We report observations of <100 keV/nucleon suprathermal (ST) H, He, O, and Fe ions in association with three separate crossings of the heliospheric current sheet that occurred near perhelia during PSP encounters 7-11. In particular, we compare and contrast the ST ion time-intensity profiles, velocity dispersion, pitch-angle distributions, spectral forms, and maximum energies during the three HCS crossings. We find that these unique ST observations are remarkably different in each case, with those during E07 posing the most serious challenges for existing models of ST ion production in the inner heliosphere. In contrast, the ISOIS observations during 4 separate HCS crossings during E08-11 appear to be consistent with a scenario in which ST ions escape out of the reconnection exhausts into the separatrix layers after getting accelerated up to ~50-100 keV/nucleon by HCS-associated magnetic reconnection-driven processes. We discuss these new observations in terms of local versus remote acceleration sources as well as in terms of expectations of existing ST ion production and propagation, including reconnection-driven and diffusive acceleration in the inner heliosphere.

How to cite: Desai, M. and the Parker Solar Probe ISOIS, SWEAP, and FIELDS Science Teams: Suprathermal Ion Observations Associated with the Heliospheric Current Sheet Crossings by Parker Solar Probe During Encounters 7-11, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3494, https://doi.org/10.5194/egusphere-egu23-3494, 2023.

Magnetic switchbacks are short magnetic field reversals ubiquitously observed in the solar wind. The origin of switchbacks remains an important open science question, because of switchbacks’ possible role in the heating and acceleration of the solar wind. Here, we report observations of 501 robust switchbacks, using magnetic and plasma measurements from the first eight encounters by the Parker Solar Probe (PSP). More than 46% (6%) of switchbacks are rotational (tangential; TD) discontinuities (RD), defined as magnetic discontinuities with large (small) relative normal components of magnetic field and proton velocity. Magnetic reconnection in the solar atmosphere can be a source of the observed RD-type switchbacks. It is discovered that: 1) the RD-to-TD ratio exponentially decays with increasing heliocentric distance at rate 0.06 [R_S^-1], and 2) TD-type switchbacks contain 64% less magnetic energy than RD-type switchbacks, suggesting that RD-type switchbacks may relax into TD-type switchbacks. It is estimated that relaxing switchbacks generated via magnetic reconnection in the solar atmosphere can transfer an additional 16% of the total reconnected magnetic energy into heating and/or accelerating the solar corona, within 11.6 [R_S] of the reconnection site. The roles of turbulence and/or waves in dissipating this energy into heating and/or accelerating the solar corona plasma are the remaining open science questions.

How to cite: Akhavan-Tafti, M., Kasper, J., Huang, J., and Thomas, L.: Magnetic Switchbacks Heat the Solar Corona, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3671, https://doi.org/10.5194/egusphere-egu23-3671, 2023.

Coronal Mass Ejections (CMEs) are large-scale eruptions from the Sun that drive shocks and turbulent sheaths ahead of them. Parker Solar Probe, Solar Orbiter and BepiColombo have recently observed several shocks/sheaths closer to the Sun than the Earth’s orbit. These studies have revealed enhanced energetic proton fluxes from in-situ observations in interplanetary space also in the sheaths preceding slow CMEs. In this presentation we discuss the internal small-scales sheath structures (e.g., mini flux ropes) and embedded magnetic fluctuations as well as related energization mechanisms. The results suggest that the CME-driven sheaths can have an important role in the acceleration of energetic particles.

How to cite: Kilpua, E. and the Emilia Kilpua: Coronal Mass Ejection driven sheath regions and proton acceleration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4437, https://doi.org/10.5194/egusphere-egu23-4437, 2023.

Understanding the physical processes underlying solar radio bursts requires both high- and low-frequency observations, as well as imaging capabilities. In this study, we implement a fully automated approach to detect and characterize type III radio bursts, image their sources in the corona, and characterize the plasma environment where the bursts are triggered. We utilize data from the Low-Frequency Array (LOFAR) and the Parker Solar Probe (PSP) to investigate several type-III radio bursts that occurred on April 3, 2019. Through data pre-processing and combining the LOFAR and PSP dynamic spectra, we study the solar radio emissions between 2.6 kHz and 80 MHz. By extracting the frequency drift and speed of the accelerated electron beams, we gain insight into the physical processes driving these bursts. Additionally, by using LOFAR interferometric observations to image the sources of the radio emission at multiple frequencies, we are able to determine the locations and kinematics of the sources in the corona. We also use Potential Field Source Surface (PFSS) modeling and magnetohydrodynamic (MHD) simulation results to determine the magnetic field configuration and plasma parameters in the vicinity of the moving emission sources. These observations and analysis provide valuable constraints on the coronal conditions that trigger solar radio bursts.

