Characterisation and comparison of slow coronal hole wind intervals at 0.13au

Small flux ropes (SFRs) are interplanetary magnetic flux ropes with durations from a few minutes to a few hours. We have built a comprehensive catalog of SFRs at Mercury using magnetometer data from the orbital phase of the MESSENGER mission (2011-2015). In the absence of solar wind plasma measurements, we developed strict identification criteria for SFRs in the magnetometer observations, including conducting force-free field fits for each flux rope. We identified a total of 48 events that met our strict criteria, with events ranging in duration from 2.5 minutes to 4 hours. Using superposed epoch analysis, we obtained the generic SFR magnetic field profile at Mercury. Due to the large variation in Mercury's heliocentric distance (0.31-0.47 AU), we split the data into two distance bins. We found that the average SFR profile is more symmetric "farther from the Sun", in line with the idea that SFRs form closer to the Sun and undergo a relaxation process in the solar wind. Based on this result, as well as the SFR durations and the magnetic field strength fall-off with heliocentric distance, we infer that the SFRs observed at Mercury are expanding as they propagate with the solar wind. We also determined that the SFR occurrence frequency is nearly four times as high at Mercury as for similarly detected events at 1 AU. Most interestingly, we found two SFR populations in our dataset, one likely generated in a quasi-periodic formation process near the heliospheric current sheet, and the other formed away from the current sheet in isolated events.

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THE STRUCTURE OF THE SOLAR WIND IN THE HELIOSPHERE DEPENDING ON THE PHASE OF THE SOLAR CYCLE: LARGE-SCALE DYNAMICS OF THE HELIOSPHERIC CURRENT SHEET

Journal of Oceanological Research ◽

10.29006/1564-2291.jor-2019.47(1).25 ◽

2019 ◽

Vol 47 (1) ◽

pp. 85-87

Author(s):

E.V. Maiewski ◽

R.A. Kislov ◽

H.V. Malova ◽

O.V. Khabarova ◽

V.Yu. Popov ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Solar Activity ◽

Solar Cycle ◽

Current Sheet ◽

Heliospheric Current Sheet ◽

High Solar Activity ◽

The Sun ◽

High Latitudes ◽

The Magnetic Field

A stationary axisymmetric MHD model of the solar wind has been constructed, which allows us to study the spatial distribution of the magnetic field and plasma characteristics at radial distances from 20 to 400 radii of the Sun at almost all heliolatitudes. The model takes into account the changes in the magnetic field of the Sun during a quarter of the solar cycle, when the dominant dipole magnetic field is replaced by a quadrupole. Selfconsistent solutions for the magnetic and velocity fields, plasma concentration and current density of the solar wind depending on the phase of the solar cycle are obtained. It is shown that during the domination of the dipole magnetic component in the solar wind heliospheric current sheet (HCS) is located in the equatorial plane, which is a part of the system of radial and transverse currents, symmetrical in the northern and southern hemispheres. As the relative contribution of the quadrupole component to the total magnetic field increases, the shape of the HCS becomes conical; the angle of the cone gradually decreases, so that the current sheet moves entirely to one of the hemispheres. At the same time, at high latitudes of the opposite hemisphere, a second conical HCS arises, the angle of which increases. When the quadrupole field becomes dominant (at maximum solar activity), both HCS lie on conical surfaces inclined at an angle of 35 degrees to the equator. The model describes the transition from the fast solar wind at high latitudes to the slow solar wind at low latitudes: a relatively gentle transition in the period of low solar activity gives way to more drastic when high solar activity. The model also predicts an increase in the steepness of the profiles of the main characteristics of the solar wind with an increase in the radial distance from the Sun. Comparison of the obtained dependences with the available observational data is discussed.

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

10.5194/egusphere-egu21-3426 ◽

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

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.

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

10.5194/egusphere-egu21-6200 ◽

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

Solar wind formation can be separated into three physical steps &#8211; source, release, and acceleration &#8211; that each leave distinct observational signatures on plasma parcels.&#160; 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. &#160;&#160;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. &#160;In the first study, we test the well-known inverse relationship between expansion factor (fs) and observed solar wind speed (vobs) 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.&#160; We find that there is no correlation between fs and vobs 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) &#8211; a direct test of the Separatrix-web (S-web) theory of slow solar wind formation.&#160; In the final study, we use our methodology to identify the source regions of the first observations from the Parker Solar Probe (PSP) mission.&#160; Our modeling enabled us to characterize the closest to the Sun observed coronal mass ejection (CME) to date as a streamer blowout.&#160; We close with future ways that ADAPT-WSA can be used to test outstanding questions of solar wind formation.

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Magnetic disconnection from the Sun: Observations of a reconnection exhaust in the solar wind at the heliospheric current sheet

Geophysical Research Letters ◽

10.1029/2005gl022406 ◽

2005 ◽

Vol 32 (5) ◽

Cited By ~ 61

Author(s):

J. T. Gosling

Keyword(s):

Solar Wind ◽

Current Sheet ◽

Heliospheric Current Sheet ◽

The Sun

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

Solnechno-Zemnaya Fizika ◽

10.12737/szf-53201904 ◽

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.

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Proton Enhancement and Decreased O[sup 6+]∕H at the Heliospheric Current Sheet: Implications for the Origin of Slow Solar Wind

10.1063/1.3395875 ◽

2010 ◽

Cited By ~ 3

Author(s):

Y. C.-M. Liu ◽

A. B. Galvin ◽

M. A. Popecki ◽

K. D. C. Simunac ◽

L. Kistler ◽

...

Keyword(s):

Solar Wind ◽

Current Sheet ◽

Heliospheric Current Sheet ◽

Slow Solar Wind

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

Solar-Terrestrial Physics ◽

10.12737/stp-53201904 ◽

2019 ◽

Vol 5 (3) ◽

pp. 29-41 ◽

Cited By ~ 3

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.

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