Change search
Link to record
Permanent link

Direct link
BETA
Nilsson, Hans
Alternative names
Publications (10 of 28) Show all publications
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
Show others...
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: 2019-04-05Bibliographically approved
Berecic, L., Behar, E., Nilsson, H., Nicolaou, G., Stenberg-Wieser, G., Wieser, M. & Goetz, C. (2018). Cometary ion dynamics observed in the close vicinity of comet 67P/Churyumov-Gerasimenko during the intermediate activity period. Astronomy and Astrophysics, 613, 1-8
Open this publication in new window or tab >>Cometary ion dynamics observed in the close vicinity of comet 67P/Churyumov-Gerasimenko during the intermediate activity period
Show others...
2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 613, p. 1-8Article in journal (Refereed) Published
Abstract [en]

Aims.Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma.We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet, very close to the nucleus and in theterminator plane.Methods.We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions (mostly usingplasma moments). We propose a statistical approach over a period of one month.Results.On average, two populations were observed, separated in phase space. The motion of the first is governed by its interactionwith the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatiblewith an ambipolar electric field. Both populations display a consistent anti-sunward velocity component.Conclusions.Cometary ions born in different regions of the coma are seen close to the nucleus of comet 67P/Churyumov–Gerasimenko with distinct motions governed in one case by the solar wind electric field and in the other case by the position relative tothe nucleus. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometaryion density in a solar wind electric field reference frame, with higher density in the negative (south) electric field hemisphere. Thereis no corresponding signature in the average magnetic field strengt

Place, publisher, year, edition, pages
EDP Sciences, 2018
National Category
Fusion, Plasma and Space Physics Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-68784 (URN)10.1051/0004-6361/201732082 (DOI)000433880200003 ()
Note

Validerad;2018;Nivå 2;2018-06-14 (andbra)

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-06-21Bibliographically approved
Slapak, R., Schillings, A., Nilsson, H., Yamauchi, M. & Westerberg, L.-G. (2018). Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales, published in Ann. Geophys., 35, 721–731,2017 [Letter to the editor]. Annales Geophysicae
Open this publication in new window or tab >>Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales, published in Ann. Geophys., 35, 721–731,2017
Show others...
2018 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576Article in journal, Letter (Refereed) Published
Place, publisher, year, edition, pages
Copernicus Publications, 2018
National Category
Aerospace Engineering Fluid Mechanics and Acoustics
Research subject
Atmospheric science; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-68587 (URN)10.5194/angeo-35-721-2017-corrigendum (DOI)
Available from: 2018-05-02 Created: 2018-05-02 Last updated: 2018-11-20Bibliographically approved
Behar, E., Tabone, B. & Nilsson, H. (2018). Dawn-dusk asymmetry induced by the Parker spiral angle in the plasma dynamics around comet 67P/Churyumov-Gerasimenko. Monthly notices of the Royal Astronomical Society, 478(2), 1570-1575
Open this publication in new window or tab >>Dawn-dusk asymmetry induced by the Parker spiral angle in the plasma dynamics around comet 67P/Churyumov-Gerasimenko
2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 478, no 2, p. 1570-1575Article in journal (Refereed) Published
Abstract [en]

When interacting, the solar wind and the ionised atmosphere of a comet exchange energy and momentum. Our aim is to understand the influence of the average Parker spiral configuration of the solar wind magnetic field on this interaction. We compare the theoretical expectations of an analytical generalised gyromotion with Rosetta observations at comet 67P/Churyumov-Gerasimenko. A statistical approach allows one to overcome the lack of upstream solar wind measurement. We find that additionally to their acceleration along (for cometary pick-up ions) or against (for solar wind ions) the upstream electric field orientation and sense, the cometary pick-up ions are drifting towards the dawn side of the coma, while the solar wind ions are drifting towards the dusk side of the coma, independent of the heliocentric distance. The dynamics of the interaction is not taking place in a plane, as often assumed in previous works.

Place, publisher, year, edition, pages
Royal Astronomical Society, 2018
National Category
Fusion, Plasma and Space Physics Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-68782 (URN)10.1093/mnras/sty1111 (DOI)000439547400010 ()2-s2.0-85048857464 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-19 (andbra)

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-08-09Bibliographically approved
Yamauchi, M., Sergienko, T., Enell, C.-F., Schillings, A., Slapak, R., Johnsen, M. G., . . . Nilsson, H. (2018). Ionospheric Response Observed by EISCAT During the 6–8 September 2017 Space Weather Event: Overview. Space Weather: The international journal of research and applications, 16(9), 1437-1450
Open this publication in new window or tab >>Ionospheric Response Observed by EISCAT During the 6–8 September 2017 Space Weather Event: Overview
Show others...
2018 (English)In: Space Weather: The international journal of research and applications, ISSN 1542-7390, E-ISSN 1542-7390, Vol. 16, no 9, p. 1437-1450Article in journal (Refereed) Published
Abstract [en]

