Pub Date : 2023-12-01DOI: 10.3847/2041-8213/ad13e9
K. P. Raju, Jagdev Singh, B. Ravindra, Muthu Priyal
The network structure seen in the solar images is the outline of supergranulation, which is the large-scale convection in the Sun with a size of about 30 Mm and a lifetime of 24 hr. We have obtained the supergranulation lane widths from the autocorrelation function of image windows from the Ca ii K spectroheliograms. The images are obtained from the 100 yr Kodaikanal data, which contains information on more than nine solar cycles. The lane widths are known to show a positive correlation with the sunspot number. It is now found that the lane widths, obtained near the mid-latitudes during the sunspot cycle minima, are strongly correlated to the following sunspot number maxima. A straight-line fit adequately describes the variation. It is also found that the correlation is weak or insignificant at other times. The strong correlation of the two parameters thus provides a simple way to predict the maximum sunspot number about 4–5 yr in advance. The results are important in space weather predictions and solar irradiance variations.
在太阳图像中看到的网络结构是超粒化的轮廓，超粒化是太阳中的大尺度对流，其大小约为 30 毫米，寿命为 24 小时。我们从 Ca ii K 分光日线图图像窗口的自相关函数中获得了超粒道宽度。这些图像来自 100 年的 Kodaikanal 数据，其中包含超过九个太阳周期的信息。车道宽度与太阳黑子数量呈正相关。现在发现，在太阳黑子周期最小值期间，在中纬度附近获得的道宽与随后的太阳黑子数最大值密切相关。直线拟合充分描述了这一变化。研究还发现，在其他时间，相关性较弱或不明显。因此，这两个参数的强相关性为提前约 4-5 年预测太阳黑子数最大值提供了一种简单的方法。这些结果对于空间天气预报和太阳辐照度变化具有重要意义。
{"title":"Correlation between Supergranular Lane Widths and Sunspot Number; A Simple Way to Predict the Amplitude of Sunspot Cycle","authors":"K. P. Raju, Jagdev Singh, B. Ravindra, Muthu Priyal","doi":"10.3847/2041-8213/ad13e9","DOIUrl":"https://doi.org/10.3847/2041-8213/ad13e9","url":null,"abstract":"The network structure seen in the solar images is the outline of supergranulation, which is the large-scale convection in the Sun with a size of about 30 Mm and a lifetime of 24 hr. We have obtained the supergranulation lane widths from the autocorrelation function of image windows from the Ca ii K spectroheliograms. The images are obtained from the 100 yr Kodaikanal data, which contains information on more than nine solar cycles. The lane widths are known to show a positive correlation with the sunspot number. It is now found that the lane widths, obtained near the mid-latitudes during the sunspot cycle minima, are strongly correlated to the following sunspot number maxima. A straight-line fit adequately describes the variation. It is also found that the correlation is weak or insignificant at other times. The strong correlation of the two parameters thus provides a simple way to predict the maximum sunspot number about 4–5 yr in advance. The results are important in space weather predictions and solar irradiance variations.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139013117","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 : 2023-12-01DOI: 10.3847/2041-8213/ad0f23
A. Kępa, M. Siarkowski, A. Awasthi, J. Sylwester, B. Sylwester
We employ the differential evolution (DE) method to analyze observations from the Solar X-Ray Monitor on board the Chandrayaan-2 spacecraft. DE belongs to the family of evolutionary algorithms that find solutions using mechanisms inspired by biological processes. This approach enables us to simultaneously calculate the distribution of the differential emission measure and elemental abundances through an iterative process. We establish a model for the emission sources of flaring plasma, incorporating temperature, emission measure, and abundances of eight elements: Mg, Al, Si, S, Ar, Ca, Fe, and Ni, for an M3.9 GOES-class solar flare that occurred on 2021 May 7 (SOL2021-05-07T19:04). Our analysis covers various phases of the flare, determining the evolution of temperature, emission measure, and elemental abundances. Additionally, utilizing data from the Spectrometer Telescope for Imaging X-rays on board the Solar Orbiter, we investigate the evolution of hard X-ray source morphology, source volume, electron density, and thermal behavior of the flaring plasma throughout the event. The results reveal notable variations in elemental abundances between photospheric and coronal values during different flare phases. This emphasizes the significance of elemental abundance information in comprehending X-ray emissions during solar flares.
