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BETA
Khotyaintsev, Yuri V.ORCID iD iconorcid.org/0000-0001-5550-3113
Alternative names
Publications (10 of 28) Show all publications
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
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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: 2019-06-18Bibliographically approved
Fu, H. S., Xu, Y., Vaivads, A. & Khotyaintsev, Y. V. (2019). Super-efficient Electron Acceleration by an Isolated Magnetic Reconnection. Astrophysical Journal Letters, 870(2), Article ID L22.
Open this publication in new window or tab >>Super-efficient Electron Acceleration by an Isolated Magnetic Reconnection
2019 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 870, no 2, article id L22Article in journal (Refereed) Published
Abstract [en]

Magnetic reconnection-the process typically lasting for a few seconds in space-is able to accelerate electrons. However, the efficiency of the acceleration during such a short period is still a puzzle. Previous analyses, based on spacecraft measurements in the Earth's magnetotail, indicate that magnetic reconnection can enhance electron fluxes up to 100 times. This efficiency is very low, creating an impression that magnetic reconnection is not good at particle acceleration. By analyzing Cluster data, we report here a remarkable magnetic reconnection event during which electron fluxes are enhanced by 10,000 times. Such acceleration, 100 times more efficient than those in previous studies, is caused by the betatron mechanism. Both reconnection fronts and magnetic islands contribute to the acceleration, with the former being more prominent.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Keywords
acceleration of particles, magnetic reconnection
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-253253 (URN)10.3847/2041-8213/aafa75 (DOI)000455938700002 ()2-s2.0-85060198327 (Scopus ID)
Note

QC 20190625

Available from: 2019-06-14 Created: 2019-06-14 Last updated: 2019-06-25Bibliographically approved
Schwartz, S. J., Avanov, L., Turner, D., Zhang, H., Gingell, I., Eastwood, J. P., . . . Wilder, F. (2018). Ion Kinetics in a Hot Flow Anomaly: MMS Observations. Geophysical Research Letters, 45(21), 11520-11529
Open this publication in new window or tab >>Ion Kinetics in a Hot Flow Anomaly: MMS Observations
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2018 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 21, p. 11520-11529Article in journal (Refereed) Published
Abstract [en]

Hot Flow Anomalies (HFAs) are transients observed at planetary bow shocks, formed by the shock interaction with a convected interplanetary current sheet. The primary interpretation relies on reflected ions channeled upstream along the current sheet. The short duration of HFAs has made direct observations of this process difficult. We employ high resolution measurements by NASA's Magnetospheric Multiscale Mission to probe the ion microphysics within a HFA. Magnetospheric Multiscale Mission data reveal a smoothly varying internal density and pressure, which increase toward the trailing edge of the HFA, sweeping up particles trapped within the current sheet. We find remnants of reflected or other backstreaming ions traveling along the current sheet, but most of these are not fast enough to out-run the incident current sheet convection. Despite the high level of internal turbulence, incident and backstreaming ions appear to couple gyro-kinetically in a coherent manner. Plain Language Summary Shock waves in space are responsible for energizing particles and diverting supersonic flows around planets and other obstacles. Explosive events known as Hot Flow Anomalies (HFAs) arise when a rapid change in the interplanetary magnetic field arrives at the bow shock formed by, for example, the supersonic solar wind plasma flow from the Sun impinging on the Earth's magnetic environment. HFAs are known to produce impacts all the way to ground level, but the physics responsible for their formation occur too rapidly to be resolved by previous satellite missions. This paper employs NASA's fleet of four Magnetospheric Multiscale satellites to reveal for the first time clear, discreet populations of ions that interact coherently to produce the extreme heating and deflection.

Place, publisher, year, edition, pages
Blackwell Publishing Ltd, 2018
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-253640 (URN)10.1029/2018GL080189 (DOI)000451832600002 ()2-s2.0-85056153852 (Scopus ID)
Note

