Explanipedia

Evidence of Time-dependent Diffusive Shock Acceleration in the 2022 September 5 Solar Energetic Particle Event Open

Xiaohang Chen, Nishtha Sachdeva, C. M. S. Cohen, D. Lario, Fan Guo , et al. · 2025

On 2022 September 5, a large solar energetic particle (SEP) event was detected by Parker Solar Probe (PSP) and Solar Orbiter (SolO) at heliocentric distances of 0.07 and 0.71 au, respectively. PSP observed an unusual velocity dispersion si…

Multimodal Imaging in the Diagnosis of Late-Stage Loeffler Endocarditis Open

Catherine Teng, Aneesh Dhore-Patil, Neal Bhachawat, Muneeb Ajaz, M. E. Hill , et al. · 2025

This case highlights the features of late-stage LE and the importance of early recognition and treatment of potentially reversible causes.

Preferential Energization of Solar Wind Ions Below the Alfvénic Surface Open

Parisa Mostafavi, V. K. Jagarlamudi, N. E. Raouafi, Juan C. Palacios, Robert C. Allen , et al. · 2025

Understanding how solar wind ions are heated and accelerated remains a central question in heliophysics. Observations consistently show that alpha particles are hotter and faster than protons, particularly close to the Sun. This suggests t…

Evidence of Time-Dependent Diffusive Shock Acceleration in the 2022 September 5 Solar Energetic Particle Event Open

Xiaohang Chen, Lulu Zhao, J. Giacalone, Nishtha Sachdeva, И. В. Соколов , et al. · 2025

On 2022 September 5, a large solar energetic particle (SEP) event was detected by Parker Solar Probe (PSP) and Solar Orbiter (SolO), at heliocentric distances of 0.07 and 0.71 au, respectively. PSP observed an unusual velocity-dispersion s…

Magnetic Reconnection–driven Energization of Protons up to ∼400 keV at the Near-Sun Heliospheric Current Sheet Open

M. I. Desai, J. F. Drake, T. D. Phan, Zhiyu Yin, M. Swisdak , et al. · 2025

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…

Magnetic Reconnection–driven Energization of Protons up to ∼400 keV at the Near-Sun Heliospheric Current Sheet Open

M. I. Desai, J. F. Drake, T. D. Phan, Zhiyu Yin, M. Swisdak , et al. · 2025

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…

Large-scale Field-aligned Flows in the Heliosheath Open

M. Opher, Marc Kornbleuth, R. B. Decker, J. D. Richardson, Ethan Bair , et al. · 2025

We use a state-of-the-art 3D MHD simulation to show that large-scale thermal pressure gradients in the heliosheath drive suprathermal particles (pickup ions with 1–5 keV) to stream along magnetic field lines faster than the cold bulk solar…

Diverse Dust Populations in the Near-Sun Environment Characterized by PSP/ISʘIS Open

M. M. Shen, J. R. Szalay, Petr Pokorný, J. G. Mitchell, M. E. Hill , et al. · 2025

The Integrated Science Investigation of the Sun energetic particle instrument suite on the Parker Solar Probe is dedicated to measuring energetic ions and electrons in the near-Sun environment. It includes a half-sky-viewing time-of-flight…

Delay of Near-relativistic Electrons with Respect to Type III Radio Bursts throughout the Inner Heliosphere Open

J. G. Mitchell, E. R. Christian, G. A. de Nolfo, C. M. S. Cohen, M. E. Hill , et al. · 2025

Energetic electrons accelerated by solar eruptive events are frequently observed to have inferred injection times that appear significantly delayed with respect to electromagnetic emission including type III radio bursts. This is noteworth…

PUI Heating in the Supersonic Solar Wind Open

Parisa Mostafavi, L. Adhikari, Bishwas L. Shrestha, G. P. Zank, M. Opher , et al. · 2025

The outer heliosphere is profoundly influenced by nonthermal energetic pickup ions (PUIs), which dominate the internal pressure of the solar wind beyond ~10 au, surpassing both solar wind and magnetic pressures. PUIs are formed mostly thro…

