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Journal articleKhotyaintsev Y, Graham DB, Vaivads A, et al., 2021,
Density fluctuations associated with turbulence and waves First observations by Solar Orbiter
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 15
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Journal articleWeiss AJ, Moestl C, Davies EE, et al., 2021,
Multi-point analysis of coronal mass ejection flux ropes using combined data from Solar Orbiter, BepiColombo, and Wind
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 9
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Journal articleKretzschmar M, Chust T, Krasnoselskikh V, et al., 2021,
Whistler waves observed by Solar Orbiter/RPW between 0.5 AU and 1 AU
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 11
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Journal articleEastwood JP, Stawarz JE, Phan TD, et al., 2021,
Solar Orbiter observations of an ion-scale flux rope confined to a bifurcated solar wind current sheet
, Astronomy & Astrophysics, Vol: 656, Pages: 1-8, ISSN: 0004-6361Context. Flux ropes in the solar wind are a key element of heliospheric dynamics and particle acceleration. When associated withcurrent sheets, the primary formation mechanism is magnetic reconnection and flux ropes in current sheets are commonly used astracers of the reconnection process.Aims. Whilst flux ropes associated with reconnecting current sheets in the solar wind have been reported, their occurrence, sizedistribution, and lifetime are not well understood.Methods. Here we present and analyse new Solar Orbiter magnetic field data reporting novel observations of a flux rope confined toa bifurcated current sheet in the solar wind. Comparative data and large-scale context is provided by Wind.Results. The Solar Orbiter observations reveal that the flux rope, which does not span the current sheet, is of ion scale, and in areconnection formation scenario, existed for a prolonged period of time as it was carried out in the reconnection exhaust. Wind is alsofound to have observed clear signatures of reconnection at what may be the same current sheet, thus demonstrating that reconnectionsignatures can be found separated by as much as ∼ 2 000 Earth radii, or 0.08 au.Conclusions. The Solar Orbiter observations provide new insight into the hierarchy of scales on which flux ropes can form, and showthat they exist down to the ion scale in the solar wind. The context provided by Wind extends the spatial scale over which reconnectionsignatures have been found at solar wind current sheets. The data suggest the local orientations of the current sheet at Solar Orbiterand Wind are rotated relative to each other, unlike reconnection observed at smaller separations; the implications of this are discussedwith reference to patchy vs. continuous reconnection scenarios.
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Journal articleLavraud B, Kieokaew R, Fargette N, et al., 2021,
Magnetic reconnection as a mechanism to produce multiple protonpopulations and beams locally in the solar wind
, Journal of Astrophysics and Astronomy, Vol: 656, Pages: 1-8, ISSN: 0250-6335Context. Spacecraft observations early revealed frequent multiple protonpopulations in the solar wind. Decades of research on their origin have focusedon processes such as magnetic reconnection in the low corona and wave-particleinteractions in the corona and locally in the solar wind.Aims.This study aimsto highlight that multiple proton populations and beams are also produced bymagnetic reconnection occurring locally in the solar wind. Methods. We use highresolution Solar Orbiter proton velocity distribution function measurements,complemented by electron and magnetic field data, to analyze the association ofmultiple proton populations and beams with magnetic reconnection during aperiod of slow Alfv\'enic solar wind on 16 July 2020. Results. At least 6reconnecting current sheets with associated multiple proton populations andbeams, including a case of magnetic reconnection at a switchback boundary, arefound during this day. This represents 2% of the measured distributionfunctions. We discuss how this proportion may be underestimated, and how it maydepend on solar wind type and distance from the Sun. Conclusions. Althoughsuggesting a likely small contribution, but which remains to be quantitativelyassessed, Solar Orbiter observations show that magnetic reconnection must beconsidered as one of the mechanisms that produce multiple proton populationsand beams locally in the solar wind.
