Solar Dynamics Research Articles

Advancing urban air quality modeling with solar radiation-included computational fluid dynamics simulations

Advancing urban air quality modeling with solar radiation-included computational fluid dynamics simulations

Magnetic Reconnection between a Solar Jet and a Filament Channel

Abstract The solar corona is highly structured by bunches of magnetic field lines forming either loops, or twisted flux ropes representing prominences/filaments, or very dynamic structures such as jets. The aim of this paper is to understand the interaction between filament channels and jets. We use high-resolution Hα spectra obtained by the ground-based telescope Télescope Héliographique pour l'Etude du Magnétisme et des Instabilités Solaires on the Canary Islands and data from Helioseismic Magnetic Imager and Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. In this paper we present a multiwavelength study of the interaction of filaments and jets. They both consist of cool plasma embedded in magnetic structures. A jet is particularly well studied in all the AIA channels with a flow reaching 100–180 km s−1. Its origin is linked to cancelling flux at the edge of the active region. Large Doppler shifts in Hα are derived in a typical area for a short time (order of minute). They correspond to flows around 140 km s−1. In conclusion we conjecture that these flows correspond to some interchange of magnetic field lines between the filament channel and the jets leading to cool plasmoid ejections or reconnection jets perpendicularly to the jet trajectory.

Coronal bright point statistics II. Magnetic polarities and mini loops

The solar corona maintains temperatures of a million Kelvin or more. The plasma heating mechanisms responsible for these extreme temperatures are still unclear. Large regions of magnetic activity in the photosphere cause extreme ultraviolet (EUV) emission in the corona. Even smaller regions with bipolar and multipolar magnetic fields can generate coronal bright points (CBPs). We performed a statistical analysis of 346 CBPs. We used Solar Dynamics Observatory (SDO) images to track CBPs on a continuous basis. Therefore, we were able to collect a database of information on the CPB's lifetime, shape, polarity, flux emergence, and merging behavior, as well as their magnetic evolution, using the SDO Helioseismic and Magnetic Imager (SDO-HMI) instrument. We searched the SDO data archive for the longest continuous interval of uninterrupted observations in 2015. The longest such interval contains 12 consecutive days of full-disk images from the EUV channels of the SDO-AIA instrument. To analyze the properties of CBPs, we employed an automated tracking algorithm to follow the evolution of the CBPs. Furthermore, we manually checked the shape, underlying magnetic polarities, and merging behavior of each CBP. We provide statistics on the magnetic polarity, emergence, and merging of CBPs. We established a relationship between the CBP's merging behavior and both its shape and magnetic polarities. Brighter CBPs are visible in all SDO-AIA channels and exhibit strong radiative energy losses. The category of CBPs with a bipolar field has the highest probability of being emissive in all SDO-AIA channels. The majority of CBPs have two opposite polarities below them. The merging of two CBPs is an unusual phenomenon that is related to complex multipolar magnetic regions. Moreover, loop-shaped CBPs usually appear above bipolar fields. Faint CBPs have shorter lifetimes and are less likely to merge with another CBP.

A Peculiar Feature of the First Ionization Potential Effect Before a Solar Flare Impulsive Phase Observed by MSS-1B, CHASE, and SDO

Abstract The impulsive phase of solar flares is often accompanied by the depletion of the elements with low first ionization potential (FIP), whose abundance decreases from the coronal level to the photospheric level, and then recovers back to the coronal level during the decay phase. Recently, we analyzed the soft X-ray spectroscopic data of the 2024 February 16 flare event observed by the Macao Science Satellite-1B/Soft X-ray Detection Units. Surprisingly, however, it is revealed that the depletion of the low-FIP elements occurred well before the flare impulsive phase. The timing of this change provides important clues about the location of magnetic reconnection, shedding light on the mass and energy transfer between different layers of the solar atmosphere. By examining the multiwavelength data from the Solar Dynamics Observatory and CHASE missions, we found that there was no filament 0.4 hr before the flare eruption. However, an erupting filament was detected in association with the flare event. Based on these features, we propose for the first time that the flare/filament eruption for this event was initiated by magnetic reconnection in the solar chromosphere, rather than in the corona as stated in the standard flare model.

