Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae394e
Hugo A. Carril, Adolfo F. Viñas, Jaume Terradas, Roberto E. Navarro and Marcel Goossens
The kinetic characteristics of resonant absorption of combined left- and right-hand polarized waves with finite amplitude are investigated. The plasma consists of a magnetized 2D slab with linearly inhomogeneous density layers. Using a 2D-3V particle-in-cell-hybrid code, we simulate this system with different layer thicknesses and different angles of the background magnetic field relative to the simulation plane. Resonant absorption excites counterpropagating kinetic Alfvén waves (KAWs) inside the layers, with frequencies consistent with large-scale kink modes. They are observed to interact nonlinearly to generate a parallel electric field, which subsequently produces density structures and accelerates protons. This causes strong heating and flat-topped distribution functions. We derive an analytical estimate for this parallel field that reproduces the most relevant signals of the dispersion relations during and after resonant absorption. The transverse particle dynamics are driven by the cross-field drift, causing the transverse temperature to oscillate and grow exponentially due to small-scale fluctuations. Therefore, the proton distribution functions are largely shaped nonresonantly by the KAW activity.
{"title":"Resonant Absorption and Fluctuations via Hybrid Simulations on Coronal Loops. II. Kinetic Description","authors":"Hugo A. Carril, Adolfo F. Viñas, Jaume Terradas, Roberto E. Navarro and Marcel Goossens","doi":"10.3847/1538-4357/ae394e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae394e","url":null,"abstract":"The kinetic characteristics of resonant absorption of combined left- and right-hand polarized waves with finite amplitude are investigated. The plasma consists of a magnetized 2D slab with linearly inhomogeneous density layers. Using a 2D-3V particle-in-cell-hybrid code, we simulate this system with different layer thicknesses and different angles of the background magnetic field relative to the simulation plane. Resonant absorption excites counterpropagating kinetic Alfvén waves (KAWs) inside the layers, with frequencies consistent with large-scale kink modes. They are observed to interact nonlinearly to generate a parallel electric field, which subsequently produces density structures and accelerates protons. This causes strong heating and flat-topped distribution functions. We derive an analytical estimate for this parallel field that reproduces the most relevant signals of the dispersion relations during and after resonant absorption. The transverse particle dynamics are driven by the cross-field drift, causing the transverse temperature to oscillate and grow exponentially due to small-scale fluctuations. Therefore, the proton distribution functions are largely shaped nonresonantly by the KAW activity.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"67 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147330158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae3c9e
Hadi Madanian and Terry Z. Liu
Collisionless shocks in space and astrophysical plasmas mediate energy exchange between charged particles and fields in two or more plasma flows. In this study we analyze the evolution of ion distributions around a reformation cycle of a quasi-parallel shock. We use multipoint in situ observations in the foreshock region of the Earth’s bow shock of a transient foreshock structure as it generates a shock. We find that backstreaming ions in the foreshock create a density and magnetic field depletion known as caviton, which locally changes the shock geometry. Gyrating suprathermal ions that emerge within the caviton and reach the upstream edge of the core create a cross-field current imbalance that results in the nonlinear growth of a new shock layer. The new shock forms from the background foreshock fields over a distance of ∼6 ion inertial lengths (li) and within 4.5–11.2 li from the main bow shock. We find that plasma compression at the new thin shock layer is due to compactification of the cold upstream ion beam by high-amplitude magnetic field–aligned electrostatic fields. At later stages, the plasma compression expands to form a new sheath.