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Journal articleWimmer-Schweingruber RF, Janitzek NP, Pacheco D, et al., 2021,
First year of energetic particle measurements in the inner heliosphere with Solar Orbiter's Energetic Particle Detector
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 53
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Journal articleCohen CMS, Christian ER, Cummings AC, et al., 2021,
PSP/IS⊙IS observations of the 29 November 2020 solar energetic particle event
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 22
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Journal articleZaslavsky A, Mann I, Soucek J, et al., 2021,
First dust measurements with the Solar Orbiter Radio and Plasma Wave instrument
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 28
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Journal articleOwen CJ, Kataria DO, Bercic L, et al., 2021,
High-cadence measurements of electron pitch-angle distributions from Solar Orbiter SWA-EAS burst mode operations
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 1
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Journal articleKilpua EKJ, Good SW, Dresing N, et al., 2021,
Multi-spacecraft observations of the structure of the sheath of an interplanetary coronal mass ejection and related energetic ion enhancement
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 11
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Journal articleMaksimovic M, Soucek J, Chust T, et al., 2021,
First observations and performance of the RPW instrument on board the Solar Orbiter mission
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361 -
Journal articleTelloni D, Scolini C, Moestl C, et al., 2021,
Study of two interacting interplanetary coronal mass ejections encountered by Solar Orbiter during its first perihelion passage Observations and modeling
, Astronomy and Astrophysics: a European journal, Vol: 656, ISSN: 0004-6361Context. Solar Orbiter, the new-generation mission dedicated to solar and heliospheric exploration, was successfully launched on February 10, 2020, 04:03 UTC from Cape Canaveral. During its first perihelion passage in June 2020, two successive interplanetary coronal mass ejections (ICMEs), propagating along the heliospheric current sheet (HCS), impacted the spacecraft.Aims. This paper addresses the investigation of the ICMEs encountered by Solar Orbiter on June 7−8, 2020, from both an observational and a modeling perspective. The aim is to provide a full description of those events, their mutual interaction, and their coupling with the ambient solar wind and the HCS.Methods. Data acquired by the MAG magnetometer, the Energetic Particle Detector suite, and the Radio and Plasma Waves instrument are used to provide information on the ICMEs’ magnetic topology configuration, their magnetic connectivity to the Sun, and insights into the heliospheric plasma environment where they travel, respectively. On the modeling side, the Heliospheric Upwind eXtrapolation model, the 3D COronal Rope Ejection technique, and the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) tool are used to complement Solar Orbiter observations of the ambient solar wind and ICMEs, and to simulate the evolution and interaction of the ejecta in the inner heliosphere, respectively.Results. Both data analysis and numerical simulations indicate that the passage of two distinct, dynamically and magnetically interacting (via magnetic reconnection processes) ICMEs at Solar Orbiter is a possible scenario, supported by the numerous similarities between EUHFORIA time series at Solar Orbiter and Solar Orbiter data.Conclusions. The combination of in situ measurements and numerical simulations (together with remote sensing observations of the corona and inner heliosphere) will significantly lead to a deeper understanding of the physical processes occurring during the CME-CME interaction.
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Journal articleHadid LZ, Edberg NJT, Chust T, et al., 2021,
Solar Orbiter's first Venus flyby: Observations from the Radio and Plasma Wave instrument
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 13
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Journal articleKollhoff A, Kouloumvakos A, Lario D, et al., 2021,
The first widespread solar energetic particle event observed by Solar Orbiter on 2020 November 29
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 28
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Journal articleD'Amicis R, Bruno R, Panasenco O, et al., 2021,
First Solar Orbiter observation of the Alfvenic slow wind and identification of its solar source
, Astronomy and Astrophysics: a European journal, Vol: 656, Pages: 1-17, ISSN: 0004-6361Context. Turbulence dominated by large-amplitude, nonlinear Alfvén-like fluctuations mainly propagating away from the Sun is ubiquitous in high-speed solar wind streams. Recent studies have demontrated that slow wind streams may also show strong Alfvénic signatures, especially in the inner heliosphere.Aims. The present study focuses on the characterisation of an Alfvénic slow solar wind interval observed by Solar Orbiter between 14 and 18 July 2020 at a heliocentric distance of 0.64 AU.Methods. Our analysis is based on plasma moments and magnetic field measurements from the Solar Wind Analyser (SWA) and Magnetometer (MAG) instruments, respectively. We compared the behaviour of different parameters to characterise the stream in terms of the Alfvénic content and magnetic properties. We also performed a spectral analysis to highlight spectral features and waves signature using power spectral density and magnetic helicity spectrograms, respectively. Moreover, we reconstruct the Solar Orbiter magnetic connectivity to the solar sources both via a ballistic and a potential field source surface (PFSS) model.Results. The Alfvénic slow wind stream described in this paper resembles, in many respects, a fast wind stream. Indeed, at large scales, the time series of the speed profile shows a compression region, a main portion of the stream, and a rarefaction region, characterised by different features. Moreover, before the rarefaction region, we pinpoint several structures at different scales recalling the spaghetti-like flux-tube texture of the interplanetary magnetic field. Finally, we identify the connections between Solar Orbiter in situ measurements, tracing them down to coronal streamer and pseudostreamer configurations.Conclusions. The characterisation of the Alfvénic slow wind stream observed by Solar Orbiter and the identification of its solar source are extremely important aspects for improving the understanding of future observ
