF away sectors. The negative phase of foF2 is delayed at solar minimum relative to it during other parts of solar cycle, which might be associated with the difference in longevity of major interplanetary solar wind drivers perturbing the Earth\textquoterights environment in different phases of solar cycle.

Liu, Jing; Liu, Libo; Zhao, Biqiang; Wan, Weixing;

Published by: Journal of Geophysical Research      Published on: 08/2012

YEAR: 2012     DOI: 10.1029/2012JA017859

interplanetary magnetic field; Ionospheric disturbance; solar sector polarity

Importance of capturing heliospheric variability for studies of thermospheric vertical winds

Using the Global Ionosphere Thermosphere Model with observed real-time heliospheric input data, the magnitude and variability of thermospheric neutral vertical winds are investigated. In order to determine the role of variability in the Interplanetary Magnetic Field (IMF) and solar wind density on the neutral wind variability, the heliospheric input data are smoothed. The effects of smoothing the IMF and solar wind and density on the vertical winds are simulated for the cases of no smoothing, 5-minute, and 12-minute smoothing. Various vertical wind acceleration terms, such as the nonhydrostatic acceleration, are quantified. Polar stereographic projections of the variabilities of vertical wind and ion flows are compared to highlight existing correlations. Overall, the smoother, that is, the less variable the IMF and solar wind parameters are, the weaker are the magnitude and the variability of the thermospheric vertical winds. Weaker IMF variability leads to smaller variability in ion flows, which in turn negatively impacts the variability and the magnitude of Joule heating. Small-scale temporal variation of the vertical wind acceleration, and thus the variability of the vertical wind, is dominated by the nonhydrostatic term that is controlled primarily by the temporal variation of the Joule heating, which in turn is related to ion flow variations that are shaped by the IMF in the high-latitude thermosphere. Wavelet analysis of the vertical wind data shows that gravity waves of \~5 and \~10-minute periods are more prominent when the model is run with high-resolution real-time IMF and solar wind data. Better capturing of the temporal variation of the IMF and solar wind parameters is crucial for modeling the variability and magnitude of thermospheric vertical winds.

Erdal, Yi\u; Ridley, Aaron; Moldwin, Mark;

Published by: Journal of Geophysical Research      Published on: 07/2012

YEAR: 2012     DOI: 10.1029/2012JA017596

gravity waves; interplanetary magnetic field; Joule heating; magnetosphere-ionosphere-thermosphere coupling; nonhydrostatic general circulation model; vertical wind variability

Spatial and temporal ion drift variability in the high -latitude F region during southward IMF

The purpose of the following research is to investigate the role and contribution of variability or structure in the ion drift to the overall Joule heating rate during times of southward interplanetary magnetic field (IMF). This investigation is limited to southward IMF because the convection patterns are generally more stable and reproducible than those seen for a northward IMF. This allows us to organize the data according to features of the convection pattern and thus produce results that can be used in model simulations of the ionosphere-thermosphere. The contribution of variability or structure in the ion drift to the overall Joule heating is organized into two parts. The first part focuses on the characteristic spatial structure in the ion drift in the F-region ionosphere and how it relates to the bulk ion flow, the large-scale spatial gradient in the bulk ion flow, and the ion temperature. We consider separately the polar cap and auroral zone during the summer and the winter at dawn and dusk during times of steady southward IMF. The second part of this investigation examines the spatial and temporal variability in the ion drift and its contribution to the total Joule heating rate in the F-region ionosphere in the summer and the winter at all magnetic local times (MLT) that are sampled by our data set. This second investigation includes more data than the first investigation by relaxing the stability conditions for southward IMF as well as allowing weaker southward IMF. These topics are investigated utilizing data from the Dynamics Explorer 2 (DE-2) satellite.

Johnson, Eric;

Published by: ProQuest Dissertations and Theses      Published on:

YEAR: 2005     DOI:

Pure sciences; F region; High-latitude; interplanetary magnetic field; Ion drift; atmosphere; 0725:Atmospheric sciences