Change search
Link to record
Permanent link

Direct link
BETA
Alternative names
Publications (10 of 96) Show all publications
Eriksson, E., Vaivads, A., Alm, L., Graham, D. B., Khotyaintsev, Y. V. & André, M. (2020). Electron Acceleration in a Magnetotail Reconnection Outflow Region Using Magnetospheric MultiScale Data. Geophysical Research Letters, 47(1), Article ID e2019GL085080.
Open this publication in new window or tab >>Electron Acceleration in a Magnetotail Reconnection Outflow Region Using Magnetospheric MultiScale Data
Show others...
2020 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 47, no 1, article id e2019GL085080Article in journal (Refereed) Published
Abstract [en]

We study Magnetospheric MultiScale observations in the outflow region of magnetotail reconnection. We estimate the power density converted via the three fundamental electron acceleration mechanisms: Fermi, betatron, and parallel electric fields. The dominant mechanism, both on average and the peak values, is Fermi acceleration with a peak power density of about +200 pW/m3. The magnetic field curvature during the most intense Fermi acceleration is comparable to the electron gyroradius, consistent with efficient electron scattering. The peak power densities due to the betatron acceleration are a factor of 3 lower than that for the Fermi acceleration, the average betatron acceleration is close to zero and slightly negative. The contribution from parallel electric fields is significantly smaller than those from the Fermi and betatron acceleration. However, the observational uncertainties in the parallel electric field measurement prevent further conclusions. There is a strong variation in the power density on a characteristic ion time scale.

Place, publisher, year, edition, pages
Blackwell Publishing, 2020
Keywords
betatron acceleration, electron acceleration, Fermi acceleration, magnetic reconnection
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-267822 (URN)10.1029/2019GL085080 (DOI)000513983400005 ()2-s2.0-85078266696 (Scopus ID)
Note

QC 20200227

Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2020-03-16Bibliographically approved
Li, W. Y., Graham, D. B., Khotyaintsev, Y. V., Vaivads, A., André, M., Min, K., . . . Burch, J. L. (2020). Electron Bernstein waves driven by electron crescents near the electron diffusion region. Nature Communications, 11(1), Article ID 141.
Open this publication in new window or tab >>Electron Bernstein waves driven by electron crescents near the electron diffusion region
Show others...
2020 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 11, no 1, article id 141Article in journal (Refereed) Published
Abstract [en]

The Magnetospheric Multiscale (MMS) spacecraft encounter an electron diffusion region (EDR) of asymmetric magnetic reconnection at Earth’s magnetopause. The EDR is characterized by agyrotropic electron velocity distributions on both sides of the neutral line. Various types of plasma waves are produced by the magnetic reconnection in and near the EDR. Here we report large-amplitude electron Bernstein waves (EBWs) at the electron-scale boundary of the Hall current reversal. The finite gyroradius effect of the outflow electrons generates the crescent-shaped agyrotropic electron distributions, which drive the EBWs. The EBWs propagate toward the central EDR. The amplitude of the EBWs is sufficiently large to thermalize and diffuse electrons around the EDR. The EBWs contribute to the cross-field diffusion of the electron-scale boundary of the Hall current reversal near the EDR.

Place, publisher, year, edition, pages
Nature Research, 2020
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-267776 (URN)10.1038/s41467-019-13920-w (DOI)000511897900002 ()31919351 (PubMedID)2-s2.0-85077697342 (Scopus ID)
Note

QC 20200304

Available from: 2020-03-04 Created: 2020-03-04 Last updated: 2020-03-04Bibliographically approved
Li, W. Y., Graham, D. B., Khotyaintsev, Y. V. V., Vaivads, A., Andre, M., Min, K., . . . Burch, J. L. (2020). Electron Bernstein waves driven by electron crescents near the electron diffusion region. Nature Communications, 11(1), Article ID 141.
Open this publication in new window or tab >>Electron Bernstein waves driven by electron crescents near the electron diffusion region
Show others...
2020 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 11, no 1, article id 141Article in journal (Refereed) Published
Abstract [en]

The Magnetospheric Multiscale (MMS) spacecraft encounter an electron diffusion region (EDR) of asymmetric magnetic reconnection at Earth's magnetopause. The EDR is characterized by agyrotropic electron velocity distributions on both sides of the neutral line. Various types of plasma waves are produced by the magnetic reconnection in and near the EDR. Here we report large-amplitude electron Bernstein waves (EBWs) at the electron-scale boundary of the Hall current reversal. The finite gyroradius effect of the outflow electrons generates the crescent-shaped agyrotropic electron distributions, which drive the EBWs. The EBWs propagate toward the central EDR. The amplitude of the EBWs is sufficiently large to thermalize and diffuse electrons around the EDR. The EBWs contribute to the cross-field diffusion of the electron-scale boundary of the Hall current reversal near the EDR.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2020
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-269041 (URN)10.1038/s41467-019-13920-w (DOI)000511897900002 ()31919351 (PubMedID)2-s2.0-85077697342 (Scopus ID)
Note