{"title":"The Role of Gyrating Ions in Reformation of a Quasi-parallel Supercritical Shock","authors":"Hadi Madanian and Terry Z. Liu","doi":"10.3847/1538-4357/ae3c9e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3c9e","url":null,"abstract":"Collisionless shocks in space and astrophysical plasmas mediate energy exchange between charged particles and fields in two or more plasma flows. In this study we analyze the evolution of ion distributions around a reformation cycle of a quasi-parallel shock. We use multipoint in situ observations in the foreshock region of the Earth’s bow shock of a transient foreshock structure as it generates a shock. We find that backstreaming ions in the foreshock create a density and magnetic field depletion known as caviton, which locally changes the shock geometry. Gyrating suprathermal ions that emerge within the caviton and reach the upstream edge of the core create a cross-field current imbalance that results in the nonlinear growth of a new shock layer. The new shock forms from the background foreshock fields over a distance of ∼6 ion inertial lengths (li) and within 4.5–11.2 li from the main bow shock. We find that plasma compression at the new thin shock layer is due to compactification of the cold upstream ion beam by high-amplitude magnetic field–aligned electrostatic fields. At later stages, the plasma compression expands to form a new sheath.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147330163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae401f
Chunyu Ji, Jiajia Liu, Wensi Wang, Zhenyong Hou, Xianyong Bai and Yuming Wang
Jets, as an essential manifestation of the release of the free magnetic energy, are ubiquitous in the solar atmosphere. We present a comprehensive analysis of a multithermal blowout jet that occurred in active region AR 13102 on 2022 September 20, using observations from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly, SDO/Helioseismic and Magnetic Imager (HMI), Interface Region Imaging Spectrograph, and Solar Upper Transition Region Imager. The jet is initiated by compact brightenings at its footpoints and exhibits a curtain-like spire with apparent rotational and weak lateral whipping motions. Time–distance analysis reveals a projected axial velocity ∼300 km s−1 and a rotational speed ∼30 km s−1. Differential emission measure analysis shows that the jet plasma spans a broad temperature range, with hot (≳10 MK) plasma concentrated near the flare loops and jet base and cooler components extending along the spire. Using the derived kinetic and thermal properties, we conclude that there is an equipartition between the jet’s kinetic energy (5.4 ± 2.4) × 1020 J and thermal energy (7.0 ± 3.6) × 1020 J. HMI vector magnetograms and nonlinear force-free field extrapolations reveal that the jet originates from a compact mixed-polarity region at the edge of the active region, where flux emergence and cancellation, a low-lying twisted magnetic flux rope with a maximum twist number of ∼2.1, and a surrounding high-Q quasi-separatrix layer are present. The observed decrease in twist after the eruption, together with the jet’s untwisting, indicates that the jet is driven by the eruption and the reconnection of the twisted flux rope, converting magnetic free energy into plasma heating and bulk motion. Our results highlight the importance of small-scale flux rope eruptions in driving blowout jets and releasing twist through magnetic reconnection and untwisting motions.
喷流作为自由磁能释放的重要表现形式，在太阳大气中无处不在。我们利用太阳动力学观测台(SDO)/大气成像组件、SDO/日震和磁成像仪（HMI）、界面区成像光谱仪和太阳上过渡区成像仪的观测数据，对2022年9月20日发生在活跃区域AR 13102的多热喷流进行了综合分析。射流是由紧凑的光亮在它的脚点开始，并表现出一个像窗帘一样的尖顶，明显的旋转和弱的横向鞭打运动。时间-距离分析显示，预计轴向速度为~ 300 km s - 1，旋转速度为~ 30 km s - 1。差射测量分析表明，喷流等离子体的温度范围很广，热等离子体（约10 MK）集中在耀斑环附近，喷流基部和较冷的成分沿塔尖延伸。利用导出的动力学和热性质，我们得出射流的动能（5.4±2.4）× 1020 J和热能（7.0±3.6）× 1020 J之间的均衡。HMI矢量磁图和非线性无力场外推表明，射流起源于活跃区边缘的致密混合极性区域，其中磁通出现和消除，低洼扭曲磁通绳，最大扭转数为~ 2.1。周围存在高q准分离矩阵层。观测到的喷发后扭曲的减少，以及喷流的解扭，表明喷流是由喷发和扭曲的通量绳的重新连接驱动的，将磁性自由能转化为等离子体加热和体运动。我们的研究结果强调了小规模通量绳喷发在驱动喷流和通过磁重联和解扭运动释放捻度方面的重要性。
