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The first two orbits of the Parker Solar Probe (PSP) spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36 Rs). Here, we present an analysis of this data to study solar…

We investigate the origin of mesoscale structures in the solar wind called microstreams defined as enhancements in solar wind speed and temperature that last several hours. They were first clearly detected in Helios and Ulysses solar wind…

Solar and Stellar Astrophysics · Physics 2023-10-24 Bahaeddine Gannouni , Victor Réville , Alexis Rouillard

The transition from subAlfv\'enic to superAlfv\'enic flow in the solar atmosphere is examined by means of Parker Solar Probe (PSP) measurements during solar encounters 8 to 14. Around 220 subAlfv\'enic periods with a duration $\ge$ 10…

One of the primary science objectives of Parker Solar Probe (PSP) is to determine the structures and dynamics of the plasma and magnetic fields at the sources of the solar wind. However, establishing the connection between {\it in situ}…

Characterizing the plasma state in the near-Sun environment is essential to constrain the mechanisms that heat and accelerate the solar wind. In this study, we use Parker Solar Probe (PSP) observations from Encounters 1 through 24 to…

We provide a simple geometric explanation for the source of switchbacks and associated large and one-sided transverse flows in the solar wind observed by Parker Solar Probe. The more radial, Sub-Parker Spiral structure of the heliospheric…

Solar and Stellar Astrophysics · Physics 2021-03-17 N. A. Schwadron , D. J. McComas

Broadly, solar wind source regions can be classified by their magnetic topology as intermittently and continuously open to the heliosphere. Early models of solar wind acceleration do not account for the fastest, non-transient solar wind…

Solar and Stellar Astrophysics · Physics 2025-08-29 B. L. Alterman

Large-scale solar ejections are well understood, but the extent to which small-scale solar features directly influence the solar wind remains an open question, primarily due to the challenges of tracing these small-scale ejections and their…

Solar and Stellar Astrophysics · Physics 2025-07-18 Jeongwoo Lee , Manolis K. Georgoulis , Rahul Sharma , Nour E. Raouafi , Qin Li , Haimin Wang

The Parker Solar Probe (PSP) spacecraft is performing the first in situ exploration of the solar wind within 0.2 au of the Sun. Initial observations confirmed the Alfv\'enic nature of aligned fluctuations of the magnetic field B and…

Regions of magnetic field with near-radial, Parker Spiral-like geometry known as quiescent regions have been observed in Parker Solar Probe data. These regions have very low $\delta B / \langle |B| \rangle$ compared to non-quiescent solar…

Solar and Stellar Astrophysics · Physics 2024-06-04 Benjamin Short , David M. Malaspina , Alexandros Chasapis , Jaye L. Verniero

Recent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which…

Motivated by recent Parker Solar Probe (PSP) observations of "switchbacks" (abrupt, large-amplitude reversals in the radial magnetic field, which exhibit Alfv\'enic correlations) we examine the dynamics of large-amplitude Alfv\'en waves in…

Parker Solar Probe (PSP) observed sub-Alfvenic solar wind intervals during encounters 8 - 14, and low-frequency magnetohydrodynamic turbulence in these regions may differ from that in super-Alfvenic wind. We apply a new mode-decomposition…

In-situ measurements by several spacecraft have revealed that the solar wind is frequently perturbed by transient structures (magnetic folds, jets, waves, flux-ropes) that propagate rapidly away from the Sun over large distances. Parker…

Solar and Stellar Astrophysics · Physics 2021-09-15 R. F. Pinto , N. Poirier , A. P. Rouillard , A. Kouloumvakos , L. Griton , N. Fargette , R. Kieokaew , B. Lavraud , A. S. Brun

The recent launches of Parker Solar Probe (PSP), Solar Orbiter (SO) and BepiColombo, along with several older spacecraft, have provided the opportunity to study the solar wind at multiple latitudes and distances from the Sun simultaneously.…

We investigate the local proton energization at magnetic discontinuities/intermittent structures and the corresponding kinetic signatures in velocity phase space in Alfv\'enic and non-Alfv\'enic wind streams observed by Parker Solar Probe.…

Plasma Physics · Physics 2023-09-15 C. A. Gonzalez , J. L. Verniero , R. Bandyopadhyay , A. Tenerani

The acceleration of the solar coronal plasma to supersonic speeds is one of the most fundamental yet unresolved problem in heliophysics. Despite the success of Parker's pioneering theory on an isothermal solar corona, the realistic solar…

Solar and Stellar Astrophysics · Physics 2022-12-21 Chen Shi , Marco Velli , Stuart D. Bale , Victor Réville , Milan Maksimović , Jean-Baptiste Dakeyo

Motivated by theoretical, numerical, and observational evidence, we explore the possibility that the critical transition between sub-Alfv\'enic flow and super-Alfv\'enic flow in the solar atmosphere takes place in fragmented and…

Solar and Stellar Astrophysics · Physics 2022-11-23 Rohit Chhiber , William H. Matthaeus , Arcadi V. Usmanov , Riddhi Bandyopadhyay , Melvyn L. Goldstein

The trace magnetic power spectrum in the solar wind is known to be characterized by a double power law at scales much larger than the proton gyro-radius, with flatter spectral exponents close to -1 found at the lower frequencies below an…

The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar Probe (PSP) mission measures the three-dimensional electron velocity distribution function. We derive the parameters of the core, halo, and strahl populations…