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Publications (10 of 24) Show all publications
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
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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
Yamauchi, M. & Slapak, R. (2018). Cusp Current System: An Energy Source View. In: Andreas Keiling Octav Marghitu Michael Wheatland (Ed.), Electric Currents in Geospace and Beyond: (pp. 339-358). Hoboken, N.J.: John Wiley & Sons
Open this publication in new window or tab >>Cusp Current System: An Energy Source View
2018 (English)In: Electric Currents in Geospace and Beyond / [ed] Andreas Keiling Octav Marghitu Michael Wheatland, Hoboken, N.J.: John Wiley & Sons, 2018, p. 339-358Chapter in book (Refereed)
Abstract [en]

Electric currents in the cusp region are reviewed from viewpoints of history and energy conversion. During late 1980s and early 1990s, there were debates on the cause of the cusp region current system (cusp Region 0 field‐aligned current [FAC] and cusp Region 1 FAC, and relevant ionospheric current). The major debates were whether the cusp part Region 1 FAC is an extension of the non‐cusp‐part dayside Region 1 FAC or whether they are generated in different regions independently. The independency of the cusp current system, which was demonstrated by many observations, suggests additional extraction of energy from the magnetosheath‐like flow (e.g., deceleration) inside the polar magnetosphere. An extra deceleration is theoretically possible by adding a substantial local obstacle such as the outflowing ionospheric ions through the mass‐loading effect, which conserves momentum but not kinetic energy. Thus, two different dynamo (J · E < 0) mechanisms most likely exist between the dayside Region 1 and 2 FACs and cusp Region 1 and 0 FACs, forming “double openness,” which was introduced by Vasyliunas [1995]. The other debates (e.g., roles of mesoscale FACs, mapping to high latitude, and current carriers problems) are also reviewed in the light of new observational knowledge after Cluster.

Place, publisher, year, edition, pages
Hoboken, N.J.: John Wiley & Sons, 2018
Series
Geophysical Monograph Series ; 235
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-68300 (URN)10.1002/9781119324522.ch20 (DOI)000476687100020 ()2-s2.0-85050429771 (Scopus ID)9781119324492 (ISBN)9781119324522 (ISBN)
Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2019-08-20Bibliographically 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
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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. 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., 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
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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
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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
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
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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
Slapak, R., Gunell, H. & Hamrin, M. (2017). Observations of multiharmonic ion-cyclotron waves due to inverse ion-cyclotron damping in the northern magnetospheric cusp. Geophysical Research Letters, 44(1), 22-29
Open this publication in new window or tab >>Observations of multiharmonic ion-cyclotron waves due to inverse ion-cyclotron damping in the northern magnetospheric cusp
2017 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, no 1, p. 22-29Article in journal (Refereed) Published
Abstract [en]

We present a case study of inverse ion-cyclotron damping taking place in the northern terrestrial magnetospheric cusp, exciting waves at the ion-cyclotron frequency and its harmonics. The ion-cyclotron waves are primarily seen as peaks in the magnetic-field spectral densities. The corresponding peaks in the electric-field spectral densities are not as profound, suggesting a background electric field noise or other processes of wave generation causing the electric spectral densities to smoothen out more compared to the magnetic counterpart. The required condition for inverse ion-cyclotron damping is a velocity shear in the magnetic field-aligned ion-bulk flow, and this condition is often naturally met for magnetosheath influx in the northern magnetospheric cusp, just as in the presented case. We note that some ion-cyclotron wave activity is present in a few similar shear events in the southern cusp, which indicates that other mechanisms generating ion-cyclotron waves may also be present during such conditions.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2017
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-61214 (URN)10.1002/2016GL071680 (DOI)000393954900003 ()2-s2.0-85010604932 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-02-10 (andbra)

Available from: 2016-12-22 Created: 2016-12-22 Last updated: 2018-11-20Bibliographically approved
Slapak, R., Hamrin, M., Pitkänen, T., Yamauchi, M., Nilsson, H., Karlsson, T. & Schillings, A. (2017). Quantification of the total ion transport in the near-Earth plasma sheet. Annales Geophysicae, 35(4), 869-877
Open this publication in new window or tab >>Quantification of the total ion transport in the near-Earth plasma sheet
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2017 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 35, no 4, p. 869-877Article in journal (Refereed) Published
Abstract [en]

