1,721,065 research outputs found
Study of cosmic-ray variability using ground-based and space-borne data
Get PDFAbstractCosmic rays (CRs) are charged particles with energies above 1 MeV, accelerated in sources outside of the Earth’s magnetosphere. The variability of their fluxes, caused by solar modulation and solar eruptive events, is an important field of astroparticle physics, and represents the main focus of this study.The main instruments to study the cosmic-ray variability are neutron monitors (NMs), located at different locations around the globe, and space-borne experiments. A NM is an integral detector so that its response is integrally related to CR fluxes via NM response function. Space-borne experiments have particle detectors that allow to directly register different CR particles.In this work both data from NMs and space-borne experiments are combined to study the variability of CRs. In particular, the reconstruction of the solar modulation potential ϕ applying the simplified force-field (FF) model of the solar modulation of cosmic rays was performed using in-situ cosmic-ray fluxes measured by both the PAMELA and AMS-02 experiments together with NM data for the period from 2006 to 2017. Validation of the FF model for periods of different solar activity levels was further performed, and it was found that such an approximation performs better during solar minima, but disagrees with the observations of up to ≈ 10% during solar maximum. This makes the FF model approach not well suited for detailed studies of the solar modulation processes. At the same time, this precision is adequate to quantify the condition of the heliospheric modulation and to study its long-term variability.To study solar energetic particle (SEP) fluxes using NM data, a new method of “effective rigidity” was proposed, allowing to reconstruct high-energy SEP integral fluences recorded during ground level enhancement (GLE) events. A significant advantage of this novel method is that it is a non parametric one and thus the spectral shape of the SEP fluence can be deduced directly from the reconstructed data. Reconstructions of the SEP fluences for two recent GLEs, #69 and #71, using this newly developed method, yield a very good agreement with the laborious method of the full fluence reconstruction using NM data, and with PAMELA measurements (for GLE #71), but disagree with earlier simplified estimations based on NM data.The NM data analysis was performed using the NM yield function by Mishev et al. [2013], which was validated using the AMS-02 data for protons and helium for a time period between 2011 to 2017 and showed the best performance among other modern yield functions.Improved knowledge of the CR variability is crucially important for e.g. CR-induced atmospheric effects, including the production of cosmogenic isotopes.Original papersOriginal papers are not included in the electronic version of the dissertation.Koldobskiy, S. A., Kovaltsov, G. A., & Usoskin, I. G. (2018). A Solar Cycle of Cosmic Ray Fluxes for 2006-2014: Comparison between PAMELA and Neutron Monitors. Journal of Geophysical Research: Space Physics, 123(6), 4479–4487. https://doi.org/10.1029/2018ja025516Self-archived versionKoldobskiy, S. A., Kovaltsov, G. A., & Usoskin, I. G. (2018). Effective Rigidity of a Polar Neutron Monitor for Recording Ground-Level Enhancements. Solar Physics, 293(7), 110. https://doi.org/10.1007/s11207-018-1326-1Self-archived versionKoldobskiy, S. A., Bindi, V., Corti, C., Kovaltsov, G. A., & Usoskin, I. G. (2019). Validation of the Neutron Monitor Yield Function Using Data From AMS-02 Experiment, 2011–2017. Journal of Geophysical Research: Space Physics, 124(4), 2367-2379. https://doi.org/10.1029/2018ja026340Self-archived versionKoldobskiy, S. A., Kovaltsov, G. A., Mishev, A. L., & Usoskin, I. G. (2019). New Method of Assessment of the Integral Fluence of Solar Energetic (> 1 GV Rigidity) Particles from Neutron Monitor Data. Solar Physics, 294(7). https://doi.org/10.1007/s11207-019-1485-8Self-archived