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Journal articleAllen RC, Cernuda I, Pacheco D, et al., 2021,
Energetic ions in the Venusian system: Insights from the first Solar Orbiter flyby
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 7
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Journal articleOwen CJ, Foster AC, Bruno R, et al., 2021,
Solar Orbiter observations of the structure of reconnection outflow layers in the solar wind
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 5
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Journal articleFedorov A, Louarn P, Owen CJ, et al., 2021,
Switchback-like structures observed by Solar Orbiter
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 4
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Journal articleChust T, Kretzschmar M, Graham DB, et al., 2021,
Observations of whistler mode waves by Solar Orbiter's RPW Low Frequency Receiver (LFR): In-flight performance and first results
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 6
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Journal articleAran A, Pacheco D, Laurenza M, et al., 2021,
Evidence for local particle acceleration in the first recurrent galactic cosmic ray depression observed by Solar Orbiter The ion event on 19 June 2020
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 1
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Journal articleLouarn P, Fedorov A, Prech L, et al., 2021,
Multiscale views of an Alfvenic slow solar wind: 3D velocity distribution functions observed by the Proton-Alpha Sensor of Solar Orbiter
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 8
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Journal articleAdhikari L, Zank GP, Zhao L-L, et al., 2021,
Evolution of anisotropic turbulence in the fast and slow solar wind: Theory and Solar Orbiter measurements
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 11
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Journal articleSoucek J, Pisa D, Kolmasova I, et al., 2021,
Solar Orbiter Radio and Plasma Waves - Time Domain Sampler: In-flight performance and first results
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 13
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Journal articleMusset S, Maksimovic M, Kontar E, et al., 2021,
Simulations of radio-wave anisotropic scattering to interpret type III radio burst data from Solar Orbiter, Parker Solar Probe, STEREO, and Wind
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 21
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Journal articleVecchio A, Maksimovic M, Krupar V, et al., 2021,
Solar Orbiter/RPW antenna calibration in the radio domain and its application to type III burst observations
, ASTRONOMY & ASTROPHYSICS, Vol: 656, ISSN: 0004-6361- Cite
- Citations: 11
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Journal articleKasper JC, Klein KG, Lichko E, et al., 2021,
<i>Parker</i><i> Solar</i><i> Probe</i> Enters the Magnetically Dominated Solar Corona
, PHYSICAL REVIEW LETTERS, Vol: 127, ISSN: 0031-9007- Cite
- Citations: 142
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Journal articleCargill PJ, Bradshaw SJ, Klimchuk JA, et al., 2021,
Static and dynamic solar coronal loops with cross-sectional area variations
, Monthly Notices of the Royal Astronomical Society, Vol: 509, Pages: 4420-4429, ISSN: 0035-8711The Enthalpy Based Thermal Evolution of Loops approximate model for static and dynamic coronal loops is developed to include the effect of a loop cross-sectional area which increases from the base of the transition region (TR) to the corona. The TR is defined as the part of a loop between the top of the chromosphere and the location where thermal conduction changes from an energy loss to an energy gain. There are significant differences from constant area loops due to the manner in which the reduced volume of the TR responds to conductive and enthalpy fluxes from the corona. For static loops with modest area variation the standard picture of loop energy balance is retained, with the corona and TR being primarily a balance between heating and conductive losses in the corona, and downward conduction and radiation to space in the TR. As the area at the loop apex increases, the TR becomes thicker and the density in TR and corona larger. For large apex areas, the coronal energy balance changes to one primarily between heating and radiation, with conduction playing an increasingly unimportant role, and the TR thickness becoming a significant fraction of the loop length. Approximate scaling laws are derived that give agreement with full numerical solutions for the density, but not the temperature. For non-uniform areas, dynamic loops have a higher peak temperature and are denser in the radiative cooling phase by of order 50 per cent than the constant area case for the examples considered. They also show a final rapid cooling and draining once the temperature approaches 1 MK. Although the magnitude of the emission measure will be enhanced in the radiative phase, there is little change in the important observational diagnostic of its temperature dependence.