我们采用差分进化（DE）方法来分析 Chandrayaan-2 号航天器上的太阳 X 射线监测器的观测数据。差分进化法属于进化算法系列，利用受生物过程启发的机制寻找解决方案。这种方法使我们能够通过迭代过程同时计算差分发射测量和元素丰度的分布。我们建立了一个燃烧等离子体发射源模型，其中包含温度、发射量和八种元素的丰度：我们为 2021 年 5 月 7 日发生的 M3.9 GOES 级太阳耀斑（SOL2021-05-07T19:04）建立了等离子体发射源模型，包括温度、发射测量值和八种元素丰度：镁、铝、硅、硒、氩、钙、铁和镍。我们的分析涵盖了耀斑的各个阶段，确定了温度、发射测量和元素丰度的演变。此外，我们还利用太阳轨道器上的 X 射线成像分光望远镜的数据，研究了整个事件期间硬 X 射线源的形态、源体积、电子密度和耀斑等离子体热行为的演变。结果显示，在不同耀斑阶段，光球和日冕值之间的元素丰度存在显著差异。这强调了元素丰度信息对于理解太阳耀斑期间 X 射线辐射的重要性。
{"title":"Investigations of Flaring Plasma Parameters during an M-class Flare Using the Differential Evolution Method and XSM/Chandrayaan-2 Observations","authors":"A. Kępa, M. Siarkowski, A. Awasthi, J. Sylwester, B. Sylwester","doi":"10.3847/2041-8213/ad0f23","DOIUrl":"https://doi.org/10.3847/2041-8213/ad0f23","url":null,"abstract":"We employ the differential evolution (DE) method to analyze observations from the Solar X-Ray Monitor on board the Chandrayaan-2 spacecraft. DE belongs to the family of evolutionary algorithms that find solutions using mechanisms inspired by biological processes. This approach enables us to simultaneously calculate the distribution of the differential emission measure and elemental abundances through an iterative process. We establish a model for the emission sources of flaring plasma, incorporating temperature, emission measure, and abundances of eight elements: Mg, Al, Si, S, Ar, Ca, Fe, and Ni, for an M3.9 GOES-class solar flare that occurred on 2021 May 7 (SOL2021-05-07T19:04). Our analysis covers various phases of the flare, determining the evolution of temperature, emission measure, and elemental abundances. Additionally, utilizing data from the Spectrometer Telescope for Imaging X-rays on board the Solar Orbiter, we investigate the evolution of hard X-ray source morphology, source volume, electron density, and thermal behavior of the flaring plasma throughout the event. The results reveal notable variations in elemental abundances between photospheric and coronal values during different flare phases. This emphasizes the significance of elemental abundance information in comprehending X-ray emissions during solar flares.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139026487","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 : 2023-12-01DOI: 10.3847/2041-8213/ad00bd
E. Mason, R. Lionello, Cooper Downs, Jon A. Linker, R. Caplan, M. DeRosa
We present in this Letter the first global comparison between traditional line-tied steady-state magnetohydrodynamic models and a new, fully time-dependent thermodynamic magnetohydrodynamic simulation of the global corona. To approximate surface magnetic field distributions and magnitudes around solar minimum, we use the Lockheed Evolving Surface-Flux Assimilation Model to obtain input maps that incorporate flux emergence and surface flows over a full solar rotation, including differential rotation and meridional flows. Each time step evolves the previous state of the plasma with a new magnetic field input boundary condition, mimicking photospheric driving on the Sun. We find that this method produces a qualitatively different corona compared to steady-state models. The magnetic energy levels are higher in the time-dependent model, and coronal holes evolve more along the following edge than they do in steady-state models. Coronal changes, as illustrated with forward-modeled emission maps, evolve on longer timescales with time-dependent driving. We discuss implications for active and quiet Sun scenarios, solar wind formation, and widely used steady-state assumptions like potential field source surface calculations.