Shock and SEP Modeling Study for the 2022 September 5 SEP Event Open

Athanasios Kouloumvakos, Nicolas Wijsen, Nicolas Wijsen, Immanuel Christopher Jebaraj, D. Lario , et al. · 2025

On 2022 September 5, during Parker Solar Probe's (PSP) 13th encounter, a fast shock wave and a related solar energetic particle (SEP) event were observed as the spacecraft approached the perihelion of its orbit. Observations from the Integ…

Termination Shock Particle Streaming Upstream at New Horizons Open

Erick Powell, M. Opher, Ethan Bair, M. E. Hill, Romina Nikoukar , et al. · 2024

A couple years before Voyager 1 and Voyager 2 (V2) crossed the termination shock (TS), instruments on board both spacecraft observed high intensities of accelerated termination shock particles (TSPs) beaming in opposite directions. This ph…

Anisotropies of 40–139 keV Ions Measured beyond the Termination Shock and in the Very Local Interstellar Medium Open

K. Dialynas, S. M. Krimigis, R. B. Decker, M. E. Hill, Romina Nikoukar , et al. · 2024

We analyze the count rates of 40–139 keV ions that were measured in situ by the Low Energy Charged Particle instrument on Voyager 1 in order to identify the suprathermal ion anisotropies beyond the termination shock and in the very local i…

Parker Solar Probe Observations of Energetic Particles in the Flank of a Coronal Mass Ejection Close to the Sun Open

N. A. Schwadron, S. D. Bale, J. W. Bonnell, A. W. Case, Michael M. Shen , et al. · 2024

We present an event observed by Parker Solar Probe (PSP) at ∼0.2 au on 2022 March 2 in which imaging and in situ measurements coincide. During this event, PSP passed through structures on the flank of a streamer blowout coronal mass ejecti…

Acceleration of Electrons and Ions by an “Almost” Astrophysical Shock in the Heliosphere Open

Immanuel Christopher Jebaraj, O. V. Agapitov, V. Krasnoselskikh, Laura Vuorinen, M. Gedalin , et al. · 2024

Collisionless shock waves, ubiquitous in the Universe, are crucial for particle acceleration in various astrophysical systems. Currently, the heliosphere is the only natural environment available for their in situ study. In this work, we s…

IS⊙IS Solar γ-Ray Measurements: Initial Observations and Calibrations Open

J. G. Mitchell, G. A. de Nolfo, E. R. Christian, R. A. Leske, J. M. Ryan , et al. · 2024

High-energy neutral solar radiation in the form of γ -rays and neutrons is produced as secondary products in solar flares. The characteristics of this emission can provide key information regarding the energization of charged particles, pa…

The solar cycle 25 multi-spacecraft solar energetic particle event catalog of the SERPENTINE project Open

N. Dresing, Aleksi Yli-Laurila, Saku Valkila, Jan Gieseler, D. E. Morosan , et al. · 2024

Context . The solar energetic particle analysis platform for the inner heliosphere (SERPENTINE) project, funded through the H2020-SPACE-2020 call of the European Union’s Horizon 2020 framework program, employs measurements of the new inner…

Observations of the 2022 September 5 Solar Energetic Particle Event at 15 Solar Radii Open

C. M. S. Cohen, R. A. Leske, E. R. Christian, A. C. Cummings, G. A. de Nolfo , et al. · 2024

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)…

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

D. G. Mitchell, M. E. Hill, D. J. McComas, C. M. S. Cohen, N. A. Schwadron , et al. · 2024

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…

 In situ Observations of Ultra-Relativistic ElectronAcceleration in the Fastest Heliospheric Shock Wave by Parker Solar Probe Open

V. Krasnoselskikh, Immanuel Christopher Jebaraj, O. V. Agapitov, Laura Vuorinen, Kyung‐Eun Choi , et al. · 2024

Collisionless shock waves (CSWs) in plasma, prevalent in diverse astrophysical contexts, are key to understanding cosmic particle acceleration. These shock waves, observable in environments from heliospheric planetary bow shocks to superno…

The science of our Sun’s astrosphere: in-situ ions from the Voyagers and remotely sensed ENAs from Cassini Open

