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Wellbrock, A., Jones, G. H., Dresing, N., Coates, A. J., Wedlund, C. S., Nilsson, H., . . . Mandt, K. (2022). Observations of a Solar Energetic Particle Event from Inside and Outside the Coma of Comet 67P. Journal of Geophysical Research - Space Physics, 127(12)
Open this publication in new window or tab >>Observations of a Solar Energetic Particle Event from Inside and Outside the Coma of Comet 67P
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2022 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 127, no 12Article in journal (Refereed) Published
Abstract [en]

We analyze observations of an SEP event at Rosetta’s target comet 67P/Churyumov-Gerasimenko during March 6th-10th 2015. The comet was 2.15AU from the Sun, with the Rosetta spacecraft approximately 70km from the nucleus placing it deep inside the comet’s coma and allowing us to study its response. The Eastern flank of an ICME also encountered Rosetta on March 6th and 7th. Rosetta’s RPC data indicate increases in ionization rates, and cometary water group pickup ions exceeding 1keV. Increased charge exchange reactions between solar wind ions and cometary neutrals also indicate increased upstream neutral populations consistent with enhanced SEP induced surface activity. In addition, the most intense parts of the event coincide with observations interpreted as an infant cometary bow shock, indicating that the SEPs may have enhanced the formation and/or intensified the observations. These solar transient events may also have pushed the cometopause closer to the nucleus.We track and discuss characteristics of the SEP event using remote observations by SOHO, WIND and GOES at the Sun, in-situ measurements at STEREO A, Mars and Rosetta, and ENLIL modeling. Based on its relatively prolonged duration, gradual and anisotropic nature and broad angular spread in the heliosphere, we determine the main particle acceleration source to be a distant ICME which emerged from the Sun on March 6th 2015 and was detected locally in the Martian ionosphere but was never encountered by 67P directly. The ICME’s shock produced SEPs for several days which traveled to the in-situ observation sites via magnetic field line connections.

Place, publisher, year, edition, pages
John Wiley & Sons, 2022
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-94256 (URN)10.1029/2022ja030398 (DOI)
Note

Godkänd;2022;Nivå 0;2022-12-02 (sofila);

Funder: STFC consolidated Grants (grant nos. ST/N000722/1, ST/S000240/1, ST/W001004/1 and ST/W00089X/1); University of Turku, Finland;  Austrian Science Fund (FWF) (grant no. P32035-N36); UK-STFC Ernest Rutherford Fellowship (grant no. ST/V004115/1); NASA O2R Grant (no. 80NSSC20K0285); Academy of Finland (grant no. 322544); CNES; ANR (grant no. ANR-15-CE31-0009-01); ESA

Available from: 2022-11-24 Created: 2022-11-24 Last updated: 2022-12-02Bibliographically approved
Nilsson, H., Behar, E., Burch, J. L., Carr, C. M., Eriksson, A. I., Glassmeier, K., . . . Karlsson, T. (2021). Birth of a Magnetosphere. In: Romain Maggiolo; Nicolas André; Hiroshi Hasegawa; Daniel T. Welling (Ed.), Magnetospheres in the Solar System: (pp. 427-440). John Wiley & Sons
Open this publication in new window or tab >>Birth of a Magnetosphere
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2021 (English)In: Magnetospheres in the Solar System / [ed] Romain Maggiolo; Nicolas André; Hiroshi Hasegawa; Daniel T. Welling, John Wiley & Sons, 2021, p. 427-440Chapter in book (Refereed)
Abstract [en]

A magnetosphere may form around an object in a stellar wind either due to the intrinsic magnetic field of the object or stellar wind interaction with the ionosphere of the object. Comets represent the most variable magnetospheres in our solar system, and through the Rosetta mission we have had the chance to study the birth and evolution of a comet magnetosphere as the comet nucleus approached the Sun. We review the birth of the comet magnetosphere as observed at comet 67P Churyumov–Gerasimenko, the formation of plasma boundaries and how the solar wind–atmosphere interaction changes character as the cometary gas cloud and magnetosphere grow in size. Mass loading of the solar wind leads to an asymmetric deflection of the solar wind for low outgassing rates. With increasing activity a solar wind ion cavity forms. Intermittent shock‐like features were also observed. For intermediate outgassing rate a diamagnetic cavity is formed inside the solar wind ion cavity, thus well separated from the solar wind. The cometary plasma was typically very structured and variable. The region of the coma dense enough to have significant collisions forms a special region with different ion chemistry and plasma dynamics as compared to the outer collision‐free region.  