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Journal articleCheng ZW, Shi JK, Torkar K, et al., 2021,
Impact of the solar wind dynamic pressure on the field-aligned currents in the magnetotail: cluster observation
, JGR: Space Physics, Vol: 126, Pages: 1-12, ISSN: 2169-9402We statistically investigate the influence of the solar wind dynamic pressure (SW Pdyn) on the field-aligned currents (FACs) in the magnetotail with 1,492 FAC cases from July to October in 2001 and 2004, which covers 74 Cluster crossings of the plasma sheet boundary layer (PSBL) in both storm time and non-storm time. The FAC density in the magnetotail is derived from the magnetic field data with the four-point measurement of Cluster, and the SW Pdyn is taken from ACE data. The results indicate the FAC density becomes stronger with increasing SW Pdyn. The statistics show that the FAC occurrence increased monotonically with SW Pdyn in the three levels (Weak: SW Pdyn < 2 nPa; Medium: 2 nPa ≤ SW Pdyn ≤ 5 nPa; Strong: SW Pdyn > 5 nPa). The FAC density increased with increasing SW Pdyn, while its footprint (invariant latitude, ILAT) in the polar region decreased with increasing SW Pdyn. The response of the FAC to SW Pdyn in the magnetotail had a north-south hemispheric asymmetry. The FAC density had a better correlation with SW Pdyn in the Northern hemisphere, while the footprint had a better correlation with SW Pdyn in the Southern hemisphere. Possible underlying mechanisms for our results are analyzed and discussed. However, it requires more observations and simulation studies to find out the mechanism of north-south asymmetry.
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Journal articleMatteini L, Laker R, Horbury T, et al., 2021,
Solar Orbiter's encounter with the tail of comet C/2019 Y4 (ATLAS): Magnetic field draping and cometary pick-up ion waves
, Astronomy and Astrophysics: a European journal, Vol: 656, ISSN: 0004-6361ontext. Solar Orbiter is expected to have flown close to the tail of comet C/2019 Y4 (ATLAS) during the spacecraft’s first perihelion in June 2020. Models predict a possible crossing of the comet tails by the spacecraft at a distance from the Sun of approximately 0.5 AU.Aims. This study is aimed at identifying possible signatures of the interaction of the solar wind plasma with material released by comet ATLAS, including the detection of draped magnetic field as well as the presence of cometary pick-up ions and of ion-scale waves excited by associated instabilities. This encounter provides us with the first opportunity of addressing such dynamics in the inner Heliosphere and improving our understanding of the plasma interaction between comets and the solar wind.Methods. We analysed data from all in situ instruments on board Solar Orbiter and compared their independent measurements in order to identify and characterize the nature of structures and waves observed in the plasma when the encounter was predicted.Results. We identified a magnetic field structure observed at the start of 4 June, associated with a full magnetic reversal, a local deceleration of the flow and large plasma density, and enhanced dust and energetic ions events. The cross-comparison of all these observations support a possible cometary origin for this structure and suggests the presence of magnetic field draping around some low-field and high-density object. Inside and around this large scale structure, several ion-scale wave-forms are detected that are consistent with small-scale waves and structures generated by cometary pick-up ion instabilities.Conclusions. Solar Orbiter measurements are consistent with the crossing through a magnetic and plasma structure of cometary origin embedded in the ambient solar wind. We suggest that this corresponds to the magnetotail of one of the fragments of comet ATLAS or to a portion of the tail that was previously disconnected and advected past the spacec
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Journal articleVolwerk M, Horbury TS, Woodham LD, et al., 2021,
Solar Orbiter’s first Venus flyby. MAG observations of structures and waves associated with the induced Venusian magnetosphere
, Astronomy and Astrophysics: a European journal, Vol: 656, ISSN: 0004-6361Context. The induced magnetosphere of Venus is caused by the interaction of the solar wind and embedded interplanetary magnetic field with the exosphere and ionosphere of Venus. Solar Orbiter entered Venus’s magnetotail far downstream, > 70 Venus radii, of the planet and exited the magnetosphere over the north pole. This offered a unique view of the system over distances that had only been flown through before by three other missions, Mariner 10, Galileo, and BepiColombo.Aims. In this study, we study the large-scale structure and activity of the induced magnetosphere as well as the high-frequency plasma waves both in the magnetosphere and in a limited region upstream of the planet where interaction with Venus’s exosphere is expected.Methods. The large-scale structure of the magnetosphere was studied with low-pass filtered data and identified events are investigated with a minimum variance analysis as well as combined with plasma data. The high-frequency plasma waves were studied with spectral analysis.Results. We find that Venus’s magnetotail is very active during the Solar Orbiter flyby. Structures such as flux ropes and reconnection sites were encountered, in addition to a strong overdraping of the magnetic field downstream of the bow shock and planet. High-frequency plasma waves (up to six times the local proton cyclotron frequency) are observed in the magnetotail, which are identified as Doppler-shifted proton cyclotron waves, whereas in the upstream solar wind, these waves appear just below the proton cyclotron frequency (as expected) but are very patchy. The bow shock is quasi-perpendicular, however, expected mirror mode activity is not found directly behind it; instead, there is strong cyclotron wave power. This is most likely caused by the relatively low plasma-β behind the bow shock. Much further downstream, magnetic hole or mirror mode structures are identified in the magnetosheath.
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