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Publications (4 of 4) Show all publications
Fuselier, S. A., Trattner, K. J., Petrinec, S. M., Denton, M. H., Toledo-Redondo, S., André, M., . . . Strangeway, R. J. (2019). Mass Loading the Earth's Dayside Magnetopause Boundary Layer and Its Effect on Magnetic Reconnection. Geophysical Research Letters, 46(12), 6204-6213
Open this publication in new window or tab >>Mass Loading the Earth's Dayside Magnetopause Boundary Layer and Its Effect on Magnetic Reconnection
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2019 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 12, p. 6204-6213Article in journal (Refereed) Published
Abstract [en]

When the interplanetary magnetic field is northward for a period of time, O+ from the high-latitude ionosphere escapes along reconnected magnetic field lines into the dayside magnetopause boundary layer. Dual-lobe reconnection closes these field lines, which traps O+ and mass loads the boundary layer. This O+ is an additional source of magnetospheric plasma that interacts with magnetosheath plasma through magnetic reconnection. This mass loading and interaction is illustrated through analysis of a magnetopause crossing by the Magnetospheric Multiscale spacecraft. While in the O+-rich boundary layer, the interplanetary magnetic field turns southward. As the Magnetospheric Multiscale spacecraft cross the high-shear magnetopause, reconnection signatures are observed. While the reconnection rate is likely reduced by the mass loading, reconnection is not suppressed at the magnetopause. The high-latitude dayside ionosphere is therefore a source of magnetospheric ions that contributes often to transient reduction in the reconnection rate at the dayside magnetopause.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2019
Keywords
magnetic reconnection, magnetosphere-ionosphere coupling, magnetopause, boundary layers
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-392876 (URN)10.1029/2019GL082384 (DOI)000477616300006 ()
Available from: 2019-09-26 Created: 2019-09-26 Last updated: 2019-12-12Bibliographically approved
Farrugia, C. J., Cohen, I. J., Vasquez, B. J., Lugaz, N., Alm, L., Torbert, R. B., . . . Pollock, C. J. (2018). Effects in the Near-Magnetopause Magnetosheath Elicited by Large-Amplitube Alfvenic Fluctuations Terminating in a Field and Flow Discontinuity. Journal of Geophysical Research - Space Physics, 123(11), 8983-9004
Open this publication in new window or tab >>Effects in the Near-Magnetopause Magnetosheath Elicited by Large-Amplitube Alfvenic Fluctuations Terminating in a Field and Flow Discontinuity
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2018 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 11, p. 8983-9004Article in journal (Refereed) Published
Abstract [en]

In this paper we report on a sequence of large-amplitude Alfvenic fluctuations terminating in a field and flow discontinuity and their effects on electromagnetic fields and plasmas in the near-magnetopause magnetosheath. An arc-polarized structure in the magnetic field was observed by the Time History of Events and Macroscale Interactions during Substorms-C in the solar wind, indicative of nonlinear Alfven waves. It ends with a combined tangential discontinuity/vortex sheet, which is strongly inclined to the ecliptic plane and at which there is a sharp rise in the density and a drop in temperature. Several effects resulting from this structure were observed by the Magnetospheric Multiscale spacecraft in the magnetosheath close to the subsolar point (11:30 magnetic local time) and somewhat south of the geomagnetic equator (-33 degrees magnetic latitude): (i) kinetic Alfven waves; (ii) a peaking of the electric and magnetic field strengths where E . J becomes strong and negative (-1 nW/m(3)) just prior to an abrupt dropout of the fields; (iii) evolution in the pitch angle distribution of energetic (a few tens of kilo-electron-volts) ions (H+, Hen+, and On+) and electrons inside a high-density region, which we attribute to gyrosounding of the tangential discontinuity/vortex sheet structure passing by the spacecraft; (iv) field-aligned acceleration of ions and electrons that could be associated with localized magnetosheath reconnection inside the high-density region; and (v) variable and strong flow changes, which we argue to be unrelated to reconnection at partial magnetopause crossings and likely result from deflections of magnetosheath flow by a locally deformed, oscillating magnetopause.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2018
National Category
Fusion, Plasma and Space Physics Geophysics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-372831 (URN)10.1029/2018JA025724 (DOI)000453227400007 ()
Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2019-12-12Bibliographically approved
Torbert, R. B., Burch, J. L., Phan, T. D., Hesse, M., Argall, M. R., Shuster, J., . . . Saito, Y. (2018). Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space. Science, 362(6421), 1391-1395
Open this publication in new window or tab >>Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space
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2018 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 362, no 6421, p. 1391-1395Article in journal (Refereed) Published
Abstract [en]