How to cite: Nedal, M., Kozarev, K., Zhang, P., and Zucca, P.: Coronal Diagnostics of Solar Type-III Radio Bursts Using LOFAR and PSP Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4502, https://doi.org/10.5194/egusphere-egu23-4502, 2023.

Just after orbit 12 closest approach, on 2 June 2022 at a distance of 14 R_S, the Integrated Science Investigation of the Sun (ISʘIS) observed a ³He-rich solar energetic particle (SEP) event.  The event was associated with an active region just over the east limb (as viewed from Earth), which erupted with an occulted C1.2 class x-ray flare and a coronal mass ejection (CME) traveling ~350 km/s.  PSP observed a type III radio burst associated with the flare, followed by a type III storm.  After the initial dispersive SEP event, ISʘIS observed a second enhancement of energetic particles contained within the associated CME as it passed over the spacecraft.  Comparisons of these two populations provide information regarding the acceleration of particles at the Sun as well as trapping or acceleration within the CME structure as different components of an individual solar event.

How to cite: Cohen, C. and the ISOIS/FIELDS/SWEAP/WISPR study team: Observations by Parker Solar Probe of a 3He-rich Solar Energetic Particle Event at 14 RS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9578, https://doi.org/10.5194/egusphere-egu23-9578, 2023.

On 15 February 2022, an impressive filament eruption was observed off the solar eastern limb from three remote-sensing viewpoints, namely Earth, STEREO-A, and Solar Orbiter. Apart from representing the most-distant observed filament at extreme ultraviolet wavelengths—captured by Solar Orbiter's field of view extending to above 6 Rs—this event was also associated with the release of a fast (~2200 km/s) coronal mass ejection (CME) that was directed towards Parker Solar Probe and BepiColombo.

Parker Solar Probe and BepiColombo were separated by 3° in latitude, 4° in longitude, and 0.03 au in radial distance at the time of the CME-driven shock arrival at the two spacecraft. The relative proximity of the two probes to each other and to the Sun (~0.365 au) allows us to study the mesoscale structure of CMEs at Mercury's orbit for the first time. We analyse similarities and differences in the magnetic structure of the CME ejecta measured at the two locations, as well as other properties such as shock/sheath characteristics, pitch-angle distributions, and impact of the interaction between the ejecta and its surroundings. Finally, we contextualise our findings within the current discussions on the need to investigate solar transients via spacecraft constellations with small separations, which have been gaining significant attention during recent years.

How to cite: Palmerio, E., Carcaboso, F., Khoo, L. Y., Sánchez-Cano, B., Nieves-Chinchilla, T., Lario, D., Rivera, Y., Pal, S., Stevens, M. L., Salman, T. M., Weiss, A. J., Lee, C. O., Whittlesey, P. L., and Heyner, D.: On the mesoscale structure of CMEs at Mercury's orbit: Parker Solar Probe and BepiColombo observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10112, https://doi.org/10.5194/egusphere-egu23-10112, 2023.

The solar wind is filled with complex turbulent dynamics that transfer energy from large length scales to progressively smaller scales. This transfer of energy generates a multitude of thin structures, such as current sheets, in the plasma with a preference for forming particularly strong gradients – a property know as intermittency – that are thought to play a role in turbulent dissipation. One of the important problems in the study of solar wind turbulence is understanding how and to what extent the nature of the turbulent dynamics vary as the solar wind expands from the Sun. However, disentangling the dynamical evolution of the turbulence from variations in the properties of different solar wind streams and temporal variations in the source region of a given stream has traditionally been challenging in the solar wind. We make use of a fortuitous alignment between NASA’s Parker Solar Probe and ESA’s Solar Orbiter spacecraft, which occurred at the end of February 2022, to examine how the turbulent fluctuations in the solar wind evolve with radial distance. During this radial alignment the two spacecraft observed the same stream of solar wind plasma, and potentially nearly the same parcel of plasma, at two different radial distances allowing us to separate the evolution with radial distance from the other sources of variability. We explore both the statistical properties of the fluctuations as well as the nature of the most intermittent structures observed by the spacecraft at different length scales in the plasma. The results demonstrate that, while the intermittent fluctuations in the components perpendicular to the radial direction are statistically similar at different radial distances, the intermittency properties in the radial direction can significantly change with distance. Comparisons of the observational results with expanding box simulations of turbulence suggest that some of the key features observed are consistent with the dynamical evolution of spherically polarised Alfvénic fluctuations under the influence of expansion. 

