ST1.2 | Exploring the inner heliosphere and solar corona with the Parker Solar Probe – Breakthrough results and synergies with Solar Orbiter
EDI
Exploring the inner heliosphere and solar corona with the Parker Solar Probe – Breakthrough results and synergies with Solar Orbiter
Convener: Volker Bothmer | Co-conveners: Olga Malandraki, Nour E. Raouafi, Alexis Rouillard, Manuela Temmer
Orals
| Tue, 25 Apr, 08:30–10:15 (CEST)
 
Room L1
Posters on site
| Attendance Wed, 26 Apr, 14:00–15:45 (CEST)
 
Hall X4
Posters virtual
| Attendance Wed, 26 Apr, 14:00–15:45 (CEST)
 
vHall ST/PS
Orals |
Tue, 08:30
Wed, 14:00
Wed, 14:00
The Sun’s atmosphere is the birthplace of multi-scale magnetic activity (e.g., flares, CMEs, jets, waves, and radio emissions). This activity drives challenging phenomena such as the heating and acceleration of the solar wind, energetic particles, and space weather impacting the whole heliosphere. Parker Solar Probe (PSP) is the first human-made object diving into the solar corona. By the EGU 2023, PSP would have completed 15 of its 24 planned orbits. PSP flew as close as 13.28 solar radii from the Sun’s center as it inches closer to its ultimate perihelion of 9.86 solar radii on 24 December 2024. PSP launched during solar activity minimum and is now experiencing increasing solar activity as the solar cycle climbs to its maximum around 2024-25. PSP data have already led to fundamental new insights into the processes driving the solar wind, CMEs, and SEPs. Remote sensing observations of the solar corona from within the Alfvén critical boundary yielded spectacular fine structures of coronal outflows not visible from 1 au. Beyond breakthroughs in solar and heliospheric physics, PSP has facilitated discoveries in the physics of planets, asteroids, comets, and dust particles. Combining the PSP and SolO observations with observations from other space-born missions and ground-based observatories (e.g., SDO, STEREO, Proba2, ACE, WIND, DSCOVR, and DKIST) and with theoretical models currently in development promise a wealth of further exciting findings. This session invites scientific contributions to all aspects of research addressed to exploring the inner heliosphere and solar corona, with a particular focus on the new observations from PSP and SolO and other complementary observations and models. The session is in collaboration with the special session dedicated to the Solar Orbiter.

Orals: Tue, 25 Apr | Room L1

Chairpersons: Volker Bothmer, Olga Malandraki, Manuela Temmer
08:30–08:35
08:35–08:45
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EGU23-3494
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On-site presentation
Mihir Desai and the Parker Solar Probe ISOIS, SWEAP, and FIELDS Science Teams

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.

08:45–08:55
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EGU23-3671
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ECS
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On-site presentation
Mojtaba Akhavan-Tafti, Justin Kasper, Jia Huang, and Luke Thomas

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 [RS-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 [RS] 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.

08:55–09:05
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EGU23-4437
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solicited
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On-site presentation
Emilia Kilpua and the Emilia Kilpua

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.

09:05–09:15
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EGU23-4502
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ECS
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On-site presentation
Mohamed Nedal, Kamen Kozarev, Peijin Zhang, and Pietro Zucca

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.

09:15–09:25
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EGU23-9578
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On-site presentation
Christina Cohen and the ISOIS/FIELDS/SWEAP/WISPR study team

Just after orbit 12 closest approach, on 2 June 2022 at a distance of 14 RS, 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.

09:25–09:35
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EGU23-10112
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ECS
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On-site presentation
Erika Palmerio, Fernando Carcaboso, Leng Ying Khoo, Beatriz Sánchez-Cano, Teresa Nieves-Chinchilla, David Lario, Yeimy Rivera, Sanchita Pal, Michael L. Stevens, Tarik M. Salman, Andreas J. Weiss, Christina O. Lee, Phyllis L. Whittlesey, and Daniel Heyner

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.

09:35–09:45
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EGU23-12288
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ECS
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On-site presentation
Julia E. Stawarz, Lloyd Woodham, Ronan Laker, Lorenzo Matteini, Timothy Horbury, Thomas Woolley, Stuart Bale, Denise Perrone, Sergio Toledo-Redondo, Luca Sorriso-Valvo, Raffaella D’Amicis, Yeimy Rivera, and Kristoff Paulson

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.

