Astronomy & Astrophysics最新文献

{"title":"High flow speeds and transition-region-like temperatures in the solar chromosphere during flux emergence","authors":"J. Leenaarts, M. van Noort, J. de la Cruz Rodríguez, S. Danilovic, C. J. Díaz Baso, T. Hillberg, P. Sütterlin, D. Kiselman, G. Scharmer, S. K. Solanki","doi":"10.1051/0004-6361/202453355","DOIUrl":"https://doi.org/10.1051/0004-6361/202453355","url":null,"abstract":"<i>Context.<i/> Flux emergence in the solar atmosphere is a complex process that causes a release of magnetic energy as heat and acceleration of solar plasma on a variety of spatial scales.<i>Aims.<i/> We aim to investigate temperatures and velocities in small-scale reconnection episodes during flux emergence.<i>Methods.<i/> We analyzed imaging spectropolarimetric data taken in the He I 1083 nm line with a spatial resolution of 0.26″, a time cadence of 2.8 s, and a spectral range corresponding to ±220 km s<sup>−1<sup/> around the line. This line is sensitive to temperatures higher than 15 kK, unlike diagnostics such as Mg II h&k, Ca II H&K, and H<i>α<i/>, which lose sensitivity already at 15 kK. The He I data is complemented by imaging spectropolarimetry in the Fe I 617.3 nm and Ca II 854.2 nm lines and imaging spectroscopy in Ca II K and H<i>α<i/> at a cadence between 12 s and 36 s. We employed inversions to determine the magnetic field and vertical velocity in the solar atmosphere. We computed He I 1083 nm profiles from a radiation-magneto-hydrodynamics simulation of the solar atmosphere to help in the interpretation of the observations.<i>Results.<i/> We find fast-evolving blob-like emission features in the He I 1083 nm triplet at locations where the magnetic field is rapidly changing direction, and these are likely sites of magnetic reconnection. We fit the line with a model consisting of an emitting layer located below a cold layer representing the fibril canopy. The modeling provides evidence that this model, while simple, catches the essential characteristics of the line formation. The morphology of the emission in the He I 1083 nm is localized and blob-like, unlike the emission in the Ca II K line, which is more filamentary.<i>Conclusions.<i/> The modeling shows that the He I 1083 nm emission features and their Doppler shifts can be caused by opposite-polarity reconnection and/or horizontal current sheets below the canopy layer in the chromosphere. Based on the high observed Doppler width and the blob-like appearance of the emission features, we conjecture that at least a fraction of them are produced by plasmoids. We conclude that transition-region-like temperatures in the deeper layers of the active region chromosphere are more common than previously thought.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"183 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The SRG/eROSITA All-Sky Survey","authors":"E. Artis, E. Bulbul, S. Grandis, V. Ghirardini, N. Clerc, R. Seppi, J. Comparat, M. Cataneo, A. von der Linden, Y. E. Bahar, F. Balzer, I. Chiu, D. Gruen, F. Kleinebreil, M. Kluge, S. Krippendorf, X. Li, A. Liu, N. Malavasi, A. Merloni, H. Miyatake, S. Miyazaki, K. Nandra, N. Okabe, F. Pacaud, P. Predehl, M. E. Ramos-Ceja, T. H. Reiprich, J. S. Sanders, T. Schrabback, S. Zelmer, X. Zhang","doi":"10.1051/0004-6361/202452584","DOIUrl":"https://doi.org/10.1051/0004-6361/202452584","url":null,"abstract":"Recent advancements in methods used in wide-area surveys have demonstrated the reliability of the number density of galaxy clusters as a viable tool for precision cosmology. Beyond testing the current cosmological paradigm, cluster number counts can also be used to investigate the discrepancies currently affecting cosmological measurements. In particular, cosmological studies based on cosmic shear and other large-scale structure probes routinely find a value for the amplitude of the fluctuations in the universe <i>S<i/>​<sub>8<sub/> = <i>σ<i/><sub>8<sub/>(Ω<sub>m<sub/>/0.3)<sup>0.5<sup/> smaller than the one inferred from the primary cosmic microwave background. In this work, we investigate this tension by measuring structure evolution across cosmic time as probed by the number counts of massive halos with the first SRG/eROSITA All-Sky Survey cluster catalog in the western Galactic hemisphere, complemented with the overlapping Dark Energy Survey Year-3, Kilo-Degree Survey, and Hyper Suprime-Cam data for weak lensing mass calibration, by implementing two different parameterizations and a model-agnostic method. In the first model, we measured the cosmic linear growth index as <i>γ<i/> = 1.19 ± 0.21, which is in tension with the standard value of <i>γ<i/> = 