The forming slow solar wind imaged along streamer rays by the wide-angle imager on Parker Solar Probe

2020 ◽  
Author(s):  
Nicolas Poirier ◽  
Athanasios Kouloumvakos ◽  
Alexis P. Rouillard ◽  
Rui Pinto ◽  
Angelos Vourlidas ◽  
...  
Keyword(s):  
Solar Wind ◽  
Heliospheric Current Sheet ◽  
Slow Solar Wind ◽  
Wide Field ◽  
Flux Tubes ◽  
Solar Origin ◽  
High Resolution Images ◽  
The Individual ◽  
Coronal Structures

<p>The Wide-field Imager for Solar PRobe (WISPR) obtained the first high-resolution images of coronal rays at heights below 15 R<sub>sun</sub> when Parker Solar Probe (PSP) was located inside 0.25 AU during the first encounter. We exploit these remarkable images to reveal the structure of coronal rays at scales that are not easily discernible in images taken from near 1 AU. To analyze and interpret WISPR observations which evolve rapidly both radially and longitudinally, we construct a latitude versus time map using full WISPR dataset from the first encounter. From the exploitation of this map and also from sequential WISPR images we show the presence of multiple sub-structures inside streamers and pseudo-streamers. WISPR unveils the fine-scale structure of the densest part of streamer rays that we identify as the solar origin of the heliospheric plasma sheet typically measured in situ in the solar wind. We exploit 3-D magneto-hydrodynamic (MHD) models and we construct synthetic white-light images to study the origin of the coronal structures observed by WISPR. Overall, including the effect of the spacecraft relative motion towards the individual coronal structures we can interpret several observed features by WISPR. Moreover, we relate some coronal rays to folds in the heliospheric current sheet that are unresolved from 1 AU. Other rays appear to form as a result of the inherently inhomogeneous distribution of open magnetic flux tubes. This work was funded by the European Research Council through the project SLOW_SOURCE - DLV-819189.</p>

Source-dependent properties of the background slow solar wind encountered by Parker Solar Probe

2021 ◽  
Author(s):  
Léa Griton ◽  
Sarah Watson ◽  
Nicolas Poirier ◽  
Alexis Rouillard ◽  
Karine Issautier ◽  
...  
Keyword(s):  
Solar Wind ◽  
Extreme Ultraviolet ◽  
Plasma Heating ◽  
Coronal Holes ◽  
Slow Solar Wind ◽  
Source Surface ◽  
Field Source ◽  
Flux Tubes ◽  
Field Lines

<p>Different states of the slow solar wind are identified from in-situ measurements by Parker Solar Probe (PSP) inside 50 solar radii from the Sun (Encounters 1, 2, 4, 5 and 6). At such distances the wind measured at PSP has not yet undergone significant transformation related to the expansion and propagation of the wind. We focus in this study on the properties of the quiet solar wind with no magnetic switchbacks. The Slow Solar Wind (SSW) states differ by their density, flux, plasma beta and magnetic pressure. PSP's magnetic connectivity established with Potential Field Source Surface (PFSS) reconstructions, tested against extreme ultraviolet (EUV) and white-light imaging, reveals the different states under study generally correspond to transitions from streamers to equatorial coronal holes. Solar wind simulations run along these differing flux tubes reproduce the slower and denser wind measured in the streamer and the more tenuous wind measured in the coronal hole. Plasma heating is more intense at the base of the streamer field lines rooted near the boundary of the equatorial hole than those rooted closer to the center of the hole. This results in a higher wind flux driven inside the streamer than deeper inside the equatorial hole. </p>

Solar Orbiter observations of magnetic Kelvin-Helmholtz waves in the solar wind

2021 ◽  
Author(s):  
Rungployphan Kieokaew ◽  
Benoit Lavraud ◽  
David Ruffolo ◽  
William Matthaeus ◽  
Yan Yang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Heliospheric Current Sheet ◽  
Shear Instability ◽  
Slow Solar Wind ◽  
Flow Shear ◽  
In Situ Observations ◽  
Set Up ◽  
Nonlinear Shear ◽  
Wind Source