Place, publisher, year, edition, pages
John Wiley & Sons, 2021
Series
Geophysical Monograph Series, ISSN 0065-8448
Keywords
comet magnetosphere, comet nucleus, cometary plasma boundaries, electric fields, ion chemistry, plasma dynamics, Rosetta plasma observations, solar wind–atmosphere interaction
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-84233 (URN)10.1002/9781119815624.ch27 (DOI)2-s2.0-85136031987 (Scopus ID)
Note

ISBN för värdpublikation: 9781119507529, 9781119815624

Available from: 2021-05-10 Created: 2021-05-10 Last updated: 2023-09-04Bibliographically approved
Alho, M., Jarvinen, R., Wedlund, C. S., Nilsson, H., Kallio, E. & Pulkkinen, T. I. (2021). Remote sensing of cometary bow shocks: modelled asymmetric outgassing and pickup ion observations. Monthly notices of the Royal Astronomical Society, 506(4), 4735-4749
Open this publication in new window or tab >>Remote sensing of cometary bow shocks: modelled asymmetric outgassing and pickup ion observations
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2021 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 506, no 4, p. 4735-4749Article in journal (Refereed) Published
Abstract [en]

Despite the long escort by the ESA Rosetta mission, direct observations of a fully developed bow shock around 67P/Churyumov-Gerasimenko have not been reported. Expanding on our previous work on indirect observations of a shock, we model the large-scale features in cometary pickup ions, and compare the results with the ESA Rosetta Plasma Consortium Ion Composition Analyser ion spectrometer measurements over the pre-perihelion portion of the escort phase. Using our hybrid plasma simulation, an empirical, asymmetric outgassing model for 67P, and varied interplanetary magnetic field (IMF) clock angles, we model the evolution of the large-scale plasma environment. We find that the subsolar bow shock standoff distance is enhanced by asymmetric outgassing with a factor of 2 to 3, reaching up to 18 000 km approaching perihelion. We find that distinct spectral features in simulated pickup ion distributions are present for simulations with shock-like structures, with the details of the spectral features depending on shock standoff distance, heliocentric distance, and IMF configuration. Asymmetric outgassing along with IMF clock angle is found to have a strong effect on the location of the spectral features, while the IMF clock angle causes no significant effect on the bow shock standoff distance. These dependences further complicate the interpretation of the ion observations made by Rosetta. Our data-model comparison shows that the large-scale cometary plasma environment can be probed by remote sensing the pickup ions, at least when the comet’s activity is comparable to that of 67P, and the solar wind parameters are known.

Place, publisher, year, edition, pages
Oxford University Press, 2021
Keywords
plasmas, shock waves, methods: numerical, techniques: miscellaneous, comets: individual: 67P
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-87624 (URN)10.1093/mnras/stab1940 (DOI)000705339100006 ()2-s2.0-85118181856 (Scopus ID)
Note

Godkänd;2021;Nivå 0;2021-12-06 (johcin);

Funder: Academy of Finland (310444)