Magnetic reconnection is an energy conversion process that occurs in many astrophysical contexts including Earth's magnetosphere, where the process can be investigated in situ by spacecraft. On 11 July 2017, the four Magnetospheric Multiscale spacecraft encountered a reconnection site in Earth's magnetotail, where reconnection involves symmetric inflow conditions. The electron-scale plasma measurements revealed (i) super-Alfvenic electron jets reaching 15,000 kilometers per second; (ii) electron meandering motion and acceleration by the electric field, producing multiple crescent-shaped structures in the velocity distributions; and (iii) the spatial dimensions of the electron diffusion region with an aspect ratio of 0.1 to 0.2, consistent with fast reconnection. The well-structured multiple layers of electron populations indicate that the dominant electron dynamics are mostly laminar, despite the presence of turbulence near the reconnection site.

Place, publisher, year, edition, pages
AMER ASSOC ADVANCEMENT SCIENCE, 2018
National Category
Fusion, Plasma and Space Physics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-373327 (URN)10.1126/science.aat2998 (DOI)000453845000056 ()30442767 (PubMedID)
Funder
Swedish National Space Board
Available from: 2019-01-15 Created: 2019-01-15 Last updated: 2019-12-12Bibliographically approved
Alm, L., André, M., Vaivads, A., Khotyaintsev, Y. V., Torbert, R. B., Burch, J. L., . . . Mauk, B. H. (2018). Magnetotail Hall Physics in the Presence of Cold Ions. Geophysical Research Letters, 45(20), 10941-10950
Open this publication in new window or tab >>Magnetotail Hall Physics in the Presence of Cold Ions
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2018 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 20, p. 10941-10950Article in journal (Refereed) Published
Abstract [en]

We present the first in situ observation of cold ionospheric ions modifying the Hall physics of magnetotail reconnection. While in the tail lobe, Magnetospheric Multiscale mission observed cold (tens of eV) E x B drifting ions. As Magnetospheric Multiscale mission crossed the separatrix of a reconnection exhaust, both cold lobe ions and hot (keV) ions were observed. During the closest approach of the neutral sheet, the cold ions accounted for similar to 30% of the total ion density. Approximately 65% of the initial cold ions remained cold enough to stay magnetized. The Hall electric field was mainly supported by the j x B term of the generalized Ohm's law, with significant contributions from the del center dot P-e and v(c) x B terms. The results show that cold ions can play an important role in modifying the Hall physics of magnetic reconnection even well inside the plasma sheet. This indicates that modeling magnetic reconnection may benefit from including multiscale Hall physics. Plain Language Summary Cold ions have the potential of changing the fundamental physics behind magnetic reconnection. Here we present the first direct observation of this process in action in the magnetotail. Cold ions from the tail lobes were able to remain cold even deep inside the much hotter plasma sheet. Even though the cold ions only accounted for similar to 30% of the total ions, they had a significant impact on the electric fields near the reconnection region.

National Category
Geophysics Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-372422 (URN)10.1029/2018GL079857 (DOI)000451510500017 ()
Funder
Swedish National Space Board, SNSB 176/15Swedish National Space Board, 158/16
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-12-12Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6997-7037

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