Hinode EIS: Updated In-flight Radiometric Calibration

Abstract We present an update to the in-flight radiometric calibration of the Hinode Extreme Ultraviolet Imaging Spectrometer (EIS), revising and extending our previous studies. We analyze full-spectral EIS observations of quiet Sun (QS) and active regions (ARs) from 2007 until 2022. Using CHIANTI version 10, we adjust the EIS relative effective areas for a selection of dates with emission measure analyses of off-limb QS. We find generally good agreement (within typically ±15%) between measured and expected line intensities. We then consider selected intensity ratios for all of the dates and apply an automatic fitting method to adjust the relative effective areas. To constrain the absolute values from 2010 and later, we force agreement between EIS and Solar Dynamics Observatory Atmospheric Imaging Assembly 193 Å observations. The resulting calibration, with an uncertainty of about ±20%, is then validated in various ways, including flare line ratios from Fe xxiv and Fe xvii, emission measure analyses of cool AR loops, and several density-dependent line ratios.

PAStar : A model for stellar surface from the Sun to active stars

The characterisation of exoplanets requires a good description of the host star. Stellar activity acts as a source of noise, which can alter planet radii as derived from the transit depth or atmospheric characterisation. Here, we propose PAStar a model to describe photospheric activity in the form of spots and faculae, which could be applied to a wide range of stellar observations, from photometric to spectroscopic time series, making it possible to correctly extract planetary and stellar properties. The adopted stellar atmosphere is a combination of three components: the quiet photosphere, spots, and faculae. The model takes into account the effects of star inclination and Doppler shifts due to stellar rotation and limb darkening, which is independent for each component. Several synthetic products have been presented to show the capabilities of the model. The model is able to retrieve the input surface-inhomogeneity configuration through photometric or spectroscopic observations. The model has been validated against optical solar data and compared to alternative stellar surface activity models; for example SOAP code . The Sun is a unique laboratory to test stellar models because of the possibility to unambiguously relate flux variations to surface inhomogeneities' configuration. This validation has been done by analysing a photometric time series from the Variability of Solar Irradiance and Gravity Oscillations (VIRGO) photometer on-board Solar and Heliospheric Observatory (SOHO) mission. Results have been compared to real solar images from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to confirm the goodness of the results in terms of surface inhomogeneities' positions and dimensions. The description of stellar activity is a fundamental step in several astrophysical contexts and it is covered by the method we present. Our model offers a flexible and valuable tool to describe the activity of stars when it is dominated by spots and faculae.

Mixed 2D-cation passivation towards improved durability of perovskite solar cells and dynamics of 2D-perovskites under light irradiation and at high temperature

Dynamics of 2D-perovskites and stabilization with mixed 2D cations with n-butylammonium iodide (BAI) and n-octylammonium iodide (OAI).

Precise and efficient modeling of stellar-activity-affected solar spectra using SOAP-GPU

Context. One of the main obstacles in exoplanet detection when using the radial velocity (RV) technique is the presence of stellar activity signal induced by magnetic regions. As the most advanced techniques to mitigate this signal are reaching a level better than one meter per second, it is difficult to evaluate their performance: instrumental systematics start to be similar in magnitude, and therefore it is impossible to know the ground truth of the stellar activity signal. In this context, a realistic simulated dataset that can provide photometry and spectroscopic outputs is needed for method development. Aims. The goal of this paper is to describe two realistic simulations of solar activity obtained from SOAP-GPU and to compare them with real data obtained from the HARPS-N solar telescope. For this purpose, both simulated spectral time series cover the time window of HARPS-N solar observation, but nothing prevents SOAP-GPU from modeling the data over different time spans. Methods. We describe two different methods of modeling solar activity using SOAP-GPU. The first models the evolution of active regions based on the spot number as a function of time. Other physical parameters are either drawn from observed solar distributions or modeled with empirical relations. The second method relies on the extraction of active regions from the Solar Dynamics Observatory (SDO) data. The location of spots and faculae on the solar disk at each timestamp are derived from the magnetogram and intensity maps and are fed into SOAP-GPU to simulate the corresponding spectra. Results. The simulated spectral time series generated with the first method shows a long-term RV behavior similar to that seen in the HARPS-N solar observations. The effect of stellar activity induced by stellar rotation is also well modeled with prominent periodicities at the stellar rotation period and its first harmonic. The comparison between the simulated spectral time series generated using SDO images and the HARPS-N solar spectra shows that SOAP-GPU can precisely model the RV time series of the Sun to a precision better than 0.9 m/s. By studying the width and depth variations of each spectral line in the HARPS-N solar and SOAP-GPU data, we find a strong correlation between the observation and the simulation for strong spectral lines, therefore supporting the modeling of the stellar activity effect at the spectral level. The correlations are weaker for shallow lines, although it is likely that their lower signal-to-noise ratio does not allow a meaningful comparison. Conclusions. We introduce two methods for modeling solar activity using SOAP-GPU. With only sunspot numbers as input, we accurately capture the long-term magnetic cycle and rotational features. Additionally, we effectively model shift and depth variations at the spectral line level by using data from SDO. These simulated solar spectral time series serve as a useful test bed for evaluating spectral-level stellar activity mitigation techniques.