QC 20200311

Available from: 2020-03-11 Created: 2020-03-11 Last updated: 2020-03-11
Khotyaintsev, Y. V., Graham, D. B., Steinvall, K., Alm, L., Vaivads, A., Johlander, A., . . . Torbert, R. B. (2020). Electron Heating by Debye-Scale Turbulence in Guide-Field Reconnection. Physical Review Letters, 124(4), Article ID 045101.
Open this publication in new window or tab >>Electron Heating by Debye-Scale Turbulence in Guide-Field Reconnection
Show others...
2020 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 4, article id 045101Article in journal (Refereed) Published
Abstract [en]

We report electrostatic Debye-scale turbulence developing within the diffusion region of asymmetric magnetopause reconnection with amoderate guide field using observations by the Magnetospheric Multiscale mission. We show that Buneman waves and beam modes cause efficient and fast thermalization of the reconnection electron jet by irreversible phase mixing, during which the jet kinetic energy is transferred into thermal energy. Our results show that the reconnection diffusion region in the presence of a moderate guide field is highly turbulent, and that electrostatic turbulence plays an important role in electron heating.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-267742 (URN)10.1103/PhysRevLett.124.045101 (DOI)000510176900004 ()
Note

QC 20200218

Available from: 2020-02-18 Created: 2020-02-18 Last updated: 2020-02-18Bibliographically approved
Hamrin, M., Gunell, H., Goncharov, O., De Spiegeleer, A., Fuselier, S., Mukherjee, J., . . . Giles, B. (2019). Can Reconnection be Triggered as a Solar Wind Directional Discontinuity Crosses the Bow Shock?: A Case of Asymmetric Reconnection. Journal of Geophysical Research - Space Physics, 124(11), 8507-8523
Open this publication in new window or tab >>Can Reconnection be Triggered as a Solar Wind Directional Discontinuity Crosses the Bow Shock?: A Case of Asymmetric Reconnection
Show others...
2019 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 11, p. 8507-8523Article in journal (Refereed) Published
Abstract [en]

Here we present some unique observations of reconnection at a quasi‐perpendicular bow shock as an interplanetary directional discontinuity (DD) is crossing it simultaneously with the Magnetospheric Multiscale (MMS) mission. There are no burst data, but available data show indications of ongoing reconnection at the shock southward of MMS: a bifurcated current sheet with signatures of Hall magnetic and electric fields, normal magnetic fields indicating a magnetic connection between the two reconnecting regions, field‐aligned currents and electric fields, E·J>0 indicating a conversion of magnetic to kinetic energy, and subspin resolution ion energy‐time spectrograms indicating ions being accelerated away from the X‐line. The DD is also observed by four upstream spacecraft (ACE, WIND, Geotail, and ARTEMIS P1) and one downstream in the magnetosheath (Cluster 4), but none of them resolve signatures of ongoing reconnection. We therefore suggest that reconnection was temporarily triggered as the DD was compressed by the shock. Reconnection at the bow shock is inevitably asymmetric with both the density and magnetic field strength being higher on one side of the X‐line (magnetosheath side) than on the other side where the plasma flow also is supersonic (solar wind side). This is different from the asymmetry exhibited at the more commonly studied case of asymmetric reconnection at the magnetopause. Asymmetric reconnection of the bow shock type has never been studied before, and the data discussed here present some first indications of the properties of the reconnection region for this type of reconnection.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-266810 (URN)10.1029/2019JA027006 (DOI)000505404700019 ()2-s2.0-85074818100 (Scopus ID)
Note

Export Date: 23 January 2020; Article. QC 20200128

Available from: 2020-01-23 Created: 2020-01-23 Last updated: 2020-02-10Bibliographically approved
Khotyaintsev, Y. V., Graham, D. B., Norgren, C. & Vaivads, A. (2019). Collisionless Magnetic Reconnection and Waves: Progress Review. Frontiers in Astronomy and Space Sciences, 6, Article ID 70.
Open this publication in new window or tab >>Collisionless Magnetic Reconnection and Waves: Progress Review
2019 (English)In: Frontiers in Astronomy and Space Sciences, ISSN 2296-987X, Vol. 6, article id 70Article, review/survey (Refereed) Published
Abstract [en]

