J. C. Kasper
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View article: The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions
The Temperature Anisotropy and Helium Abundance Features of Alfvénic Slow Solar Wind Observed by Parker Solar Probe, Helios, and Wind Missions Open
Slow solar wind is typically characterized as having low Alfvénicity, but the occasional occurrence of highly Alfvénic slow solar wind (HASSW) raises questions about its source regions and evolution. In this work, we conduct a statistical …
View article: Magnetic Reconnection–driven Energization of Protons up to ∼400 keV at the Near-Sun Heliospheric Current Sheet
Magnetic Reconnection–driven Energization of Protons up to ∼400 keV at the Near-Sun Heliospheric Current Sheet Open
We report observations of direct evidence of energetic protons being accelerated above ∼400 keV within the reconnection exhaust of a heliospheric current sheet (HCS) crossing by NASA’s Parker Solar Probe (PSP) at a distance of ∼16.25 solar…
View article: Characterization of the solar wind context during the third Mercury flyby of BepiColombo
Characterization of the solar wind context during the third Mercury flyby of BepiColombo Open
The interaction of the solar wind (SW) with the coupled magnetosphere-exosphere-surface of Mercury is complex. Charged particles released by the SW can precipitate along planetary magnetic field lines on specific areas of the surface of th…
View article: Suprathermal Electron Scattering by Narrowband Whistler Waves and Broadband Electrostatic Waves: Parker Solar Probe Observations
Suprathermal Electron Scattering by Narrowband Whistler Waves and Broadband Electrostatic Waves: Parker Solar Probe Observations Open
We utilize Parker Solar Probe measurements from the first nine perihelia to investigate suprathermal electron scattering near the Sun. We employ a normalized isotropy parameter to identify pitch-angle scattering (PAS) regions in the inner …
View article: First plasma observations at 9.8 solar radii from the SWEAP experiment
First plasma observations at 9.8 solar radii from the SWEAP experiment Open
In December of 2024, the Parker Solar Probe performed its first encounter in what is planned to be its final orbital configuration. At this distance from the Sun, it is expected that Parker will spend a large fraction of each perihelion pa…
View article: Switchback Patches Evolve into Microstreams via Magnetic Relaxation
Switchback Patches Evolve into Microstreams via Magnetic Relaxation Open
Switchbacks, defined as Alfvénic reversals in magnetic field polarity, can dissipate their magnetic energy with heliocentric distance. To further investigate this, two distinct solar wind parcels tracing back to a similar solar source regi…
View article: All models are wrong, some are useful: Model Selection with Limited Labels
All models are wrong, some are useful: Model Selection with Limited Labels Open
We introduce MODEL SELECTOR, a framework for label-efficient selection of pretrained classifiers. Given a pool of unlabeled target data, MODEL SELECTOR samples a small subset of highly informative examples for labeling, in order to efficie…
View article: Flux Rope Modeling of the 2022 September 5 Coronal Mass Ejection Observed by Parker Solar Probe and Solar Orbiter from 0.07 to 0.69 au
Flux Rope Modeling of the 2022 September 5 Coronal Mass Ejection Observed by Parker Solar Probe and Solar Orbiter from 0.07 to 0.69 au Open
As both Parker Solar Probe (PSP) and Solar Orbiter (SolO) reach heliocentric distances closer to the Sun, they present an exciting opportunity to study the structure of coronal mass ejections (CMEs) in the inner heliosphere. We present an …
View article: In situ observations of large-amplitude Alfvén waves heating and accelerating the solar wind
In situ observations of large-amplitude Alfvén waves heating and accelerating the solar wind Open
After leaving the Sun’s corona, the solar wind continues to accelerate and cools, but more slowly than expected for a freely expanding adiabatic gas. Alfvén waves are perturbations of the interplanetary magnetic field that transport energy…
View article: Multiple Subscale Magnetic Reconnection Embedded inside a Heliospheric Current Sheet Reconnection Exhaust: Evidence for Flux Rope Merging