versionOsajulkaisutOsajulkaisut eivät sisälly väitöskirjan elektroniseen versioon.Koldobskiy, S. A., Kovaltsov, G. A., & Usoskin, I. G. (2018). A Solar Cycle of Cosmic Ray Fluxes for 2006-2014: Comparison between PAMELA and Neutron Monitors. Journal of Geophysical Research: Space Physics, 123(6), 4479–4487. https://doi.org/10.1029/2018ja025516Rinnakkaistallennettu versioKoldobskiy, S. A., Kovaltsov, G. A., & Usoskin, I. G. (2018). Effective Rigidity of a Polar Neutron Monitor for Recording Ground-Level Enhancements. Solar Physics, 293(7), 110. https://doi.org/10.1007/s11207-018-1326-1Rinnakkaistallennettu versioKoldobskiy, S. A., Bindi, V., Corti, C., Kovaltsov, G. A., & Usoskin, I. G. (2019). Validation of the Neutron Monitor Yield Function Using Data From AMS-02 Experiment, 2011–2017. Journal of Geophysical Research: Space Physics, 124(4), 2367-2379. https://doi.org/10.1029/2018ja026340Rinnakkaistallennettu versioKoldobskiy, S. A., Kovaltsov, G. A., Mishev, A. L., & Usoskin, I. G. (2019). New Method of Assessment of the Integral Fluence of Solar Energetic (> 1 GV Rigidity) Particles from Neutron Monitor Data. Solar Physics, 294(7). https://doi.org/10.1007/s11207-019-1485-8Rinnakkaistallennettu versioAcademic dissertation to be presented, with the assent of the Graduate School of the University of Oulu, for public discussion in the Auditorium L2, Linnanmaa, on November 27, 2020, at 10 o’clock noon.Abstract
Cosmic rays (CRs) are charged particles with energies above 1 MeV, accelerated in sources outside of the Earth’s magnetosphere. The variability of their fluxes, caused by solar modulation and solar eruptive events, is an important field of astroparticle physics, and represents the main focus of this study.
The main instruments to study the cosmic-ray variability are neutron monitors (NMs), located at different locations around the globe, and space-borne experiments. A NM is an integral detector so that its response is integrally related to CR fluxes via NM response function. Space-borne experiments have particle detectors that allow to directly register different CR particles.
In this work both data from NMs and space-borne experiments are combined to study the variability of CRs. In particular, the reconstruction of the solar modulation potential ϕ applying the simplified force-field (FF) model of the solar modulation of cosmic rays was performed using in-situ cosmic-ray fluxes measured by both the PAMELA and AMS-02 experiments together with NM data for the period from 2006 to 2017. Validation of the FF model for periods of different solar activity levels was further performed, and it was found that such an approximation performs better during solar minima, but disagrees with the observations of up to ≈ 10% during solar maximum. This makes the FF model approach not well suited for detailed studies of the solar modulation processes. At the same time, this precision is adequate to quantify the condition of the heliospheric modulation and to study its long-term variability.
To study solar energetic particle (SEP) fluxes using NM data, a new method of “effective rigidity” was proposed, allowing to reconstruct high-energy SEP integral fluences recorded during ground level enhancement (GLE) events. A significant advantage of this novel method is that it is a non parametric one and thus the spectral shape of the SEP fluence can be deduced directly from the reconstructed data. Reconstructions of the SEP fluences for two recent GLEs, #69 and #71, using this newly developed method, yield a very good agreement with the laborious method of the full fluence reconstruction using NM data, and with PAMELA measurements (for GLE #71), but disagree with earlier simplified estimations based on NM data.
The NM data analysis was performed using the NM yield function by Mishev et al. [2013], which was validated using the AMS-02 data for protons and helium for a time period between 2011 to 2017 and showed the best performance among other modern yield functions.