Recent studies strongly suggest that a majority of the observed O+ cusp outflows will eventually escape into the solar wind, rather than be transported to the plasma sheet. Therefore, an investigation of plasma sheet flows will add to these studies and give a more complete picture of magnetospheric ion dynamics. Specifically, it will provide a greater understanding of atmospheric loss. We have used Cluster spacecraft 4 to quantify the H+ and O+ total transports in the near-Earth plasma sheet, using data covering 2001-2005. The results show that both H+ and O+ have earthward net fluxes of the orders of 1026 and 1024 s -1, respectively. The O+ plasma sheet return flux is 1 order of magnitude smaller than the O+ outflows observed in the cusps, strengthening the view that most ionospheric O+ outflows do escape. The H+ return flux is approximately the same as the ionospheric outflow, suggesting a stable budget of H+ in the magnetosphere. However, low-energy H+, not detectable by the ion spectrometer, is not considered in our study, leaving the complete magnetospheric H+ circulation an open question. Studying tailward flows separately reveals a total tailward O+ flux of about 0. 5 × 1025 s -1, which can be considered as a lower limit of the nightside auroral region O+ outflow. Lower velocity flows ( < 100kms -1) contribute most to the total transports, whereas the high-velocity flows contribute very little, suggesting that bursty bulk flows are not dominant in plasma sheet mass transport.

Place, publisher, year, edition, pages
Copernicus GmbH, 2017
National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-65090 (URN)10.5194/angeo-35-869-2017 (DOI)000406343400001 ()2-s2.0-85026464920 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-08-15 (andbra)

Available from: 2017-08-15 Created: 2017-08-15 Last updated: 2018-07-10Bibliographically approved
Schillings, A., Nilsson, H., Slapak, R., Yamauchi, M. & Westerberg, L. G. (2017). Relative outflow enhancements during major geomagnetic storms: Cluster observations. Annales Geophysicae, 5(6), 1341-1352
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
Barghouthi, I. A., Abudayyeh, H., Slapak, R. & Nilsson, H. (2016). O+ and H+ above the polar cap: Observations and semikinetic simulations (ed.). Paper presented at . Journal of Geophysical Research - Space Physics, 121(1), 459-474
Open this publication in new window or tab >>O+ and H+ above the polar cap: Observations and semikinetic simulations
2016 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 1, p. 459-474Article in journal (Refereed) Published
Abstract [en]

A 1-dimensional direct simulation Monte Carlo model is used to study the outflow of O+ and H+ ions from 1.2 RE to 15.2 RE along two flight trajectories originating from the polar cap, namely the central polar cap (CPC) and the cusp. To study the effect of varying geophysical conditions and to deduce the proper set of parameters. several parameters were varied and the results were compared to corresponding data from Cluster spacecraft. First, several sets of diffusion coefficients were considered based on using diffusion coefficients calculated by Barghouthi et al. [1998], Nilsson et al. [2013], and Abudayyeh et al. [2015b] for different altitude intervals. It was found that in the central polar cap using the diffusion coefficients reported by Barghouthi et al. [1998] for altitudes lower than 3.7 RE, zero diffusion coefficients between 3.7 and 7.5 RE and diffusion coefficients from Nilsson et al. [2013] for altitudes higher than 7.5 RE provide the best fit for O+ ions. For O+ ions in the cusp the best fit was obtained for using Barghouthi et al. [1998] diffusion coefficients for altitudes lower than 3.7 RE and Nilsson et al. [2013] diffusion coefficients for altitudes higher than that. The best fit for H+ ions in both regions was obtained by using the diffusion coefficients calculated by Abudayyeh et al. [2015b]. Also, it was found that along an ion's trajectory the most recent heating dominates. Second, the strength of centrifugal acceleration was varied by using three values for the ionospheric electric field namely: 0, 50, and 100 mV/m. It was found that the value of 50 mV/m provided the best fit for both ion species in both regions. Finally the lower altitude boundary conditions and the electron temperature were varied. Increasing the electron temperature and the lower altitude O+ parallel velocity were found to increase the access of O+ ions to higher altitudes and therefore increase the density at a given altitude. The variation of all other boundary conditions only affected the densities of the ions and not the other moments due to the overwhelming effect of wave particle interaction. Furthermore varying the parameters of one ion species has no effect on the other ion species. We also compared the energy gain per ion due to wave particle interaction, centrifugal acceleration, and ambipolar electric field and found that wave particle interaction is the most important mechanism, while ambipolar electric field is relatively unimportant especially at higher altitudes.

National Category
Aerospace Engineering
Research subject
Atmospheric science
Identifiers
urn:nbn:se:ltu:diva-3381 (URN)10.1002/2015JA021990 (DOI)000371146900033 ()2-s2.0-84959189971 (Scopus ID)133d3be4-b91c-4845-b471-2a24766935e2 (Local ID)133d3be4-b91c-4845-b471-2a24766935e2 (Archive number)133d3be4-b91c-4845-b471-2a24766935e2 (OAI)
Note
Validerad; 2016; Nivå 2; 20160114 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-2347-1871

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