Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum

Raouafi, N. E.; Matteini, Lorenzo; Squire, Jonathan; Badman, S. T.; Velli, M.; Klein, K. G.; Chen, Christopher H. K.; Matthaeus, W. H.; Szabó, Á.; Linton, M. G.; Allen, R. C.; Szalay, J. R.; Bruno, R.; Decker, R. B.; Akhavan‐Tafti, Mojtaba; Agapitov, Oleksiy; Bale, S. D.; Bandyopadhyay, R.; Battams, K.; Berčič, Laura; Bourouaine, Sofiane; Bowen, T. A.; Cattell, C. A.; Chandran, Benjamin D. G.; Chhiber, R.; Cohen, C. M. S.; D’Amicis, R.; Giacalone, J.; Hess, Phillip; Howard, R. A.; Horbury, T. S.; Jagarlamudi, V. K.; Joyce, Colin J.; Kasper, J. C.; Kinnison, James D.; Laker, R.; Liewer, Paulett C.; Malaspina, D.; Mann, Ingrid; McComas, D. J.; Niembro, Tatiana; Nieves‐Chinchilla, Teresa; Panasenco, O.; Pokorný, Petr; Pusack, A.; Pulupa, M.; Perez, Jean C.; Riley, Pete; Rouillard, A. P.; Shi, Chen; Stenborg, G.; Tenerani, Anna; Verniero, J. L.; Viall, N. M.; Vourlidas, A.; Wood, Brian E.; Woodham, L. D.; Woolley, T.

doi:10.1007/s11214-023-00952-4

Cited by 71 publications

(52 citation statements)

References 603 publications

(762 reference statements)

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“…The histogram of power-law fit index in the MHD inertial range α MHD is shown in dark red. Most of the intervals have an inertial-range spectral exponent that falls within the expected value range [−1.67, −1.5], predicted by many existing phenomenologies (Kolmogorov 1941;Iroshnikov 1964;Kraichnan 1965;Sridhar & Goldreich 1994;Goldreich & Sridhar 1997;Boldyrev 2005Boldyrev , 2006, consistent with recent observations (see, e.g., Chen et al 2020;Kasper et al 2021;Shi et al 2021;Telloni et al 2021;Zank et al 2022;Raouafi et al 2023;Sioulas et al 2023aSioulas et al , 2023b. However, for the low-frequency range fit index (α Low , dark blue), the spectral exponents have an unexpectedly wide distribution, and the majority of them are larger than −1, i.e., the corresponding low-frequency spectra are shallower than 1/f.…”

Section: Statistics Of Power Spectral Exponentssupporting

confidence: 84%

New Observations of Solar Wind 1/f Turbulence Spectrum from Parker Solar Probe

Huang

Sioulas

Shi

et al. 2023

ApJL

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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 inertial range with indices closer to [−1.5, −1.67]. The origin of the 1/f range is still under debate. In this study, we selected 109 magnetically incompressible solar wind intervals (δ∣ B ∣/∣ B ∣ ≪ 1) from Parker Solar Probe encounters 1–13 that display such double power laws, with the aim of understanding the statistics and radial evolution of the low-frequency power spectral exponents from Alfvén point up to 0.3 au. New observations from closer to the Sun show that in the low-frequency range solar wind, turbulence can display spectra much shallower than 1/f, evolving asymptotically to 1/f as advection time increases, indicating a dynamic origin for the 1/f range formation. We discuss the implications of this result on the Matteini et al. conjecture for the 1/f origin as well as example spectra displaying a triple power law consistent with the model proposed by Chandran et al., supporting the dynamic role of parametric decay in the young solar wind. Our results provide new constraints on the origin of the 1/f spectrum and further show the possibility of the coexistence of multiple formation mechanisms.