Multiple Subscale Magnetic Reconnection Embedded inside a Heliospheric Current Sheet Reconnection Exhaust: Evidence for Flux Rope Merging Open
We report observations of multiple subscale reconnecting current sheets embedded inside a large-scale heliospheric current sheet (HCS) reconnection exhaust. The discovery was made possible by the unusual skimming trajectory of Parker Solar…
View article: Flux rope modeling of the 2022 Sep 5 CME observed by Parker Solar Probe and Solar Orbiter from 0.07 to 0.69 au
Flux rope modeling of the 2022 Sep 5 CME observed by Parker Solar Probe and Solar Orbiter from 0.07 to 0.69 au Open
As both Parker Solar Probe (PSP) and Solar Orbiter (SolO) reach heliocentric distances closer to the Sun, they present an exciting opportunity to study the structure of CMEs in the inner heliosphere. We present an analysis of the global fl…
View article: Origin and Properties of the Near-subsonic Solar Wind Observed by Parker Solar Probe
Origin and Properties of the Near-subsonic Solar Wind Observed by Parker Solar Probe Open
We identify and examine the solar wind intervals near the sonic critical point (i.e., M S ∼ 1) observed by the Parker Solar Probe. The near-subsonic wind intervals show similar properties: a low density, an extremely low velocity, a low pr…
View article: Observations of the 2022 September 5 Solar Energetic Particle Event at 15 Solar Radii
Observations of the 2022 September 5 Solar Energetic Particle Event at 15 Solar Radii Open
On 2022 September 5, Parker Solar Probe (Parker) observed a large solar energetic particle (SEP) event at the unprecedented distance of only 15 R S from the Sun. The observations from the Integrated Science Investigation of the Sun (IS⊙IS)…
View article: Characterization of Turbulent Fluctuations in the Sub-Alfvénic Solar Wind
Characterization of Turbulent Fluctuations in the Sub-Alfvénic Solar Wind Open
Parker Solar Probe (PSP) observed sub-Alfvénic solar wind intervals during encounters 8–14, and low-frequency magnetohydrodynamic (MHD) turbulence in these regions may differ from that in super-Alfvénic wind. We apply a new mode decomposit…
View article: Probing Turbulent Scattering Effects on Suprathermal Electrons in the Solar Wind: Modeling, Observations, and Implications
Probing Turbulent Scattering Effects on Suprathermal Electrons in the Solar Wind: Modeling, Observations, and Implications Open
This study explores the impact of a turbulent scattering mechanism, akin to those influencing solar and galactic cosmic rays propagating in the interplanetary medium, on the population of suprathermal electrons in the solar wind. We employ…
View article: Origin and Properties of the Near Subsonic Solar Wind Observed by Parker Solar Probe
Origin and Properties of the Near Subsonic Solar Wind Observed by Parker Solar Probe Open
We identify and examine the solar wind intervals near the sonic critical point (i.e., $M_S \sim 1$) observed by the Parker Solar Probe (PSP). The near subsonic wind intervals show similar properties: a low density, an extremely low velocit…
View article: Erratum: “Parker Solar Probe Observations of High Plasma β Solar Wind from the Streamer Belt” (2023, ApJS, 265, 47)
Erratum: “Parker Solar Probe Observations of High Plasma β Solar Wind from the Streamer Belt” (2023, ApJS, 265, 47) Open
International audience
View article: Parker Solar Probe Observations of Magnetic Reconnection Exhausts in Quiescent Plasmas near the Sun
Parker Solar Probe Observations of Magnetic Reconnection Exhausts in Quiescent Plasmas near the Sun Open
Parker Solar Probe observations are analyzed for the presence of reconnection exhausts across current sheets (CSs) within R < 0.26 au during encounters 4–11. Exhausts are observed with nearly equal probability at all radial distances with …
View article: Likely Common Coronal Source of Solar Wind and <sup>3</sup>He-enriched Energetic Particles: Uncoupled Transport from the Low Corona to 0.2 au
Likely Common Coronal Source of Solar Wind and <sup>3</sup>He-enriched Energetic Particles: Uncoupled Transport from the Low Corona to 0.2 au Open
Parker Solar Probe (PSP) observations of a small dispersive event on 2022 February 27 and 28 indicate scatter-free propagation as the dominant transport mechanism between the low corona and greater than 35 solar radii. The event occurred d…
