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How does O+ outflow vary with solar wind conditions?
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Swedish Institute of Space Physics.
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 Aerospace Engineering
Research subject
Atmospheric science; Atmospheric science
Identifiers
URN: urn:nbn:se:ltu:diva-76360ISBN: 978-91-7790-465-6 (print)ISBN: 978-91-7790-466-3 (electronic)OAI: oai:DiVA.org:ltu-76360DiVA, id: diva2:1360235
Public defence
2019-11-15, Aulan, Rymdcampus, Kiruna, 09:00 (English)
Opponent
Supervisors
Available from: 2019-10-11 Created: 2019-10-11 Last updated: 2019-10-23Bibliographically approved
List of papers
1. Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales
Open this publication in new window or tab >>Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales
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2017 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 35, no 3, p. 721-731Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Copernicus Publications, 2017
National Category
Aerospace Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-63305 (URN)10.5194/angeo-35-721-2017 (DOI)000403359500002 ()2-s2.0-85020723185 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-06-30 (andbra)

Available from: 2017-05-10 Created: 2017-05-10 Last updated: 2019-10-11Bibliographically approved
2. Relative outflow enhancements during major geomagnetic storms: Cluster observations
Open this publication in new window or tab >>Relative outflow enhancements during major geomagnetic storms: Cluster observations
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2017 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 5, no 6, p. 1341-1352Article in journal (Refereed) Published
Abstract [en]

The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depending on the geomagnetic activity. However, the upper limit of the outflow rate during the largest geomagnetic storms is not well constrained due to poor spatial coverage during storm events. In this paper, we analyse six major geomagnetic storms between 2001 and 2004 using Cluster data. The six major storms fulfil the criteria of Dst 100 nT or Kp 7C. Since the shape of the magnetospheric regions (plasma mantle, lobe and inner magnetosphere) are distorted during large magnetic storms, we use both plasma beta and ion characteristics to define a spatial box where the upward OC flux scaled to an ionospheric reference altitude for the extreme event is observed. The relative enhancement of the scaled outflow in the spatial boxes as compared to the data from the full year when the storm occurred is estimated. Only OC data were used because HC may have a solar wind origin. The storm time data for most cases showed up as a clearly distinguishable separate peak in the distribution toward the largest fluxes observed. The relative enhancement in the outflow region during storm time is 1 to 2 orders of magnitude higher compared to less disturbed time. The largest relative scaled outflow enhancement is 83 (7 November 2004) and the highest scaled OC outflow observed is 2 1014 m2 s1 (29 October 2003).

Place, publisher, year, edition, pages
Copernicus GmbH, 2017
National Category
Aerospace Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-67138 (URN)10.5194/angeo-35-1341-2017 (DOI)000418075000001 ()2-s2.0-85038635321 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-01-04 (svasva)

Available from: 2018-01-02 Created: 2018-01-02 Last updated: 2019-10-11Bibliographically approved
3. O+ Escape During the Extreme Space Weather Event of 4–10 September 2017
Open this publication in new window or tab >>O+ Escape During the Extreme Space Weather Event of 4–10 September 2017
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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
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-71026 (URN)10.1029/2018SW001881 (DOI)2-s2.0-85053442508 (Scopus ID)
Note

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

Available from: 2018-09-28 Created: 2018-09-28 Last updated: 2019-10-11Bibliographically approved
4. Earth atmospheric loss through the plasma mantle and its dependence on solar wind parameters
Open this publication in new window or tab >>Earth atmospheric loss through the plasma mantle and its dependence on solar wind parameters
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2019 (English)In: Earth, Planets and Space, Vol. 71, no 70Article in journal (Refereed) Published
Abstract [en]

Atmospheric loss and ion outfow play an important role in the magnetospheric dynamics and in the evolution of the atmosphere on geological timescales—an evolution which is also dependent on the solar activity. In this paper, we investigate the total O+ outfow [s−1 ] through the plasma mantle and its dependency on several solar wind param‑ eters. The oxygen ion data come from the CODIF instrument on board the spacecraft Cluster 4 and solar wind data from the OMNIWeb database for a period of 5 years (2001–2005). We study the distribution of the dynamic pressure and the interplanetary magnetic feld for time periods with available O+ observations in the plasma mantle. We then divided the data into suitably sized intervals. Additionally, we analyse the extreme ultraviolet radiation (EUV) data from the TIMED mission. We estimate the O+ escape rate [ions/s] as a function of the solar wind dynamic pressure, the interplanetary magnetic feld (IMF) and EUV. Our analysis shows that the O+ escape rate in the plasma mantle increases with increased solar wind dynamic pressure. Consistently, it was found that the southward IMF also plays an important role in the O+ escape rate in contrast to the EUV fux which does not have a signifcant infuence for the plasma mantle region. Finally, the relation between the O+ escape rate and the solar wind energy transferred into the magnetosphere shows a nonlinear response. The O+ escape rate starts increasing with an energy input of approxi‑ mately 1011W.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
O+ outfow/escape, Plasma mantle, Solar wind, Interplanetary magnetic feld (IMF), Extreme ultraviolet (EUV), Coupling functions
National Category
Aerospace Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-74886 (URN)10.1186/s40623-019-1048-0 (DOI)000472492500001 ()2-s2.0-85067844890 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-15 (johcin)

Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-10-11Bibliographically approved
5. The fate of O+ ions observed in the plasma mantle and cusp: particle tracing modelling and Cluster observations
Open this publication in new window or tab >>The fate of O+ ions observed in the plasma mantle and cusp: particle tracing modelling and Cluster observations
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2019 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576Article in journal (Refereed) Submitted
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:ltu:diva-76359 (URN)
Available from: 2019-10-11 Created: 2019-10-11 Last updated: 2019-10-17

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