{"title":"Time-dependent Dynamics of the Corona","authors":"E. Mason, R. Lionello, Cooper Downs, Jon A. Linker, R. Caplan, M. DeRosa","doi":"10.3847/2041-8213/ad00bd","DOIUrl":"https://doi.org/10.3847/2041-8213/ad00bd","url":null,"abstract":"We present in this Letter the first global comparison between traditional line-tied steady-state magnetohydrodynamic models and a new, fully time-dependent thermodynamic magnetohydrodynamic simulation of the global corona. To approximate surface magnetic field distributions and magnitudes around solar minimum, we use the Lockheed Evolving Surface-Flux Assimilation Model to obtain input maps that incorporate flux emergence and surface flows over a full solar rotation, including differential rotation and meridional flows. Each time step evolves the previous state of the plasma with a new magnetic field input boundary condition, mimicking photospheric driving on the Sun. We find that this method produces a qualitatively different corona compared to steady-state models. The magnetic energy levels are higher in the time-dependent model, and coronal holes evolve more along the following edge than they do in steady-state models. Coronal changes, as illustrated with forward-modeled emission maps, evolve on longer timescales with time-dependent driving. We discuss implications for active and quiet Sun scenarios, solar wind formation, and widely used steady-state assumptions like potential field source surface calculations.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138607852","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 : 2023-12-01DOI: 10.3847/2041-8213/ad0bee
K. M. Yocum, O. Wilkins, J. C. Bardwell, S. N. Milam, P. Gerakines
The ortho-to-para ratio (OPR) of formaldehyde (H2CO) has been used as a probe to estimate the formation temperature of molecules in interstellar, circumstellar, and cometary environments, relying on the assumption that nuclear spin conversion is extremely slow, preserving the OPR from molecular formation. An OPR for H2CO less than 3 corresponds to a spin temperature below 30 K and has been proposed to result from formation at low temperatures within an ice, whereas an OPR of 3 is interpreted as arising from warmer formation in the gas phase. In spite of this common assumption, there is no laboratory evidence in the literature to date in support of it. Here, in the first study of its kind for H2CO, we report rotational spectroscopy measurements of the OPR of H2CO sublimated after its formation in methanol (CH3OH) ice samples that were photolyzed by ultraviolet light at 10, 15, 20, and 40 K. None of the measured OPR values correlated with the ice formation temperature.
{"title":"Gas-phase Ortho-to-para Ratio of Formaldehyde Formed at Low Temperatures in Laboratory Ices","authors":"K. M. Yocum, O. Wilkins, J. C. Bardwell, S. N. Milam, P. Gerakines","doi":"10.3847/2041-8213/ad0bee","DOIUrl":"https://doi.org/10.3847/2041-8213/ad0bee","url":null,"abstract":"The ortho-to-para ratio (OPR) of formaldehyde (H2CO) has been used as a probe to estimate the formation temperature of molecules in interstellar, circumstellar, and cometary environments, relying on the assumption that nuclear spin conversion is extremely slow, preserving the OPR from molecular formation. An OPR for H2CO less than 3 corresponds to a spin temperature below 30 K and has been proposed to result from formation at low temperatures within an ice, whereas an OPR of 3 is interpreted as arising from warmer formation in the gas phase. In spite of this common assumption, there is no laboratory evidence in the literature to date in support of it. Here, in the first study of its kind for H2CO, we report rotational spectroscopy measurements of the OPR of H2CO sublimated after its formation in methanol (CH3OH) ice samples that were photolyzed by ultraviolet light at 10, 15, 20, and 40 K. None of the measured OPR values correlated with the ice formation temperature.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138614554","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 : 2023-09-01DOI: 10.3847/2041-8213/acf133