Available from: 2021-10-25 Created: 2021-10-25 Last updated: 2022-04-01Bibliographically approved
Schillings, A., Nilsson, H., Slapak, R., Yamauchi, M. & Westerberg, L.-G. (2020). Earth’s O+ Outflow and Escape during Various Solar Wind Conditions. In: : . Paper presented at AGU Fall Meeting, "Shaping the Future of Science", Online everywhere, 1-17 December 2020. American Geophysical Union (AGU)
Open this publication in new window or tab >>Earth’s O+ Outflow and Escape during Various Solar Wind Conditions
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2020 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Ion outflow at Earth is studied since several decades and is important for the global atmospheric evolution. Over the years, spacecraft and technology improved leading to new studies and breakthrough in the field. With different mechanisms to gain energy and velocity such as field-aligned acceleration, centrifugal acceleration and transversal heating, a large amount of ions becomes gravitationally untrapped above the ionosphere. While some of these ions may enter the plasma sheet and partially be redirected towards Earth, majority of these ions reaches the high-latitude boundary region, such as the plasma mantle and are lost into the solar wind. We examined this phenomenon using Cluster European Spacecraft that covers these high-latitude regions. Here, we studied the influence of solar wind conditions on O+ outflow and escape during 7 years of observations (2001 to 2007). We found that O+ outflow is exponentially correlated with enhanced geomagnetic activity (Kp index) as well as with solar wind dynamic pressure and IMF. Under undisturbed magnetospheric conditions, the O+ outflow is typically 1012.5 m-2s-1 while it reaches 1014 m-2s-1 during major geomagnetic storms. Additionally, tracing (forward in time) about 25000 O+ ions initially observed in the plasma mantle showed that 98% of these ions escape directly through the magnetopause whereas only a few escape through the distant tail. In summary, the more disturbed the magnetosphere is, the more ion outflow and escape is observed.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2020
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-80441 (URN)
Conference
AGU Fall Meeting, "Shaping the Future of Science", Online everywhere, 1-17 December 2020
Available from: 2020-08-18 Created: 2020-08-18 Last updated: 2023-09-05Bibliographically approved
Wedlund, C. S., Behar, E., Nilsson, H., Alho, M., Kallio, E., Gunell, H., . . . Hoekstra, R. (2020). Erratum: Solar wind charge exchange in cometary atmospheres: III. Results from the Rosetta mission to comet 67P/Churyumov-Gerasimenko. Astronomy and Astrophysics, 640, Article ID C3.
Open this publication in new window or tab >>Erratum: Solar wind charge exchange in cometary atmospheres: III. Results from the Rosetta mission to comet 67P/Churyumov-Gerasimenko
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2020 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 640, article id C3Article in journal (Other academic) Published
Place, publisher, year, edition, pages
EDP Sciences, 2020
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-80713 (URN)10.1051/0004-6361/201834881e (DOI)000560451000001 ()2-s2.0-85089934663 (Scopus ID)
Note

Godkänd;2020;Nivå 0;2020-09-07 (alebob);

Erratum in: Astronomy and Astrophysics, vol. 630, article no. A37, DOI: 10.1051/0004-6361/201834881

Available from: 2020-09-07 Created: 2020-09-07 Last updated: 2023-09-04Bibliographically approved
Schillings, A., Gunell, H., Nilsson, H., De Spiegeleer, A., Ebihara, Y., Westerberg, L. G., . . . Slapak, R. (2020). The fate of O+ ions observed in the plasma mantle and cusp: particle tracing modelling and cluster observations. Annales Geophysicae, 38(3), 645-656
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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2020 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 38, no 3, p. 645-656Article in journal (Refereed) Published
Abstract [en]

Ion escape is of particular interest for studying the evolution of the atmosphere on geological timescales. Previously, using Cluster-CODIF data, we investigated the oxygen ion outflow from the plasma mantle for different solar wind conditions and geomagnetic activity. We found significant correlations between solar wind parameters, geomagnetic activity (Kp index), and the O+ outflow. From these studies, we suggested that O+ ions observed in the plasma mantle and cusp have enough energy and velocity to escape the magnetosphere and be lost into the solar wind or in the distant magnetotail. Thus, this study aims to investigate where the ions observed in the plasma mantle end up. In order to answer this question, we numerically calculate the trajectories of O+ ions using a tracing code to further test this assumption and determine the fate of the observed ions. Our code consists of a magnetic field model (Tsyganenko T96) and an ionospheric potential model (Weimer 2001) in which particles initiated in the plasma mantle region are launched and traced forward in time. We analysed 131 observations of plasma mantle events in Cluster data between 2001 and 2007, and for each event 200 O+ particles were launched with an initial thermal and parallel bulk velocity corresponding to the velocities observed by Cluster. After the tracing, we found that 98 % of the particles are lost into the solar wind or in the distant tail. Out of these 98 %, 20 % escape via the dayside magnetosphere.

Place, publisher, year, edition, pages
Copernicus Publications, 2020
National Category
Fluid Mechanics and Acoustics Aerospace Engineering
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-76359 (URN)10.5194/angeo-38-645-2020 (DOI)000538406700001 ()2-s2.0-85085934066 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-07-01 (johcin)

Available from: 2019-10-11 Created: 2019-10-11 Last updated: 2023-10-24Bibliographically approved
Schillings, A., Gunell, H., Nilsson, H., De Spiegeleer, A., Ebihara, Y., Westerberg, L.-G., . . . Slapak, R. (2020). The fate of O+ ions observed in the plasma mantle: particle tracing modelling and Cluster observations. In: : . Paper presented at AGU Fall Meeting, "Shaping the Future of Science", Online everywhere, 1-17 December 2020. American Geophysical Union (AGU)
Open this publication in new window or tab >>The fate of O+ ions observed in the plasma mantle: particle tracing modelling and Cluster observations
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2020 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

