Search Results - "Usoskin, I. G"

Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23 by Gopalswamy, N., Xie, H., Yashiro, S., Akiyama, S., Makela, P., Usokin, I. G.

“…Solar cycle 23 witnessed the most complete set of observations of coronal mass ejections (CMEs) associated with the Ground Level Enhancement (GLE) events. We…”
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Unusual activity of the Sun during recent decades compared to the previous 11,000 years by Solanki, S. K, Usoskin, I. G, Kromer, B, Schüssler, M, Beer, J

“…Direct observations of sunspot numbers are available for the past four centuries, but longer time series are required, for example, for the identification of a…”
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Recalibration of the Sunspot-Number: Status Report by Clette, F., Lefèvre, L., Chatzistergos, T., Hayakawa, H., Carrasco, V. M. S., Arlt, R., Cliver, E. W., Wit, T. Dudok de, Friedli, T. K., Karachik, N., Kopp, G., Lockwood, M., Mathieu, S., Muñoz-Jaramillo, A., Owens, M., Pesnell, D., Pevtsov, A., Svalgaard, L., Usoskin, I. G., Driel-Gesztelyi, L. van, Vaquero, J. M.

“…We report progress on the ongoing recalibration of the Wolf sunspot number (SN) and group-sunspot number (GN) following the release of version 2.0 of SN in…”
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A New Calibrated Sunspot Group Series Since 1749: Statistics of Active Day Fractions by Usoskin, I. G., Kovaltsov, G. A., Lockwood, M., Mursula, K., Owens, M., Solanki, S. K.

“…Although sunspot-number series have existed since the mid-nineteenth century, they are still the subject of intense debate, with the largest uncertainty being…”
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GLE and Sub-GLE Redefinition in the Light of High-Altitude Polar Neutron Monitors by Poluianov, S. V., Usoskin, I. G., Mishev, A. L., Shea, M. A., Smart, D. F.

“…The conventional definition of ground-level enhancement (GLE) events requires a detection of solar energetic particles (SEP) by at least two differently…”
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Sunspot positions and sizes for 1825-1867 from the observations by Samuel Heinrich Schwabe by Arlt, R., Leussu, R., Giese, N., Mursula, K., Usoskin, I. G.

“…Samuel Heinrich Schwabe made 8486 drawings of the solar disc with sunspots in the period from 1825 November 5 to 1867 December 29. We have measured sunspot…”
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Neutron monitor yield function: New improved computations by Mishev, A. L., Usoskin, I. G., Kovaltsov, G. A.

“…A ground‐based neutron monitor (NM) is a standard tool to measure cosmic ray (CR) variability near Earth, and it is crucially important to know its yield…”
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Estimating the frequency of extremely energetic solar events, based on solar, stellar, lunar, and terrestrial records by Schrijver, C. J., Beer, J., Baltensperger, U., Cliver, E. W., Güdel, M., Hudson, H. S., McCracken, K. G., Osten, R. A., Peter, T., Soderblom, D. R., Usoskin, I. G., Wolff, E. W.

“…The most powerful explosions on the Sun – in the form of bright flares, intense storms of solar energetic particles (SEPs), and fast coronal mass ejections…”
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Tests of Sunspot Number Sequences: 3. Effects of Regression Procedures on the Calibration of Historic Sunspot Data by Lockwood, M., Owens, M. J., Barnard, L., Usoskin, I. G.

“…We use sunspot-group observations from the Royal Greenwich Observatory (RGO) to investigate the effects of intercalibrating data from observers with different…”
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Dependence of the Sunspot-Group Size on the Level of Solar Activity and its Influence on the Calibration of Solar Observers by Usoskin, I. G., Kovaltsov, G. A., Chatzistergos, T.

“…We study the distribution of the sunspot-group size (area) and its dependence on the level of solar activity. We show that the fraction of small groups is not…”
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Occurrence Probability of Large Solar Energetic Particle Events: Assessment from Data on Cosmogenic Radionuclides in Lunar Rocks by Kovaltsov, G. A., Usoskin, I. G.

“…We revisited assessments of the occurrence probability distribution of large events in solar energetic particles (SEP), based on measurements of cosmogenic…”
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A Test of the Active-Day Fraction Method of Sunspot Group Number Calibration: Dependence on the Level of Solar Activity by Willamo, T., Usoskin, I. G., Kovaltsov, G. A.

“…The method of active-day fraction (ADF) was proposed recently to calibrate different solar observers to standard observational conditions. The result of the…”
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Possible effect of extreme solar energetic particle events of September–October 1989 on polar stratospheric aerosols: a case study by Mironova, I. A, Usoskin, I. G

“…The main ionization source of the middle and low Earth's atmosphere is related to energetic particles coming from outer space. Usually it is ionization from…”
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Cosmic Ray Induced Ion Production in the Atmosphere by Bazilevskaya, G. A., Usoskin, I. G., Flückiger, E. O., Harrison, R. G., Desorgher, L., Bütikofer, R., Krainev, M. B., Makhmutov, V. S., Stozhkov, Y. I., Svirzhevskaya, A. K., Svirzhevsky, N. S., Kovaltsov, G. A.

“…An overview is presented of basic results and recent developments in the field of cosmic ray induced ionisation in the atmosphere, including a general…”
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Ionization effect of solar particle GLE events in low and middle atmosphere by Usoskin, I. G., Kovaltsov, G. A., Mironova, I. A., Tylka, A. J., Dietrich, W. F.

“…Using a new reconstruction of the solar proton energy spectra for Ground Level Enhancement (GLE) events, based on fits to measurements from ground-based and…”
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Tests of Sunspot Number Sequences: 2. Using Geomagnetic and Auroral Data by Lockwood, M., Owens, M. J., Barnard, L., Scott, C. J., Usoskin, I. G., Nevanlinna, H.

“…We compare four sunspot-number data sequences against geomagnetic and terrestrial auroral observations. The comparisons are made for the original Solar…”
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Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation by Semeniuk, K., Fomichev, V. I., McConnell, J. C., Fu, C., Melo, S. M. L., Usoskin, I. G.

“…The impact of NOx and HOx production by three types of energetic particle precipitation (EPP), auroral zone medium and high energy electrons, solar proton…”
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Possible effect of extreme solar energetic particle event of 20 January 2005 on polar stratospheric aerosols: direct observational evidence by Mironova, I. A, Usoskin, I. G, Kovaltsov, G. A, Petelina, S. V

“…Energetic cosmic rays are the main source of ionization of the low-middle atmosphere, leading to associated changes in atmospheric properties. Via the…”
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Cosmogenic Isotope Variability During the Maunder Minimum: Normal 11-year Cycles Are Expected by Poluianov, S. V., Usoskin, I. G., Kovaltsov, G. A.

“…The amplitude of the 11-year cycle measured in the cosmogenic isotope 10 Be during the Maunder Minimum is comparable to that during the recent epoch of high…”
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Grand Minima of Solar Activity and the Mean-Field Dynamo by Usoskin, I. G., Sokoloff, D., Moss, D.

“…We demonstrate that a simple solar dynamo model, in the form of a Parker migratory dynamo with random fluctuations of the dynamo governing parameters and…”
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