Kenneth Carrell, Ronald Wilhelm, F. Olsen, Andrew Tom, Garath Vetters, Anna McElhannon
Boo” (2021, ApJL, 916, L12) Kenneth Carrell , Ronald Wilhelm , Faith Olsen, Andrew Tom, Garath Vetters, and Anna McElhannon 1 Physics & Geosciences, Angelo State University, 2601 W. Avenue N, San Angelo, TX 76909, USA 2 Department of Physics & Astronomy, University of Kentucky, 177 Chem.-Phys. Building, 505 Rose Street, Lexington, KY 40506, USA kenneth.carrell@angelo.edu Received 2023 August 16; published 2023 September 5
Kenneth Carrell, Ronald Wilhelm, Faith Olsen, Andrew Tom, Garath vetter, and Anna McElhannon .(2021, 4月1日，916,L12)2肯塔基大学物理与天文学系，177，化学系-物理系;美国肯塔基州列克星敦市玫瑰街505号楼40506 kenneth.carrell@angelo.edu收到2023年8月16日;2023年9月5日出版
{"title":"Erratum: “The Changing Lightcurve of the Double-mode RR Lyrae Variable Star V338 Boo” (2021, ApJL, 916, L12)","authors":"Kenneth Carrell, Ronald Wilhelm, F. Olsen, Andrew Tom, Garath Vetters, Anna McElhannon","doi":"10.3847/2041-8213/acf133","DOIUrl":"https://doi.org/10.3847/2041-8213/acf133","url":null,"abstract":"Boo” (2021, ApJL, 916, L12) Kenneth Carrell , Ronald Wilhelm , Faith Olsen, Andrew Tom, Garath Vetters, and Anna McElhannon 1 Physics & Geosciences, Angelo State University, 2601 W. Avenue N, San Angelo, TX 76909, USA 2 Department of Physics & Astronomy, University of Kentucky, 177 Chem.-Phys. Building, 505 Rose Street, Lexington, KY 40506, USA kenneth.carrell@angelo.edu Received 2023 August 16; published 2023 September 5","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124757393","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 : 2023-09-01DOI: 10.3847/2041-8213/acefd1
Y. Marrocchi, M. Piralla, F. Tissot
The recent advent of nontraditional isotopic systems has revealed that meteorites display a fundamental isotopic dichotomy between noncarbonaceous (NC) and carbonaceous (C) groups, which represent material from the inner and outer solar system, respectively. On the basis of iron isotope anomalies, this view has recently been challenged in favor of a circumsolar disk structured into three distinct reservoirs (the so-called isotopic trichotomy). In this scenario, the CI chondrites—a rare type of carbonaceous chondrites with chemical composition similar to that of the Sun’s photosphere—would sample a distinct source region than other carbonaceous chondrites, located beyond Saturn’s orbit. Here, we report a model based on the available data for both mass-dependent fractionation of Te stable isotopes and mass-independent Fe nucleosynthetic anomalies. On the basis of the Te–Fe isotopic correlation defined by all carbonaceous chondrites including CIs, we show that the NC-CC dichotomy extends to Fe isotopes. Our finding thus supports (i) the existence of only two reservoirs in the early solar system and (ii) the ubiquitous presence of CI-like dust throughout the carbonaceous reservoir. Our approach also reveals that the carrier phase of 54Fe anomalies corresponds to Fe–Ni metal beads mostly located within chondrules. Finally, we propose that the CC chondrule component records a constant mix of refractory inclusions and NC-like dust.