0.55 but in good statistical agreement with other large-scale structure probes. The second model is a phenomenological scenario in which we rescale the linear matter power spectrum at low redshift to investigate a potential reduction of structure formation, and it provided similar results. Finally, in a third strategy, we considered a standard ΛCDM cosmology, but we separated the cluster catalog into five redshift bins, measuring the cosmological parameters in each and inferring the evolution of the structure formation, finding hints of a reduction. Interestingly, the <i>S<i/>​<sub>8<sub/> value inferred from the number counts of the cluster eRASS1 when we add a degree of freedom to the matter power spectrum recovers the value inferred by cosmic shear studies. The observed reduction in the growth rate or systematic uncertainties associated with various measurements may account for the discrepancy in the <i>S<i/>​<sub>8<sub/> values suggested between cosmic shear probes and eROSITA cluster number counts and <i>Planck<i/> CMB measurements.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"102 4 Pt 1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tension of the toroidal magnetic field in reconnection plasmoids and relativistic jets","authors":"Krzysztof Nalewajko","doi":"10.1051/0004-6361/202553662","DOIUrl":"https://doi.org/10.1051/0004-6361/202553662","url":null,"abstract":"The toroidal magnetic field is a key ingredient of relativistic jets launched by certain accreting astrophysical black holes, and of plasmoids emerging from the tearing instability during magnetic reconnection, which is a candidate dissipation mechanism in jets. Tension of the toroidal field is an anisotropic force that can compress local energy and momentum densities. We investigate this effect in plasmoids produced during relativistic reconnection initiated from a Harris layer by means of kinetic particle-in-cell numerical simulations, varying the system size (including 3D cases), magnetisation, or guide field. We find that: (1) plasmoid cores are dominated by plasma energy density for guide fields up to <i>B<i/><sub><i>z<i/><sub/> ∼ <i>B<i/><sub>0<sub/>; (2) relaxed ‘monster’ plasmoids compress plasma energy density only modestly (by a factor of ∼3 above the initial level for the drifting particle population); (3) energy density compressions by factors ≳10 are achieved during plasmoid mergers, especially with the emergence of secondary plasmoids. This kinetic-scale effect can be combined with a global focusing of the jet Poynting flux along the quasi-cylindrical bunched spine (a proposed jet layer adjacent to the cylindrical core) due to poloidal line bunching (a prolonged effect of tension in the jet toroidal field) to enhance the luminosity of rapid radiation flares from blazars. The case of M87 as a misaligned blazar is discussed.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"58 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143737138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing the interstellar medium toward GRB 221009A through X-ray dust scattering","authors":"B. Vaia, Ž. Bošnjak, A. Bracco, S. Campana, P. Esposito, V. Jelić, A. Sacchi, A. Tiengo","doi":"10.1051/0004-6361/202453158","DOIUrl":"https://doi.org/10.1051/0004-6361/202453158","url":null,"abstract":"The observation of 21 X-ray dust-scattering rings around the extraordinarily bright gamma-ray burst (GRB) 221009A provides a unique opportunity to study the interstellar medium (ISM) through which the X-ray radiation traveled in our Galaxy and, by extension, in the host galaxy as well. In particular, since the ring intensity and radius at a given time depend on the amount of dust and on its distance, respectively, <i>XMM-Newton<i/> and <i>Swift<i/> images allowed us to map the ISM around the direction of the GRB with better resolution than in the existing optical- and infrared-based 3D dust maps, both in the plane of the sky (a few arcminutes) and along the line of sight (from ≃1 pc for dust clouds within 1 kpc to ≃100 pc for structures at distances larger than 10 kpc). As a consequence, we could revise prior estimates of the GRB soft X-ray fluence, obtaining a ∼35% lower value, which, however, still indicates a substantial excess with respect to the extrapolation of the spectral models constrained by hard X-ray observations. Additionally, we detect significant spectral variability in two azimuthal sectors of the X-ray rings, which can be fully attributed to different Galactic absorption in these two directions. The comparison of the total hydrogen column density inferred from spectral fitting, with the Galactic contribution derived from the intensity of the X-ray rings, in the same sectors allowed us to more robustly constrain the absorption in the host galaxy to <i>N<i/><sub>H, <i>z<i/> = 0.151<sub/> = (3.7 ± 0.3)×10<sup>21<sup/> cm<sup>−2<sup/>. This result is relevant not only for characterizing the ISM of the host galaxy and understanding how the GRB radiation might have affected it, but also for modeling the broadband spectrum of the GRB afterglow and constraining the properties of a possible underlying supernova.