Minimal Magnetic States of the Sun and the Solar Wind: Implications for the Origin of the Slow Solar Wind

2015 ◽  
pp. 227-247
Author(s):  
E. W. Cliver ◽  
R. von Steiger
Keyword(s):  
Solar Wind ◽  
Slow Solar Wind ◽  
The Sun ◽  
Magnetic States

scholarly journals The evolution of inverted magnetic fields through the inner heliosphere

2020 ◽  
Vol 494 (3) ◽  
pp. 3642-3655 ◽  
Author(s):  
Allan R Macneil ◽  
Mathew J Owens ◽  
Robert T Wicks ◽  
Mike Lockwood ◽  
Sarah N Bentley ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Radial Distance ◽  
Occurrence Rate ◽  
Slow Solar Wind ◽  
The Sun ◽  
Radial Evolution ◽  
In Transit ◽  
The Magnetic Field ◽  
Inner Heliosphere

ABSTRACT Local inversions are often observed in the heliospheric magnetic field (HMF), but their origins and evolution are not yet fully understood. Parker Solar Probe has recently observed rapid, Alfvénic, HMF inversions in the inner heliosphere, known as ‘switchbacks’, which have been interpreted as the possible remnants of coronal jets. It has also been suggested that inverted HMF may be produced by near-Sun interchange reconnection; a key process in mechanisms proposed for slow solar wind release. These cases suggest that the source of inverted HMF is near the Sun, and it follows that these inversions would gradually decay and straighten as they propagate out through the heliosphere. Alternatively, HMF inversions could form during solar wind transit, through phenomena such velocity shears, draping over ejecta, or waves and turbulence. Such processes are expected to lead to a qualitatively radial evolution of inverted HMF structures. Using Helios measurements spanning 0.3–1 au, we examine the occurrence rate of inverted HMF, as well as other magnetic field morphologies, as a function of radial distance r, and find that it continually increases. This trend may be explained by inverted HMF observed between 0.3 and 1 au being primarily driven by one or more of the above in-transit processes, rather than created at the Sun. We make suggestions as to the relative importance of these different processes based on the evolution of the magnetic field properties associated with inverted HMF. We also explore alternative explanations outside of our suggested driving processes which may lead to the observed trend.

scholarly journals Solar wind and kinetic heliophysics

2018 ◽  
Vol 36 (6) ◽  
pp. 1607-1630 ◽  
Author(s):  
Eckart Marsch
Keyword(s):  
Solar Wind ◽  
Interplanetary Space ◽  
Coronal Holes ◽  
Heavy Ion ◽  
Alfven Waves ◽  
Distribution Functions ◽  
Slow Solar Wind ◽  
Alfvén Waves ◽  
The Sun ◽  
Collisionless Dissipation

Abstract. This paper reviews recent aspects of solar wind physics and elucidates the role Alfvén waves play in solar wind acceleration and turbulence, which prevail in the low corona and inner heliosphere. Our understanding of the solar wind has made considerable progress based on remote sensing, in situ measurements, kinetic simulation and fluid modeling. Further insights are expected from such missions as the Parker Solar Probe and Solar Orbiter. The sources of the solar wind have been identified in the chromospheric network, transition region and corona of the Sun. Alfvén waves excited by reconnection in the network contribute to the driving of turbulence and plasma flows in funnels and coronal holes. The dynamic solar magnetic field causes solar wind variations over the solar cycle. Fast and slow solar wind streams, as well as transient coronal mass ejections, are generated by the Sun's magnetic activity. Magnetohydrodynamic turbulence originates at the Sun and evolves into interplanetary space. The major Alfvén waves and minor magnetosonic waves, with an admixture of pressure-balanced structures at various scales, constitute heliophysical turbulence. Its spectra evolve radially and develop anisotropies. Numerical simulations of turbulence spectra have reproduced key observational features. Collisionless dissipation of fluctuations remains a subject of intense research. Detailed measurements of particle velocity distributions have revealed non-Maxwellian electrons, strongly anisotropic protons and heavy ion beams. Besides macroscopic forces in the heliosphere, local wave–particle interactions shape the distribution functions. They can be described by the Boltzmann–Vlasov equation including collisions and waves. Kinetic simulations permit us to better understand the combined evolution of particles and waves in the heliosphere.