Magnetic reconnection is a fundamental process whereby microscopic plasma processes cause macroscopic changes in magnetic field topology, leading to explosive energy release. Waves and turbulence generated during the reconnection process can produce particle diffusion and anomalous resistivity, as well as heat the plasma and accelerate plasma particles, all of which can impact the reconnection process. We review progress on waves related to reconnection achieved using high resolution multi-point in situ observations over the last decade, since early Cluster and THEMIS observations and ending with recent Magnetospheric Multiscale results. In particular, we focus on the waves most frequently observed in relation to reconnection, ranging from low-frequency kinetic Alfven waves (KAW), to intermediate frequency lower hybrid and whistler-mode waves, electrostatic broadband and solitary waves, as well as the high-frequency upper hybrid, Langmuir, and electron Bernstein waves. Significant progress has been made in understanding localization of the different wave modes in the context of the reconnection picture, better quantification of generation mechanisms and wave-particle interactions, including anomalous resistivity. Examples include: temperature anisotropy driven whistlers in the flux pileup region, anomalous effects due to lower-hybrid waves, upper hybrid wave generation within the electron diffusion region, wave-particle interaction of electrostatic solitary waves. While being clearly identified in observations, some of the wave processes remain challenging for reconnection simulations (electron Bernstein, upper hybrid, Langmuir, whistler), as the instabilities (streaming, loss-cone, shell) which drive these waves require high resolution of distribution functions in phase space, and realistic ratio of Debye to electron inertia scales. We discuss how reconnection configuration, i.e., symmetric vs. asymmetric, guide-field vs. antiparallel, affect wave occurrence, generation, effect on particles, and feedback on the overall reconnection process. Finally, we outline some of the major open questions, such as generation of electromagnetic radiation by reconnection sites and role of waves in triggering/onset of reconnection.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
magnetic reconnection, turbulence, waves, instabilities, kinetic plasma processes
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-265460 (URN)10.3389/fspas.2019.00070 (DOI)000499869100001 ()2-s2.0-85079168221 (Scopus ID)
Note

QC 20191216

Available from: 2019-12-16 Created: 2019-12-16 Last updated: 2020-03-09Bibliographically approved
Fu, H. S., Cao, J. B., Cao, D., Wang, Z., Vaivads, A., Khotyaintsev, Y. V., . . . Huang, S. Y. (2019). Evidence of Magnetic Nulls in Electron Diffusion Region. Geophysical Research Letters, 46(1), 48-54
Open this publication in new window or tab >>Evidence of Magnetic Nulls in Electron Diffusion Region
Show others...
2019 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 1, p. 48-54Article in journal (Refereed) Published
Abstract [en]

Theoretically, magnetic reconnection—the process responsible for solar flares and magnetospheric substorms—occurs at the X‐line or radial null in the electron diffusion region (EDR). However, whether this theory is correct is unknown, because the radial null (X‐line) has never been observed inside the EDR due to the lack of efficient techniques and the scarcity of EDR measurements. Here we report such evidence, using data from the recent MMS mission and the newly developed First‐Order Taylor Expansion (FOTE) Expansion technique. We investigate 12 EDR candidates at the Earth's magnetopause and find radial nulls (X‐lines) in all of them. In some events, spacecraft are only 3 km (one electron inertial length) away from the null. We reconstruct the magnetic topology of these nulls and find it agrees well with theoretical models. These nulls, as reconstructed for the first time inside the EDR by the FOTE technique, indicate that the EDR is active and the reconnection process is ongoing.

Plain Language Summary: Magnetic reconnection is a key process responsible for many explosive phenomena in nature such as solar flares and magnetospheric substorms. Theoretically, such process occurs at the X‐line or radial null in the electron diffusion region (EDR). However, whether this theory is correct is still unknown, because the radial null (X‐line) has never been observed inside the EDR due to the lack of efficient technique and the scarcity of EDR measurements. Here we report such evidence, using data from the recent MMS mission and the newly developed FOTE technique.