{"title":"Iron Isotope Constraints on the Structure of the Early Solar System","authors":"Y. Marrocchi, M. Piralla, F. Tissot","doi":"10.3847/2041-8213/acefd1","DOIUrl":"https://doi.org/10.3847/2041-8213/acefd1","url":null,"abstract":"The recent advent of nontraditional isotopic systems has revealed that meteorites display a fundamental isotopic dichotomy between noncarbonaceous (NC) and carbonaceous (C) groups, which represent material from the inner and outer solar system, respectively. On the basis of iron isotope anomalies, this view has recently been challenged in favor of a circumsolar disk structured into three distinct reservoirs (the so-called isotopic trichotomy). In this scenario, the CI chondrites—a rare type of carbonaceous chondrites with chemical composition similar to that of the Sun’s photosphere—would sample a distinct source region than other carbonaceous chondrites, located beyond Saturn’s orbit. Here, we report a model based on the available data for both mass-dependent fractionation of Te stable isotopes and mass-independent Fe nucleosynthetic anomalies. On the basis of the Te–Fe isotopic correlation defined by all carbonaceous chondrites including CIs, we show that the NC-CC dichotomy extends to Fe isotopes. Our finding thus supports (i) the existence of only two reservoirs in the early solar system and (ii) the ubiquitous presence of CI-like dust throughout the carbonaceous reservoir. Our approach also reveals that the carrier phase of 54Fe anomalies corresponds to Fe–Ni metal beads mostly located within chondrules. Finally, we propose that the CC chondrule component records a constant mix of refractory inclusions and NC-like dust.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129520382","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 : 2023-09-01DOI: 10.3847/2041-8213/acf21c
S. Alnussirat, R. Livi, D. E. Larson, A. Rahmati, P. Whittlesey, O. Romeo, S. Badman, Milo Buitrago-Casas, Juan Carlos, Martínez Oliveros, M. Pulupa, S. Bale, J. Huang, J. Verniero, N. R. fi, D. Mitchell, D. J. McComas, Matt Hill, Christina Cohen
During Encounter 11, Parker Solar Probe observed a low-energy dispersive ions event of solar origin. The event was observed in the SPAN-I and IS⊙IS EPI-Lo sensors. The event started at a few MeV energy in the EPI-Lo sensor and progressed down in energy to ≈1 keV and merged with the bulk of the solar wind. This event is substantially different from typical solar energetic particles because the energetic population shows a distinct peak in the energy spectrum that descends in energy (not a power-law tail). In this Letter, we explore this event’s nature, origin, and characteristics.
{"title":"Dispersive Suprathermal Ion Events Observed by the Parker Solar Probe Mission","authors":"S. Alnussirat, R. Livi, D. E. Larson, A. Rahmati, P. Whittlesey, O. Romeo, S. Badman, Milo Buitrago-Casas, Juan Carlos, Martínez Oliveros, M. Pulupa, S. Bale, J. Huang, J. Verniero, N. R. fi, D. Mitchell, D. J. McComas, Matt Hill, Christina Cohen","doi":"10.3847/2041-8213/acf21c","DOIUrl":"https://doi.org/10.3847/2041-8213/acf21c","url":null,"abstract":"During Encounter 11, Parker Solar Probe observed a low-energy dispersive ions event of solar origin. The event was observed in the SPAN-I and IS⊙IS EPI-Lo sensors. The event started at a few MeV energy in the EPI-Lo sensor and progressed down in energy to ≈1 keV and merged with the bulk of the solar wind. This event is substantially different from typical solar energetic particles because the energetic population shows a distinct peak in the energy spectrum that descends in energy (not a power-law tail). In this Letter, we explore this event’s nature, origin, and characteristics.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132660938","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 : 2023-09-01DOI: 10.3847/2041-8213/aced9b
A. Galli, I. Baliukin, M. Kornbleuth, M. Opher, S. Fuselier, Justyna M. Sokół, K. Dialynas, M. Dayeh, V. Izmodenov, J. Richardson
Measuring energetic neutral atoms (ENAs) allows for the remote observation of ion populations from the frontiers of our heliosphere. In this study, we compare the ENAs observed with the IBEX-Lo instrument onboard the Interstellar Boundary Explorer with ENA predictions from two heliosphere models. In contrast to previous studies, this paper presents model-data comparisons for the energy range 50 eV–2 keV over one full solar cycle not only in the upwind direction (Voyager 1 and Voyager 2 sky directions), but also for the north pole, south pole, port tail lobe, and downwind directions. The two heliosphere models produce the same basic result: there is a large gap (1 to 2 orders of magnitude in ENA intensity at 100 eV) between ENA data and model predictions between 100 and 500 eV for all sky directions. The reason for this gap is not understood yet. While some explanations are plausible and will be investigated in future studies, other explanations are excluded.