Long-term properties of coronal off-limb structures

Extracting plasma structures in the solar corona (e.g. jets, loops, prominences) from spacecraft imagery data is essential in order to ascertain their unique properties and for our understanding of their evolution. Hence, our aim is to detect all coronal off-limb structures over a solar cycle and to analyse their statistical properties. In particular, we investigated the intensity and density evolution of these coronal structures, with a specific focus on active longitudes in the corona, that is, longitudinal regions where the solar activity is unequivocally dominant. We developed a methodology based on mathematical morphology (MM) algorithms to extract these coronal structures from extreme ultraviolet (EUV) images taken by the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) in the 304 wavelength channel during Solar Cycle (SC) 24. The resulting dataset consists of $877,843$ structures spanning the whole period from June 2010 to December 2021 with a three-hour cadence. We assessed the main characteristics of these coronal off-limb structures, such as their length, width, area, perimeter, latitude, and longitude (evaluated at the centre of the structures), as well as their intensity corrected for the charge-coupled device (CCD) sensitivity degradation of the AIA instrument. Regarding most of these properties, we find similar trends to the behaviour of the on-disk features, including the butterfly diagram and the structures that migrate towards the polar regions (also referred to as `rush-to-the-poles' structures) expanding during the rising phase of SC 24 until the reversal of the magnetic field at the solar poles. We uncover an interesting distribution: lower-intensity coronal structures seem to behave differently with respect to higher-intensity structures. The butterfly diagram is clearly shaped by the high-intensity structures, while the lower-intensity structures are more dispersed and survive during the declining phase of SC 24. We also find evidence of the existence of active longitudes in the corona and of their dependence on differential rotation and latitude.

Fractional Partial Differential Equation Modeling for Solar Cell Charge Dynamics

Fractional Partial Differential Equation Modeling for Solar Cell Charge Dynamics

131 and 304 Å Emission Variability Increases Hours Prior to Solar Flare Onset

Abstract Thermal changes in coronal loops are well studied, both in quiescent active regions and in flaring scenarios. However, relatively little attention has been paid to loop emission in the hours before the onset of a solar flare; here, we present the findings of a study of over 50 off-limb flares of Geostationary Operational Environmental Satellite class C5.0 and above. We investigated the integrated emission variability for Solar Dynamics Observatory Atmospheric Imaging Assembly channels 131, 171, 193, and 304 Å for 6 hr before each flare and compared these quantities to the same time range and channels above active regions without proximal flaring. We find significantly increased emission variability in the 2–3 hr before flare onset, particularly for the 131 and 304 channels. This finding suggests a potential new flare prediction methodology. The emission trends between the channels are not consistently well correlated, suggesting a somewhat chaotic thermal environment within the coronal portion of the loops that disturbs the commonly observed heating and cooling cycles of quiescent active region loops. We present our approach and the resulting statistics and discuss the implications for heating sources in these preflaring active regions.