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"41 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ALMA-IMF","authors":"M. Valeille-Manet, S. Bontemps, T. Csengeri, T. Nony, F. Motte, A. M. Stutz, A. Gusdorf, A. Ginsburg, R. Galván-Madrid, P. Sanhueza, M. Bonfand, N. Brouillet, P. Dell’Ova, F. Louvet, N. Cunningham, M. Fernández-López, F. Herpin, F. Wyrowski, R. H. Álvarez-Gutiérrez, M. Armante, A. E. Guzmán, N. Kessler, A. Koley, J. Salinas, T. Yoo, L. Bronfman, N. Le Nestour","doi":"10.1051/0004-6361/202451291","DOIUrl":"https://doi.org/10.1051/0004-6361/202451291","url":null,"abstract":"<i>Context.<i/> High-mass prestellar cores are extremely rare. Until recently, the search for such objects has been hampered by small sample sizes, leading to large ambiguities in their lifetimes and hence the conditions in the cores in which high-mass stars (≳8 M<sub>⊙<sub/>) form.<i>Aims.<i/> Here we leverage the large sample (~580 cores) detected in the ALMA-IMF survey to identify both protostellar and prestellar cores to estimate their relative lifetimes.<i>Methods.<i/> We used CO and SiO outflows to identify protostellar cores. We present a new automated method based on aperture line emission and background subtraction to systematically detect outflows associated with each of the 141 most massive cores. Massive cores that are not driving an outflow in either tracer are identified as prestellar. After careful scrutiny of the sample, we derived statistical lifetime estimates for the prestellar phase.<i>Results.<i/> Our automated method allows the efficient detection of CO and SiO outflows and has a performance efficiency similar to that of more cumbersome classical techniques. We identified 30 likely prestellar cores with M≳ 8 M<sub>⊙<sub/>, of which 12 have core masses M≳ 16 M<sub>⊙<sub/>. The latter group contains the best candidates for high-mass star precursors. Moreover, most of these 12 high-mass prestellar cores are located inside the crowded central regions of the protoclusters, where most high-mass stars are expected to form. Using the relative ratios of prestellar to protostellar cores, and assuming a high-mass protostellar lifetime of 300 kyr, we derive a prestellar core lifetime of 120 kyr to 240 kyr for cores with masses 8 M<sub>⊙<sub/> < M < 16 M<sub>⊙<sub/>. For 30 M<sub>⊙<sub/> < M < 55 M<sub>⊙<sub/>, the lifetimes range from 50 kyr to 100 kyr. The spread in timescales reflects different assumptions for scenarios for the mass reservoir evolution. These timescales are remarkably long compared to the 4 kyr to 15 kyr free-fall time of the cores. Hence, we suggest that high-mass cores live ~10 to 30 free-fall times, with a tentative trend of a slight decrease with core mass. Such high ratios suggest that the collapse of massive cores is slowed down by non-thermal support of turbulent, magnetic or rotational origin at or below the observed scale.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"89 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gone with the wind: the outward migration of eccentric giant planets in windy disks","authors":"Gaylor Wafflard-Fernandez, Geoffroy Lesur","doi":"10.1051/0004-6361/202453541","DOIUrl":"https://doi.org/10.1051/0004-6361/202453541","url":null,"abstract":"<i>Context.<i/> Recent studies indicate that circumstellar disks exhibit weak turbulence, with their dynamics and evolution being primarily influenced by magnetic winds. However, most numerical studies have focused on planet-disk interactions in turbulent disk models.<i>Aims.<i/> We aim to explore how wind-driven accretion affects the orbital and eccentricity evolution of a Jovian planet within a magnetized disk. Conversely, we seek to determine to what extent such a planet can modify the accretion behavior and the wind dynamics.<i>Methods.<i/> We performed high-resolution 3D global non-ideal magneto-hydrodynamic (MHD) simulations of a massive gap-carving planet interacting with a wind-launching disk, using the accelerated code IDEFIX. We considered the influence of the gap shape on planet migration by restarting a “fixed-planet” simulation at three different times, from which the planet evolved freely in the disk.