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Kenneth H Schatten - One of the best experts on this subject based on the ideXlab platform.

  • fair space weather for Solar cycle 24
    Geophysical Research Letters, 2005
    Co-Authors: Kenneth H Schatten
    Abstract:

    [1] We discuss the polar field precursor method of Solar activity forecasting, first developed 3 decades ago. Using this method the peak amplitude of the next Solar cycle (24) is estimated at 124 ± 30 in terms of smoothed F10.7 Radio Flux and 80 ± 30 in terms of smoothed international or Zurich Sunspot number (Ri or Rz). This may be regarded as a “fair space weather” long term forecast. To support this prediction, direct measurements are obtained from the Wilcox and Mount Wilson Solar Observatories. Additionally, coronal features do not show the characteristics of well-formed polar coronal holes associated with typical Solar minima, but rather resemble stunted polar field levels. The question is raised: why have the Sun's polar fields not strengthened comparably in the 2000–2005 time period, as in the previous few decades? The dramatic field changes seen suggest the importance of field motions associated with photospheric (e.g. meridional) flows for the Sun's dynamo. Flows may also play a role in active region development, e.g., it is possible that field magnification occurs through surface processes, namely active region field strengthening (sunspot growth) through the influx of like photospheric magnetic regions, and even the influx of ERs (ephemeral regions), wherein the same sign (like) flux could be differentially drawn into spots of that sign, leading to field growth.

Uitenbroek H. - One of the best experts on this subject based on the ideXlab platform.

  • Machine learning initialization to accelerate Stokes profile inversions
    'EDP Sciences', 2021
    Co-Authors: Gafeira Ricardo, Quintero Noda C., Ruiz Cobo B., Orozco Suárez David, Uitenbroek H.
    Abstract:

    Context. At present, an exponential growth in scientific data from current and upcoming Solar Observatories is expected. Most of the data consist of high spatial and temporal resolution cubes of Stokes profiles taken in both local thermodynamic equilibrium (LTE) and non-LTE spectral lines. The analysis of such Solar observations requires complex inversion codes. Hence, it is necessary to develop new tools to boost the speed and efficiency of inversions and reduce computation times and costs. Aims. In this work we discuss the application of convolutional neural networks (CNNs) as a tool to advantageously initialize Stokes profile inversions. Methods. To demonstrate the usefulness of CNNs, we concentrate in this paper on the inversion of LTE Stokes profiles. We use observations taken with the spectropolarimeter on board the Hinode spacecraft as a test bench mark. First, we carefully analyse the data with the SIR inversion code using a given initial atmospheric model. The code provides a set of atmospheric models that reproduce the observations well. These models are then used to train a CNN. Afterwards, the same data are again inverted with SIR but using the trained CNN to provide the initial guess atmospheric models for SIR. Results. The CNNs allow us to significantly reduce the number of inversion cycles when used to compute initial guess model atmospheres ('assisted inversions'), therefore decreasing the computational time for LTE inversions by a factor of two to four. CNNs alone are much faster than assisted inversions, but the latter are more robust and accurate. CNNs also help to automatically cluster pixels with similar physical properties, allowing the association with different Solar features on the Solar surface, which is useful when inverting huge datasets where completely different regimes are present. The advantages and limitations of machine learning techniques for estimating optimum initial atmospheric models for spectral line inversions are discussed. Finally, we describe a python wrapper for the SIR and DeSIRe codes that allows for the easy setup of parallel inversions. The tool implements the assisted inversion method described in this paper. The parallel wrapper can also be used to synthesize Stokes profiles with the RH code. Conclusions. The assisted inversions can speed up the inversion process, but the efficiency and accuracy of the inversion results depend strongly on the Solar scene and the data used for the CNN training. This method (assisted inversions) will not obviate the need for analysing individual events with the utmost care but will provide Solar scientists with a much better opportunity to sample large amounts of inverted data, which will undoubtedly broaden the physical discovery space. © ESO 2021.All the network training and inference has been done using Keras with Tensorflow back-end. All the plots were done using matplotlib python package. This work has been supported by the Spanish Ministry of Economy and Competitiveness through projects ESP-201677548-C5-1-R and by Spanish Science Ministry "Centro de Excelencia Severo Ochoa" Program under grant SEV-2017-0709 and project RTI2018-096886-BC51. D. O. S. also acknowledges financial support through the Ramon y Cajal fellowship. CQN acknowledges the Research Council of Norway through its Centres of Excellence scheme, project number 262622. This work was supported by Fundacao para a Cioncia e a Tecnologia (FCT) through the research grants [UID/FIS/04434/2019,] UIDB/04434/2020 and UIDP/04434/2020.Peer reviewe

