Robert C. Allen
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A tale of two shocks Open
Context. Energetic particles in interplanetary space are normally measured on timescales that are long compared to the ion gyroperiod. Such observations by necessity average out the microphysics associated with the acceleration and transpo…
Solving the Mystery of the Electron Radiation Belt at Uranus: Leveraging Knowledge of Earth's Radiation Belts in a Re‐Examination of Voyager 2 Observations Open
Voyager 2 provided the only direct measurement of the radiation environment at Uranus and established the well‐accepted characterization of a system with a weaker ion radiation belt and surprisingly intense electron radiation belt. Recent …
Spatial Variability and Correlation Lengths Within Stream Interaction Regions at 1 au: Comparison Between ACE and Wind Open
Understanding the spatial variability and correlation lengths throughout Stream Interaction Regions (SIRs) has importance both for fundamentally understanding the structuring of the solar wind and SIRs and for space weather operations. SIR…
View article: Examining the Radial Evolution of a Corotating Interaction Region Observed at STEREO-A and MAVEN
Examining the Radial Evolution of a Corotating Interaction Region Observed at STEREO-A and MAVEN Open
Corotating interaction regions (CIRs) are long-lasting solar wind structures that persist over multiple solar rotations. These structures accelerate particles throughout the heliosphere and can impart significant energy onto planetary iono…
Simultaneous Ion Arrival Times during the Rise Phase of <sup>3</sup>He-rich Solar Energetic Particle Events Open
We have investigated the arrival times of species H–Fe in 3 He-rich solar energetic particle (SEP) events to determine if a common acceleration mechanism is responsible for all the ions, assuming that if the particles arrive simultaneously…
View article: Preferential Energization of Solar Wind Ions Below the Alfvénic Surface
Preferential Energization of Solar Wind Ions Below the Alfvénic Surface Open
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…
Solving the mystery of the electron radiation belt at Uranus: Leveraging Knowledge of Earth’s Radiation Belts in a re-examination of Voyager 2 Observations Open
Voyager 2 provided the only direct measurement of the radiation environment at Uranus and established the well-accepted characterization of a system with a weaker ion radiation belt and surprisingly intense electron radiation belt. Recent …
View article: Identifying Fast Plasma Injections in Data From Saturn
Identifying Fast Plasma Injections in Data From Saturn Open
In Paranicas et al. (2020), https://doi.org/10.1029/2020ja028299 , we reported on a method to estimate the inflow speed of interchange injections in Saturn's magnetosphere. The procedure relies on phase space density conservation and mappi…
View article: Structural and functional analysis of VYD222: a broadly neutralizing antibody against SARS-CoV-2 variants
Structural and functional analysis of VYD222: a broadly neutralizing antibody against SARS-CoV-2 variants Open
Extensive mutations in SARS-CoV-2 spike protein have rendered most therapeutic monoclonal antibodies (mAbs) ineffective. However, here we describe VYD222 (pemivibart), a human mAb re-engineered from ADG20 (adintrevimab), which maintains po…
Automated classification of MESSENGER plasma observations via unsupervised transfer learning Open
Our methodology demonstrates a proof of concept of the applicability of transfer learning for heliophysics, a machine learning technique where knowledge learned from one task is reused to perform a similar unsupervised learning task with a…
View article: Polytropic Behavior in Corotating Interaction Regions: Evidence of Alfvénic Heating
Polytropic Behavior in Corotating Interaction Regions: Evidence of Alfvénic Heating Open
Corotating interaction regions (CIRs) are recurring structures in the solar wind, characterized by interactions between fast and slow solar wind streams that compress and heat plasma. This study investigates the polytropic behavior of dist…
Solar Energetic Particle Events with Extremely High <sup>3</sup>He Content Observed by Solar Orbiter Open
We performed a survey of 3 He-rich events using observations from the Suprathermal Ion Spectrograph on the Solar Orbiter mission from 2020 to 2024. We identified 57 3 He-rich events, each showing clear 3 He enhancements above the backgroun…
The Radial Variation of Suprathermal Particles in Stream Interaction Regions: Comparisons between Solar Orbiter, ACE, and STEREO-A Open
With the launch of Solar Orbiter, the intensity and composition of suprathermal particles have been sampled within the inner heliosphere at distances between ∼0.3 and 1 au. This includes a multitude of observations of suprathermal ions ass…
