The radial evolution of a single solar wind plasma parcel

Radial alignments between pairs of spacecraft is the only way to observationally investigate the turbulent evolution of the solar wind as it expands throughout interplanetary space. On September 2020 Parker Solar Probe (PSP) and Solar Orbiter (SolO) were nearly perfectly radially aligned, with PSP orbiting around its perihelion at 0.1 au (and crossing the nominal Alfv&#233;n point) and SolO at 1 au. PSP/SolO joint observations of the same solar wind plasma allow the extraordinary and unprecedented opportunity to study how the turbulence properties of the solar wind evolve in the inner heliosphere over the wide distance of 0.9 au. The radial evolution of (i) the MHD properties (such as radial dependence of low- and high-frequency breaks, compressibility, Alfv&#233;nic content of the fluctuations), (ii) the polarization status, (iii) the presence of wave modes at kinetic scale as well as their distribution in the plasma instability-temperature anisotropy plane are just few instances of what can be addressed. Of furthest interest is the study of whether and how the cascade transfer and dissipation rates evolve with the solar distance, since this has great impact on the fundamental plasma physical processes related to the heating of the solar wind. In this talk I will present some of the results obtained by exploiting the PSP/SolO alignment data.

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Non-adiabatic interaction of ions with solar wind discontinuities

10.5194/egusphere-egu2020-20301 ◽

2020 ◽

Author(s):

Alexander Vinogradov ◽

Anton Artemyev ◽

Ivan Vasko ◽

Alexei Vasiliev ◽

Anatoly Petrukovich

Keyword(s):

Solar Wind ◽

Observational Data ◽

Solar Wind Plasma ◽

Theoretical Models ◽

High Amplitude ◽

Small Scale ◽

Ion Scattering ◽

Ion Temperature ◽

Wide Range ◽

Radial Evolution

According to Helios, Ulysses, New Horizons measurements at a wide range of distances from the Sun, radial evolution of solar wind ion temperature significantly deviates from the adiabatic expansion model:&#160; additional heating of the solar wind plasma is required to describe observational data. Solution of the solar wind heating problem is extremely important both for understanding the structure of the heliosphere and for adequately describing the atmospheres of distant stars. Solar wind magnetic field is turbulent and this turbulence is dominated by numerous small-scale high-amplitude coherent structures &#8211; such as quasi-1D discontinuities. Modern theoretical models predict that quasi-1D discontinuities can play important role in solar wind heating. We collected the statistics of MMS observations of thin quasi-1D discontinuities in the solar wind to reveal their characteristics. Analyzing observational data, we construct the discontinuity model and use it to consider non-adiabatic interaction of ions with solar wind discontinuities. We mainly focus on discontinuity roles in solar wind ion scattering and thermalization. This presentation shows how discontinuity configuration affects the scattering rates.

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Solar wind radial evolution via future multi-spacecraft in-situ observations

10.5194/egusphere-egu2020-7451 ◽

2020 ◽

Author(s):

Štěpán Štverák ◽

Milan Maksimovic ◽

Petr Hellinger ◽

Pavel M. Trávníček

Keyword(s):

Solar Wind ◽

Large Scale ◽

Single Point ◽

Solar Wind Plasma ◽

Future Events ◽

In Situ Observations ◽

Radial Evolution ◽

The Individual

Our understanding of the solar wind evolution, its energy budget, and role of the key mechanisms providing the energy exchange between the plasma particles and electromagnetic fluctuations along the expansion, is highly limited by the single point nature of most in situ spacecraft measurements. Obviously it is difficult to observe and track the individual processes in space and time from this narrow perspective. One way to improve our knowledge of these large-scale variations is to employ multi-spacecraft observations, namely rather rare so called line-up events where one can potentially observe the true evolution of individual solar wind plasma parcels. A pioneering work in this field was done using Helios I&II missions. Here we present an analyses of using such tool for future events predicted to be available from the very recent missions Parker Solar Probe and Solar Orbiter (and optionally BepiColombo).

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The Radial Evolution of Solar Wind Speeds (Postprint)

10.21236/ada557896 ◽

2012 ◽

Author(s):

S. L. McGregor ◽

W. J. Hughes ◽

C. N. Arge ◽

D. Odstreil ◽

N. A. Schwadron

Keyword(s):

Solar Wind ◽

Wind Speeds ◽

Radial Evolution

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A review of the SCOSTEP’s 5-year scientific program VarSITI—Variability of the Sun and Its Terrestrial Impact

Progress in Earth and Planetary Science ◽

10.1186/s40645-021-00410-1 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Kazuo Shiokawa ◽

Katya Georgieva

Keyword(s):

Solar Wind ◽

Interplanetary Space ◽

Solar Wind Plasma ◽

The Sun ◽

Scientific Program ◽

Solar Cycles ◽

Grand Minimum ◽

The Earth ◽

Earth Connection ◽

Near Future

AbstractThe Sun is a variable active-dynamo star, emitting radiation in all wavelengths and solar-wind plasma to the interplanetary space. The Earth is immersed in this radiation and solar wind, showing various responses in geospace and atmosphere. This Sun–Earth connection variates in time scales from milli-seconds to millennia and beyond. The solar activity, which has a ~11-year periodicity, is gradually declining in recent three solar cycles, suggesting a possibility of a grand minimum in near future. VarSITI—variability of the Sun and its terrestrial impact—was the 5-year program of the scientific committee on solar-terrestrial physics (SCOSTEP) in 2014–2018, focusing on this variability of the Sun and its consequences on the Earth. This paper reviews some background of SCOSTEP and its past programs, achievements of the 5-year VarSITI program, and remaining outstanding questions after VarSITI.

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