{"title":"On the Thermal and Magnetic Properties of an Active Region Jet","authors":"Chunyu Ji, Jiajia Liu, Wensi Wang, Zhenyong Hou, Xianyong Bai and Yuming Wang","doi":"10.3847/1538-4357/ae401f","DOIUrl":"https://doi.org/10.3847/1538-4357/ae401f","url":null,"abstract":"Jets, as an essential manifestation of the release of the free magnetic energy, are ubiquitous in the solar atmosphere. We present a comprehensive analysis of a multithermal blowout jet that occurred in active region AR 13102 on 2022 September 20, using observations from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly, SDO/Helioseismic and Magnetic Imager (HMI), Interface Region Imaging Spectrograph, and Solar Upper Transition Region Imager. The jet is initiated by compact brightenings at its footpoints and exhibits a curtain-like spire with apparent rotational and weak lateral whipping motions. Time–distance analysis reveals a projected axial velocity ∼300 km s−1 and a rotational speed ∼30 km s−1. Differential emission measure analysis shows that the jet plasma spans a broad temperature range, with hot (≳10 MK) plasma concentrated near the flare loops and jet base and cooler components extending along the spire. Using the derived kinetic and thermal properties, we conclude that there is an equipartition between the jet’s kinetic energy (5.4 ± 2.4) × 1020 J and thermal energy (7.0 ± 3.6) × 1020 J. HMI vector magnetograms and nonlinear force-free field extrapolations reveal that the jet originates from a compact mixed-polarity region at the edge of the active region, where flux emergence and cancellation, a low-lying twisted magnetic flux rope with a maximum twist number of ∼2.1, and a surrounding high-Q quasi-separatrix layer are present. The observed decrease in twist after the eruption, together with the jet’s untwisting, indicates that the jet is driven by the eruption and the reconnection of the twisted flux rope, converting magnetic free energy into plasma heating and bulk motion. Our results highlight the importance of small-scale flux rope eruptions in driving blowout jets and releasing twist through magnetic reconnection and untwisting motions.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147330217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae2be4
Peter H. Keys, Ryan J. Campbell, Dylan K. J. Magill, Mateus A. Keating, Mihalis Mathioudakis, David B. Jess, Damian J. Christian, Arthur Berberyan, Samuel D. T. Grant, Shahin Jafarzadeh, Marco Stangalini and Robertus Erdélyi
Bright points (BPs) are small-scale, dynamic features that are ubiquitous across the solar disc and are often associated with the underlying magnetic field. Using broadband photospheric images obtained with the Visible Broadband Imager at the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), the properties of BPs have been analyzed with DKIST for the first time at the highest spatial resolutions achievable. BPs were observed to have an average lifetime of 95 ± 29 s and a mean transverse velocity of 1.60 ± 0.41 km s−1. The BPs had a log-normal area distribution with a peak at 2300 km2. Transverse velocities and lifetimes across the DKIST images were comparable and consistent with previous studies. The area distribution of the DKIST data peaked in areas significantly lower than those from the literature. This was explored further and was observed to be due to an overestimation of BP areas due to the merging of close features when the spatial resolution is reduced, in tandem with possible oversplitting of features in the DKIST images. Furthermore, the effect of variable seeing in the data was determined. This showed that the average spatial resolution of the data was around , in comparison to the theoretical diffraction limit of . Accounting for the influence of seeing, the peak of the area distribution of BPs in the DKIST data was estimated as 4800 km2, which is still significantly lower than previously observed.