09:45–09:55
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EGU23-12976
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On-site presentation
Ziqi Wu, Jiansen He, Chuanpeng Hou, Jingyu Peng, and Die Duan

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.

09:55–10:05
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EGU23-17541
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On-site presentation
Andrea Larosa, Christopher H. K. Chen, Jack McIntyre, and Vamsee K. Jagarlamudi

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.

10:05–10:15
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EGU23-17376
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Highlight
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On-site presentation
Nour E. Raouafi, Guillermo Stenborg, Dan B. Seaton, Haimin Wang, Jason Wang, Craig E. DeForest, Stuart D. Bale, James F. Drake, Vadim M. Uritsky, Judith T. Karpen, Carl R. DeVore, Alphonse C. Sterling, Timothy S. Horbury, Louise K. Harra, Sofiane Bourouaine, Justin C. Kasper, Pankaj Kumar, Tai D. Phan, and Marco Velli

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.

Posters on site: Wed, 26 Apr, 14:00–15:45 | Hall X4

Chairpersons: Volker Bothmer, Olga Malandraki, Manuela Temmer
X4.248
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EGU23-1386
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Carlos Larrodera and Manuela Temmer

The launch of new spacecraft such as Parker Solar Probe or Solar Orbiter allow us to measure in-situ at different radial distances the physical magnitudes of ICMEs. With that, we are able to quantify the evolution of ICMEs and their substructures at a specific radial distance in order to better understand the interaction processes that occur with the background solar wind.
Using multiple spacecraft covering the inner heliosphere, we extract plasma and magnetic field parameters from several ICMEs to relate the physical processes responsible for the formation of the different substructures. We present ICME case studies that prepare for a large statistical analysis.

How to cite: Larrodera, C. and Temmer, M.: Study of the evolution of interplanetary coronal mass ejections in the inner heliosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1386, https://doi.org/10.5194/egusphere-egu23-1386, 2023.

X4.249
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EGU23-5698
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ECS
Greta Cappello, Manuela Temmer, and Astrid Veronig

Parker Solar Probe (PSP) and Solar Orbiter (SolO) observe the Sun from unprecedented close-in orbits out of the Sun-Earth line. In combination with EUV imagery from STEREO and SDO, these unique and high-resolution data from different vantage points will give us new insights into the early evolution of coronal mass ejections (CMEs) in the low corona and inner heliosphere. For a case study, we apply 3D CME reconstruction methods to relate different CME substructures as observed in white-light coronagraphs like WISPR aboard PSP, to EUV off-limb structures for an erupting event. We interpret the results in terms of projection and Thomson scattering effects.

How to cite: Cappello, G., Temmer, M., and Veronig, A.: Substructures of coronal mass ejections (CMEs) and their solar source region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5698, https://doi.org/10.5194/egusphere-egu23-5698, 2023.

X4.250
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EGU23-7326
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ECS
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Tomáš Formánek, David Píša, Jan Souček, Ondřej Santolík, Antonio Vecchio, Milan Maksimovic, Javier Rodríguez-Pacheco, Timothy Horbury, and Christopher John Owen

Type III radio emissions are often observed by the Solar Orbiter spacecraft in the solar wind. They arise from a mode conversion of Langmuir waves generated by electron beams ejected from the Sun. In this study, we analyze sources of type III radio emissions that occurred after July 2020. We use data from the Radio and plasma waves (RPW), Energetic particle detector (EPD), Magnetometer (MAG), and Solar Wind Analyzer (SWA) instruments. We identify in-situ type III events and examine various parameters that may have influenced their generation mechanism. We use the maximum amplitude (MAMP) data product from the Time Domain Sampler (TDS) receiver of the RPW instrument for continuous tracking of Langmuir wave packets. For in-situ type III events throughout the Solar Orbiter mission, we study the wave polarization of the locally generated Langmuir waves measured in the Y-Z plane of the spacecraft reference frame. Using data from the EPD instrument, we obtain electron beam velocities for several in-situ events. We show that the electron beam velocity for those events is higher than predicted by previous studies.

How to cite: Formánek, T., Píša, D., Souček, J., Santolík, O., Vecchio, A., Maksimovic, M., Rodríguez-Pacheco, J., Horbury, T., and Owen, C. J.: Analysis of type III radio emissions observed by the Solar Orbiter spacecraft close to their source locations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7326, https://doi.org/10.5194/egusphere-egu23-7326, 2023.