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Section: Statistics Of Power Spectral Exponentssupporting

confidence: 84%

New Observations of Solar Wind 1/f Turbulence Spectrum from Parker Solar Probe

Huang

Sioulas

Shi

et al. 2023

ApJL

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“…There were numerous speculations on the role the SBs play in the solar wind dynamics closer to the Sun. The distinct observation of SBs in the PSP measurements within 0.2 au due to high Alfvén velocities at those distances put them at the center stage and reignited the interest in these features and gave a new impetus for this research topic (Bale et al 2019;Kasper et al 2019;Dudok de Wit et al 2020;Raouafi et al 2023).…”

Section: Introductionmentioning

confidence: 93%

Occurrence and Evolution of Switchbacks in the Inner Heliosphere: Parker Solar Probe Observations

Jagarlamudi

Raouafi

Bourouaine

et al. 2023

ApJL

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Since its launch in 2018, the Parker Solar Probe (PSP) mission revealed the presence of numerous fascinating phenomena occurring closer to the Sun, such as the presence of ubiquitous switchbacks (SBs). The SBs are large magnetic field deflections of the local magnetic field relative to a background field. We investigated the statistical properties of the SBs during the first 10 encounters between 13.28 and 58 solar radii (R ⊙) using data from the SWEAP and FIELDS suites on board PSP. We find that the occurrence percentage of small deflections with respect to the Parker spiral decreases with radial distance (R). In contrast, the occurrence percentage of the large deflections (SBs) increases with R, as does the SB patches. We also find that the occurrence of SBs correlates with the bulk velocity of the solar wind, i.e., the higher the solar wind velocity, the higher the SB occurrence. For V sw ≤ 400 km s−1, the SB occurrence percentage shows a constantly increasing trend between 13 and 58 R ⊙. However, for V sw > 400 km s−1, the occurrence percentage saturates beyond 35 R ⊙. The occurrence percentage of mini SB patches (<60 s) shows a decreasing trend with R, while the occurrence percentage of long-duration SB patches (>200 s) increases with R. Sub-Alfvénic regions that we analyzed during Encounters 8–10 have not shown any SBs. This analysis of the PSP data hints that some of the SBs are decaying and some are being created in situ.

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“…On the other hand, the electric potential can only provide a small fraction of the total acceleration of the faster streams. Meanwhile, PSP and Solar Orbiter observations have dramatically shown the widespread presence of highly coherent large-amplitude Alfvénic fluctuations, often termed switchbacks, near the Sun (Bale et al 2019;Kasper et al 2019;Telloni et al 2022a;Raouafi et al 2023a). These structures occur in both the fast and slow wind near the Sun, but the magnitude of the velocity fluctuation scales with the Alfvén speed (Matteini et al 2015), and their amplitude is thus typically larger in the faster wind.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the Energy Budget in the Solar Wind from 13.3 to 100 Solar Radii

Halekas

Bale

Berthomier

et al. 2023

ApJ

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A variety of energy sources, ranging from dynamic processes, such as magnetic reconnection and waves, to quasi-steady terms, such as plasma pressure, may contribute to the acceleration of the solar wind. We utilize a combination of charged particle and magnetic field observations from the Parker Solar Probe (PSP) to attempt to quantify the steady-state contribution of the proton pressure, the electric potential, and the wave energy to the solar wind proton acceleration observed by PSP between 13.3 and ∼100 solar radii (R ☉). The proton pressure provides a natural kinematic driver of the outflow. The ambipolar electric potential acts to couple the electron pressure to the protons, providing another definite proton acceleration term. Fluctuations and waves, while inherently dynamic, can act as an additional effective steady-state pressure term. To analyze the contributions of these terms, we utilize radial binning of single-point PSP measurements, as well as repeated crossings of the same stream at different distances on individual PSP orbits (i.e., fast radial scans). In agreement with previous work, we find that the electric potential contains sufficient energy to fully explain the acceleration of the slower wind streams. On the other hand, we find that the wave pressure plays an increasingly important role in the faster wind streams. The combination of these terms can explain the continuing acceleration of both slow and fast wind streams beyond 13.3 R ☉.

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Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum

Cited by 71 publications

References 603 publications

New Observations of Solar Wind 1/f Turbulence Spectrum from Parker Solar Probe

New Observations of Solar Wind 1/f Turbulence Spectrum from Parker Solar Probe

Occurrence and Evolution of Switchbacks in the Inner Heliosphere: Parker Solar Probe Observations

Quantifying the Energy Budget in the Solar Wind from 13.3 to 100 Solar Radii

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