亮点（bp）是小规模的动态特征，在整个太阳圆盘上无处不在，通常与潜在的磁场有关。利用美国国家科学基金会Daniel K. Inouye太阳望远镜（DKIST）的可见光宽带成像仪获得的宽带光球图像，DKIST首次以可实现的最高空间分辨率分析了bp的特性。bp的平均寿命为95±29秒，平均横向速度为1.60±0.41 km s−1。bp面积呈对数正态分布，峰值在2300 km2处。DKIST图像上的横向速度和寿命与以前的研究相比较和一致。DKIST数据的区域分布在明显低于文献数据的区域中达到峰值。我们对此进行了进一步的探讨，并观察到这是由于在空间分辨率降低时，由于合并了相近的特征而导致BP区域的高估，以及DKIST图像中可能出现的特征过度分裂。此外，还确定了数据中变量视觉的影响。这表明，与理论衍射极限相比，数据的平均空间分辨率约为。考虑到观测的影响，DKIST数据中bp面积分布的峰值估计为4800 km2，这仍显著低于以前观测到的值。
{"title":"Small-scale Bright Point Characteristics at High-resolution with the Daniel K. Inouye Solar Telescope","authors":"Peter H. Keys, Ryan J. Campbell, Dylan K. J. Magill, Mateus A. Keating, Mihalis Mathioudakis, David B. Jess, Damian J. Christian, Arthur Berberyan, Samuel D. T. Grant, Shahin Jafarzadeh, Marco Stangalini and Robertus Erdélyi","doi":"10.3847/1538-4357/ae2be4","DOIUrl":"https://doi.org/10.3847/1538-4357/ae2be4","url":null,"abstract":"Bright points (BPs) are small-scale, dynamic features that are ubiquitous across the solar disc and are often associated with the underlying magnetic field. Using broadband photospheric images obtained with the Visible Broadband Imager at the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), the properties of BPs have been analyzed with DKIST for the first time at the highest spatial resolutions achievable. BPs were observed to have an average lifetime of 95 ± 29 s and a mean transverse velocity of 1.60 ± 0.41 km s−1. The BPs had a log-normal area distribution with a peak at 2300 km2. Transverse velocities and lifetimes across the DKIST images were comparable and consistent with previous studies. The area distribution of the DKIST data peaked in areas significantly lower than those from the literature. This was explored further and was observed to be due to an overestimation of BP areas due to the merging of close features when the spatial resolution is reduced, in tandem with possible oversplitting of features in the DKIST images. Furthermore, the effect of variable seeing in the data was determined. This showed that the average spatial resolution of the data was around , in comparison to the theoretical diffraction limit of . Accounting for the influence of seeing, the peak of the area distribution of BPs in the DKIST data was estimated as 4800 km2, which is still significantly lower than previously observed.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"98 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147330157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae3a98
Maja Lujan Niemeyer, Eiichiro Komatsu, José Luis Bernal, Chris Byrohl, Robin Ciardullo, Olivia Curtis, Daniel J. Farrow, Steven L. Finkelstein, Karl Gebhardt, Caryl Gronwall, Gary J. Hill, Matt J. Jarvis, Donghui Jeong, Erin Mentuch Cooper, Deeshani Mitra, Shiro Mukae, Julian B. Muñoz, Masami Ouchi, Shun Saito, Donald P. Schneider and Lutz Wisotzki
We present a measurement of the Lyα intensity mapping power spectrum from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We measure the cross-power spectrum of the Lyα intensity and Lyα-emitting galaxies (LAEs) in a redshift range of 1.9 ≤ z ≤ 3.5. We calculate the intensity from HETDEX spectra that do not contain any detected LAEs above a signal-to-noise ratio of 5.5. To produce a power spectrum model and its covariance matrix, we simulate the data using lognormal mocks for the LAE catalog and Lyα intensity in redshift space. The simulations include the HETDEX sensitivity, selection function, and mask. The measurements yield the product of the LAE bias, the intensity bias, the mean intensity of undetected sources, and the ratio of the actual and fiducial redshift-space distortion parameters, (6.7 ± 3.1), (11.7 ± 1.4), and (8.3 ± 1.5) × 10−22 erg s−1 cm−2 arcsec−2 Å−1 in three redshift bins centered at , 2.6, and 3.2, respectively. The results are reasonably consistent with cosmological hydrodynamical simulations that include Lyα radiative transfer. They are, however, significantly smaller than previous results from cross-correlations of quasars with Lyα intensity. These results demonstrate the statistical power of HETDEX for Lyα intensity mapping and pave the way for a more comprehensive analysis. They will also be useful for constraining models of Lyα emission from galaxies used in modern cosmological simulations of galaxy formation and evolution.