The atmospheric evolution on geological timescales is partly given by the atmospheric escape. This escape includes ion escape and particularly O+ ions. How much O+ ions escape from the Earth is the main focus of this study. Using the Tsyganenko and Weimer models to represent the magnetic and electric fields respectively, we traced 26200 O+ ions trajectories forward in time and studied their final positions in the Earth’s environment. Starting in the plasma mantle, the initial positions, thermal and parallel bulk velocities of O+ ions are taken from the European Cluster observations between 2001 and 2007. Most (98%) of the ions observed in the plasma mantle escape the Earth’s magnetosphere, with 20% of them directly through the dayside magnetopause.  An interesting feature of the 80% escaping ions left is that very few reach the distant tail, they rather escape through the nightside magnetopause. Finally, no significant correlation was found between magnetospheric disturbed conditions and the final positions of the traced O+ ions.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2020
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-80440 (URN)
Conference
AGU Fall Meeting, "Shaping the Future of Science", Online everywhere, 1-17 December 2020
Available from: 2020-08-18 Created: 2020-08-18 Last updated: 2023-09-05Bibliographically approved
Schillings, A., Slapak, R., Nilsson, H., Yamauchi, M., Dandouras, I. & Westerberg, L.-G. (2019). Earth atmospheric loss through the plasma mantle and its dependence on solar wind parameters. Paper presented at 1880-5981. Earth Planets and Space, 71(70)
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, ISSN 1343-8832, E-ISSN 1880-5981, 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)
Conference
1880-5981
Note

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

Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2023-10-24Bibliographically approved
Schillings, A., Slapak, R., Nilsson, H., Yamauchi, M., Dandouras, I. & Westerberg, L.-G. (2019). Earth atmospheric loss through the plasma mantle and its dependence onsolar wind parameters. In: : . Paper presented at EGU General Assembly 2019, 7–12 April 2019, Vienna, Austria.
Open this publication in new window or tab >>Earth atmospheric loss through the plasma mantle and its dependence onsolar wind parameters
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2019 (English)Conference paper (Refereed)
National Category
Aerospace Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-73466 (URN)
Conference
EGU General Assembly 2019, 7–12 April 2019, Vienna, Austria
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2023-10-24Bibliographically approved
Alho, M., Wedlund, C. S., Nilsson, H., Kallio, E., Jarvinen, R. & Pulkkinen, T. (2019). Hybrid modeling of cometary plasma environments: II. Remote-sensing of a cometary bow shock. Astronomy and Astrophysics, 630, Article ID A45.
Open this publication in new window or tab >>Hybrid modeling of cometary plasma environments: II. Remote-sensing of a cometary bow shock
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2019 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 630, article id A45Article in journal (Refereed) Published
Abstract [en]

Context. The ESA Rosetta probe has not seen direct evidence of a fully formed bow shock at comet 67P/Churyumov–Gerasimenko (67P). Ion spectrometer measurements of cometary pickup ions measured in the vicinity of the nucleus of 67P are available and may contain signatures of the large-scale plasma environment.

Aims. The aim is to investigate the possibility of using pickup ion signatures to infer the existence or nonexistence of a bow shock-like structure and possibly other large-scale plasma environment features.

Methods. A numerical plasma model in the hybrid plasma description was used to model the plasma environment of a comet. Simulated pickup ion spectra were generated for different interplanetary magnetic field conditions. The results were interpreted through test particle tracing in the hybrid simulation solutions.

Results. Features of the observed pickup ion energy spectrum were reproduced, and the model was used to interpret the observation to be consistent with a shock-like structure. We identify (1) a spectral break related to the bow shock, (2) a mechanism for generating the spectral break, and (3) a dependency of the energy of the spectral break on the interplanetary magnetic field magnitude and bow shock standoff distance.

Place, publisher, year, edition, pages
EDP Sciences, 2019
Keywords
comets: general, comets: individual: 67P/Churyumov-Gerasimenko, methods: numerical / plasmas / shock waves, techniques: miscellaneous
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-76347 (URN)10.1051/0004-6361/201834863 (DOI)000486989400044 ()2-s2.0-85097198795 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-10-10 (johcin)

Available from: 2019-10-10 Created: 2019-10-10 Last updated: 2021-12-13Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-7787-2160

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