Improved knowledge of the CR variability is crucially important for e.g. CR-induced atmospheric effects, including the production of cosmogenic isotopes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Cosmogenic isotopes produced by galactic cosmic rays and extreme solar events in the Earth’s atmosphere
Get PDFOriginal papersOriginal papers are not included in the electronic version of the dissertation.Golubenko, K., Rozanov, E., Mironova, I., Karagodin, A., & Usoskin, I. (2020). Natural sources of ionization and their impact on atmospheric electricity. Geophysical Research Letters, 47(12), e2020GL088619. https://doi.org/10.1029/2020GL088619Self-archived versionGolubenko, K., Rozanov, E., Kovaltsov, G., Leppänen, A.-P., Sukhodolov, T., & Usoskin, I. (2021). Application of CCM SOCOL-AERv2-BE to cosmogenic beryllium isotopes: Description and validation for polar regions. Geoscientific Model Development, 14(12), 7605–7620. https://doi.org/10.5194/gmd-14-7605-2021Self-archived versionGolubenko, K., Rozanov, E., Kovaltsov, G., & Usoskin, I. (2022). Zonal mean distribution of cosmogenic isotope (7Be, 10Be, 14C, and 36Cl) production in stratosphere and troposphere. Journal of Geophysical Research: Atmospheres, 127(16), e2022JD036726. https://doi.org/10.1029/2022JD036726Self-archived versionUusitalo, J., Golubenko, K., Arppe, L., Brehm, N., Hackman, T., Hayakawa, H., Helama, S., Mizohata, K., Miyake, F., Mäkinen, H., Nöjd, P., Tanskanen, E., Tokanai, F., Rozanov, E., Wacker, L., Usoskin, I., Oinonen, M. (2023). Transient offset in 14C after the Carrington event recorded by polar tree rings. Manuscript submitted for publication.OsajulkaisutOsajulkaisut eivät sisälly väitöskirjan elektroniseen versioon.Golubenko, K., Rozanov, E., Mironova, I., Karagodin, A., & Usoskin, I. (2020). Natural sources of ionization and their impact on atmospheric electricity. Geophysical Research Letters, 47(12), e2020GL088619. https://doi.org/10.1029/2020GL088619Rinnakkaistallennettu versioGolubenko, K., Rozanov, E., Kovaltsov, G., Leppänen, A.-P., Sukhodolov, T., & Usoskin, I. (2021). Application of CCM SOCOL-AERv2-BE to cosmogenic beryllium isotopes: Description and validation for polar regions. Geoscientific Model Development, 14(12), 7605–7620. https://doi.org/10.5194/gmd-14-7605-2021Rinnakkaistallennettu versioGolubenko, K., Rozanov, E., Kovaltsov, G., & Usoskin, I. (2022). Zonal mean distribution of cosmogenic isotope (7Be, 10Be, 14C, and 36Cl) production in stratosphere and troposphere. Journal of Geophysical Research: Atmospheres, 127(16), e2022JD036726. https://doi.org/10.1029/2022JD036726Rinnakkaistallennettu versioUusitalo, J., Golubenko, K., Arppe, L., Brehm, N., Hackman, T., Hayakawa, H., Helama, S., Mizohata, K., Miyake, F., Mäkinen, H., Nöjd, P., Tanskanen, E., Tokanai, F., Rozanov, E., Wacker, L., Usoskin, I., Oinonen, M. (2023). Transient offset in 14C after the Carrington event recorded by polar tree rings. Manuscript submitted for publication.Academic Dissertation to be presented with the assent of the Graduate School of the University of Oulu, for public discussion in the Auditorium IT115, on December 15, 2023, at 12 o’clock noo
Imprints of long-term solar variability on cosmic rays and terrestrial archives
Get PDFAbstractGalactic cosmic rays (GCRs) arriving at Earth, interact with nuclei of atmospheric gases leading to the production of cosmogenic radionuclides. The latter, following a series of processes, are eventually stored in terrestrial archives such as ice cores and tree rings. The information that can be collected, traces back millions of years. Since the solar activity has a large impact on GCRs, via modulation processes in the heliosphere, one can gain knowledge about the solar activity in the past using the cosmogenic radionuclide records. The primary goal of our study is to reconstruct the solar activity in the past combining all the available information from different cosmogenic radionuclides and databases obtained from different locations on Earth. The principle idea is that, using terrestrial archives and existing models of radionuclide production, the GCR flux can be reconstructed over the past millennia. Thereafter, the solar activity, after applying a model correlating the GCR flux to different solar parameters, can be reconstructed. To achieve this it was necessary to develop an empirical model reconstructing the tilt angle of the Heliospheric Current Sheet (HCS), one of the important heliospheric factors influencing cosmic ray propagation inside the heliosphere. The HCS tilt has been traced with observations since 1976. Following, a semi-empirical model of GCR modulation in the heliosphere was developed using measurements and reconstructions of the heliospheric parameters that play a major role in the modulation processes. In particular these are the open solar magnetic flux, the solar magnetic polarity and the HCS tilt angle. With this model the cosmic ray variability on Earth in millennial time scales was reconstructed