Solar Cycle in the Heliosphere and Cosmic Rays

Bazilevskaya, G. A.; Cliver, E. W.; Kovaltsov, Gennady A.; Ling, A. G.; Shea, M. A.; Smart, D. F.; Usoskin, Ilya

doi:10.1007/s11214-014-0084-0

Cited by 40 publications

(17 citation statements)

References 137 publications

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“…Bazilevskaya et al, 2014;Balogh et al, 2014), similarly as the unusual Solar Minimum 23/24 (e.g. Dikpati, 2013) was weaker comparing with the previous minima.…”

Section: Introductionmentioning

confidence: 74%

Energy Spectrum of the Recurrent Variation of Galactic Cosmic Rays During the Solar Minimum of Cycles 23/24

Gil

Alania

2016

Sol Phys

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The Sun during the recent epoch of solar activity operated in a different way than during the last 60 years, being less active. We study temporal changes of the energy spectrum of the first three harmonics of the 27-day variation of the galactic cosmic rays (GCR) intensity during the unusual, recent solar minimum, between Solar Cycles 23 and 24 (SC 23/24) and compare with four previous minima. We show that the energy spectrum of the amplitudes of the recurrent variation of the GCR intensity is hard in the maximum epochs and is soft in the minimum epochs during Solar Cycles 20 -24, but with peculiarities during the Solar Minimum 23/24. In particular, while the energy/rigidity spectrum of the amplitudes of the first harmonic of the recurrent variation of the GCR intensity behaves practically the same as for previous epochs, the energy/rigidity spectrum of the amplitudes of the second and the third harmonics demonstrates a pronounced softening. We attribute this phenomenon to the decrease of the extension of the heliosphere caused by the decrease of the solar-wind dynamic pressure during the unusual Solar Minimum 23/24.

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“…Bazilevskaya et al, 2014;Balogh et al, 2014), similarly as the unusual Solar Minimum 23/24 (e.g. Dikpati, 2013) was weaker comparing with the previous minima.…”

Section: Introductionmentioning

confidence: 74%

Energy Spectrum of the Recurrent Variation of Galactic Cosmic Rays During the Solar Minimum of Cycles 23/24

Gil

Alania

2016

Sol Phys

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“…Over the last decades, the lower-energy part of the SEP spectrum, which cannot be assessed by NMs, was evaluated from satellite-borne data (Vainio et al, 2009;Bazilevskaya et al, 2014). On the other hand, when one goes back in time, strong SEP/GLE events can be estimated from indirect proxies -cosmogenic radionuclides produced by cosmic rays in the atmosphere and stored in natural archives, such as tree trunks or ice cores (Beer et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Analysis of Ground Level Enhancements (GLE): Extreme solar energetic particle events have hard spectra

Asvestari

Willamo

Gil

et al. 2017

Advances in Space Research

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Nearly 70 Ground Level Enhancements (GLEs) of cosmic rays have been recorded by the worldwide neutron monitor network since the 1950s depicting a big variety of energy spectra of solar energetic particles (SEP). Here we studied a statistical relation between the event-integrated intensity of GLEs (calculated as count-rate relative excess, averaged over all available polar neutron monitors, and expressed in percent-hours) and the hardness of the solar particle energy spectra. For each event the integral omnidirectional event-integrated fluences of particles with energy above 30 MeV (F 30 ) and above 200 MeV (F 200 ) were computed using the reconstructed spectra, and the ratio between the two fluences was considered as a simple index of the event's hardness. We also provided a justification of the spectrum estimate in the form of the Band-function, using direct PAMELA data for GLE 71 (17-May-2012). We found that, while there is no clear relation between the intensity and the hardness for weak events, all strong events with the intensity greater 100 %*hr are characterized by a very hard spectrum. This implies * Corresponding author Email address: ilya.usoskin@oulu.fi (I.G. Usoskin) December 9, 2016 that a hard spectrum can be securely assumed for all extreme GLE events, e.g., those studied using cosmogenic isotope data in the past. Preprint submitted to Advances in Space Research

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“…Extracting HMF data from these radionuclides, however, is a much more indirect process than inferring them from sunspot or geomagnetic data. The extracted cosmic ray record may be affected by such factors as terrestrial climate effects on the deposition into the reservoirs in which they are measured, geomagnetic field variability, variations in the local interstellar spectrum of cosmic rays, and high‐energy solar energetic particle events (sometimes referred to as “solar cosmic rays”) [ Usoskin et al , ; Webber et al , ; Miyake et al , ; Bazilevskaya et al , ; Güttler et al , ; McCracken and Beer , ].…”

Section: Introductionmentioning

confidence: 99%

Near‐Earth heliospheric magnetic field intensity since 1750: 2. Cosmogenic radionuclide reconstructions

Owens

Cliver

McCracken³

et al. 2016

JGR Space Physics

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This is Part 2 of a study of the near‐Earth heliospheric magnetic field strength, B, since 1750. Part 1 produced composite estimates of B from geomagnetic and sunspot data over the period 1750–2013. Sunspot‐based reconstructions can be extended back to 1610, but the paleocosmic ray (PCR) record is the only data set capable of providing a record of solar activity on millennial timescales. The process for converting 10Be concentrations measured in ice cores to B is more complex than with geomagnetic and sunspot data, and the uncertainties in B derived from cosmogenic nuclides (~20% for any individual year) are much larger. Within this level of uncertainty, we find reasonable overall agreement between PCR‐based B and the geomagnetic‐ and sunspot number‐based series. This agreement was enhanced by excising low values in PCR‐based B attributed to high‐energy solar proton events. Other discordant intervals, with as yet unspecified causes remain included in our analysis. Comparison of 3 year averages centered on sunspot minimum yields reasonable agreement between the three estimates, providing a means to investigate the long‐term changes in the heliospheric magnetic field into the past even without a means to remove solar proton events from the records.

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Solar Cycle in the Heliosphere and Cosmic Rays

Cited by 40 publications

References 137 publications

Energy Spectrum of the Recurrent Variation of Galactic Cosmic Rays During the Solar Minimum of Cycles 23/24

Energy Spectrum of the Recurrent Variation of Galactic Cosmic Rays During the Solar Minimum of Cycles 23/24

Analysis of Ground Level Enhancements (GLE): Extreme solar energetic particle events have hard spectra

Near‐Earth heliospheric magnetic field intensity since 1750: 2. Cosmogenic radionuclide reconstructions

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