Dominance of 2 Minute Oscillations near the Alfvén Surface

Abstract Alfvén waves, considered one of the primary candidates for heating and accelerating the fast solar wind, are ubiquitous in spacecraft observations, yet their origin remains elusive. In this study, we analyze data from the first 19 encounters of the Parker Solar Probe and report the dominance of 2 minute oscillations near the Alfvén surface. The frequency-rectified trace magnetic power spectral density (PSD) of these oscillations indicates that the fluctuation energy is concentrated around 2 minutes for the “youngest” solar wind. Further analysis using wavelet spectrograms reveals that these oscillations primarily consist of outward-propagating, spherically polarized Alfvén wave bursts. Through Doppler analysis, we show that the wave frequency observed in the spacecraft frame can be mapped directly to the launch frequency at the base of the corona, where previous studies have identified a distinct peak around 2 minutes (~8 mHz) in the spectrum of swaying motions of coronal structures observed by the Solar Dynamics Observatory Atmospheric Imaging Assembly. These findings strongly suggest that the Alfvén waves originate from the solar atmosphere. Furthermore, statistical analysis of the PSD deformation beyond the Alfvén surface supports the idea of dynamic formation of the otherwise absent 1/f range in the solar wind turbulence spectrum.

Solar shape variations across cycles 24 and 25: Observations from 2010 to 2023

The longest continuous time-series of solar oblateness measurements, initiated in 2010 and still ongoing, has been obtained from data collected by the Helioseismic Magnetic Imager (HMI) aboard NASA's Solar Dynamics Observatory (SDO). Based on HMI data, we developed two methods for determining the solar oblateness at 617.33\,nm in the continuum . The first method involves determining solar oblateness using HMI solar disk images and limb observations from twenty-three SDO satellite roll calibration maneuvers between 2010 and 2023 . Through meticulous analysis of these observation sequences, we obtained a precise measurement of solar oblateness using this technique, yielding a value of 9.02 (pm 0.72)times 10$^ $ (6.28pm 0.50\,kilometers), unaffected by brightness contamination from sunspots and magnetically induced excess emission. We also verified the polarization independence of light, showing consistent HMI solar oblateness measurements across Stokes states. Interestingly, our solar oblateness time-series, based on HMI solar disk images and limb observations, seems to be in anti-phase with solar activity. The second method we used relies on determining solar oblateness from HMI helioseismic inference of internal rotation. With this approach, we obtained a solar oblateness of 8.40 (pm 0.02)times 10$^ $ (5.85pm 0.01 kilometers) with a variation in phase with solar activity (0.05times 10$^ $ (0.04\,kilometers at 1\,sigma ) over an 11--year sunspot cycle). This outcome is troubling as it conflicts with our results obtained from the HMI solar limb observations

Far-side Active Regions Based on Helioseismic and EUV Measurements: A New Data Set for Heliospheric Machine Learning Advancements

Active Regions (ARs) are regions of strong magnetic flux in the solar atmosphere. Understanding the global evolution of ARs is critical for solar magnetism as well as for accurate space-weather forecasting. We present the first far-side AR data set based on EUV observation and helioseismic measurements. For the EUV observations, we use synchronic maps at 304 Å comprised of observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly and the Solar TErrestrial RElations Observatory/Extreme UltraViolet Imager, in heliocentric orbit with direct vantages into the Sun’s far hemisphere. We used the brightening of the solar transition region in EUV/304 Å maps as a proxy for the magnetic regions. For the far-side helioseismic measurements, we used seismic phase-shift maps of the Sun’s far hemisphere, computed from helioseismic Dopplergrams observed by NSO/Global Oscillations Network Group (GONG). In this study, we present the first global EUV AR data set of the whole Sun, providing several basic parameters, such as location, area, tilt angle, EUV brightness, and latitudinal/longitudinal extents of the identified ARs. We also present a similar data set for the far-side GONG ARs where the helioseismic phase shift parameters are included. Helioseismic far-side GONG ARs are examined, and their success at predicting strong ARs is assessed. We discuss the temporal and spatial evolution for the EUV AR signatures and far-side GONG AR signatures during the ascending and maximum phases of Solar Cycle 24 (2010 May–2016 May). We examine the correlation between the helioseismic signatures and the respective EUV source distributions in the Sun’s far hemisphere. We present the first far-side AR butterfly diagram based on helioseismic measurements.

