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Stenberg Wieser, Gabriella
Alternative names
Publications (10 of 10) Show all publications
Nilsson, H., Möslinger, A., Williamson, H. N., Bergman, S., Gunell, H., Stenberg Wieser, G., . . . Holmström, M. (2022). Upstream solar wind speed at comet 67P: reconstruction method, model comparison, and results. Astronomy and Astrophysics, 659, Article ID A18.
Open this publication in new window or tab >>Upstream solar wind speed at comet 67P: reconstruction method, model comparison, and results
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2022 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 659, article id A18Article in journal (Refereed) Published
Abstract [en]

Context: Rosetta followed comet 67P at heliocentric distances from 1.25 to 3.6 au. The solar wind was observed for much of this time, but was significantly deflected and to some extent slowed down by the interaction with the coma.

Aims: We use the different changes in the speed of H+ and He2+ when they interact with the coma to estimate the upstream speed of the solar wind. The different changes in the speed are due to the different mass per charge of the particles, while the electric force per charge due to the interaction is the same. A major assumption is that the speeds of H+ and He2+ were the same in the upstream region. This is investigated.

Methods: We derived a method for reconstructing the upstream solar wind from H+ and He2+ observations. The method is based on the assumption that the interaction of the comet with the solar wind can be described by an electric potential that is the same for both H+ and He2+. This is compared to estimates from the Tao model and to OMNI and Mars Express data that we propagated to the observation point.

Results: The reconstruction agrees well with the Tao model for most of the observations, in particular for the statistical distribution of the solar wind speed. The electrostatic potential relative to the upstream solar wind is derived and shows values from a few dozen volts at large heliocentric distances to about 1 kV during solar events and close to perihelion. The reconstructed values of the solar wind for periods of high electrostatic potential also agree well with propagated observations and model results.

Conclusions: The reconstructed upstream solar wind speed during the Rosetta mission agrees well with the Tao model. The Tao model captures some slowing down of high-speed streams as compared to observations at Earth or Mars. At low solar wind speeds, below 400 km s-1, the agreement is better between our reconstruction and Mars observations than with the Tao model. The magnitude of the reconstructed electrostatic potential is a good measure of the slowing-down of the solar wind at the observation point.

Place, publisher, year, edition, pages
EDP Sciences, 2022
Keywords
Acceleration of particles, Comets: general, Comets: individual: C67P, Plasmas, Space vehicles: instruments
National Category
Astronomy, Astrophysics and Cosmology Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-193059 (URN)10.1051/0004-6361/202142867 (DOI)000761966800004 ()2-s2.0-85125761748 (Scopus ID)
Funder
Swedish Research Council, 2015-04187The European Space Agency (ESA)
Available from: 2022-03-21 Created: 2022-03-21 Last updated: 2023-01-16Bibliographically approved
Persson, M., Futaana, Y., Nilsson, H., Stenberg Wieser, G., Hamrin, M., Fedorov, A., . . . Barabash, S. (2019). Heavy Ion Flows in the Upper Ionosphere of the Venusian North Pole. Journal of Geophysical Research - Space Physics, 124(6), 4597-4607
Open this publication in new window or tab >>Heavy Ion Flows in the Upper Ionosphere of the Venusian North Pole
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2019 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 6, p. 4597-4607Article in journal (Refereed) Published
Abstract [en]