Place, publisher, year, edition, pages
2000 Florida Ave NW Washington, DC 20009, USA: American Geophysical Union (AGU), 2019
Keywords
Electron diffusion region, Magnetic null, Magnetic reconnection, FOTE method, Magnetic topology, Reconstruction
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-253246 (URN)10.1029/2018GL080449 (DOI)000456938600006 ()2-s2.0-85059894810 (Scopus ID)
Available from: 2019-06-14 Created: 2019-06-14 Last updated: 2020-01-30Bibliographically approved
Cozzani, G., Retino, A., Califano, F., Alexandrova, A., Contel, O. L., Khotyaintsev, Y., . . . Burch, J. L. (2019). In situ spacecraft observations of a structured electron diffusion region during magnetopause reconnection. Physical review. E, 99(4), Article ID 043204.
Open this publication in new window or tab >>In situ spacecraft observations of a structured electron diffusion region during magnetopause reconnection
Show others...
2019 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 99, no 4, article id 043204Article in journal (Refereed) Published
Abstract [en]

The electron diffusion region (EDR) is the region where magnetic reconnection is initiated and electrons are energized. Because of experimental difficulties, the structure of the EDR is still poorly understood. A key question is whether the EDR has a homogeneous or patchy structure. Here we report Magnetospheric Multiscale (MMS) spacecraft observations providing evidence of inhomogeneous current densities and energy conversion over a few electron inertial lengths within an EDR at the terrestrial magnetopause, suggesting that the EDR can be rather structured. These inhomogenenities are revealed through multipoint measurements because the spacecraft separation is comparable to a few electron inertial lengths, allowing the entire MMS tetrahedron to be within the EDR most of the time. These observations are consistent with recent high-resolution and low-noise kinetic simulations.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-249783 (URN)10.1103/PhysRevE.99.043204 (DOI)000463898200002 ()31108651 (PubMedID)2-s2.0-85064403029 (Scopus ID)
Note

QC 20190429

Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2020-03-09Bibliographically approved
Liu, C. M., Vaivads, A., Graham, D. B., Khotyaintsev, Y. V., Fu, H. S., Johlander, A., . . . Giles, B. L. (2019). Ion-Beam-Driven Intense Electrostatic Solitary Waves in Reconnection Jet. Geophysical Research Letters, 46(22), 12702-12710
Open this publication in new window or tab >>Ion-Beam-Driven Intense Electrostatic Solitary Waves in Reconnection Jet
Show others...
2019 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 22, p. 12702-12710Article in journal (Refereed) Published
Abstract [en]

Electrostatic solitary waves (ESWs) have been reported inside reconnection jets, but their source and role remain unclear hitherto. Here we present the first observational evidence of ESWs generation by cold ion beams inside the jet, by using high‐cadence measurements from the Magnetospheric Multiscale spacecraft in the Earth's magnetotail. Inside the jet, intense ESWs with amplitude up to 30 mV m−1 and potential up to ~7% of the electron temperature are observed in association with accelerated cold ion beams. Instability analysis shows that the ion beams are unstable, providing free energy for the ESWs. The waves are observed to thermalize the beams, thus providing a new channel for ion heating inside the jet. Our study suggests that electrostatic turbulence can play an important role in the jet dynamics.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
reconnection jet; dipolarization front; electrostatic solitary waves; ion beam instability; wave-particle interations; ion heating
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-266811 (URN)10.1029/2019GL085419 (DOI)000498353500001 ()2-s2.0-85075517573 (Scopus ID)
Note

Export Date: 23 January 2020; Article QC 20200129

Available from: 2020-01-23 Created: 2020-01-23 Last updated: 2020-01-30Bibliographically approved
Alm, L., Andre, M., Graham, D. B., Khotvaintsev, Y. V., Vaivads, A., Chappell, C. R., . . . Vines, S. K. (2019). MMS Observations of Multiscale Hall Physics in the Magnetotail. Geophysical Research Letters
Open this publication in new window or tab >>MMS Observations of Multiscale Hall Physics in the Magnetotail
Show others...
2019 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007Article in journal (Refereed) Published
Abstract [en]

We present Magnetospheric Multiscale mission (MMS) observations of Hall physics in the magnetotail, which compared to dayside Hall physics is a relatively unexplored topic. The plasma consists of electrons, moderately cold ions (T similar to 1.5 keV) and hot ions (T similar to 20 keV). MMS can differentiate between the cold ion demagnetization region and hot ion demagnetization regions, which suggests that MMS was observing multiscale Hall physics. The observed Hall electric field is compared with a generalized Ohm's law, accounting for multiple ion populations. The cold ion population, despite its relatively high initial temperature, has a significant impact on the Hall electric field. These results show that multiscale Hall physics is relevant over a much larger temperature range than previously observed and is relevant for the whole magnetosphere as well as for other astrophysical plasma.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2019
Keywords
cold ions, Hall physics, reconnection, multiscale, MMS, magnetotail
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-261017 (URN)10.1029/2019GL084137 (DOI)000485377500001 ()2-s2.0-85071908165 (Scopus ID)
Note

QC 20191002

Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2020-01-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1654-841x

Search in DiVA

Show all publications