{"title":"Lyα Intensity Mapping in HETDEX: Galaxy-Lyα Intensity Cross-power Spectrum","authors":"Maja Lujan Niemeyer, Eiichiro Komatsu, José Luis Bernal, Chris Byrohl, Robin Ciardullo, Olivia Curtis, Daniel J. Farrow, Steven L. Finkelstein, Karl Gebhardt, Caryl Gronwall, Gary J. Hill, Matt J. Jarvis, Donghui Jeong, Erin Mentuch Cooper, Deeshani Mitra, Shiro Mukae, Julian B. Muñoz, Masami Ouchi, Shun Saito, Donald P. Schneider and Lutz Wisotzki","doi":"10.3847/1538-4357/ae3a98","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3a98","url":null,"abstract":"We present a measurement of the Lyα intensity mapping power spectrum from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We measure the cross-power spectrum of the Lyα intensity and Lyα-emitting galaxies (LAEs) in a redshift range of 1.9 ≤ z ≤ 3.5. We calculate the intensity from HETDEX spectra that do not contain any detected LAEs above a signal-to-noise ratio of 5.5. To produce a power spectrum model and its covariance matrix, we simulate the data using lognormal mocks for the LAE catalog and Lyα intensity in redshift space. The simulations include the HETDEX sensitivity, selection function, and mask. The measurements yield the product of the LAE bias, the intensity bias, the mean intensity of undetected sources, and the ratio of the actual and fiducial redshift-space distortion parameters, (6.7 ± 3.1), (11.7 ± 1.4), and (8.3 ± 1.5) × 10−22 erg s−1 cm−2 arcsec−2 Å−1 in three redshift bins centered at , 2.6, and 3.2, respectively. The results are reasonably consistent with cosmological hydrodynamical simulations that include Lyα radiative transfer. They are, however, significantly smaller than previous results from cross-correlations of quasars with Lyα intensity. These results demonstrate the statistical power of HETDEX for Lyα intensity mapping and pave the way for a more comprehensive analysis. They will also be useful for constraining models of Lyα emission from galaxies used in modern cosmological simulations of galaxy formation and evolution.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147330161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae3da8
Aritra Chakrabarty, Gijs D. Mulders, Artyom Aguichine and Natalie Batalha
The demographics of Kepler planets provide a key testbed for models of planet formation and evolution, particularly for explaining the radius valley separating super-Earths and sub-Neptunes. A primordial interpretation based on differences in bulk densities—where rocky and water-rich planets form via migration pathways—offers an alternative to atmospheric loss scenarios. Updated interior structure models of water worlds with adiabatic steam atmospheres reproduce the observed valley near ∼2 R⊕ more accurately. Furthermore, migration models from our Genesis library suggest that these formation pathways can also account for the distinct period distributions of super-Earths and sub-Neptunes, as well as the emergence of the hot Neptune desert. Motivated by this, we develop a Bayesian hierarchical mixture model for close-in Kepler planets (P < 100 days), combining rocky planets and water worlds without H/He envelopes. The inferred mass distributions of rocky and water-rich planets peak at ∼2.6 and ∼7 M⊕, respectively, with the water mass fraction of water worlds peaking at ∼41%. Water worlds provide a good representation of the Kepler sub-Neptune population, with the radius cliff emerging as a “waterfall”—a sharp decline in their occurrence. However, our mass–radius analysis shows that water worlds alone cannot explain planets with R ≳ 3 R⊕, implying that at least ∼20% of sub-Neptunes in the sample are enriched in H/He gas.
{"title":"The Radius Cliff is a Waterfall: Explaining Sub-Neptune Exoplanets with Steam Worlds","authors":"Aritra Chakrabarty, Gijs D. Mulders, Artyom Aguichine and Natalie Batalha","doi":"10.3847/1538-4357/ae3da8","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3da8","url":null,"abstract":"The demographics of Kepler planets provide a key testbed for models of planet formation and evolution, particularly for explaining the radius valley separating super-Earths and sub-Neptunes. A primordial interpretation based on differences in bulk densities—where rocky and water-rich planets form via migration pathways—offers an alternative to atmospheric loss scenarios. Updated interior structure models of water worlds with adiabatic steam atmospheres reproduce the observed valley near ∼2 R⊕ more accurately. Furthermore, migration models from our Genesis library suggest that these formation pathways can also account for the distinct period distributions of super-Earths and sub-Neptunes, as well as the emergence of the hot Neptune desert. Motivated by this, we develop a Bayesian hierarchical mixture model for close-in Kepler planets (P < 100 days), combining rocky planets and water worlds without H/He envelopes. The inferred mass distributions of rocky and water-rich planets peak at ∼2.6 and ∼7 M⊕, respectively, with the water mass fraction of water worlds peaking at ∼41%. Water worlds provide a good representation of the Kepler sub-Neptune population, with the radius cliff emerging as a “waterfall”—a sharp decline in their occurrence. However, our mass–radius analysis shows that water worlds alone cannot explain planets with R ≳ 3 R⊕, implying that at least ∼20% of sub-Neptunes in the sample are enriched in H/He gas.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147329758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae40b5