K. Dialynas, S. M. Krimigis, R. B. Decker, M. E. Hill, Romina Nikoukar · 2024

The path-breaking observations of the two Voyager spacecraft over the past two decades, have revolutionized our understanding of interplanetary space within our solar bubble. The crossings of the Voyagers (V1, V2) of the Termination S…

Parker Solar Probe observations of collisional effects on thermalizing the young solar wind Open

Parisa Mostafavi, Robert C. Allen, V. K. Jagarlamudi, Sofiane Bourouaine, Samuel T. Badman , et al. · 2024

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 …

Evidence of a Thick Heliopause Boundary Layer Resulting from Active Magnetic Reconnection with the Interstellar Medium Open

D. L. Turner, Adam Michael, Elena Provornikova, Marc Kornbleuth, M. Opher , et al. · 2024

Voyager 1 and 2 data from the vicinity of the heliopause and very local interstellar medium are reexamined to better understand the confounding lack of rotation in the magnetic field ( B -field) across the heliopause observed by both Voyag…

Analyses of ∼0.05–2 MeV Ions Associated with the 2022 February 16 Energetic Storm Particle Event Observed by Parker Solar Probe Open

J. Giacalone, C. M. S. Cohen, D. J. McComas, Xiaohang Chen, M. A. Dayeh , et al. · 2023

We present analyses of 0.05–2 MeV ions from the 2022 February 16 energetic storm particle event observed by Parker Solar Probe's (PSP) IS⊙IS/EPI-Lo instrument at 0.35 au from the Sun. This event was characterized by an enhancement in ion f…

Pushing the Frontier of Solar & Space Physics: Exploration of the Heliosphere and the Very Local Interstellar Medium by an Interstellar Probe Open

P. C. Brandt, B. L. Alterman, Erika Alvarez, D. N. Baker, S. D. Bale , et al. · 2023

Whitepaper #038 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research. Additional topics: outer heliosphere; space-based missions/projects; emerging opportunities.

A future Interstellar Probe on the dynamic heliosphere and its interaction with the very local interstellar medium Open

K. Dialynas, P. C. Brandt, L. F. Burlaga, D. B. Berdichevsky, R. B. Decker , et al. · 2023

Whitepaper #096 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research; infrastructure/workforce/other programmatic. Additional topics: outer heliosphere; emerging opportunities; other progr…

Cosmic Rays Measurements on an Interstellar Probe: A Bold Approach to Concluding the Second Century of Space Aged Science Open

M. E. Hill, Robert C. Allen, P. C. Brandt, R. B. Decker, M. Gkioulidou , et al. · 2023

Whitepaper #169 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research. Additional topics: outer heliosphere; space-based missions/projects; emerging opportunities.

Observations of Extremely 3He-Rich Solar Energetic Particle Events from Parker Solar Probe Open

R. A. Leske, E. R. Christian, C. M. S. Cohen, A. C. Cummings, A. J. Davis , et al. · 2023

Since its launch in 2018, the Integrated Science Investigation of the Sun (ISOIS) instrument suite on Parker Solar Probe has observed numerous periods of $^{3}$He-rich solar energetic particle (SEP) events. Notable among them are some very…

Parker Solar Probe Energetic Particle Observations of the September 5, 2022 SEP Event Open

C. M. S. Cohen, Eric Christian, A. C. Cummings, Andrew D. Davis, G. A. de Nolfo , et al. · 2023

On September 5, 2022 Parker Solar Probe (Parker) was less than 17 RS from the Sun when the Integrated Science Investigation of the Sun (ISʘIS) observed an intense solar energetic particle (SEP) event associated with a strong soft x-ray fla…

Solar wind with Hydrogen Ion charge Exchange and Large-Scale Dynamics (SHIELD) DRIVE Science Center Open

M. Opher, J. D. Richardson, G. P. Zank, V. Florinski, J. Giacalone , et al. · 2023

Most stars generate winds and move through the interstellar medium that surrounds them. This movement creates a cocoon formed by the deflection of these winds that envelops and protects the stars. We call these “cocoons” astrospheres. The …

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