  • Study of the polarization produced by the Zeeman effect in the Solar MgI b lines
    'Oxford University Press (OUP)', 2020
    Co-Authors: Noda Q.c., Katsukawa Y., Shimizu T., Ruiz Cobo B., Kubo M., Oba T., Uitenbroek H., Carlsson M., Orozco Suárez David, Kawabata Y.
    Abstract:

    The next generation of Solar Observatories aim to understand the magnetism of the Solar chromosphere. Therefore, it is crucial to understand the polarimetric signatures of chromospheric spectral lines. For this purpose, we here examine the suitability of the three Fraunhofer MgI b1, b2, and b4 lines at 5183.6, 5172.7, and 5167.3 Å, respectively. We start by describing a simplified atomic model of only six levels and three line transitions for computing the atomic populations of the 3p-4s (multiplet number 2) levels involved in the Mg I b line transitions assuming non-local thermodynamic conditions and considering only the Zeeman effect using the field-free approximation. We test this simplified atom against more complex ones finding that, although there are differences in the computed profiles, they are small compared with the advantages provided by the simple atom in terms of speed and robustness. After comparing the three MgI lines, we conclude that the most capable one is the b2 line as b1 forms at similar heights and always shows weaker polarization signals, while b4 is severely blended with photospheric lines. We also compare Mg I b2 with the KI D1 and Ca II 8542 Å lines finding that the former is sensitive to the atmospheric parameters at heights that are in between those covered by the latter two lines. This makes MgI b2 an excellent candidate for future multiline observations that aim to seamlessly infer the thermal and magnetic properties of different features in the lower Solar atmosphere. © 2018 The Author(s).We appreciate the help of the anonymous referee that, during the revision process, provided us comments and suggestions that allowed improving the manuscript. CQN acknowledges the support of the ISAS/JAXA International Top Young Fellowship and the JSPS KAKENHI grant number 18K13596. The SUNRISE-3 project is supported in Japan by the funding from ISAS/JAXA for the smallscale program for novel Solar observations and the JSPS KAKENHI grant numbers 18H03723 and 18H05234. This research was supported by the Research Council of Norway through its Centres of Excellence scheme, project number 262622. This work has also been supported by Spanish Ministry of Economy and Competitiveness through the project ESP-2016-77548-C5-1-R. DOS also acknowledges financial support through the Ramon y Cajal fellowships

  • Study of the polarization produced by the Zeeman effect in the Solar Mg I b lines
    'Oxford University Press (OUP)', 2018
    Co-Authors: Noda C. Quintero, Katsukawa Y., Shimizu T., Kubo M., Oba T., Uitenbroek H., Carlsson M., Suárez D. Orozco, Cobo B. Ruiz, Kawabata Y.
    Abstract:

    The next generation of Solar Observatories aim to understand the magnetism of the Solar chromosphere. Therefore, it is crucial to understand the polarimetric signatures of chromospheric spectral lines. For this purpose, we here examine the suitability of the three Fraunhofer Mg I b1, b2, and b4 lines at 5183.6, 5172.7, and 5167.3 A, respectively. We start by describing a simplified atomic model of only 6 levels and 3 line transitions for computing the atomic populations of the 3p-4s (multiplet number 2) levels involved in the Mg I b line transitions assuming non-local thermodynamic conditions and considering only the Zeeman effect using the field-free approximation. We test this simplified atom against more complex ones finding that, although there are differences in the computed profiles, they are small compared with the advantages provided by the simple atom in terms of speed and robustness. After comparing the three Mg I lines, we conclude that the most capable one is the b2 line as b1 forms at similar heights and always show weaker polarization signals while b4 is severely blended with photospheric lines. We also compare Mg I b2 with the K I D1 and Ca II 8542 A lines finding that the former is sensitive to the atmospheric parameters at heights that are in between those covered by the latter two lines. This makes Mg I b2 an excellent candidate for future multi-line observations that aim to seamlessly infer the thermal and magnetic properties of different features in the lower Solar atmosphere.Comment: 14 pages, 11 figures, and 5 table