<i>Results.<i/> For a strong initial magnetization and a sufficiently deep planet gap, we find that the planet becomes moderately eccentric and its migration is slow, unsteady, and mostly outward. This migration pattern is due to the gap’s radial asymmetry which enhances the inner Lindblad torque while reducing the outer Lindblad torque. We show that eccentricity can grow up to 6–8% and is likely driven by a finite-amplitude instability triggered by first-order external Lindblad resonances. These moderate eccentricity values periodically modulate the gap accretion rate and wind mass loss rate, possibly leading to the formation of discrete structures in CO outflows.<i>Conclusions.<i/> Slow outward migration and eccentricity growth appear to be common outcomes of planet-disk-wind interactions, which may contribute significantly to both the long orbital periods and the moderate eccentricities of warm jupiters. Additionally, eccentric massive protoplanets embedded in circumstellar disks could play a role in generating structured outflows.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"25 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143737194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Data-constrained 3D magnetohydrodynamics simulation of a spiral jet caused by an unstable flux rope embedded in a fan–spine configuration","authors":"Z. F. Li, J. H. Guo, X. Cheng, M. D. Ding, L. P. Chitta, H. Peter, S. Poedts, D. Calchetti","doi":"10.1051/0004-6361/202452156","DOIUrl":"https://doi.org/10.1051/0004-6361/202452156","url":null,"abstract":"Spiral jets are impulsive plasma ejections that typically show an apparent rotational motion. Their generation, however, is still not understood thoroughly. Based on a high-resolution vector magnetogram from the Polarimetric and Helioseismic Imager on board Solar Orbiter, we constructed a data-constrained three-dimensional (3D) magnetohydrodynamics (MHD) model, aiming to disclose the eruption mechanism of a tiny spiral jet at a moss region observed on March 3, 2022. The initial configuration of the simulation consists of an extrapolated coronal magnetic field based on the vector magnetogram and an inserted unstable flux rope constructed by the regularized Biot-Savart laws method. Our results highlight the critical role of the fan-spine configuration in forming the spiral jet, and confirm the collapse of the pre-existing magnetic null to a curved 3D current sheet where external reconnection takes places. It is further disclosed that the flux rope quickly moves upward, reconnecting with the field lines near the outer spine, thereby enabling the transfer of twisting and cool material from the flux rope to the open field, giving rise to the tiny spiral jet we observed. The notable similarities between these characteristics and those for larger-scale jets suggest that spiral jets, regardless of their scale, essentially share the same eruption mechanism.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"73 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution, speed, and precession of the parsec-scale jet in the 3C 84 radio galaxy","authors":"M. Foschi, J. L. Gómez, A. Fuentes, I. Cho, A. P. Marscher, S. Jorstad","doi":"10.1051/0004-6361/202453406","DOIUrl":"https://doi.org/10.1051/0004-6361/202453406","url":null,"abstract":"We present high-resolution images of the radio source 3C 84 at 43 GHz from 121 observations conducted by the BEAM-ME monitoring program between 2010 and 2023. Imaging was performed using the recent forward modeling imaging method eht-imaging; it achieved a resolution of 80 μas, which is a factor of ∼2−3 better than traditional imaging methods such as CLEAN. The sequence of images depicts the growth and expansion of the parsec-scale relativistic jet in 3C 84; it clearly shows a complex internal structure with bending in the jet and changes in its launching direction and expansion speed. We report measurements of the expansion speed over time, which show that the jet goes through three regimes, marked by the start and end of a hot spot frustration phase. The high resolution of the images also allowed us to measure the projected launching direction as a function of time, and we find an irregular variation pattern. Our results confirm previous studies of the morphological transition undergone by 3C 84 and provide quantitative measurements of the jet’s kinematic properties over a decade-long timescale.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"216 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysing the flux stability of stellar calibrator candidates with TESS","authors":"E. Tonucci, T. A. van Kempen, J.