Huanzhou Yang, Eric T. Wolf, Cheng-Cheng Liu, 成诚 刘, Yunqian Zhu, Owen B. Toon and Dorian S. Abbot
Clouds are the largest source of uncertainty in climate simulations. For exoplanets, cloud simulation is particularly challenging because of the lack of observational data to tune parameterized cloud models. Here we apply Community Aerosol and Radiation Model for Atmospheres (CARMA), a size-resolved bin cloud microphysics model, to the atmospheric global climate model Community Atmosphere Model (CAM6) and simulate exoplanets with a range of planetary rotation rates. CARMA produces fewer liquid clouds than the native CAM6 parameterized cloud microphysics scheme (Morrison–Gettelman two-moment microphysics, MG), more ice clouds, and a significantly different ice cloud size distribution. Overall, this leads to a decrease in the magnitude of the net CRE by 4–10 W m−2, which is unlikely to change the determination of habitability from a climate perspective in most cases. The difference in ice cloud size distribution is likely to strongly affect transmission spectral retrievals. Our work confirms that the MG parameterized cloud microphysics scheme can produce reasonable climate simulation when extrapolated to some exoplanet contexts and highlights the value of resolved cloud microphysics for evaluating parameterized schemes and for interpreting observations.
{"title":"The Effect of Planetary Rotation Period on Clouds in a Global Climate Model with a Bin Microphysics Scheme","authors":"Huanzhou Yang, Eric T. Wolf, Cheng-Cheng Liu, 成诚 刘, Yunqian Zhu, Owen B. Toon and Dorian S. Abbot","doi":"10.3847/1538-4357/ae40b5","DOIUrl":"https://doi.org/10.3847/1538-4357/ae40b5","url":null,"abstract":"Clouds are the largest source of uncertainty in climate simulations. For exoplanets, cloud simulation is particularly challenging because of the lack of observational data to tune parameterized cloud models. Here we apply Community Aerosol and Radiation Model for Atmospheres (CARMA), a size-resolved bin cloud microphysics model, to the atmospheric global climate model Community Atmosphere Model (CAM6) and simulate exoplanets with a range of planetary rotation rates. CARMA produces fewer liquid clouds than the native CAM6 parameterized cloud microphysics scheme (Morrison–Gettelman two-moment microphysics, MG), more ice clouds, and a significantly different ice cloud size distribution. Overall, this leads to a decrease in the magnitude of the net CRE by 4–10 W m−2, which is unlikely to change the determination of habitability from a climate perspective in most cases. The difference in ice cloud size distribution is likely to strongly affect transmission spectral retrievals. Our work confirms that the MG parameterized cloud microphysics scheme can produce reasonable climate simulation when extrapolated to some exoplanet contexts and highlights the value of resolved cloud microphysics for evaluating parameterized schemes and for interpreting observations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147329759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae3e7e
Niankun Yu, Han Zheng, Chao-Wei Tsai, Pei Zuo, Luis C. Ho, Amélie Saintonge, Zheng Zheng, Nathan Deg, Ningyu Tang, Xin Ai, Junzhi Wang, Xiang Jie and Di Li
Polar-ring galaxies (PRGs) host an outer ring of gas and stars oriented nearly perpendicular to the main stellar body. They represent extreme examples of misaligned systems and provide valuable insights into galaxy interactions, gas accretion, and peculiar gas dynamics. We compile a complete sample of kinematically confirmed PRGs and collect their H i measurements. Combining literature data with new observations from the Five-hundred-meter Aperture Spherical Telescope, we detect H i emission in 22 sources, identify 1 potential H i absorption feature, and find 4 nondetections among 40 confirmed PRGs. Compared to galaxies in the ALFALFA and xGASS surveys, PRGs predominantly occupy the green valley or quenched regimes but exhibit higher gas fractions than typical early-type galaxies, suggesting gas accretion. The H i profile asymmetry and shape for PRGs are not consistent with those of the ALFALFA sample with p < 0.05. We examine their Tully–Fisher relation (TFR) and baryonic TFR (bTFR), linking the systems’ rotation velocities to their masses. The extreme outliers in TFRs for the control sample tend to display single-peaked H i profiles. PRGs do not follow a tight TFR or bTFR if the H I resides primarily in the host galaxy. But the scatter decreases significantly if we assume the gas is mainly distributed in the polar ring. Spatially resolved H i observations are essential to disentangling the gas distributions and kinematics in PRGs, which are key to understanding their formation mechanisms.