How to cite: Stawarz, J. E., Woodham, L., Laker, R., Matteini, L., Horbury, T., Woolley, T., Bale, S., Perrone, D., Toledo-Redondo, S., Sorriso-Valvo, L., D’Amicis, R., Rivera, Y., and Paulson, K.: The Evolution of Turbulence in the Inner Heliosphere: Insights from the February 2022 Radial Alignment between Parker Solar Probe and Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12288, https://doi.org/10.5194/egusphere-egu23-12288, 2023.

The solar wind, except for the coronal mass ejection events, is traditionally divided into two groups, fast wind and slow wind. However, the origin and releasing mechanism of highly variable slow winds are still a riddle. The slow wind is generally believed to have low Alfvénicity, while the fast wind shows high Alfvénicity. However, Parker Solar Probe shows that highly Alfvénic slow winds take a large proportion of the near-Sun pristine slow winds, suggesting similar sources with the Alfvénic fast winds. Helium abundance (Nα/Np) also bears information about the source region and release mechanism of the slow winds. The typical value of helium abundance in slow winds can be as low as 1% or even lower, while it stays around 4% in fast winds. During its 8th encounter, PSP observed intervals of helium-poor (Nα/Np~0.1%) and helium-normal (Nα/Np~1%) Alfvénic solar winds on two sides of the heliospheric current sheet. We calculate and compare the alpha-particle properties, plasma parameters, collisional age, and magnetic fluctuations in these intervals statistically. In addition, we check the magnetic connection from PSP to the Sun during these intervals with two-step ballistic backmapping. We conclude that the helium-poor winds originate from large quiescent magnetic loops and experience sufficient collisions before and during release. In contrast, helium-normal winds originate from low-latitude coronal holes and experience preferential acceleration and heating due to wave-particle interactions. These results suggest that Alfvénic slow solar winds likely have multiple origins.

How to cite: Wu, Z., He, J., Hou, C., Peng, J., and Duan, D.: Near-Sun Alfvenic Slow Solar Wind with Variable Helium Abundance: PSP observation and source tracing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12976, https://doi.org/10.5194/egusphere-egu23-12976, 2023.

One of the most intriguing discoveries of the Parker Solar Probe mission is the presence of magnetic field reversals, known as Switchbacks (SBs), in the near Sun environment. Their origins are still unclear and many mechanisms for their generations have been proposed. On top of that their interactions with the background solar wind turbulence is not yet understood. In this work we investigate whether the SBs can be considered as part of the background solar wind turbulence or as a population of separate structures. We address this problem by studying the distributions of different measures of the turbulence and SBs and their radial evolution. These results are valuable for the understanding of switchbacks formation and of how turbulence affects the generation of structures in the solar wind.  

How to cite: Larosa, A., Chen, C. H. K., McIntyre, J., and Jagarlamudi, V. K.: The interplay between Solar Wind Turbulence and magnetic Switchbacks in the inner Heliospere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17541, https://doi.org/10.5194/egusphere-egu23-17541, 2023.

We present an overview of EUV solar observations showing evidence for ubiquitous small-scale jetting activity (i.e., a.k.a. jetlets) driven by magnetic reconnection that might be the primary driver of the solar wind at its source. The jetlets, like the solar wind and the heating of the coronal plasma, are omnipresent throughout the solar cycle. Each event arises from small-scale reconnection of opposite polarity magnetic fields producing a short-lived jet of hot plasma and Alfvén waves into the corona. The discrete nature of the jetlets leads to intermittent outflows from the corona, which homogenize as they propagate away from the Sun and form the solar wind. This discovery establishes the importance of small-scale magnetic reconnection in solar and stellar atmospheres in understanding ubiquitous phenomena such as coronal heating and solar wind acceleration. Based on previous analyses linking the switchbacks to the magnetic network, we also argue that these new observations might provide the link between the magnetic activity at the base of the corona and the switchback solar wind phenomenon. These new observations need to be put in the bigger picture of the role of magnetic reconnection and the diverse form of jetting in the solar atmosphere.

How to cite: Raouafi, N. E., Stenborg, G., Seaton, D. B., Wang, H., Wang, J., DeForest, C. E., Bale, S. D., Drake, J. F., Uritsky, V. M., Karpen, J. T., DeVore, C. R., Sterling, A. C., Horbury, T. S., Harra, L. K., Bourouaine, S., Kasper, J. C., Kumar, P., Phan, T. D., and Velli, M.: Magnetic Reconnection as the Driver of the Solar Wind, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17376, https://doi.org/10.5194/egusphere-egu23-17376, 2023.