QC 20190618

Available from: 2019-06-15 Created: 2019-06-15 Last updated: 2019-06-18Bibliographically approved
Huang, S. Y., Yuan, Z. G., Fu, H. S., Vaivads, A., Sahraoui, F., Khotyaintsev, Y. V., . . . Wang, D. D. (2018). Observations of Whistler Waves in the Magnetic Reconnection Diffusion Region. In: 2ND URSI ATLANTIC RADIO SCIENCE MEETING (AT-RASC): . Paper presented at 2nd URSI Atlantic Radio Science Meeting (AT-RASC), MAY 28-JUN 01, 2018, Meloneras, SPAIN. IEEE
Open this publication in new window or tab >>Observations of Whistler Waves in the Magnetic Reconnection Diffusion Region
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2018 (English)In: 2ND URSI ATLANTIC RADIO SCIENCE MEETING (AT-RASC), IEEE , 2018Conference paper, Published paper (Refereed)
Abstract [en]

Whistler waves are believed to play an important role during magnetic reconnection. In this paper, we report the simultaneous occurrence of two types of the whistler waves in the magnetotail reconnection diffusion region. The first type is observed in the pileup region of downstream and propagates away along the field lines to downstream, and is possibly generated by the electron temperature anisotropy at the magnetic equator. The second type is found around the separatrix region and propagates towards the X-line, and is possibly aenerated by the electron beam-driven whistler instability or Cerenkov emission from electron phase-space holes. Our observations of two different types of whistler waves are well consistent with recent kinetic simulations, and suggest that the observed whistler waves are the consequences of magnetic reconnection.Moreover, we statistically investigate the whistler waves in the magnetotail reconnection region, and construct the global distribution and occurrence rate of the whistler waves based on the two-dimensional reconnection model. It is found that the occurrence rate of the whistler waves is large in the separatrix region (113,1B0j>0.4) and pileup region ([B,./Bol<0.2, 161>45'), but very small in the X-line region. The statistical results are well consistent with the case study.

Place, publisher, year, edition, pages
IEEE, 2018
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-253491 (URN)10.23919/URSI-AT-RASC.2018.8471382 (DOI)000462069500089 ()978-90-82598-73-5 (ISBN)
Conference
2nd URSI Atlantic Radio Science Meeting (AT-RASC), MAY 28-JUN 01, 2018, Meloneras, SPAIN
Note

QC 20190826

Available from: 2019-06-15 Created: 2019-06-15 Last updated: 2019-08-26Bibliographically approved
Johlander, A., Vaivads, A., Khotyaintsev, Y. V., Gingell, I., Schwartz, S. J., Giles, B. L., . . . Russell, C. T. (2018). Shock ripples observed by the MMS spacecraft: ion reflection and dispersive properties. Plasma Physics and Controlled Fusion, 60, Article ID 125006.
Open this publication in new window or tab >>Shock ripples observed by the MMS spacecraft: ion reflection and dispersive properties
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2018 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 60, article id 125006Article in journal (Refereed) Published
Abstract [en]

Shock ripples are ion-inertial-scale waves propagating within the front region of magnetized quasi-perpendicular collisionless shocks. The ripples are thought to influence particle dynamics and acceleration at shocks. With the four magnetospheric multiscale (MMS) spacecraft, it is for the first time possible to fully resolve the small scale ripples in space. We use observations of one slow crossing of the Earth’s non-stationary bow shock by MMS. From multi-spacecraft measurements we show that the non-stationarity is due to ripples propagating along the shock surface. We find that the ripples are near linearly polarized waves propagating in the coplanarity plane with a phase speed equal to the local Alfvén speed and have a wavelength close to 5 times the upstream ion inertial length. The dispersive properties of the ripples resemble those of Alfvén ion cyclotron waves in linear theory. Taking advantage of the slow crossing by the four MMS spacecraft, we map the shock-reflected ions as a function of ripple phase and distance from the shock. We find that ions are preferentially reflected in regions of the wave with magnetic field stronger than the average overshoot field, while in the regions of lower magnetic field, ions penetrate the shock to the downstream region.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-253498 (URN)10.1088/1361-6587/aae920 (DOI)000449418100001 ()2-s2.0-85056350872 (Scopus ID)
Note

QC 20190710

Available from: 2019-06-15 Created: 2019-06-15 Last updated: 2019-07-10Bibliographically approved
Fu, H. S., Vaivads, A., Khotyaintsev, Y. V., André, M., Cao, J. B., Olshevsky, V., . . . Retino, A. (2017). Intermittent energy dissipation by turbulent reconnection. Geophysical Research Letters, 44(1), 37-43
Open this publication in new window or tab >>Intermittent energy dissipation by turbulent reconnection
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2017 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, no 1, p. 37-43Article in journal (Refereed) Published
Abstract [en]