{"title":"Insights into the Physical Nature of Polar-ring Galaxies from H I Observations","authors":"Niankun Yu, Han Zheng, Chao-Wei Tsai, Pei Zuo, Luis C. Ho, Amélie Saintonge, Zheng Zheng, Nathan Deg, Ningyu Tang, Xin Ai, Junzhi Wang, Xiang Jie and Di Li","doi":"10.3847/1538-4357/ae3e7e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3e7e","url":null,"abstract":"Polar-ring galaxies (PRGs) host an outer ring of gas and stars oriented nearly perpendicular to the main stellar body. They represent extreme examples of misaligned systems and provide valuable insights into galaxy interactions, gas accretion, and peculiar gas dynamics. We compile a complete sample of kinematically confirmed PRGs and collect their H i measurements. Combining literature data with new observations from the Five-hundred-meter Aperture Spherical Telescope, we detect H i emission in 22 sources, identify 1 potential H i absorption feature, and find 4 nondetections among 40 confirmed PRGs. Compared to galaxies in the ALFALFA and xGASS surveys, PRGs predominantly occupy the green valley or quenched regimes but exhibit higher gas fractions than typical early-type galaxies, suggesting gas accretion. The H i profile asymmetry and shape for PRGs are not consistent with those of the ALFALFA sample with p < 0.05. We examine their Tully–Fisher relation (TFR) and baryonic TFR (bTFR), linking the systems’ rotation velocities to their masses. The extreme outliers in TFRs for the control sample tend to display single-peaked H i profiles. PRGs do not follow a tight TFR or bTFR if the H I resides primarily in the host galaxy. But the scatter decreases significantly if we assume the gas is mainly distributed in the polar ring. Spatially resolved H i observations are essential to disentangling the gas distributions and kinematics in PRGs, which are key to understanding their formation mechanisms.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"245 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147330268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-03DOI: 10.3847/1538-4357/ae3aa5
Kunihiko Tanaka, Makoto Nagai and Kazuhisa Kamegai
We present Atacama Large Millimeter/submillimeter Array [C i] 3P1–3P0 imaging of the central 6.6 × 4.2 pc2 region of the Galaxy encompassing the circumnuclear disk (CND). The data reveal low-density ( cm−3) molecular gas with inward motion, widespread both inside and outside the CND. The normalized [C i] to CS 7–6 intensity difference decreases inwardly from R = 4 pc to 1.7 pc and azimuthally along the CND’s rotation, likely tracing paths of low-density gas inflow. By projecting spaxels into orbital coordinates assuming a velocity field model, we identify four kinematic features: a pair of spiral outer streamers toward the CND, inner streamers extending to 0.5 pc from Sgr A*, an outer disk at R ∼ 3–6 pc, and the rotating ring at R = 2 pc. P–P–V correlation between the inner streamers and H42α indicates gas supply to the mini-spiral through the western arc (WA) and northern arm (NA). The total inflowing mass is 1.5 × 104M⊙, 1.7 times the mass of the rotating ring. The identified flows can be organized into two main pathways connecting the CND exterior and interior: “WA flow” feeding the mini-spiral WA via the CND, and “NA flow” bypassing the purely rotating orbit. The inflow rate along the former is approximately constant (0.1–0.16 M⊙ yr−1), implying a CND dwelling time comparable to its orbital period and supporting the CND’s transient nature. We also identify two [C i]-bright clumps (CBCs) lacking dense-gas counterparts near the contact point between the northern outer streamer and the CND. Apparently intact against tidal disruption despite subcritical densities, the CBCs may represent a chemically young phase shortly after formation in colliding flows.
