Narrow coronal holes in Yohkoh soft X-ray images and the slow solar wind

Appearance of measurements of the interplanetary medium parameters with high temporal resolution gave rise to a variety of investigations of turbulent cascade at ion kinetic scales at which processes of plasma heating was believed to operate. Our recent studies based on high frequency plasma measurements at Spektr-R spacecraft have shown that the turbulent cascade was not stable and dynamically changed depending on the plasma conditions in different large-scale solar wind structures. These changes was most significant at the kinetic scales of the turbulent cascade. Slow undisturbed solar wind was characterized by the consistency of the spectra to the predictions of the kinetic Alfven wave turbulence model. On the other hand, the discrepancy between the model predictions and registered spectra were found in stream interaction regions characterized by crucial steepening of spectra at the kinetic scales with slopes having values up to -(4-5). This discrepancy was clearly shown for plasma compression region Sheath in front of the magnetic clouds and CIR in front of high speed streams associated with coronal holes. Present study is focused on the break preceding the kinetic scales. Currently the characteristic plasma parameters associated with the formation of the break is still debated. Number of studies demonstrated that the break was consistent with distinct characteristic frequencies for different values &#8203;&#8203;of the plasma proton parameter beta &#946;p. Present study consider the ratio between the break frequency determined for ion flux fluctuation spectra according to Spektr-R data and several characteristic plasma frequencies used traditionally in such cases. The value of this ratio is statistically compared for different large-scale solar wind streams. We analyze both the classical spectrum view with two slopes and one break and the spectrum with flattening between magnetohydrodynamic and kinetic scales.&#160; Our results show that for the Sheath and CIR regions characterized typically by &#946;p &#8804;1 the break corresponds statistically to the frequency determined by the proton gyroradius. At the same time such correspondence are not observed either for the undisturbed slow solar wind with similar &#946;p value or for disturbed flows associated with interplanetary manifestations of coronal mass ejections, where &#946;p << 1. The results also shows that in slow undisturbed solar wind the break is closer to the frequency determined by the inertial proton length. Thus, apparently the transition between streams of different speeds may result in the change of dissipation regimes and plays role in plasma heating at these areas. This work was supported by the RFBR grant No. 19-02-00177a

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

10.5194/egusphere-egu21-14779 ◽

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

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.&#160;

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Solar wind and kinetic heliophysics

Annales Geophysicae ◽

10.5194/angeo-36-1607-2018 ◽

2018 ◽

Vol 36 (6) ◽

pp. 1607-1630 ◽

Cited By ~ 5

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.

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The contribution of X-ray polar blowout jets to the solar wind mass and energy

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313011046 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 239-242 ◽

Cited By ~ 1

Author(s):

Giannina Poletto ◽

Alphonse C. Sterling ◽

Stefano Pucci ◽

Marco Romoli

Keyword(s):

Solar Wind ◽

Kinetic Energy ◽

Energy Budget ◽

Coronal Mass Ejections ◽

Mass Flux ◽

Large Scale ◽

Coronal Holes ◽

Magnetic Loop ◽

Small Scale ◽

X Ray

AbstractBlowout jets constitute about 50% of the total number of X-ray jets observed in polar coronal holes. In these events, the base magnetic loop is supposed to blow open in what is a scaled-down representation of two-ribbon flares that accompany major coronal mass ejections (CMEs): indeed, miniature CMEs resulting from blowout jets have been observed. This raises the question of the possible contribution of this class of events to the solar wind mass and energy flux. Here we make a first crude evaluation of the mass contributed to the wind and of the energy budget of the jets and related miniature CMEs, under the assumption that small-scale events behave as their large-scale analogs. This hypothesis allows us to adopt the same relationship between jets and miniature-CME parameters that have been shown to hold in the larger-scale events, thus inferring the values of the mass and kinetic energy of the miniature CMEs, currently not available from observations. We conclude our work estimating the mass flux and the energy budget of a blowout jet, and giving a crude evaluation of the role possibly played by these events in supplying the mass and energy that feeds the solar wind.

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Observations of Slow Solar Wind from Equatorial Coronal Holes

The Astrophysical Journal ◽

10.3847/1538-4357/ab2add ◽

2019 ◽

Vol 880 (2) ◽

pp. 146 ◽

Cited By ~ 7

Author(s):

Y.-M. Wang ◽

Y.-K. Ko

Keyword(s):

Solar Wind ◽

Coronal Holes ◽

Slow Solar Wind

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Study of alpha particle properties across rarefaction regions

10.5194/egusphere-egu21-2864 ◽

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

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.

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Solar Wind and Kinetic Heliophysics

10.5194/angeo-2018-36 ◽

2018 ◽

Cited By ~ 1

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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Highlight Results from Ulysses

Symposium - International Astronomical Union ◽

10.1017/s0074180900219931 ◽

2001 ◽

Vol 203 ◽

pp. 525-532

Author(s):

R. G. Marsden

Keyword(s):

Solar Wind ◽

Solar Minimum ◽

High Speed ◽

Full Range ◽

Coronal Holes ◽

Radial Component ◽

Slow Solar Wind ◽

Solar Wind Flow ◽

Low Energy Ions ◽

Inner Heliosphere

Launched in October 1990, the ESA-NASA Ulysses mission has conducted the very first survey of the heliosphere within 5 AU of the Sun over the full range of heliolatitudes. The first polar passes took place in 1994 and 1995, enabling Ulysses to characterise the global structure of the heliosphere at solar minimum, when the corona adopts its simplest configuration. The most important findings to date include a confirmation of the uniform nature of the high-speed (~ 750 km s−1) solar wind flow from the polar coronal holes, filling two-thirds of the volume of the inner heliosphere; the sharp boundary, existing from the chromosphere through the corona, between fast and slow solar wind streams; the latitude independence of the radial component of the heliospheric magnetic field; the lower-than-expected latitude gradient of galactic and anomalous cosmic rays; the continued existence of recurrent increases in the flux of low-energy ions and electrons up to the highest latitudes.

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The origin of slow Alfvénic solar wind at solar minimum

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3422 ◽

2019 ◽

Vol 492 (1) ◽

pp. 39-44 ◽

Cited By ~ 10

Author(s):

D Stansby ◽

L Matteini ◽

T S Horbury ◽

D Perrone ◽

R D’Amicis ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Alpha Particle ◽

Coronal Holes ◽

Slow Solar Wind ◽

Kinetic Properties ◽

Fast Solar Wind ◽

Lower Corona ◽

Field Lines ◽

Slow Wind

ABSTRACT Although the origins of slow solar wind are unclear, there is increasing evidence that at least some of it is released in a steady state on overexpanded coronal hole magnetic field lines. This type of slow wind has similar properties to the fast solar wind, including strongly Alfvénic fluctuations. In this study, a combination of proton, alpha particle, and electron measurements are used to investigate the kinetic properties of a single interval of slow Alfvénic wind at 0.35 au. It is shown that this slow Alfvénic interval is characterized by high alpha particle abundances, pronounced alpha–proton differential streaming, strong proton beams, and large alpha-to-proton temperature ratios. These are all features observed consistently in the fast solar wind, adding evidence that at least some Alfvénic slow solar wind also originates in coronal holes. Observed differences between speed, mass flux, and electron temperature between slow Alfvénic and fast winds are explained by differing magnetic field geometry in the lower corona.

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