and used as an input parameter in existing models, calculating the production and deposition of the cosmogenic radionuclides ¹⁴C and ¹⁰Be. The results were then compared with the data aiming to achieve the best fit that will lead to best reconstruction of the solar activity.Original papersOriginal papers are not included in the electronic version of the dissertation.Usoskin, I. G., Arlt, R., Asvestari, E., Hawkins, E., Käpylä, M., Kovaltsov, G. A., Krivova, N., Lockwood, M., Mursula, K., O’Reilly, J., Owens, M., Scott, C. J., Sokoloff, D. D., Solanki, S. K., Soon, W., & Vaquero, J. M. (2015). The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets. Astronomy & Astrophysics, 581, A95. https://doi.org/10.1051/0004-6361/201526652Asvestari, E., & Usoskin, I. G. (2016). An empirical model of heliospheric cosmic ray modulation on long-term time scale. Journal of Space Weather and Space Climate, 6, A15. https://doi.org/10.1051/swsc/2016011Asvestari, E., Usoskin, I. G., Kovaltsov, G. A., Owens, M. J., & Krivova, N. (2016). Test of different sunspot number series against the cosmogenic isotope records. Manuscript submitted for publication.Asvestari, E., Willamo, T., Gil, A., Usoskin, I. G., Kovaltsov, G. A., Mikhailov, V. V., & Mayorov, A. (in press). Analysis of Ground Level Enhancements (GLE): Extreme solar energetic particle events have hard spectra. Advances in Space Research. https://doi.org/10.1016/j.asr.2016.08.043Self-archived versionOsajulkaisutOsajulkaisut eivät sisälly väitöskirjan elektroniseen versioon.Usoskin, I. G., Arlt, R., Asvestari, E., Hawkins, E., Käpylä, M., Kovaltsov, G. A., Krivova, N., Lockwood, M., Mursula, K., O’Reilly, J., Owens, M., Scott, C. J., Sokoloff, D. D., Solanki, S. K., Soon, W., & Vaquero, J. M. (2015). The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets. Astronomy & Astrophysics, 581, A95. https://doi.org/10.1051/0004-6361/201526652Asvestari, E., & Usoskin, I. G. (2016). An empirical model of heliospheric cosmic ray modulation on long-term time scale. Journal of Space Weather and Space Climate, 6, A15. https://doi.org/10.1051/swsc/2016011Asvestari, E., Usoskin, I. G., Kovaltsov, G. A., Owens, M. J., & Krivova, N. (2016). Test of different sunspot number series against the cosmogenic isotope records. Manuscript submitted for publication.Asvestari, E., Willamo, T., Gil, A., Usoskin, I. G., Kovaltsov, G. A., Mikhailov, V. V., & Mayorov, A. (in press). Analysis of Ground Level Enhancements (GLE): Extreme solar energetic particle events have hard spectra. Advances in Space Research. https://doi.org/10.1016/j.asr.2016.08.043Rinnakkaistallennettu versioAcademic Dissertation to be presented with the assent of the Doctoral Trainning Committee of Technology and Natural Sciences of the University of Oulu for public discussion in the Auditorium IT116, Linnanmaa, on 2nd December, 2016, at 12 o’clock.Abstract
Galactic cosmic rays (GCRs) arriving at Earth, interact with nuclei of atmospheric gases leading to the production of cosmogenic radionuclides. The latter, following a series of processes, are eventually stored in terrestrial archives such as ice cores and tree rings. The information that can be collected, traces back millions of years. Since the solar activity has a large impact on GCRs, via modulation processes in the heliosphere, one can gain knowledge about the solar activity in the past using the cosmogenic radionuclide records. The primary goal of our study is to reconstruct the solar activity in the past combining all the available information from different cosmogenic radionuclides and databases obtained from different locations on Earth. The principle idea is that, using terrestrial archives and existing models of radionuclide production, the GCR flux can be reconstructed over the past millennia. Thereafter, the solar activity, after applying a model correlating the GCR flux to different solar parameters, can be reconstructed. To achieve this it was necessary to develop an empirical model reconstructing the tilt angle of the Heliospheric Current Sheet (HCS), one of the important heliospheric factors influencing cosmic ray propagation inside the heliosphere. The HCS tilt has been traced with observations since 1976. Following, a semi-empirical model of GCR modulation in the heliosphere was developed using measurements and reconstructions of the heliospheric parameters that play a major role in the modulation processes. In particular these are the open solar magnetic flux, the solar magnetic polarity and the HCS tilt angle. With this model the cosmic ray variability on Earth in millennial time scales was reconstructed and used as an input parameter in existing models, calculating the production and deposition of the cosmogenic radionuclides ¹⁴C and ¹⁰Be. The results were then compared with the data aiming to achieve the best fit that will lead to best reconstruction of the solar activity
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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