Magnetic reconnectionthe process responsible for many explosive phenomena in both nature and laboratoryis efficient at dissipating magnetic energy into particle energy. To date, exactly how this dissipation happens remains unclear, owing to the scarcity of multipoint measurements of the diffusion region at the sub-ion scale. Here we report such a measurement by Clusterfour spacecraft with separation of 1/5 ion scale. We discover numerous current filaments and magnetic nulls inside the diffusion region of magnetic reconnection, with the strongest currents appearing at spiral nulls (O-lines) and the separatrices. Inside each current filament, kinetic-scale turbulence is significantly increased and the energy dissipation, Ej, is 100 times larger than the typical value. At the jet reversal point, where radial nulls (X-lines) are detected, the current, turbulence, and energy dissipations are surprisingly small. All these features clearly demonstrate that energy dissipation in magnetic reconnection occurs at O-lines but not X-lines.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2017
Keywords
turbulent reconnection, energy dissipation, turbulence, magnetic nulls, current filaments, intermittence
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-253251 (URN)10.1002/2016GL071787 (DOI)000393954900005 ()2-s2.0-85010638265 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20190625

Available from: 2019-06-14 Created: 2019-06-14 Last updated: 2019-06-25Bibliographically approved
Graham, D. B., Khotyaintsev, Y. V., Vaivads, A. & Andre, M. (2016). Electrostatic solitary waves and electrostatic waves at the magnetopause. Journal of Geophysical Research - Space Physics, 121(4), 3069-3092
Open this publication in new window or tab >>Electrostatic solitary waves and electrostatic waves at the magnetopause
2016 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 4, p. 3069-3092Article in journal (Refereed) Published
Abstract [en]

Electrostatic solitary waves (ESWs) are characterized by localized bipolar electric fields parallel to the magnetic field and are frequently observed in space plasmas. In this paper a study of ESWs and field-aligned electrostatic waves, which do not exhibit localized bipolar fields, near the magnetopause is presented using the Cluster spacecraft. The speeds, length scales, field strengths, and potentials are calculated and compared with the local plasma conditions. A large range of speeds is observed, suggesting different generation mechanisms. In contrast, a smaller range of length scales normalized to the Debye length lambda(D) is found. For ESWs the average length between the positive and negative peak fields is 9 lambda(D), comparable to the average half wavelength of electrostatic waves. Statistically, the lengths and speeds of ESWs and electrostatic waves are shown to be similar. The length scales and potentials of the ESWs are consistent with predictions for stable electron holes. The maximum ESW potentials are shown to be constrained by the length scale and the magnetic field strength at the magnetopause and in the magnetosheath. The observed waves are consistent with those generated by the warm bistreaming instability, beam-plasma instability, and electron-ion instabilities, which account for the observed speeds and length scales. The large range of wave speeds suggests that the waves can couple different electron populations and electrons with ions, heating the plasma and contributing to anomalous resistivity.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-253470 (URN)10.1002/2015JA021527 (DOI)000379960300018 ()
Funder
Swedish National Space Board, 128/11:2 77/13
Note

QC 20190624

Available from: 2019-06-15 Created: 2019-06-15 Last updated: 2019-06-24Bibliographically approved
Soucek, J., Åhlén, L., Bale, S., Bonnell, J., Boudin, N., Brienza, D., . . . Zaslavsky, A. (2016). EMC Aspects Of Turbulence Heating Observer (THOR) Spacecraft. In: Proceedings Of 2016 Esa Workshop On Aerospace Emc (Aerospace Emc): . Paper presented at 2016 ESA Workshop on Aerospace EMC, Aerospace EMC 2016; Valencia; Spain; 23 May 2016 through 25 May 2016. Institute of Electrical and Electronics Engineers (IEEE), Article ID 7504544.
Open this publication in new window or tab >>EMC Aspects Of Turbulence Heating Observer (THOR) Spacecraft
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2016 (English)In: Proceedings Of 2016 Esa Workshop On Aerospace Emc (Aerospace Emc), Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7504544Conference paper, Published paper (Refereed)
Abstract [en]