{"title":"ALMA [C I] Image of the Circumnuclear Disk of the Milky Way: Inflowing Low-density Molecular Gas","authors":"Kunihiko Tanaka, Makoto Nagai and Kazuhisa Kamegai","doi":"10.3847/1538-4357/ae3aa5","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3aa5","url":null,"abstract":"We present Atacama Large Millimeter/submillimeter Array [C i] 3P1–3P0 imaging of the central 6.6 × 4.2 pc2 region of the Galaxy encompassing the circumnuclear disk (CND). The data reveal low-density ( cm−3) molecular gas with inward motion, widespread both inside and outside the CND. The normalized [C i] to CS 7–6 intensity difference decreases inwardly from R = 4 pc to 1.7 pc and azimuthally along the CND’s rotation, likely tracing paths of low-density gas inflow. By projecting spaxels into orbital coordinates assuming a velocity field model, we identify four kinematic features: a pair of spiral outer streamers toward the CND, inner streamers extending to 0.5 pc from Sgr A*, an outer disk at R ∼ 3–6 pc, and the rotating ring at R = 2 pc. P–P–V correlation between the inner streamers and H42α indicates gas supply to the mini-spiral through the western arc (WA) and northern arm (NA). The total inflowing mass is 1.5 × 104M⊙, 1.7 times the mass of the rotating ring. The identified flows can be organized into two main pathways connecting the CND exterior and interior: “WA flow” feeding the mini-spiral WA via the CND, and “NA flow” bypassing the purely rotating orbit. The inflow rate along the former is approximately constant (0.1–0.16 M⊙ yr−1), implying a CND dwelling time comparable to its orbital period and supporting the CND’s transient nature. We also identify two [C i]-bright clumps (CBCs) lacking dense-gas counterparts near the contact point between the northern outer streamer and the CND. Apparently intact against tidal disruption despite subcritical densities, the CBCs may represent a chemically young phase shortly after formation in colliding flows.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147330288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-02DOI: 10.3847/1538-4357/ae3950
Rhyan Sawyer and Jasper Halekas
The lunar surface exhibits small-scale crustal magnetic fields that can give rise to various interactions when subjected to the incident solar wind plasma. These lunar crustal magnetic fields exhibit scale lengths that are much smaller than the typical convected ion gyroradius within the solar wind, leading to an effective demagnetization of the ions. Thus, these lunar crustal magnetic fields provide a natural environment within which Hall electric fields and various current structures may be generated. This study reports observations from THEMIS–ARTEMIS during a periselene of 14 km to the lunar surface and examines the plasma environment within the vicinity of various crustal magnetic fields. The reported observations suggest a Hall interaction region that extends downstream of prominent regions of crustal magnetization. Within these extended interaction regions we report a Hall electric field of 2–3 mV m−1 and oriented upward and sunward, as well as a northward current carried by southward ExB drifting electrons. Lastly, Hall electric fields were observed above the lunar crustal magnetic fields oriented downward and antisunward, as well as parallel currents directed toward the lunar surface, and were consistently observed when the magnetic footpoint was within the cusp region.
{"title":"New Observations of an Extended Hall Interaction Region Downstream of Lunar Crustal Magnetic Fields","authors":"Rhyan Sawyer and Jasper Halekas","doi":"10.3847/1538-4357/ae3950","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3950","url":null,"abstract":"The lunar surface exhibits small-scale crustal magnetic fields that can give rise to various interactions when subjected to the incident solar wind plasma. These lunar crustal magnetic fields exhibit scale lengths that are much smaller than the typical convected ion gyroradius within the solar wind, leading to an effective demagnetization of the ions. Thus, these lunar crustal magnetic fields provide a natural environment within which Hall electric fields and various current structures may be generated. This study reports observations from THEMIS–ARTEMIS during a periselene of 14 km to the lunar surface and examines the plasma environment within the vicinity of various crustal magnetic fields. The reported observations suggest a Hall interaction region that extends downstream of prominent regions of crustal magnetization. Within these extended interaction regions we report a Hall electric field of 2–3 mV m−1 and oriented upward and sunward, as well as a northward current carried by southward ExB drifting electrons. Lastly, Hall electric fields were observed above the lunar crustal magnetic fields oriented downward and antisunward, as well as parallel currents directed toward the lunar surface, and were consistently observed when the magnetic footpoint was within the cusp region.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147329664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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