<p>The Kelvin-Helmholtz instability (KHI) is a nonlinear shear-driven instability that develops at the interfaces between shear flows in plasmas. KHI is ubiquitous in plasmas and has been observed in situ at planetary interfaces and at the boundaries of coronal mass ejections in remote-sensing observations. KHI is also expected to develop at flow shear interfaces in the solar wind, but while it was hypothesized to play an important role in the mixing of plasmas and exciting solar wind fluctuations, its direct observation in the solar wind was still lacking. We report first in-situ observations of ongoing KHI in the solar wind using Solar Orbiter during its cruise phase. The KHI is found in a shear layer in the slow solar wind near the Heliospheric Current Sheet. We find that the observed conditions satisfy the KHI onset criterion from linear theory and the steepening of the shear boundary layer is consistent with the development of KH vortices. We further investigate the solar wind source of this event to understand the conditions that support KH growth. In addition, we set up a local MHD simulation using the empirical values to reproduce the observed KHI. This observed KHI in the solar wind provides robust evidence that shear instability develops in the solar wind, with obvious implications in the driving of solar wind fluctuations and turbulence. The reasons for the lack of previous such measurements are also discussed.</p>

Understanding Solar Wind Formation by Identifying the Origins of In Situ Observations 

2021 ◽  
Author(s):  
Samantha Wallace ◽  
Nicholeen M. Viall ◽  
Charles N. Arge
Keyword(s):  
Solar Wind ◽  
Solar Wind Speed ◽  
Source Region ◽  
Heliospheric Current Sheet ◽  
Slow Solar Wind ◽  
The Sun ◽  
Flux Transport ◽  
Model Driven ◽  
In Situ Observations

<p>Solar wind formation can be separated into three physical steps – source, release, and acceleration – that each leave distinct observational signatures on plasma parcels.  The Wang-Sheeley-Arge (WSA) model driven by Air Force Data Assimilative Photospheric Flux Transport (ADAPT) time-dependent photospheric field maps now has the ability to connect in situ observations more rigorously to their precise source at the Sun, allowing us to investigate the physical processes involved in solar wind formation.   In this talk, I will highlight my PhD dissertation research in which we use the ADAPT-WSA model to either characterize the solar wind emerging from specific sources, or investigate the formation process of various solar wind populations.  In the first study, we test the well-known inverse relationship between expansion factor (f<sub>s</sub>) and observed solar wind speed (v<sub>obs</sub>) for solar wind that emerges from a large sampling of pseudostreamers, to investigate if field line expansion plays a physical role in accelerating the solar wind from this source region.  We find that there is no correlation between f<sub>s</sub> and v<sub>obs</sub> at pseudostreamer cusps. In the second study, we determine the source locations of the first identified quasiperiodic density structures (PDSs) inside 0.6 au. Our modeling provides confirmation of these events forming via magnetic reconnection both near to and far from the heliospheric current sheet (HCS) – a direct test of the Separatrix-web (S-web) theory of slow solar wind formation.  In the final study, we use our methodology to identify the source regions of the first observations from the Parker Solar Probe (PSP) mission.  Our modeling enabled us to characterize the closest to the Sun observed coronal mass ejection (CME) to date as a streamer blowout.  We close with future ways that ADAPT-WSA can be used to test outstanding questions of solar wind formation.</p>

Quasi-stationary current sheets of the solar origin in the heliosphere

2020 ◽  
Author(s):  
Roman Kislov
Keyword(s):  
Solar Wind ◽  
Current Sheet ◽  
Solar Magnetic Field ◽  
Heliospheric Current Sheet ◽  
Simplified Approach ◽  
Solar Origin ◽  
Dipole Component ◽  
Order Components ◽  
The Impact

<p>The solar magnetic field (SMF) has historically been considered as dipole in order to build models of the radially expanding corona, that is, the solar wind in the solar minimum. The simplified approach suggests the existence of only one quasi-stationary current sheet (QCS) of solar origin in the heliosphere, namely, the heliospheric current sheet (HCS). However, the SMF becomes more complicated over the solar cycle, comprising higher-order components. The overlapping of the dipole and multipole components of the SMF suggests a formation of more than one QCS in the corona, which may expand further to the heliosphere. We study the impact of the quadrupole and octupole harmonics of the SMF on the formation and spatial characteristics of QCSs, building a stationary axisymmetric MHD model of QCSs in the heliosphere. It is shown that if the dipole component dominates, a single QCS appears in the solar wind at low heliolatitudes as the classic HCS. In other cases, the number of QCSs varies from one to three, depending on the relative input of the quadrupole and octupole components. QCSs possess a conic form and may occur at a wide variety of heliolatitudes. The existence of QCSs opens wide opportunities for explanations of puzzling observations of cosmic rays and energetic particles in the heliosphere and, at the same time, raises a risk of misinterpretation of in situ crossings of QCSs because of mixing up the HCS and higherheliolatitude QCSs, which can be significantly disturbed in the dynamical solar wind.</p>

