Origin of the solar wind: A novel approach to link in situ  and remote observations

Peleikis, Thies; Kruse, Martin; Berger, L.; Wimmer‐Schweingruber, R. F.

doi:10.1051/0004-6361/201629727

Cited by 9 publications

(7 citation statements)

References 16 publications

(12 reference statements)

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“…We should note that the backmapping of the magnetic field (and nominal Parker spiral) is done up to the source surface only using the solar wind speed, measured during the onset of the SEP event. However, the uncertainty of the estimated s/c footpoint positions could be as large ±10 • (e.g., Ippolito et al 2005) or even larger, if the magnetic field configuration below the source surface is taken into account (Klein et al 2008;Lario et al 2016;Peleikis et al 2017).…”

Section: Discussionmentioning

confidence: 99%

Strong non-radial propagation of energetic electrons in solar corona

Klassen

Dresing

Gómez-Herrero

et al. 2018

A&A

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Analyzing the sequence of solar energetic electron events measured at both STEREO-A (STA) and STEREO-B (STB) spacecraft during 17–21 July 2014, when their orbital separation was 34°, we found evidence of a strong non-radial electron propagation in the solar corona below the solar wind source surface. The impulsive electron events were associated with recurrent flare and jet (hereafter flare/jet) activity at the border of an isolated coronal hole situated close to the solar equator. We have focused our study on the solar energetic particle (SEP) event on 17 July 2014, during which both spacecraft detected a similar impulsive and anisotropic energetic electron event suggesting optimal connection of both spacecraft to the parent particle source, despite the large angular separation between the parent flare and the nominal magnetic footpoints on the source surface of STA and STB of 68° and 90°, respectively. Combining the remote-sensing extreme ultraviolet (EUV) observations, in-situ plasma, magnetic field, and energetic particle data we investigated and discuss here the origin and the propagation trajectory of energetic electrons in the solar corona. We find that the energetic electrons in the energy range of 55–195 keV together with the associated EUV jet were injected from the flare site toward the spacecraft’s magnetic footpoints and propagate along a strongly non-radial and inclined magnetic field below the source surface. From stereoscopic (EUV) observations we estimated the inclination angle of the jet trajectory and the respective magnetic field of 63° ± 11° relative to the radial direction. We show how the flare accelerated electrons reach very distant longitudes in the heliosphere, when the spacecraft are nominally not connected to the particle source. This example illustrates how ballistic backmapping can occasionally fail to characterize the magnetic connectivity during SEP events. This finding also provides an additional mechanism (one among others), which may explain the origin of widespread SEP events.

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Section: Discussionmentioning

confidence: 99%

Strong non-radial propagation of energetic electrons in solar corona

Klassen

Dresing

Gómez-Herrero

et al. 2018

A&A

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“…The same approach has been applied in Heidrich-Meisner et al (2016) and Peleikis et al (2016), Peleikis et al (2017). Firstly, a solar wind package is mapped back ballistically to the source surface at 2.5 R under the assumption that the solar wind speed is constant between the source surface and the observer.…”

Section: Data Selection Solar Wind Characterisation and Methodsmentioning

confidence: 99%

“…To link the in situ observations with the photosphere, we apply a combination of ballistic back-mapping and the PFSS model (Schatten et al 1969;Altschuler & Newkirk 1969). The same approach has been applied in Heidrich-Meisner et al (2016) and Peleikis et al (2016); Peleikis et al (2017). Firstly, a solar wind package is mapped back ballistically to the source surface at 2.5R under the assumption that the solar wind speed is constant between the source surface and the observer.…”

Section: Data Selection Solar Wind Characterisation and Methodsmentioning

confidence: 99%

Evolution of an equatorial coronal hole structure and the released coronal hole wind stream: Carrington rotations 2039 to 2050