X4.251
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EGU23-8514
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ECS
Vamsee Krishna Jagarlamudi, Nour E Raouafi, Sofiane Bourouaine, Parisa Mostafavi, and Andrea Larosa

Since its launch, 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 ten encounters between 13.3 and 70 Solar Radii using data from the SWEAP and FIELDS suites onboard PSP . We find that the occurrence rate of small deflections with respect to the Parker spiral decreases with radial distance (R). In contrast, the occurrence rate of the large deflections (SBs) increases with R, as does the occurrence rate of 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 slow wind, the SB occurrence rate shows a constantly increasing trend between 13.3 and 70 solar radii. However, for fast wind, the occurrence rate saturates beyond 35 solar radii. Sub-Alfvenic regions encountered during encounters 8-10 have not shown significant SBs. This analysis of the PSP data hints that some of the SBs are decaying and some are being created in-situ.

How to cite: Jagarlamudi, V. K., Raouafi, N. E., Bourouaine, S., Mostafavi, P., and Larosa, A.: Occurrence and evolution of switchbacks between 13.3 to 70 solar radii: PSP Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8514, https://doi.org/10.5194/egusphere-egu23-8514, 2023.

X4.252
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EGU23-2914
Gabor Toth

Magnetic switchbacks are rapid high amplitude reversals of the radial
magnetic field in the solar wind that do not involve a heliospheric
current sheet crossing. First seen sporadically in the seventies in
Mariner and Helios data, switchbacks were later observed by the
Ulysses spacecraft beyond 1 au and have been recently identified as a
typical component of solar wind fluctuations in the inner heliosphere
by the Parker Solar Probe spacecraft. We provide a simple yet
predictive theory for the formation of these magnetic reversals: the
switchbacks are produced by the shear of circularly polarized Alfven
waves by a transversely varying radial wave propagation velocity.  The
wave speed can be modulated by variations in bulk velocity, radial
magnetic field, density or any combination of these.  We provide an
analytic expression for the magnetic field variation as a function of
the wave velocity shear, establish the necessary and sufficient
conditions for the formation of switchbacks and show that the
mechanism works in a realistic solar wind scenario. The suggested
mechanism is in full agreement with Parker Solar Probe observations,
including the shape of the switchbacks, the correlations of the
components of the magnetic field, and the dependence of various
quantities on radial distance.  We show conclusively that this is the
fundamental process that creates switchbacks.

How to cite: Toth, G.: A Simple yet Correct Theory for the Formation of Magnetic Switchbacks Observed by Parker Solar Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2914, https://doi.org/10.5194/egusphere-egu23-2914, 2023.

X4.253
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EGU23-10158
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ECS
Judit Szente, Bartholomeus van der Holst, and Enrico Landi

We use the Space Weather Modeling Framework's Alfvén Wave Solar atmosphere Model to simualte the origin and evolution of solar wind plasma during multiple SO and PSP flybys.   Synthetic spectral and narrow band imaging, synthetic spectra and in-situ plasma data are used to study the heating and acceleration of the coronal plasma and solar wind in the inner heliosphere. We identify large scale structures the spacecrafts pass through: current sheet crossings, plasmas of different origins. When data is available we simultaneously simulate non-equilibrium ionization of minor heavy ions in the solar wind along the SO trajectory and study how the plasma charge states represent the different origins of solar wind and also how the out-of-equilibrium charge states change the synthetic remote sensing observations compared to using equilibrium assumptions. 

How to cite: Szente, J., van der Holst, B., and Landi, E.: Context studies of Parker Solar Probe and Solar Orbiter flybys using synthetic in-situ and remote-sensing observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10158, https://doi.org/10.5194/egusphere-egu23-10158, 2023.

X4.254
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EGU23-15607
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ECS
Shota Chiba, Takeshi Imamura, and Munehito Shoda

The solar wind is a supersonic plasma flow streamed from the solar corona. The acceleration of the solar wind mainly occurs in the outer corona at heliocentric distances of about 2­–10 RS (= solar radii), where the coronal heating by magnetohydrodynamic waves and the wave-induced magnetic pressure are thought to play major roles in the acceleration. The mechanisms have not been fully confirmed because the acceleration region is where no spacecrafts have ever reached to date. Recently, however, an inner heliosphere observation network is getting ready, by such as NASA’s Parker Solar Probe and ESA's Solar orbiter and BepiColombo.

