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Context.Coronal mass ejections (CMEs) are large-scale structures of magnetized plasma that erupt from the corona into interplanetary space. The launch of Solar Orbiter (SolO) in 2020 enables in situ measurements of CMEs in the innermost heliosphere, at such distances where CMEs can be observed remotely within the inner field of view of heliospheric imagers (HIs). It thus provides the opportunity for investigations into the correspondence of the CME substructures measured in situ and observed remotely. We studied a CME that started on 2022 March 10 and was measured in situ by SolO at ∼0.44 au.

Aims.Combining remote observations of CMEs from wide-angle imagers and in situ measurements in the innermost heliosphere allows us to compare CME properties derived through both techniques, validate the estimates, and better understand CME evolution, specifically the size and radial expansion, within 0.5 au.

Methods.We compared the evolution of different CME substructures observed in images from the HIs on board the Ahead Solar Terrestrial Relations Observatory (STEREO-A) and the CME signatures measured in situ by SolO. The CME is found to possess a density enhancement at its rear edge in both remote and in situ observations, which validates the use of the signature of density enhancement following the CMEs to accurately identify the CME rear edge. We also estimated and compared the radial size and radial expansion speed of different substructures in both observations.

Results.The evolution of the CME front and rear edges in remote images is consistent with the in situ CME measurements. The radial expansion (i.e., radial size and radial expansion speed) of the whole CME structure consisting of the magnetic ejecta and the sheath is consistent with the in situ estimates obtained at the same time from SolO. However, we do not find such consistencies for the magnetic ejecta region inside the CME because it is difficult to identify the magnetic ejecta edges in the remote images.

 

In situ measurements from spacecraft typically provide a time series at a single location through coronal mass ejections (CMEs), and they have been one of the main methods to investigate CMEs. The CME properties derived from these in situ measurements are affected by temporal changes that occur as the CME passes over the spacecraft, such as radial expansion and aging, as well as spatial variations within a CME. This study uses multispacecraft measurements of the same CME at close separations to investigate both the spatial variability (how different a CME profile is when probed by two spacecraft close to each other) and the so-called aging effect (the effect of the time evolution on in situ properties). We compile a database of 19 events from the past 4 decades measured by two spacecraft with a radial separation of <0.2 au and an angular separation of <10°. We find that the average magnetic field strength measured by the two spacecraft differs by 18% of the typical average value, which highlights nonnegligible spatial or temporal variations. For one particular event, measurements taken by the two spacecraft allow us to quantify and significantly reduce the aging effect to estimate the asymmetry of the magnetic field strength profile. This study reveals that single-spacecraft time series near 1 au can be strongly affected by aging and that correcting for self-similar expansion does not capture the whole aging effect.

 

The BigCode community, an open-scientific collaboration working on the responsible development of Large Language Models for Code (Code LLMs), introduces StarCoder and StarCoderBase: 15.5B parameter models with 8K context length, infilling capabilities and fast large-batch inference enabled by multi-query attention. StarCoderBase is trained on 1 trillion tokens sourced from The Stack, a large collection of permissively licensed GitHub repositories with inspection tools and an opt-out process. We fine-tuned StarCoderBase on 35B Python tokens, resulting in the creation of StarCoder. We perform the most comprehensive evaluation of Code LLMs to date and show that StarCoderBase outperforms every open Code LLM that supports multiple programming languages and matches or outperforms the OpenAI code-cushman-001 model. Furthermore, StarCoder outperforms every model that is fine-tuned on Python, can be prompted to achieve 40% pass@1 on HumanEval, and still retains its performance on other programming languages. We take several important steps towards a safe open-access model release, including an improved PII redaction pipeline and a novel attribution tracing tool, and make the StarCoder models publicly available under a more commercially viable version of the Open Responsible AI Model license. 

Abstract The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium 1 , which is assumed to dominate the total extragalactic dispersion. Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs 2 , in at least one case there is evidence for an extreme magneto-ionic local environment 3,4 and a compact persistent radio source 5 . Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. The estimated host-galaxy dispersion measure of approximately $${903}_{-111}^{+72}$$ 903 − 111 + 72 parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of FRB host galaxies 2,6 , far exceeds the dispersion-measure contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host-galaxy identifications. 

Context.3C 84 is a nearby radio source with a complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates the use of very-long-baseline interferometry (VLBI) above the hitherto available maximum frequency of 86 GHz.

Aims.Using ultrahigh resolution VLBI observations at the currently highest available frequency of 228 GHz, we aim to perform a direct detection of compact structures and understand the physical conditions in the compact region of 3C 84.

Methods.We used Event Horizon Telescope (EHT) 228 GHz observations and, given the limited (u, v)-coverage, applied geometric model fitting to the data. Furthermore, we employed quasi-simultaneously observed, ancillary multi-frequency VLBI data for the source in order to carry out a comprehensive analysis of the core structure.

Results.We report the detection of a highly ordered, strong magnetic field around the central, supermassive black hole of 3C 84. The brightness temperature analysis suggests that the system is in equipartition. We also determined a turnover frequency ofν_m = (113 ± 4) GHz, a corresponding synchrotron self-absorbed magnetic field ofB_SSA = (2.9 ± 1.6) G, and an equipartition magnetic field ofB_eq = (5.2 ± 0.6) G. Three components are resolved with the highest fractional polarisation detected for this object (m_net = (17.0 ± 3.9)%). The positions of the components are compatible with those seen in low-frequency VLBI observations since 2017–2018. We report a steeply negative slope of the spectrum at 228 GHz. We used these findings to test existing models of jet formation, propagation, and Faraday rotation in 3C 84.

Conclusions.The findings of our investigation into different flow geometries and black hole spins support an advection-dominated accretion flow in a magnetically arrested state around a rapidly rotating supermassive black hole as a model of the jet-launching system in the core of 3C 84. However, systematic uncertainties due to the limited (u, v)-coverage, however, cannot be ignored. Our upcoming work using new EHT data, which offer full imaging capabilities, will shed more light on the compact region of 3C 84.

 

We discussWindobservations of a long and slow magnetic cloud (MC) propagating through large‐amplitude Alfvén waves (LAAWs). The MC axis has a strong component along GSEX, as also confirmed by a Grad‐Shafranov reconstruction. It is overtaking the solar wind at a speed roughly equal to the upstream Alfvén speed, leading to a weak shock wave 17 hr ahead. We give evidence to show that the nominal sheath region is populated by LAAWs: (i) a well‐defined de Hoffmann‐Teller frame in which there is excellent correlation between the field and flow vectors, (ii) constant field and total pressure, and (iii) an Alfvén ratio (i.e., ratio of kinetic‐to‐magnetic energy of the fluctuations) near unity at frequencies much lower than the ion cyclotron frequency in the spacecraft frame. In the region where the LAAWs approach the MC's front boundary there are field and flow discontinuities. At the first, magnetic reconnection is taking place, as deduced from a stress balance test (Walén test). This severs connection of some field lines to the Sun and the solar wind strahl disappears. There follows a 2‐hr interval where the magnetic field strength is diminished while pressure balance is maintained. Here the bidirectionality of the suprathermal electron flows is intermittently disrupted. This interval ends with a slow expansion fan downstream of which there is a dropout of halo electrons just inside the front boundary of the MC. This study illustrates an untypical case of a slow MC interacting with LAAWs in the slow solar wind.