Differential Rotation of Individual Sunspots and Pores

The analysis of the rotation rate of individual sunspots and pores was performed according to the data from the processing of observations by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager in the period 2010–2024. Sunspots stood out in the images in the continuum. To accurately track the spots, we processed five images for each day. To determine the polarity of the magnetic field, we superimposed the contours of sunspots on observations of magnetic fields at the same time. This made it possible to track the movement of more than 210,000 individual sunspots and pores. It is found that the rotation rate is influenced by the rotation rate of the solar atmosphere and the systematic proper motions of the spots. Sunspots and pores of the leading polarity have a rate of meridional movement ≈2.4% faster than spots of the trailing polarity. We also found that regular sunspots, which have umbrae and penumbrae, rotate ≈1.5% faster than solar pores, in which penumbrae are absent. The dependence of the rotation rate on the area is found. For sunspots with an area of S > 10 μhm, the rotation rate is practically independent of the area. Small sunspots, with an area of S < 10 μhm, rotate ≈1.7% more slowly.

Bidirectional propagating brightenings in arch filament systems observed by Solar Orbiter/EUI

Arch filament systems (AFSs) are chromospheric and coronal manifestations of emerging magnetic flux. Using high spatial resolution observations taken at a high cadence by the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter, we identified small-scale elongated brightenings within the AFSs. These brightenings appear as bidirectional flows along the threads of AFSs. For our study, we investigated the coordinated observations of the AFSs acquired by the EUI instrument and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) on 2022 March 4 and 17. We analyzed 15 bidirectional propagating brightenings from EUI 174 Å images. These brightenings reached propagating speeds of 100–150 km s−1. The event observed on March 17 exhibits blob-like structures, which may be signatures of plasmoids and due to magnetic reconnection. In this case, we also observed counterparts in the running difference slit-jaw images in the 1400 Å passbands taken by the Interface Region Imaging Spectrograph (IRIS). Most events show co-temporal intensity variations in all AIA EUV passbands. Together, this implies that these brightenings in the AFSs are dominated by emission from cool plasma with temperatures well below 1 MK. The Polarimetric and Helioseismic Imager (PHI) on board Solar Orbiter provides photospheric magnetograms at a similar spatial resolution as EUI and from the same viewing angle. The magnetograms taken by PHI show signatures of flux emergence beneath the brightenings. This suggests that the events in the AFSs are triggered by magnetic reconnection that may occur between the newly emerging magnetic flux and the preexisting magnetic field structures in the middle of the AFSs. This would also give a natural explanation for the bidirectional propagation of the brightenings near the apex of the AFSs. The interaction of the preexisting field and the emerging flux may be important for mass and energy transfer within the AFSs.

Analyzing Electron Beam-Induced Coronal Extreme Ultraviolet Emissions and Solar Radio Bursts Type III During M-Class Flares: A Preliminary Study

Abstract Solar flare events are triggered by the process of magnetic reconnection, which leads to a sudden release of stored magnetic energy and intensifies the electromagnetic emissions across the entire spectrum. In this preliminary study, we investigate the role of accelerated electron beams from acceleration site in enhancing Extreme Ultraviolet (EUV) emissions in the solar corona and generating metric solar radio bursts type III (SRBT III) during M-class flare events. By focusing on six flare events associated with SRBT III, which occurred between June 15, 2024, and June 25, 2024, we utilize data from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and the Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) network to conduct our analysis. Our analysis involves examining the temporal and spatial patterns of coronal 171 Å EUV emissions and Type III radio bursts during these M-class flare events. Additionally, we conducted a visual inspection of 171 A EUV image in the active region to observe changes in the coronal loops and structural modifications throughout the flare. Our findings reveal a significant temporal correlation between the EUV and Type III radio emissions, along with noticeable structural modifications in the EUV images. These observations suggest that accelerated electron beams originating from the acceleration site play a crucial role in driving both phenomena.

A Precursor to Solar Prominence Eruptions: Detection and Analysis of EUV Prominence Oscillations

The eruption of prominences can have a significant influence on the solar–terrestrial environment. However, accurately predicting these eruptions remains a challenge. We apply automated detection methods for extreme ultraviolet (EUV) prominences observed by the twin spacecraft from the Solar Terrestrial Relations Observatory (STEREO) mission and the Solar Dynamics Observatory near Earth. We study an event, during 2011 March, when each STEREO spacecraft is in quadrature with respect to the Earth. For two time ranges, we obtain longitudinal height profiles as a function of time. We also track the corresponding EUV filaments across the solar disk, which reveal the emergence of ultra-long-period oscillations in the EUV filament channels. Our analysis shows a correlation between the prominence’s increasing height and the oscillation periods, suggesting a potential link to the subsequent eruption observed by the STEREO spacecraft off-limb. These findings offer new insights into prominence dynamics and may pave the way for improved eruption prediction.