Turbulence Heating ObserveR (THOR) is a spacecraft mission dedicated to the study of plasma turbulence in near-Earth space. The mission is currently under study for implementation as a part of ESA Cosmic Vision program. THOR will involve a single spinning spacecraft equipped with state of the art instruments capable of sensitive measurements of electromagnetic fields and plasma particles. The sensitive electric and magnetic field measurements require that the spacecraft-generated emissions are restricted and strictly controlled; therefore a comprehensive EMC program has been put in place already during the study phase. The THOR study team and a dedicated EMC working group are formulating the mission EMC requirements already in the earliest phase of the project to avoid later delays and cost increases related to EMC. This article introduces the THOR mission and reviews the current state of its EMC requirements.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-253642 (URN)10.1109/AeroEMC.2016.7504544 (DOI)000386313000006 ()2-s2.0-84980378208 (Scopus ID)9789292213039 (ISBN)
Conference
2016 ESA Workshop on Aerospace EMC, Aerospace EMC 2016; Valencia; Spain; 23 May 2016 through 25 May 2016
Note

QC 20190821

Available from: 2019-06-15 Created: 2019-06-15 Last updated: 2019-08-21Bibliographically approved
Fu, H. S., Cao, J. B., Vaivads, A., Khotyaintsev, Y. V., Andre, M., Dunlop, M., . . . Eriksson, E. (2016). Identifying magnetic reconnection events using the FOTE method. Journal of Geophysical Research - Space Physics, 121(2), 1263-1272
Open this publication in new window or tab >>Identifying magnetic reconnection events using the FOTE method
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2016 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 2, p. 1263-1272Article in journal (Refereed) Published
Abstract [en]

A magnetic reconnection event detected by Cluster is analyzed using three methods: Single-spacecraft Inference based on Flow-reversal Sequence (SIFS), Multispacecraft Inference based on Timing a Structure (MITS), and the First-Order Taylor Expansion (FOTE). Using the SIFS method, we find that the reconnection structure is an X line; while using the MITS and FOTE methods, we find it is a magnetic island (O line). We compare the efficiency and accuracy of these three methods and find that the most efficient and accurate approach to identify a reconnection event is FOTE. In both the guide and nonguide field reconnection regimes, the FOTE method is equally applicable. This study for the first time demonstrates the capability of FOTE in identifying magnetic reconnection events; it would be useful to the forthcoming Magnetospheric Multiscale (MMS) mission. ion

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2016
Keywords
magnetic reconnection, MMS mission, FOTE method, magnetic null, X line, O line
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-253248 (URN)10.1002/2015JA021701 (DOI)000373002100023 ()2-s2.0-84975698091 (Scopus ID)
Available from: 2019-06-14 Created: 2019-06-14 Last updated: 2019-06-25Bibliographically approved
Johlander, A., Vaivads, A., Khotyaintsev, Y. V., Retinò, A. & Dandouras, I. (2016). Ion Injection At Quasi-Parallel Shocks Seen By The Cluster Spacecraft. Astrophysical Journal Letters, 817(1), Article ID L4.
Open this publication in new window or tab >>Ion Injection At Quasi-Parallel Shocks Seen By The Cluster Spacecraft
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2016 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 817, no 1, article id L4Article in journal (Refereed) Published
Abstract [en]

Collisionless shocks in space plasma are known to be capable of accelerating ions to very high energies through diffusive shock acceleration (DSA). This process requires an injection of suprathermal ions, but the mechanisms producing such a suprathermal ion seed population are still not fully understood. We study acceleration of solar wind ions resulting from reflection off short large-amplitude magnetic structures (SLAMSs) in the quasi-parallel bow shock of Earth using in situ data from the four Cluster spacecraft. Nearly specularly reflected solar wind ions are observed just upstream of a SLAMS. The reflected ions are undergoing shock drift acceleration (SDA) and obtain energies higher than the solar wind energy upstream of the SLAMS. Our test particle simulations show that solar wind ions with lower energy are more likely to be reflected off the SLAMS, while high-energy ions pass through the SLAMS, which is consistent with the observations. The process of SDA at SLAMSs can provide an effective way of accelerating solar wind ions to suprathermal energies. Therefore, this could be a mechanism of ion injection into DSA in astrophysical plasmas.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016
Keywords
acceleration of particles, cosmic rays, shock waves, solar wind
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-253499 (URN)10.3847/2041-8205/817/1/L4 (DOI)000369370900004 ()2-s2.0-84955301605 (Scopus ID)
Note

QC 20190625

Available from: 2019-06-15 Created: 2019-06-15 Last updated: 2019-06-25Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-5550-3113

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