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4 results on '"LaMoury, A. T."'

1. Self-Similarity of ICME Flux Ropes: Observations by Radially Aligned Spacecraft in the Inner Heliosphere

Author

Good, S. W., Kilpua, E. K. J., LaMoury, A. T., Forsyth, R. J., Eastwood, J. P., and Möstl, C.

Subjects
Physics - Space Physics
Abstract

Interplanetary coronal mass ejections (ICMEs) are a significant feature of the heliospheric environment and the primary cause of adverse space weather at the Earth. ICME propagation, and the evolution of ICME magnetic field structure during propagation, are still not fully understood. We analyze the magnetic field structures of 18 ICME magnetic flux ropes observed by radially aligned spacecraft in the inner heliosphere. Similarity in the underlying flux rope structures is determined through the application of a simple technique that maps the magnetic field profile from one spacecraft to the other. In many cases, the flux ropes show very strong underlying similarities at the different spacecraft. The mapping technique reveals similarities that are not readily apparent in the unmapped data and is a useful tool when determining whether magnetic field time series observed at different spacecraft are associated with the same ICME. Lundquist fitting has been applied to the flux ropes and the rope orientations have been determined; macroscale differences in the profiles at the aligned spacecraft may be ascribed to differences in flux rope orientation. Assuming that the same region of the ICME was observed by the aligned spacecraft in each case, the fitting indicates some weak tendency for the rope axes to reduce in inclination relative to the solar equatorial plane and to align with the solar east-west direction with heliocentric distance., Comment: 35 pages, 10 figures

Published
2019
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2. Transient upstream mesoscale structures: drivers of solar-quiet space weather.

Author

Kajdič, Primož, Blanco-Cano, Xóchitl, Turc, Lucile, Archer, Martin, Raptis, Savvas, Liu, Terry Z., Pfau-Kempf, Yann, LaMoury, Adrian T., Yufei Hao, Escoubet, Philippe C., Omidi, Nojan, Sibeck, David G., Boyi Wang, Hui Zhang, Yu Lin, and Zhaojin Rong

Subjects
SPACE environment, CORONAL mass ejections, MAGNETIC storms, SOLAR wind, GEOMAGNETISM, AURORAS, SOLAR cycle
Abstract

In recent years, it has become increasingly clear that space weather disturbances can be triggered by transient upstream mesoscale structures (TUMS), independently of the occurrence of large-scale solar wind (SW) structures, such as interplanetary coronal mass ejections and stream interaction regions. Different types of magnetospheric pulsations, transient perturbations of the geomagnetic field and auroral structures are often observed during times when SW monitors indicate quiet conditions, and have been found to be associated to TUMS. In this mini-review we describe the space weather phenomena that have been associated with four of the largest-scale and the most energetic TUMS, namely, hot flow anomalies, foreshock bubbles, travelling foreshocks and foreshock compressional boundaries. The space weather phenomena associated with TUMS tend to be more localized and less intense compared to geomagnetic storms. However, the quiet time space weather may occur more often since, especially during solar minima, quiet SW periods prevail over the perturbed times. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Solar wind control of magnetosheath jet formation: Low and high IMF cone angle regimes and solar cycle dependence

Author

Vuorinen, Laura, Hietala, Heli, LaMoury, Adrian T., Koller, Florian, and Plaschke, Ferdinand

Abstract

Magnetosheath jets are dynamic pressure enhancements that frequently emerge from the Earth's bow shock. Earthward propagating jets can traverse the magnetosheath and eventually impact the subsolar magnetopause. The occurrence of jets is strongly influenced by solar wind and interplanetary magnetic field (IMF) conditions. Most importantly, jets are known to occur significantly more often downstream of the quasi-parallel shock than the quasi-perpendicular shock. However, as the quasi-perpendicular configuration is more common at the Earth's bow shock, quasi-perpendicular jets can represent a significant fraction of jets. To better understand the solar wind influence on jet formation in these two different shock regimes, we use Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft magnetosheath observations and OMNI solar wind measurements to study jets in the subsolar magnetosheath separately during low and high IMF cone angles. We find that during low IMF cone angles (downstream of the quasi-parallel shock) jet occurrence near the bow shock is not sensitive to other solar wind parameters. However, during high IMF cone angles (downstream of the quasi-perpendicular shock) jet occurrence is higher during low IMF strength, low density, high beta, and high Alfvén Mach numberconditions. This suggests that quasi-perpendicular shock dynamics amplified by higher betaand Alfvén Mach number can lead to formation of jets. As solar wind conditions vary throughout the solar cycle, we also present a statistical model of jet occurrence as a function of solar wind conditions and use it to estimate the yearly jet occurrence rates throughout solar cycle 24., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

4. Journal of Geophysical Research: Space Physics / Magnetosheath Jet Occurrence Rate in Relation to CMEs and SIRs

Author

Koller, Florian, Temmer, Manuela, Preisser, Luis, Geyer, Paul, Plaschke, Ferdinand, Jian, Lan K., Roberts, Owen W., Hietala, Heli, LaMoury, Adrian T., Koller, Florian, Temmer, Manuela, Preisser, Luis, Geyer, Paul, Plaschke, Ferdinand, Jian, Lan K., Roberts, Owen W., Hietala, Heli, and LaMoury, Adrian T.

Abstract

Magnetosheath jets constitute a significant coupling effect between the solar wind (SW) and the magnetosphere of the Earth. In order to investigate the effects and forecasting of these jets, we present the first-ever statistical study of the jet production during large-scale SW structures like coronal mass ejections (CMEs), stream interaction regions (SIRs) and high speed streams (HSSs). Magnetosheath data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft between January 2008 and December 2020 serve as measurement source for jet detection. Two different jet definitions were used to rule out statistical biases induced by our jet detection method. For the CME and SIR + HSS lists, we used lists provided by literature and expanded on incomplete lists using OMNI data to cover the time range of May 1996 to December 2020. We find that the number and total time of observed jets decrease when CME-sheaths hit the Earth. The number of jets is lower throughout the passing of the CME-magnetic ejecta (ME) and recovers quickly afterward. On the other hand, the number of jets increases during SIR and HSS phases. We discuss a few possibilities to explain these statistical results., Fonds zur Förderung der Wissenschaftlichen Forschung P 33285, Version of record

Published
2022
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