Investigation of the inverse velocity dispersion in a solar energetic particle event observed by Solar Orbiter Open
Context. Solar energetic particle (SEP) events provide crucial insights into particle acceleration and transport mechanisms in the heliosphere. Inverse velocity dispersion (IVD) events, characterized by higher-energy particles that arrive …
View article: Inter-Calibration of Solar Orbiter's Heavy Ion Sensor and Suprathermal Ion Spectrograph
Inter-Calibration of Solar Orbiter's Heavy Ion Sensor and Suprathermal Ion Spectrograph Open
Proper characterization of particle energization in the solar wind requires observations from thermal through energetic particles of multiple elements. Observations of in situ particles in different energy ranges require different instrume…
On the identification of the solar sources of 3He-rich solar energetic events Open
Solar energetic particle (SEP) events with compositional anomalies such as the highly elevated 3He/4He ratio have been known for more than half a century, but their origin is still not well-understood. This is largely because of the diffic…
Impacts of Solar Wind Driving on Interhemispheric Asymmetries in the Polar Cap Open
A key component of solar wind-magnetosphere-ionosphere coupling manifests in the high-latitude field-aligned currents and the spatial extent of open magnetic flux in the polar cap. This in turn drives changes in the cross-polar cap potenti…
Investigating Solar Sources of Helium-Rich and Helium-Poor SEP Events in 2024 using Solar Orbiter Open
Title: Investigating Solar Sources of 3He-Rich and 3He-Poor SEP Events in 2024 usingSolar Orbiter HETAuthors:Sindhuja. G1, Robert F. Schweingruber1, Patrick Kühl1, Alexander Kollhoff1, Zheyi Ding1, SebastianFleth1, LarsBerger1, Javier Rodr…
Solar Energetic Particles in Solar Cycle #25: Observations and Comparisons with Previous Cycles Open
As Solar Cycle #25 reaches its peak of activity, Solar Orbiter is observing a substantial increase in solar flares, coronal mass ejections (CMEs), and solar energetic particles (SEPs). Specifically, the Energetic Particle Detector (EPD) on…
A Tale of Two Shocks Open
It was the best of times, it was the worst of times – for two traveling interplanetary shocks observed by Solar Orbiter on November 29 and 30 in 2023. We investigate these two very dissimilar shocks which were observed within less than 27 …
The relationship of inverse velocity dispersion SEP event characteristics with footpoint location: A survey of Solar Orbiter observations Open
Investigations of Solar Energetic Particle (SEP) events have long utilized the dispersive nature of onset times, i.e., earlier arrival of higher energy particles compared to lower energy populations, to infer information such as path lengt…
View article: Evolution of the flux tube instability parameters in plasma injections at Saturnian magnetosphere &#160;
Evolution of the flux tube instability parameters in plasma injections at Saturnian magnetosphere   Open
The evolution of the flux tube stability parameters in plasma injections at the Saturnian magnetosphere is reviewed. Plasma injections result from an imbalance in the centrifugal, total pressure gradient, and magnetic tension forces acting…
View article: Cataloging Stream Interaction Regions at MAVEN: A Cross-comparative Study with STEREO-A
Cataloging Stream Interaction Regions at MAVEN: A Cross-comparative Study with STEREO-A Open
Stream interaction regions (SIRs) are long-lasting solar wind structures that result from stable fast solar wind interacting with preceding slow solar wind. These structures have been examined in depth throughout the heliosphere, particula…
Ion Phase Space Density Profiles Within the Magnetosphere of Saturn: Investigating the Source of Suprathermal Ions Open
Phase space density (PSD) profiles at fixed values of the first two adiabatic invariants (; magnetic moment and ; longitudinal invariant) versus L shell provide a quantitative way to investigate the sources, losses, and radial transport of…
Thermodynamic Characterization of Solar Wind Interaction Regions Using PSP Observations: Evidence of Subadiabatic and Superadiabatic States Open
This study provides a detailed analysis of the thermodynamic behavior within stream interaction regions (SIRs), focusing on an effective polytropic index assessment of 25 distinct events. To improve the accuracy of the effective polytropic…
Radial evolution of interplanetary coronal mass ejection-associated particle acceleration observed by Solar Orbiter and ACE Open
On 2022 March 10 a coronal mass ejection erupted from the Sun, resulting in Solar Orbiter observations at 0.45 au of both dispersive solar energetic particles arriving prior to the interplanetary coronal mass ejection (ICME) and locally ac…