Radio occultation observations cover the acceleration region fully and can obtain information complementary to in-situ observations. The radio occultation observations are conducted during the passage of a spacecraft on the opposite side of the sun as seen from the Earth. Inhomogeneity of coronal plasma density structure traversing the ray path disturbs radio waves' frequency, so we can interpret the received frequency fluctuations as density fluctuations in the coronal plasma. Previous observations detected quasi-periodic components thought to represent magnetoacoustic waves (e.g, Efimov et al., 2012; Miyamoto et al., 2014). The details of the detected waves still have not been investigated.

A recent MHD simulation have reproduced the formation of the solar wind based on the wave/turbulence-driven scenario, in which ubiquitous presence of density fluctuation is found. We applied the spectral analysis to the density fluctuations to compare them with the wave components observed by radio occultation observations conducted by JAXA’s Akatsuki spacecraft in 2016. The time-spatial spectrum of density fluctuations has two components whose phase speeds correspond to the Alfvén speed and sound speed, and these two components are considered to be fast and slow modes. The dominant periods of the slow modes in the model are longer than 100 s, which is consistent with the density fluctuations observed by the radio occultation. The periods of the fast modes in the model are about 20–100 s; such short-period components are also seen in the radio occultation observations. These different modes might have been observed by radio occultation simultaneously.

How to cite: Chiba, S., Imamura, T., and Shoda, M.: Density oscillations in the solar corona seen in radio occultation measurements  and a MHD simulation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15607, https://doi.org/10.5194/egusphere-egu23-15607, 2023.

X4.255
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EGU23-11900
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ECS
Simon Good, Oskari Rantala, Anna-Sofia Jylhä, Christopher Chen, and Emilia Kilpua

A statistical study of magnetic field power spectra in interplanetary coronal mass ejections (ICMEs) observed by Parker Solar Probe and Solar Orbiter has been performed. The ICMEs had characteristically low proton beta, with values well below unity in all cases. The spectral index was typically near –5/3 and radially invariant in the inertial range, similar to solar wind near the heliospheric current sheet, and steepened to values below –3 in the kinetic range. The break frequency between the inertial and kinetic ranges evolved approximately linearly with radial distance and was closer in scale to the proton inertial length than the proton gyroscale. Magnetic compressibility was invariant with radial distance, in contrast to the solar wind generally. Removal of the background flux rope field gives spectra with shallower slopes at low frequencies (i.e. large spatial scales) and reveals shorter correlation lengths in the magnetic field.

How to cite: Good, S., Rantala, O., Jylhä, A.-S., Chen, C., and Kilpua, E.: Magnetic field spectra of ICMEs observed by Parker Solar Probe and Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11900, https://doi.org/10.5194/egusphere-egu23-11900, 2023.

Posters virtual: Wed, 26 Apr, 14:00–15:45 | vHall ST/PS

vSP.1
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EGU23-4352
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Philippe Lamy and Julien Wojak

There are few possibilities to put the in-situ measurements of the coronal electron density such as obtained by the Parker Solar Probe (PSP) in the context of the 3D configuration of the corona and its structure. One of them consists in using MHD models relying on synoptic maps of the photospheric magnetic field, but their accuracy is subject to questions, especially in the case of complex coronae of the maximum type. The 2D inversion of white-light coronagraphic images requires the simplified assumption of spherical symmetry of the corona which basically washes out the longitudinal variations. We will present preliminary results of a new method which makes use of the 3D time-dependent tomographic reconstruction of the coronal electron density based on accurately corrected and calibrated LASCO-C2 images of the polarized brightness of the corona. It is performed over a sliding window of 14 days (half a Carrington rotation) centered at the times of the PSP perihelion with a time interval of 4 days. The resulting “cubes” of the 3D electron density Ne are visualized from six different vantage points and with movies. The orbit of PSP is projected on a synoptic map of Ne extracted from the cubes at a heliocentric distance of 5.5 Rs; the track extends from Perihelion-5 days to Perihelion+5 days. The electron density at the heliocentric distances of PSP is extrapolated radially from the values at 5.5 Rs using an inverse square law and compared with the in-situ measurements collected by PSP/FIELDS. We will present results from the first PSP encounters.