-P. Beaulieu, L. Bernard","doi":"10.1051/0004-6361/202452893","DOIUrl":"https://doi.org/10.1051/0004-6361/202452893","url":null,"abstract":"<i>Context<i/>. The ESA space mission Ariel requires bright sources that are stable at the level of 100 ppm over 6 hours in order to accurately measure exoplanet atmospheres through transmission spectroscopy. To ensure this, in-flight instrument calibration can be performed by observing stellar calibrators.<i>Aims<i/>. In this study, a stellar calibrator candidate list distributed over the sky is created and a flux variability analysis is performed to identify the best stellar calibrators for transit spectroscopy of exoplanet atmospheres with Ariel.<i>Methods<i/>. A starting candidate sample of 1937 solar-type stars is created using the all-sky surveys Two Micron All Sky Survey and <i>Gaia<i/>. Using stellar light curves from the Transit Exoplanet Survey Satellite (TESS), the flux variability of each star is characterised by computing its Lomb-Scargle periodogram and reduced chi-squared. This enables the elimination of stars with detectable variability from the sample.<i>Results<i/>. Approximately 22.2% of stars from the starting sample pass the selection as potential calibrators. These do not all necessarily meet Ariel's stability requirement, although some will. No correlation between flux stability and stellar properties is found, as long as the correct value ranges for the parameters are chosen, like a surface temperature between 5000 and 6300 K. The only exception is stellar magnitude: Noise in TESS data increases as stars get dimmer, so, a high percentage of faint stars passes the selection since their variability is more likely hidden within the inherent TESS noise. Contrarily, stars brighter than 5 mag cannot be used as calibrators.<i>Conclusions<i/>. A list of 430 promising bright calibration targets distributed over the sky has been selected. These can potentially be used as stellar calibrators for the Ariel mission. Targets from this list will have to be further studied to determine which ones possess a flux stability better than 100 ppm over 6 hours.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"73 3 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection asymmetry in solar energetic particle events","authors":"S. Dalla, A. Hutchinson, R. A. Hyndman, K. Kihara, N. V. Nitta, L. Rodríguez-García, T. Laitinen, C. O. G. Waterfall, D. S. Brown","doi":"10.1051/0004-6361/202453000","DOIUrl":"https://doi.org/10.1051/0004-6361/202453000","url":null,"abstract":"<i>Context.<i/> Solar energetic particles (SEPs) are detected in interplanetary space in association with solar flares and coronal mass ejections (CMEs). The magnetic connection between the observing spacecraft and the solar active region (AR) source of the event is a key parameter in determining whether SEPs are observed and the particle event’s properties.<i>Aims.<i/> We investigate whether an east-west asymmetry in the detection of SEP events is present in observations and discuss its possible link to the corotation of magnetic flux tubes with the Sun.<i>Methods.<i/> We used a published dataset of 239 CMEs recorded between 2006 and 2017 that had source regions both on the Sun’s front and far sides as seen from Earth. We produced distributions of occurrences of in situ SEP intensity enhancements associated with the CME events versus Δ<i>ϕ<i/>, the longitudinal separation between the source AR and the spacecraft magnetic footpoint based on the nominal Parker spiral. We focussed on protons of energy > 10 MeV measured by STEREO A, STEREO B, and GOES at 1 au. We also considered occurrences of 71–112 keV electron events detected by MESSENGER between 0.31 and 0.47 au.<i>Results.<i/> We find an east-west asymmetry with respect to the best magnetic connection (Δ<i>ϕ<i/> = 0) in the detection of > 10 MeV proton events and of 71–112 keV electron events. For protons, observers for which the source AR is on the eastern side of the spacecraft footpoint and not well connected (−180° < Δ<i>ϕ<i/> < −40°) are 93% more likely to detect an SEP event compared to observers with +40° < Δ<i>ϕ<i/> < +180°. The asymmetry may be a signature of the corotation of magnetic flux tubes with the Sun since, for events with Δ<i>ϕ<i/> < 0, corotation sweeps particle-filled flux tubes towards the observing spacecraft, while for Δ<i>ϕ<i/> > 0 it moves them away. Alternatively, it may be related to asymmetric acceleration or propagation effects.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"36 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}