scholarly journals EISCAT measurements of the solar wind

1996 ◽  
Vol 14 (12) ◽  
pp. 1235-1245 ◽  
Author(s):  
A. R. Breen ◽  
W. A. Coles ◽  
R. R. Grall ◽  
M. T. Klinglesmith ◽  
J. Markkanen ◽  
...  
Keyword(s):  
Solar Wind ◽  
Slow Solar Wind ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
Final Velocity ◽  
Flow Vector ◽  
Fast Wind ◽  
Interaction Regions ◽  
Slow Wind ◽  
Eiscat Measurements

Abstract. EISCAT observations of interplanetary scintillation have been used to measure the velocity of the solar wind at distances between 15 and 130 R⊙ (solar radii) from the Sun. The results show that the solar wind consists of two distinct components, a fast stream with a velocity of ~800 km s–1 and a slow stream at ~400 km s–1. The fast stream appears to reach its final velocity much closer to the Sun than expected. The results presented here suggest that this is also true for the slow solar wind. Away from interaction regions the flow vector of the solar wind is purely radial to the Sun. Observations have been made of fast wind/slow wind interactions which show enhanced levels of scintillation in compression regions.

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>

Study of alpha particle properties across rarefaction regions

2021 ◽  
Author(s):  
Tereza Durovcova ◽  
Jana Šafránková ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Alpha Particle ◽  
Solar Wind Speed ◽  
Coronal Holes ◽  
Distribution Functions ◽  
Alpha Particles ◽  
Slow Solar Wind ◽  
The Sun ◽  
Wind Source

<p>Two large-scale interaction regions between the fast solar wind emanating from coronal holes and the slow solar wind coming from streamer belt are usually distinguished. When the fast stream pushes up against the slow solar wind ahead of it, a compressed interaction region that co-rotates with the Sun (CIR) is created. It was already shown that the relative abundance of alpha particles, which usually serve as one of solar wind source identifiers can change within this region. By symmetry, when the fast stream outruns the slow stream, a corotating rarefaction region (CRR) is formed. CRRs are characterized by a monotonic decrease of the solar wind speed, and they are associated with the regions of small longitudinal extent on the Sun. In our study, we use near-Earth measurements complemented by observations at different heliocentric distances, and focus on the behavior of alpha particles in the CRRs because we found that the large variations of the relative helium abundance (AHe) can also be observed there. Unlike in the CIRs, these variations are usually not connected with the solar wind speed and alpha-proton relative drift changes. We thus apply a superposed-epoch analysis of identified CRRs with a motivation to determine the global profile of alpha particle parameters through these regions. Next, we concentrate on the cases with largest AHe variations and investigate whether they can be associated with the changes of the solar wind source region or whether there is a relation between the AHe variations and the non-thermal features in the proton velocity distribution functions like the temperature anisotropy and/or presence of the proton beam.</p>

Preliminary results of Space Weather conditions encountered by BepiColombo during the first phase of its cruise

2020 ◽  
Author(s):  
Beatriz Sanchez-Cano ◽  
Richard Moissl ◽  
Daniel Heyner ◽  
Juhani Huovelin ◽  
M. Leila Mays ◽  
...  
Keyword(s):  
Solar Wind ◽  
Space Weather ◽  
High Speed ◽  
Weather Conditions ◽  
Slow Solar Wind ◽  
Astronomical Unit ◽  
The Sun ◽  
Preliminary Results ◽  
Outer Planets ◽  
Interaction Regions

<p>Planetary Space Weather is the discipline that studies the state of the Sun and how it interacts with the interplanetary and planetary environments. It is driven by the Sun’s activity, particularly through large eruptions of plasma (known as coronal mass ejections, CMEs), solar wind stream interaction regions (SIR) formed by the interaction of high-speed solar wind streams with the preceding slower solar wind, and bursts of solar energetic particles (SEPs) that form radiation storms. This is an emerging topic, whose real-time forecast is very challenging because among other factors, it needs a continuous coverage of its variability within the whole heliosphere as well as of the Sun’s activity to improve forecasting. <br />The long cruise of BepiColombo constitutes an exceptional opportunity for studying the Space Weather evolution within half-astronomical unit (AU), as well as in certain parts of its journey, can be used as an upstream solar wind monitor for Venus, Mars and even the outer planets. This work will present preliminary results of the Space Weather conditions encountered by BepiColombo since its launch until mid-2020, which includes data from the solar minimum of activity and few slow solar wind structures. Data come from three of its instruments that are operational for most of the cruise phase, i.e., the BepiColombo Radiation Monitor (BERM), the Mercury Planetary Orbiter Magnetometer (MPO-MAG), and the Solar Intensity X-ray and particle Spectrometer (SIXS). Modelling support for the data observations will be also presented with the so-called solar wind ENLIL simulations.</p>

scholarly journals Quasi-Periodic Releases of Streamer Blobs and Velocity Variability of the Slow Solar Wind near the Sun