Investigating explosive events in a 3D quiet-Sun model: Transition region and coronal response

Transition region explosive events are characterized by the non-Gaussian profiles of the emission lines that form at transition region temperatures, and they are believed to be manifestations of small-scale reconnection events in the transition region. Traditionally, the enhanced emission at the line wings is interpreted as bi-directional outflows generated by the reconnection of oppositely directed magnetic fields. We investigate whether the 2D picture also holds in a more realistic setup of a 3D radiation magnetohydrodynamic (MHD) quiet-Sun model. We also compare the thermal responses in the transition region and corona of different events. We took a 3D self-consistent quiet-Sun model extending from the upper convection zone to the lower corona calculated using the MURaM code. We first synthesized the Si iv line profiles from the model and then located the profiles which show signatures of bi-directional flows. These tend to appear along network lanes, and most do not reach coronal temperatures. We isolated two hot events (around 1 MK) and one cool event (order of 0.1 MK) and examined the magnetic field evolution in and around these selected events. Furthermore, we investigated why some explosive events reach coronal temperatures, while most remain cool. We also examined the emission of these events as seen in the 174 AA passband of the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter and all coronal passbands of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The field lines around two events reconnect at small angles (i.e., they undergo component reconnection). The third case is associated with the relaxation of a highly twisted flux rope. All three events reveal signatures in the synthesized EUI 174 AA images. The intensity variations in two events are dominated by variations of the coronal emissions, while the cool component seen in the respective channel contributes significantly to the intensity variation in one case. In comparison, one hot event is embedded in regions with higher magnetic field strength and heating rates while the densities are comparable, and the other hot event is heated to coronal temperatures mainly because of the low density. Small-scale heating events seen in the extreme-ultraviolet (EUV) channels of AIA or EUI might be hot or cool. Our results imply that the major difference between the events in which coronal counterparts dominate or not is the amount of converted magnetic energy and/or density in and around the reconnection region.

Detecting and sizing the Earth with PLATO: A feasibility study based on solar data

Context. The PLAnetary Transits and Oscillations of stars (PLATO) mission will observe the same area of the sky continuously for at least two years in an effort to detect transit signals of an Earth-like planet orbiting a solar-like star. Aims. We aim to study how short-term solar-like variability caused by oscillations and granulation would affect PLATO’s ability to detect and size Earth if PLATO were to observe the Solar System itself. We also compare different approaches to mitigate noise caused by short-term solar-like variability and perform realistic transit fitting of transit signals in PLATO-like light curves. Methods. We injected Earth-like transit signals onto real solar data taken by the Helioseismic and Magnetic Imager (HMI) instrument on board the Solar Dynamics Observatory (SDO). We isolated short-term stellar variability in the HMI observations by removing any variability with characteristic timescales longer than five hours using a smooth Savitzky-Golay filter. We then added a noise model for a variety of different stellar magnitudes computed by PlatoSim assuming an observation by all 24 normal cameras. We first compared four different commonly used treatments of correlated noise in the time domain by employing them in a transit fitting scheme. We then tried to recover pairs of transit signals using an algorithm similar to the transit least squares algorithm. Finally, we performed transit fits using realistic priors on planetary and stellar parameters and assessed how accurately the pair of two injected transits was recovered. Results. We find that short-term solar-like variability affects the correct retrieval of Earth-like transit signals in PLATO data. Variability models accounting for variations with typical timescales at the order of one hour are sufficient to mitigate these effects. We find that when the limb-darkening coefficients of the host star are properly constrained, the impact parameter does not negatively affect the detectability of a transit signal or the retrieved transit parameters, except for high values (b &gt; 0.8). For bright targets (8.5–10.5 mag), the transit signal of an Earth analogue can reliably be detected in PLATO data. For faint targets a detection is still likely, though the results of transit search algorithms have to be verified by transit-fitting algorithms to avoid false positive detections being flagged. For bright targets (V-mag ≤ 9.5), the radius of an Earth-like planet orbiting a solar-like star can be correctly determined at a precision of 3% or less, assuming that at least two transit events are observed and the characteristics of the host star are well understood.