Helios Observations of Quasiperiodic Density Structures in the Slow Solar Wind at 0.3, 0.4, and 0.6 AU

Matteo, Simone Di; Viall, N. M.; Kepko, L.; Wallace, Samantha; Arge, C. N.; MacNeice, P. J.

doi:10.1029/2018ja026182

Cited by 39 publications

(73 citation statements)

References 136 publications

(179 reference statements)

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“…They are shown in Figure 8a and b by dashed vertical lines. Such density structures were noticed in past in situ measurements taken near 1 au (Viall, et al 2008), in Helios data between 0.3 and 0.6 au (Di Matteo et al 2019) and separately in the spectral analysis of COR2A imagery (Viall, & Vourlidas 2015). Combined STA and PSP observations allow, for the first time, investigation of the origin of individual features.…”

Section: Tracing Density Structures From Psp Back To the Sunsupporting

confidence: 58%

Relating Streamer Flows to Density and Magnetic Structures at the Parker Solar Probe

Rouillard

Kouloumvakos

Vourlidas

et al. 2020

ApJS

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The physical mechanisms that produce the slow solar wind are still highly debated. Parker Solar Probe's (PSP 's) second solar encounter provided a new opportunity to relate in situ measurements of the nascent slow solar wind with white-light images of streamer flows. We exploit data taken by the Solar and Heliospheric Observatory (SOHO), the Solar TErrestrial RElations Observatory (STEREO) and the Wide Imager on Solar Probe to reveal for the first time a close link between imaged streamer flows and the high-density plasma measured by the Solar Wind Electrons Alphas and Protons (SWEAP) experiment. We identify different types of slow winds measured by PSP that we relate to the spacecraft's magnetic connectivity (or not) to streamer flows. SWEAP measured highdensity and highly variable plasma when PSP was well connected to streamers but more tenuous wind with much weaker density variations when it exited streamer flows. STEREO imaging of the release and propagation of small transients from the Sun to PSP reveals that the spacecraft was continually impacted by the southern edge of streamer transients. The impact of specific density structures is marked by a higher occurrence of magnetic field reversals measured by the FIELDS magnetometers. Magnetic reversals originating from the streamers are associated with larger density variations compared with reversals originating outside streamers. We tentatively interpret these findings in terms Corresponding author: Alexis P. Rouillard arouillard@irap.omp.eu arXiv:2001.01993v1 [astro-ph.SR] 7 Jan 2020 2 Rouillard et al. of magnetic reconnection between open magnetic fields and coronal loops with different properties, providing support for the formation of a subset of the slow wind by magnetic reconnection.

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Section: Tracing Density Structures From Psp Back To the Sunsupporting

confidence: 58%

Relating Streamer Flows to Density and Magnetic Structures at the Parker Solar Probe

Rouillard

Kouloumvakos

Vourlidas

et al. 2020

ApJS

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“…Our results indicate that the quasiperiodic mesoscale structures within the SIR were previously structures in the uncompressed slower solar wind ahead and are consistent with the belief that these structures are created at the time of solar wind generation. Evidence for a solar source of periodic density structures includes remote sensing of these structures down to a few solar radii (Viall & Vourlidas, 2015;Viall et al, 2010) and in situ studies using both Helios (Di Matteo et al, 2019) and L1 observations (Kepko et al, 2016;Viall, Spence, and Kasper 2009). Kepko et al (2016) recently examined a 12-hr interval of solar wind that contained periodic density structures, which previously had been studied as driving magnetospheric pulsations (Kepko & Spence, 2003).…”

Section: Journal Of Geophysical Research: Space Physicsmentioning

confidence: 99%

“…It is important to note that these periodic density structures in the solar wind are not propagating waves. Rather, they are coherent mesoscale structures created very early in the formation of the solar wind, which then advect outward in quasi pressure balance (DeForest et al, 2018;Di Matteo et al, 2019;Kepko et al, 2016;Viall & Vourlidas, 2015;Viall, Spence, & Kasper, 2009;Viall, Spence, Vourlidas, & Howard, 2010).…”

Section: Introductionmentioning

confidence: 99%

The Source, Significance, and Magnetospheric Impact of Periodic Density Structures Within Stream Interaction Regions