Solar Physics ◽  
2009 ◽  
Vol 258 (1) ◽  
pp. 129-140 ◽  
Author(s):  
H. Q. Song ◽  
Y. Chen ◽  
K. Liu ◽  
S. W. Feng ◽  
L. D. Xia
Keyword(s):  
Solar Wind ◽  
Slow Solar Wind ◽  
The Sun

scholarly journals Diamagnetic structures as a basis of quasi-stationary slow solar wind

2019 ◽  
Vol 5 (3) ◽  
pp. 36-49
Author(s):  
Виктор Еселевич ◽  
Viktor Eselevich
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Plasma Density ◽  
Neutral Line ◽  
Angular Size ◽  
Radial Component ◽  
Slow Solar Wind ◽  
Small Scale ◽  
The Sun ◽  
Streamer Belt

The results presented in this review reflect the fundamentals of the modern understanding of the nature of the structure of the slow solar wind (SW) along the entire length from the Sun to the Earth's orbit. It is known that the source of the slow quasi-stationary SW on the Sun is the belt and the chains of coronal streamers The streamer belt encircles the entire Sun as a wave-like surface (skirt), representing a sequence of pairs of rays with increased brightness (plasma density) or two lines of rays located close to each other. Neutral line of the radial component of the solar global magnetic field goes along the belt between the rays of each of these pairs. The streamer belt extends in the heliosphere is as the heliospheric plasma sheet (HPS). Detailed analysis of data from Wind and IMP-8 satellites showed that HPS sections on the Earth orbit are registered as a sequence of diamagnetic tubes with high density plasma and low interplanetary magnetic field. They represent an extension of rays with increased brightness of the streamer belt near the Sun. Their angular size remains the same over the entire way from the Sun to the Earth's orbit. Each HPS diamagnetic tube has a fine internal structure on several scales, or fractality. In other words, diamagnetic tube is a set of nested diamagnetic tubes, whose angular size can vary by almost two orders of magnitude. These sequences of diamagnetic tubes that form the base of slow SW on the Earth's orbit has a more general name — diamagnetic structures (DS). In the final part of this article, a comparative analysis of several events was made, based on the results of this review. He made it possible to find out the morphology and nature of the origin of the new term “diamagnetic plasmoids” SW (local amplifications of plasma density), which appeared in several articles published during 2012–2018. The analysis carried out at the end of this article, for the first time, showed that the diamagnetic plasmoids SW are the small-scale component of the fractal diamagnetic structures of the slow SW, considered in this review.

scholarly journals Solar Wind and Kinetic Heliophysics

2018 ◽  
Author(s):  
Eckart Marsch
Keyword(s):  
Solar Wind ◽  
Interplanetary Space ◽  
Coronal Holes ◽  
Heavy Ion ◽  
Alfven Waves ◽  
Distribution Functions ◽  
Slow Solar Wind ◽  
Alfvén Waves ◽  
The Sun ◽  
Collisionless Dissipation

Abstract. This lecture reviews recent aspects of solar wind physics and elucidates the role Alfvén waves play in solar wind acceleration and turbulence, which prevail in the low corona and inner heliosphere. Our understanding of the solar wind has made considerable progress based on remote sensing, in-situ measurements, kinetic simulation and fluid modeling. Further insights are expected from such missions as the Parker Solar Probe and Solar Orbiter. The sources of the solar wind have been identified in the chromospheric network, Transition region and corona of the sun. Alfvén waves excited by reconnection in the network contribute to the driving of turbulence and plasma flows in funnels and coronal holes. The dynamic solar magnetic field causes solar wind variations over the solar cycle. Fast and slow solar wind streams, as well as transient coronal mass ejections are generated by the sun’s magnetic activity. Magnetohydrodynamic turbulence originates at the sun and evolves into interplanetary space. The major Alfvén waves and minor magnetosonic waves, with an admixture of pressurebalanced structures at various scales, constitute heliophysical turbulence. Its spectra evolve radially and develop anisotropies. Numerical simulations of turbulence spectra have reproduced key observational features. Collisionless dissipation of fluctuations remains a subject of intense research. Detailed measurements of particle velocity distributions have revealed non-maxwellian electrons, strongly anisotropic protons and heavy ion beams. Besides macroscopic forces in the heliosphere local wave-particle interactions shape the distribution functions. They can be described by the Boltzmann–Vlasov equation including collisions and waves. Kinetic simulations permit us to better understand the combined evolution of particles and waves in the heliosphere.

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