scholarly journals Current sheets from Ulysses observation

2011 ◽  
Vol 29 (2) ◽  
pp. 237-249 ◽  
Author(s):  
B. Miao ◽  
B. Peng ◽  
G. Li
Keyword(s):  
Solar Wind ◽  
Current Sheet ◽  
Solar Wind Plasma ◽  
Mhd Turbulence ◽  
Automatic Data ◽  
Flux Tubes ◽  
Current Sheets ◽  
Solar Origin ◽  
Turbulence Intermittency ◽  
Solar Wind Magnetic Field

Abstract. Current sheet is a significant source of solar wind MHD turbulence intermittency. It has long been recognized that these structures can arise from non-linear interactions of MHD turbulence. Alternatively, they may also be relic structures in the solar wind that have a solar origin, e.g., magnetic walls of flux tubes that separate solar wind plasma into distinct parcels. Identifying these structures in the solar wind is crucial to understanding the properties of the solar wind MHD turbulence. Using Ulysses observations we examine 3-year worth of solar wind magnetic field data when the Ulysses is at low latitude during solar minimum. Extending the previous work of Li (2007, 2008), we develop an automatic data analysis method of current sheet identification. Using this method, we identify more than 28000 current sheets. Various properties of the current sheet are obtained. These include the distributions of the deflection angle across the current sheet, the thickness of the current sheet and the waiting time statistics between current sheets.

scholarly journals The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration

2021 ◽  
Author(s):  
Christopher Chen ◽  
Benjamin Chandran ◽  
Lloyd Woodham ◽  
Shaela Jones ◽  
Jean Perez ◽  
...  
Keyword(s):  
Solar Wind ◽  
Turbulence Models ◽  
Heliospheric Current Sheet ◽  
Angular Distance ◽  
Slow Solar Wind ◽  
Turbulence Energy ◽  
Streamer Belt ◽  
Solar Wind Acceleration ◽  
Solar Wind Turbulence ◽  
Wind Turbulence

<p>The fourth orbit of Parker Solar Probe (PSP) reached heliocentric distances down to 27.9 Rs, allowing solar wind turbulence and acceleration mechanisms to be studied in situ closer to the Sun than previously possible. The turbulence properties were found to be significantly different in the inbound and outbound portions of PSP's fourth solar encounter, likely due to the proximity to the heliospheric current sheet (HCS) in the outbound period. Near the HCS, in the streamer belt wind, the turbulence was found to have lower amplitudes, higher magnetic compressibility, a steeper magnetic field spectrum (with spectral index close to -5/3 rather than -3/2), a lower Alfvenicity, and a "1/f" break at much lower frequencies. These are also features of slow wind at 1 au, suggesting the near-Sun streamer belt wind to be the prototypical slow solar wind. The transition in properties occurs at a predicted angular distance of ~4 degrees from the HCS, suggesting ~8 degrees as the full-width of the streamer belt wind at these distances. While the majority of the Alfvenic turbulence energy fluxes measured by PSP are consistent with those required for reflection-driven turbulence models of solar wind acceleration, the fluxes in the streamer belt are significantly lower than the model predictions, suggesting that additional mechanisms are necessary to explain the acceleration of the streamer belt solar wind.</p>

scholarly journals Origin and Acceleration of Fast and Slow Solar Wind

2004 ◽  
Vol 219 ◽  
pp. 563-574
Author(s):  
Giannina Poletto
Keyword(s):  
Solar Wind ◽  
Spectral Range ◽  
High Speed ◽  
Heliocentric Distance ◽  
Coronal Plasma ◽  
Slow Solar Wind ◽  
Controversial Issues ◽  
Heliospheric Observatory ◽  
Slow Wind