We investigate the heavy ion density and velocity in the Venusian upper ionosphere near the North Pole, using the Ion Mass Analyzer, a part of the Analyzer of Space Plasmas and Energetic Atoms 4, together with the magnetic field instruments on Venus Express. The measurements were made during June-July 2014, covering the aerobraking campaign with lowered altitude measurements (similar to 130 km). The plasma scale heights are similar to 15 km below 150-km altitude and similar to 200 km at 150-400-km altitude. A clear trend of dusk-to-dawn heavy ion flow across the polar ionosphere was found, with speeds of similar to 2-10 km/s. In addition, the flow has a significant downward radial velocity component. The flow pattern does not depend on the interplanetary magnetic field directions nor the ionospheric magnetization states. Instead, we suggest a thermal pressure gradient between the equatorial and polar terminator regions, induced by the decrease in density between the regions, as the dominant mechanism driving the ion flow. Plain Language Summary We have calculated the ion density and velocities in the Venusian polar ionosphere using measurements from the Ion Mass Analyzer on board the Venus Express spacecraft. During June-July 2014 the periapsis was lowered to similar to 130 km, which allowed for measurements down to low altitudes of the ionosphere near the North Pole. The plasma scale heights are similar to 15 km below 150-km altitude and similar to 200 km at 150-400 km, which is similar to what was found near the equatorial region by the Pioneer Venus mission. In addition, there is a clear trend of dusk-to-dawn flow, along the terminator, for the heavy ions. This is surprising, as a general flow from day-to-night is expected for the Venusian ionosphere due to the long nights and significant heating of the dayside upper atmosphere. The interplanetary magnetic field direction does not appear to affect the ion flow pattern. Instead, we propose a thermal pressure gradient as the dominant accelerating mechanism, induced by the decrease in density from the equator toward the pole.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2019
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-162017 (URN)10.1029/2018JA026271 (DOI)000477723100049 ()2-s2.0-85067394643 (Scopus ID)
Available from: 2019-08-12 Created: 2019-08-12 Last updated: 2023-03-23Bibliographically approved
Stenberg, G., Oscarsson, T., André,, M., Vaivads, A., Backrud, M., Khotyaintsev, Y., . . . Décréau, P. M. (2007). Internal structure and spatial dimensions of whistler wave regions in the magnetopause boundary layer. Annales Geophysicae, 25, 2439-2451
Open this publication in new window or tab >>Internal structure and spatial dimensions of whistler wave regions in the magnetopause boundary layer
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2007 (English)In: Annales Geophysicae, Vol. 25, p. 2439-2451Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-8304 (URN)
Available from: 2008-01-16 Created: 2008-01-16 Last updated: 2018-06-09Bibliographically approved
Stenberg, G. (2006). Att upptäcka universum.. LMNT-nytt (2), 23
Open this publication in new window or tab >>Att upptäcka universum.
2006 (Swedish)In: LMNT-nytt, ISSN 1402-0041, no 2, p. 23-Article in journal (Other (popular science, discussion, etc.)) Published
Identifiers
urn:nbn:se:umu:diva-12158 (URN)
Available from: 2007-03-24 Created: 2007-03-24 Last updated: 2018-06-09Bibliographically approved
Reiniusson, A., Stenberg, G., Norqvist, P., Eriksson, A. & Rönnmark, K. (2006). Enhancement of electric and magnetic wave fields at density gradients. Annales Geophysicae, 24, 367-79
Open this publication in new window or tab >>Enhancement of electric and magnetic wave fields at density gradients
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2006 (English)In: Annales Geophysicae, Vol. 24, p. 367-79Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-11974 (URN)
Available from: 2007-03-17 Created: 2007-03-17 Last updated: 2018-06-09Bibliographically approved
Stenberg, G. (2006). Snart stjärnklart i Umeå.. Populär Astronomi (1), 30-31
Open this publication in new window or tab >>Snart stjärnklart i Umeå.
2006 (Swedish)In: Populär Astronomi, ISSN 1650-7177, no 1, p. 30-31Article in journal (Other (popular science, discussion, etc.)) Published
Identifiers
urn:nbn:se:umu:diva-12157 (URN)
Available from: 2007-03-23 Created: 2007-03-23 Last updated: 2018-06-09Bibliographically approved
Backrud-Ivgren, M., Stenberg, G., André, M., Morooka, M., Hobara, Y., Joko, S. & Rönnmark, K. (2005). Cluster observations and theoretical identification of broadband waves in the auroral region. Annales Geophysicae, 23, 3739-3752
Open this publication in new window or tab >>Cluster observations and theoretical identification of broadband waves in the auroral region
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2005 (English)In: Annales Geophysicae, Vol. 23, p. 3739-3752Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-12151 (URN)
Available from: 2007-03-23 Created: 2007-03-23 Last updated: 2018-06-09Bibliographically approved
Stenberg, G., Oscarsson, T., André, M., Vaivads, A., Morooka, M., Cornilleau-Wehrlin, N., . . . Décréau, P. (2005). Electron-scale sheets of whistlers close to the magnetopause. Annales Geophysicae, 23(12), 3715-3725
Open this publication in new window or tab >>Electron-scale sheets of whistlers close to the magnetopause
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2005 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 23, no 12, p. 3715-3725Article in journal (Refereed) Published
Abstract [en]

Whistler emissions close to the magnetopause on the magnetospheric side are investigated using the four Cluster spacecraft. The waves are found to be generated in thin (electron-scale) sheets moving with the plasma drift velocity. A feature in the electron data coincides with the waves; hot magnetospheric electrons disappear for a few satellite spins. This produces or enhances a temperature anisotropy, which is found to be responsible for the generation of the whistler mode waves. The high energy electrons are thought to be lost through the magnetopause and we suggest that the field lines, on which the waves are generated, are directly connected to a reconnection diffusion region at the magnetopause.

Place, publisher, year, edition, pages
Göttingen: Copernicus gesellschaft, 2005
Keywords
magnetospheric physics, magnetopause, cusp and boundary layers, space plasma physics, magnetic reconnection, waves and instabilities
National Category
Astronomy, Astrophysics and Cosmology Geology Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:umu:diva-4596 (URN)10.5194/angeo-23-3715-2005 (DOI)000235008400013 ()2-s2.0-30844473789 (Scopus ID)
Available from: 2005-05-13 Created: 2005-05-13 Last updated: 2023-03-24Bibliographically approved
Sundqvist, D., Vaivads, A., André, M., Wahlund, J.-E., Hobara, Y., Joko, S., . . . Stenberg, G. (2005). Multi-spacecraft determination of wave characteristics near the proton gyrofrequency in high altitude cusp. Annales Geophysicae, 23, 983-95
Open this publication in new window or tab >>Multi-spacecraft determination of wave characteristics near the proton gyrofrequency in high altitude cusp
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2005 (English)In: Annales Geophysicae, Vol. 23, p. 983-95Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-12153 (URN)
Available from: 2007-03-23 Created: 2007-03-23 Last updated: 2018-06-09Bibliographically approved
Stenberg, G., Oscarsson, T., André, M., Backrud, M., Khotyaintsev, Y., Vaivads, A., . . . Décréau, P. Electron-scale structures indicating patchy reconnection at the magnetopause?.
Open this publication in new window or tab >>Electron-scale structures indicating patchy reconnection at the magnetopause?
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(English)Manuscript (preprint) (Other academic)
National Category
Meteorology and Atmospheric Sciences Astronomy, Astrophysics and Cosmology Geology
Identifiers
urn:nbn:se:umu:diva-4597 (URN)
Available from: 2005-05-13 Created: 2005-05-13 Last updated: 2018-06-09Bibliographically approved
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