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O+ Escape During the Extreme Space Weather Event of 4–10 September 2017
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Swedish Institute of Space Physics, Kiruna, Sweden.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Swedish Institute of Space Physics, Kiruna, Sweden.
EISCAT Scientific Association, Kiruna, Sweden.
Swedish Institute of Space Physics, Lund, Sweden.
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2018 (English)In: Space Weather: The international journal of research and applications, ISSN 1542-7390, E-ISSN 1542-7390, Vol. 16, no 9, p. 1363-1376Article in journal (Refereed) Published
Abstract [en]

We have investigated the consequences of extreme space weather on ion outflow from the polar ionosphere by analyzing the solar storm that occurred early September 2017, causing a severe geomagnetic storm. Several X-flares and coronal mass ejections were observed between 4 and 10 September. The first shock—likely associated with a coronal mass ejection—hit the Earth late on 6 September, produced a storm sudden commencement, and began the initial phase of the storm. It was followed by a second shock, approximately 24 hr later, that initiated the main phase and simultaneously the Dst index dropped to Dst = −142 nT and Kp index reached Kp = 8. Using COmposition DIstribution Function data on board Cluster satellite 4, we estimated the ionospheric O+ outflow before and after the second shock. We found an enhancement in the polar cap by a factor of 3 for an unusually high ionospheric O+ outflow (mapped to an ionospheric reference altitude) of 1013 m−2 s−1. We suggest that this high ionospheric O+ outflow is due to a preheating of the ionosphere by the multiple X-flares. Finally, we briefly discuss the space weather consequences on the magnetosphere as a whole and the enhanced O+ outflow in connection with enhanced satellite drag.

Place, publisher, year, edition, pages
Blackwell Publishing, 2018. Vol. 16, no 9, p. 1363-1376
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
URN: urn:nbn:se:ltu:diva-71026DOI: 10.1029/2018SW001881Scopus ID: 2-s2.0-85053442508OAI: oai:DiVA.org:ltu-71026DiVA, id: diva2:1251951
Note

Validerad;2018;Nivå 2;2018-10-17 (johcin) 

Available from: 2018-09-28 Created: 2018-09-28 Last updated: 2019-10-11Bibliographically approved
In thesis
1. How does O+ outflow vary with solar wind conditions?
Open this publication in new window or tab >>How does O+ outflow vary with solar wind conditions?
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The entire solar system including Earth is enveloped in a region of space where the Sun’s magnetic field dominates, this region is called the heliosphere. Due to this position in the heliosphere, a strong coupling exists between the Sun and our planet. The Sun continuously ejects particles, the solar wind, which is composed mainly of protons, electrons as well as some helium and heavier elements. These high energetic particles then hit the Earth and are partly deflected by the Earth’s magnetosphere (the region around Earth governed by the geomagnetic field). Depending on the strength of the solar wind hitting our planet, the magnetosphere is disturbed and perturbations can be seen down to the lower atmosphere.

The upper atmosphere is affected by short wave-length solar radiation that ionise the neutral atoms, this region is referred to as the ionosphere. In the ionosphere, some of the heavier ion populations, such as O+, are heated and accelerated through several processes and flow upward. In the polar regions (polar cap, cusp and plasma mantle) these mechanisms are particularly efficient and when the ions have enough energy to escape the Earth’s gravity, they move outward along open magnetic field lines. These outflowing ions may be lost into interplanetary space.

Another aspect that influences O+ ions are disturbed magnetospheric conditions. They correlate with solar active periods, such as coronal holes or the development of solar active regions. From these regions, strong ejections emerge, called coronal mass ejections (CMEs). When these CMEs interact with Earth, they produce a compression of the magnetosphere as well as reconnection between the terrestrial magnetic field lines and the interplanetary magnetic field (IMF) lines, which very often leads to geomagnetic storms. The energy in the solar wind as well as the coupling to the magnetosphere increase during geomagnetic storms and therefore the energy input to the ionosphere. This in turn increases the O+ outflow. In addition, solar wind parameter variations such as the dynamic pressure or the IMF also influence the outflowing ions.

Our observations are made with the Cluster mission, a constellation of 4 satellites flying around Earth in the key magnetospheric regions where we usually observe ion outflow. In this thesis, we estimated O+ outflow for different solar wind parameters (IMF, solar wind dynamic pressure) and extreme ultraviolet radiations (EUV) as well as for extreme geomagnetic storms. We found that O+ outflow increases exponentially with enhanced geomagnetic activity (Kp index) and about 2 orders of magnitude during extreme geomagnetic storms compared to quiet conditions. Furthermore, our investigations on solar wind parameters showed that O+ outflow increases for high dynamic pressure and southward IMF, as well as with EUV radiations. Finally, the fate of O+ ions from the plasma mantle were studied based on Cluster observations and simulations. These results confirm that ions observed in the plasma mantle have sufficient energy to be lost in the solar wind.

Place, publisher, year, edition, pages
Luleå University of Technology, 2019. p. 169
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:ltu:diva-76360 (URN)978-91-7790-465-6 (ISBN)978-91-7790-466-3 (ISBN)
Public defence
2019-11-15, Aulan, Rymdcampus, Kiruna, 09:00 (English)
Opponent
Supervisors
Available from: 2019-10-11 Created: 2019-10-11 Last updated: 2019-10-18Bibliographically approved

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