Before the advent of the Solar and Heliospheric Observatory (SOHO, launched in 1995), we had little information on how coronal plasma gets accelerated to the high speed measured in situ. The Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO, acquiring UV data over the first few solar radii, a region unexplored in this spectral range, allowed us to build a profile of the outflow plasma speed vs. heliocentric distance, based on empirical constraints. Still, much has to be learnt about the behavior of solar wind in the extended corona. In the following, after briefly reviewing the general properties of the solar wind, I'll focus on controversial issues — like the identification of the sources of fast and slow wind, and the acceleration of fast vs. slow wind streams — and I'll illustrate recent contributions to the solution of these problems.

scholarly journals Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum

2009 ◽  
Vol 27 (10) ◽  
pp. 3909-3922 ◽  
Author(s):  
A. B. Galvin ◽  
M. A. Popecki ◽  
K. D. C. Simunac ◽  
L. M. Kistler ◽  
L. Ellis ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Minimum ◽  
Large Scale ◽  
Slow Solar Wind ◽  
Transient Event ◽  
Large Scale Structures ◽  
Close Proximity ◽  
Scale Structures

Abstract. STEREO has now completed the first two years of its mission, moving from close proximity to Earth in 2006/2007 to more than 50 degrees longitudinal separation from Earth in 2009. During this time, several large-scale structures have been observed in situ. Given the prevailing solar minimum conditions, these structures have been predominantly coronal hole-associated solar wind, slow solar wind, their interfaces, and the occasional transient event. In this paper, we extend earlier solar wind composition studies into the current solar minimum using high-resolution (1-h) sampling times for the charge state analysis. We examine 2-year trends for iron charge states and solar wind proton speeds, and present a case study of Carrington Rotation 2064 (December 2007) which includes minor ion (He, Fe, O) kinetic and Fe composition parameters in comparison with proton and magnetic field signatures at large-scale structures observed during this interval.

Analysis of the Internal structure of the Streamer Blow Out Observed by the Parker Solar Probe during the First Solar Encounter

2020 ◽  
Author(s):  
Teresa Nieves-Chinchilla ◽  
Adam Szabo ◽  
Kelly E. Korreck ◽  
Nathalia Alzate ◽  
Laura A. Balmaceda ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Internal Structure ◽  
Flux Rope ◽  
Internal Force ◽  
Slow Solar Wind ◽  
Angle Distribution ◽  
The Hours ◽  
The Magnetic Field

<p>We present an analysis of the internal structure of a coronal mass ejection (CME) detected by in situ<span> </span>instruments onboard the Parker Solar Probe (PSP) spacecraft during its first solar encounter. On 2018 November 11 at 23:53 UT, the FIELDS magnetometer measured an increase in strength of the magnetic field as well as a coherent change in the field direction. The SWEAP instrument simultaneously detected the low proton temperature and signatures of bi-directionality in the electron pitch angle distribution (PAD). These signatures are indicative of a CME embedded in the slow solar wind. In conjunction with PSP was the STEREO A spacecraft, which enabled the remote observation of a streamer blow-out by the SECCHI suite of instruments. The source at the Sun of the slow and well-structured<span> fl</span>ux-rope was identified in an overlying streamer.</p><p>Our detailed inspection of the internal transient structure magnetic properties suggests high complexity in deviations from an ideal<span> </span>flux rope 3D topology. Reconstructions of the magnetic field conguration reveal a highly distorted structure consistent with the highly elongated `bubble' observed remotely. A double-ring substructure observed in the SECCHI-COR2 eld of view (FOV) is suggestive of a double internal<span> </span>flux rope. Furthermore, we describe a scenario in which mixed topology of a closed<span> </span>flux rope is combined with the magnetically open structure, which helps explain the<span> </span>flux dropout observed in the measurements of the electron PAD. Our justication for this is the plethora of structures observed by the EUV imager (SECCHI-EUVI) in the hours preceding the streamer blowout evacuation. Finally, taking advantage of the unique observations from PSP, we explore the first stages of the effects of coupling with the solar wind and the evolutionary processes in the magnetic structure. We found evidence of bifurcated current sheets in the structure boundaries suggestive of magnetic reconnection. Our analysis of the internal force imbalance indicates that internal Lorentz forces continue to dominate the evolution of the structure in the COR2 FOV and serves as the main driver of the internal<span> fl</span>ux rope distortion as detected in situ at PSP solar distance.</p>

Sign in / Sign up

Export Citation Format

Share Document