R. Seguin - One of the best experts on this subject based on the ideXlab platform.

  • The Heliophysics Coverage Registry: An integrated metadata system for coordinated, multi-mission Solar Observatories
    arXiv: Instrumentation and Methods for Astrophysics, 2018
    Co-Authors: Neal E. Hurlburt, Ryan Timmons, R. Seguin
    Abstract:

    Modern studies of the Sun involve coordinated observations collected from a collage of instruments on the ground and in orbit. Each instrument has its own constraints, such as field of view, duty cycle, and scheduling and commanding windows, that must both be coordinated during operations and be discoverable for analyses of the resulting data. Details on the observed Solar features, i.e. sunspots or filaments, and Solar events, i.e. flares or coronal mass ejections, are also incorporated to help guide data discovery and data analysis pipelines. The Heliophysics Coverage Registry (HCR) provides a standards-based system for collecting and presenting observations collected by distributed, ground and space based Solar Observatories which form an integrated Heliophysics system. The HCR currently supports all instruments on the Interface Region Imaging Spectrograph (IRIS) and Hinode missions as well as associated ground-based Observatories. Here we present an overview of the HCR along with details on how it provides scientists with tools to make flexible searches on observation metadata in coordination with searches of Solar features and events.

Seguin Ralph - One of the best experts on this subject based on the ideXlab platform.

  • The Heliophysics Coverage Registry: An integrated metadata system for coordinated, multi-mission Solar Observatories
    2018
    Co-Authors: Hurlburt Neal, Timmons Ryan, Seguin Ralph
    Abstract:

    Modern studies of the Sun involve coordinated observations collected from a collage of instruments on the ground and in orbit. Each instrument has its own constraints, such as field of view, duty cycle, and scheduling and commanding windows, that must both be coordinated during operations and be discoverable for analyses of the resulting data. Details on the observed Solar features, i.e. sunspots or filaments, and Solar events, i.e. flares or coronal mass ejections, are also incorporated to help guide data discovery and data analysis pipelines. The Heliophysics Coverage Registry (HCR) provides a standards-based system for collecting and presenting observations collected by distributed, ground and space based Solar Observatories which form an integrated Heliophysics system. The HCR currently supports all instruments on the Interface Region Imaging Spectrograph (IRIS) and Hinode missions as well as associated ground-based Observatories. Here we present an overview of the HCR along with details on how it provides scientists with tools to make flexible searches on observation metadata in coordination with searches of Solar features and events.Comment: in ADASS XXVII, Santiago, Chile, 4 pages, 3 figure

Kawabata Y. - One of the best experts on this subject based on the ideXlab platform.

  • Study of the polarization produced by the Zeeman effect in the Solar MgI b lines
    'Oxford University Press (OUP)', 2020
    Co-Authors: Noda Q.c., Katsukawa Y., Shimizu T., Ruiz Cobo B., Kubo M., Oba T., Uitenbroek H., Carlsson M., Orozco Suárez David, Kawabata Y.
    Abstract:

    The next generation of Solar Observatories aim to understand the magnetism of the Solar chromosphere. Therefore, it is crucial to understand the polarimetric signatures of chromospheric spectral lines. For this purpose, we here examine the suitability of the three Fraunhofer MgI b1, b2, and b4 lines at 5183.6, 5172.7, and 5167.3 Å, respectively. We start by describing a simplified atomic model of only six levels and three line transitions for computing the atomic populations of the 3p-4s (multiplet number 2) levels involved in the Mg I b line transitions assuming non-local thermodynamic conditions and considering only the Zeeman effect using the field-free approximation. We test this simplified atom against more complex ones finding that, although there are differences in the computed profiles, they are small compared with the advantages provided by the simple atom in terms of speed and robustness. After comparing the three MgI lines, we conclude that the most capable one is the b2 line as b1 forms at similar heights and always shows weaker polarization signals, while b4 is severely blended with photospheric lines. We also compare Mg I b2 with the KI D1 and Ca II 8542 Å lines finding that the former is sensitive to the atmospheric parameters at heights that are in between those covered by the latter two lines. This makes MgI b2 an excellent candidate for future multiline observations that aim to seamlessly infer the thermal and magnetic properties of different features in the lower Solar atmosphere. © 2018 The Author(s).We appreciate the help of the anonymous referee that, during the revision process, provided us comments and suggestions that allowed improving the manuscript. CQN acknowledges the support of the ISAS/JAXA International Top Young Fellowship and the JSPS KAKENHI grant number 18K13596. The SUNRISE-3 project is supported in Japan by the funding from ISAS/JAXA for the smallscale program for novel Solar observations and the JSPS KAKENHI grant numbers 18H03723 and 18H05234. This research was supported by the Research Council of Norway through its Centres of Excellence scheme, project number 262622. This work has also been supported by Spanish Ministry of Economy and Competitiveness through the project ESP-2016-77548-C5-1-R. DOS also acknowledges financial support through the Ramon y Cajal fellowships

