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Low-energy (order 10 eV) ion flow in the magnetotail lobes inferred from spacecraft wake observations
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
Centre d’Etude Spatiale des Rayonnements, Centre National de la Recherche Scientifique, Toulouse, Toulouse, France.
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2006 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 33, L06110-1-L06110-4 p.Article in journal (Refereed) Published
Abstract [en]

Cold ionospheric ions with eV energies are common inthe magnetosphere and can travel far out in the magnetotail.However, they are difficult to measure with conventional ionspectrometers mounted on spacecraft, since the potential of asunlit spacecraft often reaches several tens of volts. In thispaper we present two alternative methods of measuring thecold-ion flow with the Cluster spacecraft and apply them onone case in the magnetotail at 18 RE: 1. Ion spectrometer incombination with artificial spacecraft potential control;2. Deriving ion flow velocity (both perpendicular andparallel) from electric field instruments. The secondmethod takes advantage of the effect on the doubleprobeinstrument of the wake formed behind a spacecraftin a plasma flow. The results from the two methods showgood agreement and are also consistent with polar windmodels and previous measurements at lower altitudes,confirming the continuation of low-energy ion outflows.

Place, publisher, year, edition, pages
American Geophysical Union , 2006. Vol. 33, L06110-1-L06110-4 p.
Keyword [en]
low-energy ions, plasma flow, polar wind, spacecraft wake, Cluster satellites, measurement technique, ion outflow
National Category
Fusion, Plasma and Space Physics
Research subject
Space and Plasma Physics
Identifiers
URN: urn:nbn:se:uu:diva-100646DOI: 10.1029/2005GL025179OAI: oai:DiVA.org:uu-100646DiVA: diva2:210734
Note
Corrected in Geophysical Research Letters, 33, 14102 (2006).Available from: 2009-04-04 Created: 2009-04-04 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Low-Energy Ion Escape from the Terrestrial Polar Regions
Open this publication in new window or tab >>Low-Energy Ion Escape from the Terrestrial Polar Regions
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The contemporary terrestrial atmosphere loses matter at a rate of around 100,000 tons per year. A major fraction of the net mass loss is constituted by ions, mainly H+ and O+, which escape from the Earth’s ionosphere in the polar regions. Previously, the outflow has only been measured at low altitudes, but to understand what fraction actually escapes and does not return, the measurements should be conducted far from the Earth. However, at large geocentric distances the outflowing ions are difficult to detect with conventional ion instruments on spacecraft, since the spacecraft electrostatic potential normally exceeds the equivalent energy of the ions. This also means that little is known about the ion outflow properties and distribution in space far from the Earth.

In this thesis, we present a new method to measure the outflowing low-energy ions in those regions where they previously have been invisible. The method is based on the detection by electric field instruments of the large wake created behind a spacecraft in a flowing, low-energy plasma. Since ions with low energy will create a larger wake, the method is more sensitive to light ions, and our measured outflow is essentially the proton outflow.

Applying this new method on data from the Cluster spacecraft, we have been able to make an extensive statistical study of ion outflows from 5 to 19 Earth radii in the magnetotail lobes. We show that cold proton outflows dominate in these large regions of the magnetosphere in both flux and density. Our outflow values of low-energy protons are close to those measured at low altitudes, which confirms that the ionospheric outflows continue far back in the tail and contribute significantly to the magnetospheric content. We also conclude that most of the ions are escaping and not returning, which improves previous estimates of the global outflow. The total loss of protons due to high-latitude escape is found to be on the order of 1026 protons/s.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 91 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 640
Keyword
space physics, ion outflow, polar wind, auroral upflows, atmospheric escape, magnetotail lobes, spacecraft wake, electric field measurements
National Category
Fusion, Plasma and Space Physics
Research subject
Space and Plasma Physics
Identifiers
urn:nbn:se:uu:diva-100650 (URN)978-91-554-7512-3 (ISBN)
Public defence
2009-05-20, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2009-04-28 Created: 2009-04-04 Last updated: 2009-04-30Bibliographically approved

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