Kepko

Viall

2019

JGR Space Physics

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We present several examples of magnetospheric ultralow frequency pulsations associated with stream interaction regions and demonstrate that the observed magnetospheric pulsations were also present in the solar wind number density. The distance of the solar wind monitor ranged from just upstream of Earth's bow shock to 261 RE, with a propagation time delay of up to 90 min. The number density oscillations far upstream of Earth are offset from similar oscillations observed within the magnetosphere by the advection timescale, suggesting that the periodic dynamic pressure enhancements were time stationary structures, passively advecting with the ambient solar wind. The density structures are larger than Earth's magnetosphere and slowly altered the dynamic pressure enveloping Earth, leading to a quasi‐static and globally coherent “forced‐breathing” of Earth's dayside magnetospheric cavity. The impact of these periodic solar wind density structures was observed in both magnetospheric magnetic field and energetic particle data. We further show that the structures were initially smaller‐amplitude, spatially larger, structures in the upstream slow solar wind and that the higher‐speed wind compressed and amplified these preexisting structures leading to a series of quasiperiodic density structures with periods typically near 20 min. Similar periodic density structures have been observed previously at L1 and in remote images, but never in the context of solar wind shocks and discontinuities. The existence of periodic density structures within stream interaction regions may play an important role in magnetospheric particle acceleration, loss, and transport, particularly for outer zone electrons that are highly responsive to ultralow frequency wave activity.

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“…Though relating terrestrial geomagnetic pulsations to solar oscillations is an intriguing possibility, subsequent work addressing whether the solar wind contains imprints of solar oscillation modes has yielded conflicting results (Kepko et al 8 ). Recent studies have reported the presence of quasi-periodic density structures in the solar corona (Viall and Vourlidas) 23 , in the solar wind from 0.3 to 0.6 AU (Di Matteo et al) 24 , and at L1 (Kepko et al) 25 . These periodicities are in the range 60-130 mins, and our results (25-27 minutes) do not compare favourably.…”

Section: Discussion: a Possible Source Of The Ripplesmentioning

confidence: 99%

Quasi-periodic ripples in high latitude electron content, the geomagnetic field, and the solar wind

Birch

Hargreaves

2020

Sci Rep

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in this study we present evidence for the existence of quasi-periodic ripples in the f-region electron content at high latitude, the magnetic flux density at geosynchronous orbit, and the solar wind dynamic pressure and IMF flux density at L1. The ripples are shown to be continually present during all 14 days of observations in different years and seasons, and at all local times, though they are generally small in magnitude relative to the background. The frequencies of all the parameters are, on average, remarkably similar, and the amplitudes of the selected peaks of some parameters show strong correlations for which regression formulae are given. these results support the proposition that the ripples propagate from the solar wind to the f-region, and that they are a related, persistent phenomenon.Spatial and temporal structuring in the F-region of the ionosphere is a well-known phenomenon which has been observed on many occasions. The structures usually extend along the geomagnetic field and are, therefore, almost vertical at high latitudes.This paper is based on observations of quasi-periodic electron density structures in the high latitude F-region using the EISCAT Svalbard radar. A previous paper 1 , covering 24 hours of observations over 4 days in February and March 2015, showed the presence of F-region electron density structures with a median periodicity of about 22 minutes. The present investigation extends the scope of this study to include a further 10 days of electron density data in different years and seasons. Similar structures are reported in the geomagnetic field, and in the solar wind particle flux and IMF flux density. The relationship between these structures is investigated, and evidence for their origin is discussed.www.nature.com/scientificreports www.nature.com/scientificreports/ giving the electron content variations as a "ratio". (Refer to Validation of the smoothing procedure, comments regarding the efficacy of spectral analysis as an alternative approach, and the testing of this method using random data.) Using this smoothing procedure, Fig. 2 shows the variations in the electron content ratio derived for all four days over the height range 237.50 to 354.85 km; the variations appear to be quasi-periodic in nature. Peaks with magnitudes ≥1.03 were selected (see Selection criteria), and the 53 intervals between the 57 selected peaks are summarised in a histogram (Fig. 3). (Throughout this analysis, for any given set of data, there are occasional data gaps or intervals of bad data. Consequently, if n is the number of peaks sampled, the number of inter-peak periods can be less than n − 1). The median inter-peak period over all four days is 22 minutes, with quartiles at 18 and 26 minutes (Table 1a), and the daily medians are in the range 20-26 minutes. It is not obvious whether there was a dynamic component to the structures because these observations were made with a single, field-aligned radar beam. Scientific RepoRtS |(2020) 10:1313 | https://doi.

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Helios Observations of Quasiperiodic Density Structures in the Slow Solar Wind at 0.3, 0.4, and 0.6 AU

Cited by 39 publications

References 136 publications

Relating Streamer Flows to Density and Magnetic Structures at the Parker Solar Probe

Relating Streamer Flows to Density and Magnetic Structures at the Parker Solar Probe

The Source, Significance, and Magnetospheric Impact of Periodic Density Structures Within Stream Interaction Regions

Quasi-periodic ripples in high latitude electron content, the geomagnetic field, and the solar wind

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