Heidrich-Meisner

Peleikis

Kruse

et al. 2017

A&A

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Context. The Sun is a highly dynamic environment that exhibits dynamic behavior on many different timescales. Variability is observed both in closed and in open field line regions in the solar corona. In particular, coronal holes exhibit temporal and spatial variability. Signatures of these coronal dynamics are inherited by the coronal hole wind streams that originate in these regions and can effect the Earth's magnetosphere. Both the cause of the observed variabilities and how these translate to fluctuations in the in situ observed solar wind is not yet fully understood. Aims. During solar activity minimum the structure of the magnetic field typically remains stable over several Carrington rotations (CRs). But how stable is the solar magnetic field? Here, we address this question by analyzing the evolution of a coronal hole structure and the corresponding coronal hole wind stream emitted from this source region over 12 consecutive CRs in 2006. Methods. To this end, we link in situ observations of Solar Wind Ion Composition Spectrometer (SWICS) onboard the Advanced Composition Explorer (ACE) with synoptic maps of Michelson Doppler imager (MDI) on the Solar and Heliospheric Observatory (SOHO) at the photospheric level through a combination of ballistic back-mapping and a potential field source surface (PFSS) approach. Together, these track the evolution of the open field line region that is identified as the source region of a recurring coronal hole wind stream. Under the assumptions of the freeze-in scenario for charge states in the solar wind, we derive freeze-in temperatures and determine the order in which the different charge state ratios of ion pairs appear to freeze-in. We call the combination of freeze-in temperatures derived from in situ observed ion density ratios and freeze-in order a minimal electron temperature profile and investigate its variability. Results. The in situ properties and the PFSS model together probe the lateral magnetic field configuration, the minimal temperature profiles allow to constrain the radial structure. We find that the shape of the open field line region and to some extent also the solar wind properties are influenced by surrounding more dynamic closed loop regions. We show that the freeze-in order can change within a coronal hole wind stream on small timescales and illustrate a mechanism that can cause changes in the freeze-in order. The inferred minimal temperature profile is variable even within coronal hole wind and is in particular most variable in the outer corona.

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“…Other authors have backmapped solar wind measured at 1 AU to try and determine the exact location on the Sun from which it originated (e.g. Neugebauer et al 1998;Fu et al 2015;Fazakerley et al 2016;Peleikis et al 2017;Zhao et al 2017). This method assumes that the solar wind travels along magnetic field lines between the Sun's surface and magnetic field source surface at 2.5rs (solar radii), which are computed using a potential field source surface model, and then travels radially and at a constant speed to the insitu observer.…”

Section: Comparison With Other Categorisation Schemesmentioning

confidence: 99%

Diagnosing solar wind origins usingin situmeasurements in the inner heliosphere

Stansby

Horbury

Matteini

2018

Monthly Notices of the Royal Astronomical Society

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Robustly identifying the solar sources of individual packets of solar wind measured in interplanetary space remains an open problem. We set out to see if this problem is easier to tackle using solar wind measurements closer to the Sun than 1 AU, where the mixing and dynamical interaction of different solar wind streams is reduced. Using measurements from the Helios mission, we examined how the proton core temperature anisotropy and cross helicity varied with distance. At 0.3 AU there are two clearly separated anisotropic and isotropic populations of solar wind, that are not distinguishable at 1 AU. The anisotropic population is always Alfvénic and spans a wide range of speeds. In contrast the isotropic population has slow speeds, and contains a mix of Alfvénic wind with constant mass fluxes, and non-Alfvénic wind with large and highly varying mass fluxes. We split the in-situ measurements into three categories according these observations, and suggest that these categories correspond to wind that originated in the core of coronal holes, in or near active regions or the edges of coronal holes, and as small transients form streamers or pseudostreamers. Although our method by itself is simplistic, it provides a new tool that can be used in combination with other methods for identifying the sources of solar wind measured by Parker Solar Probe and Solar Orbiter.

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Origin of the solar wind: A novel approach to link in situ and remote observations

Cited by 9 publications

References 16 publications

Strong non-radial propagation of energetic electrons in solar corona

Strong non-radial propagation of energetic electrons in solar corona

Evolution of an equatorial coronal hole structure and the released coronal hole wind stream: Carrington rotations 2039 to 2050

Diagnosing solar wind origins usingin situmeasurements in the inner heliosphere

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