View article: Characterization of Turbulent Fluctuations in the Sub-Alfvenic Solar Wind
Characterization of Turbulent Fluctuations in the Sub-Alfvenic Solar Wind Open
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 …
View article: Helium Abundance Periods Observed by the Solar Probe Cup on Parker Solar Probe: Encounters 1–14
Helium Abundance Periods Observed by the Solar Probe Cup on Parker Solar Probe: Encounters 1–14 Open
Parker Solar Probe is a mission designed to explore the properties of the solar wind closer than ever before. Detailed particle observations from the Solar Probe Cup (SPC) have primarily focused on examining the proton population in the so…
View article: Zone of Preferential Heating for Minor Ions in the Solar Wind
Zone of Preferential Heating for Minor Ions in the Solar Wind Open
The properties of minor ions in the solar wind are important indicators of the state of the solar corona and the heating processes it undergoes as it expands. Evidence of preferential heating of minor ions has been observed in the solar wi…
View article: Switchback Patches Evolve into Microstreams via Magnetic Relaxation
Switchback Patches Evolve into Microstreams via Magnetic Relaxation Open
Magnetic switchbacks are distinct magnetic structures characterized by their abrupt reversal in the radial component of the magnetic field within the pristine solar wind. Switchbacks are believed to lose magnetic energy with heliocentric d…
View article: Parker Solar Probe observations of collisional effects on thermalizing the young solar wind
Parker Solar Probe observations of collisional effects on thermalizing the young solar wind Open
Solar wind ions exhibit distinct kinetic non-thermal features such as preferential heating and acceleration of alpha particles compared to protons. On the other hand, Coulomb collisions in the solar wind act to eliminate these non-thermal …
View article: Probing Turbulent Scattering Effects on Suprathermal Electrons in the Solar Wind: Modeling, Observations and Implications
Probing Turbulent Scattering Effects on Suprathermal Electrons in the Solar Wind: Modeling, Observations and Implications Open
This study explores the impact of a turbulent scattering mechanism, akin to those influencing solar and galactic cosmic rays propagating in the interplanetary medium, on the population of suprathermal electrons in the solar wind. We employ…
View article: Weak Solar Radio Bursts from the Solar Wind Acceleration Region Observed by the Parker Solar Probe and Its Probable Emission Mechanism
Weak Solar Radio Bursts from the Solar Wind Acceleration Region Observed by the Parker Solar Probe and Its Probable Emission Mechanism Open
The Parker Solar Probe (PSP) provides us with an unprecedentedly close approach to the observation of the Sun and hence the possibility of directly understanding the elementary process that occurs on the kinetic scale of particles' collect…
View article: Skewness and kurtosis of solar wind proton distribution functions: The normal inverse-Gaussian model and its implications
Skewness and kurtosis of solar wind proton distribution functions: The normal inverse-Gaussian model and its implications Open
Context. In the solar wind (SW), the particle distribution functions are generally not Gaussian. They present nonthermal features that are related to underlying acceleration and heating processes. These processes are critical in the overal…
View article: Switchbacks and Associated Magnetic Holes Observed near the Alfvén Critical Surface
Switchbacks and Associated Magnetic Holes Observed near the Alfvén Critical Surface Open
During recent solar encounters, the Parker Solar Probe (PSP) began its initial dips below the Alfvén critical surface to measure in situ the sub-Alfvénic coronal wind. While the near-Sun super-Alfvénic solar wind is shown to be dominated b…
View article: Weak Solar Radio Bursts from the Solar Wind Acceleration Region Observed by Parker Solar Probe and Its Probable Emission Mechanism
Weak Solar Radio Bursts from the Solar Wind Acceleration Region Observed by Parker Solar Probe and Its Probable Emission Mechanism Open
The Parker Solar Probe (PSP) provides us the unprecedentedly close approach observation to the Sun, and hence the possibility of directly understanding the "elementary process" which occurs in the kinetic scale of particles collective inte…