How to cite: Lamy, P. and Wojak, J.: Connecting Coronal 3D Electron Density from Tomographic Reconstruction to In-situ Measurements from Parker Solar Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4352, https://doi.org/10.5194/egusphere-egu23-4352, 2023.

vSP.2
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EGU23-7866
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ECS
Xueyi wang, Sandra Chapman, Richard Dendy, and Bogdan Hnat
The high Reynolds number solar wind flow provides a natural laboratory for the study of turbulence in-situ. Parker Solar Probe samples the solar wind between 0.2 AU to 1 AU, providing an opportunity to study how turbulence evolves in the expanding solar wind. We obtain the scaling exponents and
scale breaks of wavelet power spectra of magnetic field fluctuations sampled by PSP/FIELDS. We identified multiple, long-duration intervals of uniform
solar wind turbulence, selected to exclude coherent structures such as pressure pulses and current sheets, and in which the primary proton population
velocity varies by less than 20% of its mean value. All selected events span the spectral scales from the approximately 1/f range at low frequencies, through the magnetohydrodynamic (MHD) inertial range of turbulence and into the kinetic range, below the ion gyrofrequency. We estimate the power spectral density (PSD) using a Haar wavelet decomposition which provides accurate estimates of the exponents. There is a clear transition between Kolmogorov 5/3 and Iroshnikov-Kraichnan 3/2 scaling inwards of 0.5 0.6AU. In some cases, we find two ranges of scaling within the inertial range, with scaling exponents that can be discriminated within uncertainties in the wavelet PSD. These correspond to relatively small plasma beta. Since the PSD estimated scaling exponents are a central prediction of turbulence theories, these results provide new insights into our understanding of the evolution of turbulence in the solar wind.
 

 

How to cite: wang, X., Chapman, S., Dendy, R., and Hnat, B.: Wavelet determination of magnetohydrodynamic range power spectral exponents in solar wind turbulence seen by Parker Solar Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7866, https://doi.org/10.5194/egusphere-egu23-7866, 2023.

vSP.3
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EGU23-11319
Nina Dresing, Laura Rodríguez-García, Immanuel Jebaraj, Alexander Warmuth, Samantha Wallace, Laura Balmaceda, Tatiana Podladchikova, Du Toit Strauss, Athanasios Kouloumvakos, Christian Palmroos, Vratislav Krupar, Jan Gieseler, Zigong Xu, Grant Mitchell, Christina Cohen, Georgia de Nolfo, Erika Palmerio, Fernando Carcaboso, Emilia Kilpua, and Beatriz Sanchez-Cano

The widespread SEP event of 17 April 2021 was observed by five longitudinally well-separated observers in the inner heliosphere covering distances to the Sun from 0.42 to 1 au: BepiColombo, Parker Solar Probe, Solar Orbiter, STEREO A, and close-to-Earth spacecraft. The event, which produced relativistic electrons and protons, was associated with a complex and long-lasting solar eruption involving a long-duration flare, a medium-fast Coronal Mass Ejection (CME), an EUV wave and a complex solar radio burst activity lasting for 40 minutes including type II bursts, marking the presence of a shock, as well as four distinct groups of type III bursts. Our comprehensive analysis of the multi-spacecraft in-situ and remote-sensing observations suggests different source regions for the electron and proton SEP event with a stronger shock contribution for the proton event and a more likely flare-related source of the electron event. We furthermore determine that the four distinct injection episodes, marked by the radio type III burst groups, cover a longitudinal range of about 110° and were a main ingredient for the wide SEP spread. We consider this a new scenario that must be taken into account as a potential contributor to widespread SEP events.

How to cite: Dresing, N., Rodríguez-García, L., Jebaraj, I., Warmuth, A., Wallace, S., Balmaceda, L., Podladchikova, T., Strauss, D. T., Kouloumvakos, A., Palmroos, C., Krupar, V., Gieseler, J., Xu, Z., Mitchell, G., Cohen, C., de Nolfo, G., Palmerio, E., Carcaboso, F., Kilpua, E., and Sanchez-Cano, B.: The reason for the wide particle spread during the 17 April 2021 SEP event, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11319, https://doi.org/10.5194/egusphere-egu23-11319, 2023.