{"title":"The Discrepancy between Observed and Predicted Heliospheric Energetic Neutral Atoms below Solar Wind Energy","authors":"A. Galli, I. Baliukin, M. Kornbleuth, M. Opher, S. Fuselier, Justyna M. Sokół, K. Dialynas, M. Dayeh, V. Izmodenov, J. Richardson","doi":"10.3847/2041-8213/aced9b","DOIUrl":"https://doi.org/10.3847/2041-8213/aced9b","url":null,"abstract":"Measuring energetic neutral atoms (ENAs) allows for the remote observation of ion populations from the frontiers of our heliosphere. In this study, we compare the ENAs observed with the IBEX-Lo instrument onboard the Interstellar Boundary Explorer with ENA predictions from two heliosphere models. In contrast to previous studies, this paper presents model-data comparisons for the energy range 50 eV–2 keV over one full solar cycle not only in the upwind direction (Voyager 1 and Voyager 2 sky directions), but also for the north pole, south pole, port tail lobe, and downwind directions. The two heliosphere models produce the same basic result: there is a large gap (1 to 2 orders of magnitude in ENA intensity at 100 eV) between ENA data and model predictions between 100 and 500 eV for all sky directions. The reason for this gap is not understood yet. While some explanations are plausible and will be investigated in future studies, other explanations are excluded.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132783746","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 : 2023-08-31DOI: 10.3847/2041-8213/acf0c6
P. Levens, A. Norton, M. Linton, K. Knizhnik, Y. Liu
We measure current helicity (H r c ) as well as proxies for twist (α r ) and writhe (W) in the isolated magnetic knots of three delta (δ)-sunspots and report that the observations are consistent with a kink instability acting on a highly twisted flux tube. δ-spots are active regions (ARs) in which positive and negative umbrae share a penumbra. We identify and isolate “magnetic knots,” i.e., opposite polarity umbrae that are in close proximity and forming the δ-configuration, in ARs NOAA 11158, 11267, and 11476 as observed with data from the Solar Dynamic Observatory Helioseismic and Magnetic Imager. We find that H r c , α r , and W have the same sign for each magnetic knot, as predicted in simulations of a kink instability acting on highly twisted flux tubes. The deformed flux tube causing the δ-formation, the magnetic knot, is only a portion of the entire AR and demonstrates the potential for the kink instability to act on a smaller spatial scale within the AR. Each magnetic footpoint contains a single sign of the radial current, J r , which suggests that we are observing the core of the flux rope without return currents. As a counterexample, we analyze one β-spot that shows H r c and α r have the opposite signs of W. While our observations support the formation mechanism of the magnetic knots in δ-spots being the kink instability, a much larger sample is needed to determine confidently the prevalence of the kink instability as the cause of flux tube deformation.