  • Study of the polarization produced by the Zeeman effect in the Solar Mg I b lines
    'Oxford University Press (OUP)', 2018
    Co-Authors: Quintero Noda C., Uitenbroek Han, Carlsson Mats, Orozco Suarez D., Katsukawa Y., Shimizu T., Ruiz Cobo B., Kubo M., Oba T., Kawabata Y.
    Abstract:

    The next generation of Solar Observatories aim to understand the magnetism of the Solar chromosphere. Therefore, it is crucial to understand the polarimetric signatures of chromospheric spectral lines. For this purpose, we here examine the suitability of the three Fraunhofer Mg I b1, b2, and b4 lines at 5183.6, 5172.7, and 5167.3 Å, respectively. We start by describing a simplified atomic model of only six levels and three line transitions for computing the atomic populations of the 3p-4s (multiplet number 2) levels involved in the Mg I b line transitions assuming non-local thermodynamic conditions and considering only the Zeeman effect using the field-free approximation. We test this simplified atom against more complex ones finding that, although there are differences in the computed profiles, they are small compared with the advantages provided by the simple atom in terms of speed and robustness. After comparing the three Mg I lines, we conclude that the most capable one is the b2 line as b1 forms at similar heights and always shows weaker polarization signals, while b4 is severely blended with photospheric lines. We also compare Mg I b2 with the K I D1 and Ca II 8542 Å lines finding that the former is sensitive to the atmospheric parameters at heights that are in between those covered by the latter two lines. This makes Mg I b2 an excellent candidate for future multiline observations that aim to seamlessly infer the thermal and magnetic properties of different features in the lower Solar atmosphere

  • Study of the polarization produced by the Zeeman effect in the Solar Mg I b lines
    'Oxford University Press (OUP)', 2018
    Co-Authors: Noda C. Quintero, Katsukawa Y., Shimizu T., Kubo M., Oba T., Uitenbroek H., Carlsson M., Suárez D. Orozco, Cobo B. Ruiz, Kawabata Y.
    Abstract:

    The next generation of Solar Observatories aim to understand the magnetism of the Solar chromosphere. Therefore, it is crucial to understand the polarimetric signatures of chromospheric spectral lines. For this purpose, we here examine the suitability of the three Fraunhofer Mg I b1, b2, and b4 lines at 5183.6, 5172.7, and 5167.3 A, respectively. We start by describing a simplified atomic model of only 6 levels and 3 line transitions for computing the atomic populations of the 3p-4s (multiplet number 2) levels involved in the Mg I b line transitions assuming non-local thermodynamic conditions and considering only the Zeeman effect using the field-free approximation. We test this simplified atom against more complex ones finding that, although there are differences in the computed profiles, they are small compared with the advantages provided by the simple atom in terms of speed and robustness. After comparing the three Mg I lines, we conclude that the most capable one is the b2 line as b1 forms at similar heights and always show weaker polarization signals while b4 is severely blended with photospheric lines. We also compare Mg I b2 with the K I D1 and Ca II 8542 A lines finding that the former is sensitive to the atmospheric parameters at heights that are in between those covered by the latter two lines. This makes Mg I b2 an excellent candidate for future multi-line observations that aim to seamlessly infer the thermal and magnetic properties of different features in the lower Solar atmosphere.Comment: 14 pages, 11 figures, and 5 table