We present ionospheric plasma conditions observed by the EISCAT radars in Tromsø and on Svalbard, covering 68°–81° geomagnetic latitude, during 6–8 September 2017. This is a period when X2.2 and X9.3 X‐ray flares occurred, two interplanetary coronal mass ejections (ICMEs) arrived at the Earth accompanied by enhancements of MeV‐range energetic particle flux in both the solar wind (SEP event) and inner magnetosphere, and an AL < −2,000 substorm took place. (1) Both X flares caused enhancement of ionospheric electron density for about 10 min. The X9.3 flare also increased temperatures of both electrons and ions over 69°–75° geomagnetic latitude until the X‐ray flux decreased below the level of X‐class flares. However, the temperature was not enhanced after the previous X2.2 flare in the prenoon sector. (2) At around 75° geomagnetic latitude, the prenoon ion upflow flux slightly increased the day after the X9.3 flare, which is also after the first ICME and a SEP event, while no outstanding enhancement was found at the time of these X flares. (3) The upflow velocity sometimes decreased when the interplanetary magnetic field (IMF) turned southward. (4) Before the first ICME arrival after the SEP event under weak IMF with Bz ~0 nT, a substorm‐like expansion of the auroral arc signature took place without local geomagnetic signature near local midnight, while no notable change was observed after the ICME arrival. (5) AL reached <−2,000 nT only after the arrival of the second ICME with strongly southward IMF. Causality connections between the solar/solar wind event and the ionospheric responses remain unclear.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-71230 (URN)10.1029/2018SW001937 (DOI)2-s2.0-85053439748 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-18 (johcin) 

Available from: 2018-10-18 Created: 2018-10-18 Last updated: 2019-03-27Bibliographically approved
Schillings, A., Nilsson, H., Slapak, R., Wintoft, P., Yamauchi, M., Wik, M., . . . Carr, C. (2018). O+ Escape During the Extreme Space Weather Event of 4–10 September 2017. Space Weather: The international journal of research and applications, 16(9), 1363-1376
Open this publication in new window or tab >>O+ Escape During the Extreme Space Weather Event of 4–10 September 2017
Show others...
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: 2018-10-17Bibliographically approved
Behar, E., Tabone, B., Saillenfest, M., Henri, P., Deca, J., Lindkvist, J., . . . Nilsson, H. (2018). Solar wind dynamics around a comet: A 2D semi-analytical kinetic model. Astronomy and Astrophysics, 620, Article ID A35.
Open this publication in new window or tab >>Solar wind dynamics around a comet: A 2D semi-analytical kinetic model
Show others...
2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 620, article id A35Article in journal (Refereed) Published
Abstract [en]

Aims.We aim at analytically modelling the solar wind proton trajectories during their interaction with a partially ionised cometaryatmosphere, not in terms of bulk properties of the flow but in terms of single particle dynamics.Methods.We first derive a generalised gyromotion, in which the electric field is reduced to its motional component. Steady-stateis assumed, and simplified models of the cometary density and of the electron fluid are used to express the force experienced byindividual solar wind protons during the interaction.Results.A three-dimensional (3D) analytical expression of the gyration of two interacting plasma beams is obtained. Applying it to acomet case, the force on protons is always perpendicular to their velocity and has an amplitude proportional to 1/r2. The solar winddeflection is obtained at any point in space. The resulting picture presents a caustic of intersecting trajectories, and a circular regionis found that is completely free of particles. The particles do not lose any kinetic energy and this absence of deceleration, togetherwith the solar wind deflection pattern and the presence of a solar wind ion cavity, is in good agreement with the general results of theRosettamission.Conclusions.The qualitative match between the model and thein situdata highlights how dominant the motional electric field isthroughout most of the interaction region for the solar wind proton dynamics. The model provides a simple general kinetic descriptionof how momentum is transferred between these two collisionless plasmas. It also shows the potential of this semi-analytical modelfor a systematic quantitative comparison to the data.

Place, publisher, year, edition, pages
EDP Sciences, 2018
National Category
Fusion, Plasma and Space Physics Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-68781 (URN)10.1051/0004-6361/201832736 (DOI)000451249600003 ()2-s2.0-85051991586 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-12-05 (svasva)

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2019-01-10Bibliographically approved
Schillings, A., Slapak, R., Nilsson, H., Yamauchi, M. & Westerberg, L.-G. (2017). Atmospheric loss during major geomagnetic storms: Cluster observations. In: : . Paper presented at European Geosciences Union General Assembly 2017, Vienna, Austria, 23-28 April 2017.
Open this publication in new window or tab >>Atmospheric loss during major geomagnetic storms: Cluster observations
Show others...
2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Fluid Mechanics and Acoustics Aerospace Engineering
Research subject
Fluid Mechanics; Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-62336 (URN)
Conference
European Geosciences Union General Assembly 2017, Vienna, Austria, 23-28 April 2017
Available from: 2017-03-08 Created: 2017-03-08 Last updated: 2017-11-24Bibliographically approved
Slapak, R., Schillings, A., Nilsson, H., Yamauchi, M. & Westerberg, L.-G. (2017). Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales. Annales Geophysicae, 35(3), 721-731
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
Show others...
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: 2018-11-20Bibliographically approved
Slapak, R., Nilsson, H., Schillings, A., Yamauchi, M., Westerberg, L.-G. & Dandouras, I. (2017). Atmospheric outflow from the terrestrial magnetosphere: implications forescape on evolutionary time scales. In: : . Paper presented at European Geosciences Union General Assembly 2017, Vienna, Austria, 23-28 April 2017.
Open this publication in new window or tab >>Atmospheric outflow from the terrestrial magnetosphere: implications forescape on evolutionary time scales
Show others...
2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Fluid Mechanics and Acoustics Aerospace Engineering
Research subject
Fluid Mechanics; Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-62328 (URN)
Conference
European Geosciences Union General Assembly 2017, Vienna, Austria, 23-28 April 2017
Available from: 2017-03-08 Created: 2017-03-08 Last updated: 2017-11-24Bibliographically approved
Organisations

Search in DiVA

Show all publications