我们在三个δ (δ)-太阳黑子的孤立磁节中测量了电流的螺旋度(H r c)以及扭曲(α r)和扭曲(W)的代用物，并报告了观测结果与高扭曲磁管上的扭结不稳定性相一致。δ斑是正负影共用半影的活动区域。我们识别并分离了“磁结”，即在ARs NOAA 11158, 11267和11476中，用太阳动力观测站日震和磁成像仪的数据观测到的相反极性的薄膜，它们靠近并形成了δ配置。我们发现H r c， α r和W对于每个磁结具有相同的符号，正如在高扭流管上的扭结不稳定性模拟中所预测的那样。引起δ-形成的变形磁通管，即磁结，只是整个磁通圈的一部分，并表明了磁通圈不稳定性在更小的空间尺度上发挥作用的可能性。每个磁脚点包含一个径向电流的符号，J r，这表明我们正在观察没有回流电流的磁通圈的核心。作为一个反例，我们分析了一个β点，表明H r c和α r具有与w相反的符号。虽然我们的观察支持δ点中磁结的形成机制是扭结不稳定性，但需要更大的样本来确定扭结不稳定性是磁管变形的原因。
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Pub Date : 2023-08-31DOI: 10.3847/2041-8213/aceefe
Jianghao 江豪 Huyan 呼延, V. Kulkarni, Suraj Poudel, N. Tejos, C. Péroux, S. López
Abundances of chemical elements in the interstellar and circumgalactic media of high-redshift galaxies offer important constraints on the nucleosynthesis by early generations of stars. Damped Lyα absorbers (DLAs) in spectra of high-redshift background quasars are excellent sites for obtaining robust measurements of element abundances in distant galaxies. Past studies of DLAs at redshifts z > 4 have measured abundances of ≲0.01 solar. Here we report the discovery of a DLA at z = 4.7372 with an exceptionally high degree of chemical enrichment. We estimate the H i column density in this absorber to be log (N H I/cm−2) = 20.48 ± 0.15. Our analysis shows unusually high abundances of carbon and oxygen ([C/H] = 0.88 ± 0.17, [O/H] = 0.71 ± 0.16). Such a high level of enrichment a mere 1.2 Gyr after the Big Bang is surprising because of insufficient time for the required amount of star formation. To our knowledge, this is the first supersolar absorber found at z > 4.5. We find the abundances of Si and Mg to be [Si/H] = −0.56−0.35+0.40 and [Mg/H] = 0.59−0.50+0.27 , confirming the metal-rich nature of this absorber. By contrast, Fe shows a much lower abundance ([Fe/H] = −1.53−0.15+0.15 ). We discuss implications of our results for galactic chemical evolution models. The metallicity of this absorber is higher than that of any other known DLA and is >2 orders of magnitude above predictions of chemical evolution models and the N H I-weighted mean metallicity from previous studies at z > 4.5. The relative abundances (e.g., [O/Fe] = 2.29 ± 0.05, [C/Fe] = 2.46 ± 0.08) are also highly unusual compared to predictions for enrichment by early stars.
{"title":"Discovery of Super-enriched Gas ∼1 Gyr after the Big Bang","authors":"Jianghao 江豪 Huyan 呼延, V. Kulkarni, Suraj Poudel, N. Tejos, C. Péroux, S. López","doi":"10.3847/2041-8213/aceefe","DOIUrl":"https://doi.org/10.3847/2041-8213/aceefe","url":null,"abstract":"Abundances of chemical elements in the interstellar and circumgalactic media of high-redshift galaxies offer important constraints on the nucleosynthesis by early generations of stars. Damped Lyα absorbers (DLAs) in spectra of high-redshift background quasars are excellent sites for obtaining robust measurements of element abundances in distant galaxies. Past studies of DLAs at redshifts z > 4 have measured abundances of ≲0.01 solar. Here we report the discovery of a DLA at z = 4.7372 with an exceptionally high degree of chemical enrichment. We estimate the H i column density in this absorber to be log (N H I/cm−2) = 20.48 ± 0.15. Our analysis shows unusually high abundances of carbon and oxygen ([C/H] = 0.88 ± 0.17, [O/H] = 0.71 ± 0.16). Such a high level of enrichment a mere 1.2 Gyr after the Big Bang is surprising because of insufficient time for the required amount of star formation. To our knowledge, this is the first supersolar absorber found at z > 4.5. We find the abundances of Si and Mg to be [Si/H] = −0.56−0.35+0.40 and [Mg/H] = 0.59−0.50+0.27 , confirming the metal-rich nature of this absorber. By contrast, Fe shows a much lower abundance ([Fe/H] = −1.53−0.15+0.15 ). We discuss implications of our results for galactic chemical evolution models. The metallicity of this absorber is higher than that of any other known DLA and is >2 orders of magnitude above predictions of chemical evolution models and the N H I-weighted mean metallicity from previous studies at z > 4.5. The relative abundances (e.g., [O/Fe] = 2.29 ± 0.05, [C/Fe] = 2.46 ± 0.08) are also highly unusual compared to predictions for enrichment by early stars.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131182358","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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