scholarly journals Measurements of the time-dependent cosmic-ray Sun shadow with seven years of IceCube data: Comparison with the Solar cycle and magnetic field models

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
M. G. Aartsen ◽  
R. Abbasi ◽  
M. Ackermann ◽  
J. Adams ◽  
J. A. Aguilar ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Cosmic Ray ◽  
Time Dependent ◽  
Data Comparison

scholarly journals Cosmic-ray propagation around the Sun: investigating the influence of the solar magnetic field on the cosmic-ray Sun shadow

2020 ◽  
Vol 633 ◽  
pp. A83
Author(s):  
J. Becker Tjus ◽  
P. Desiati ◽  
N. Döpper ◽  
H. Fichtner ◽  
J. Kleimann ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Solar Cycle ◽  
Cosmic Rays ◽  
Solar Magnetic Field ◽  
Cosmic Ray ◽  
High Energy ◽  
High Solar Activity ◽  
The Sun ◽  
Theoretical Understanding

The cosmic-ray Sun shadow, which is caused by high-energy charged cosmic rays being blocked and deflected by the Sun and its magnetic field, has been observed by various experiments, such as Argo-YBJ, Tibet, HAWC, and IceCube. Most notably, the shadow’s size and depth was recently shown to correlate with the 11-year solar cycle. The interpretation of such measurements, which help to bridge the gap between solar physics and high-energy particle astrophysics, requires a solid theoretical understanding of cosmic-ray propagation in the coronal magnetic field. It is the aim of this paper to establish theoretical predictions for the cosmic-ray Sun shadow in order to identify observables that can be used to study this link in more detail. To determine the cosmic-ray Sun shadow, we numerically compute trajectories of charged cosmic rays in the energy range of 5−316 TeV for five different mass numbers. We present and analyze the resulting shadow images for protons and iron, as well as for typically measured cosmic-ray compositions. We confirm the observationally established correlation between the magnitude of the shadowing effect and both the mean sunspot number and the polarity of the magnetic field during the solar cycle. We also show that during low solar activity, the Sun’s shadow behaves similarly to that of a dipole, for which we find a non-monotonous dependence on energy. In particular, the shadow can become significantly more pronounced than the geometrical disk expected for a totally unmagnetized Sun. For times of high solar activity, we instead predict the shadow to depend monotonously on energy and to be generally weaker than the geometrical shadow for all tested energies. These effects should become visible in energy-resolved measurements of the Sun shadow, and may in the future become an independent measure for the level of disorder in the solar magnetic field.

scholarly journals Solar Cycle Variation of Cosmic ray Intensity along with Interplanetary and Solar Wind Plasma Parameters

2008 ◽  
Vol 45 (3) ◽  
pp. 63-68 ◽  
Author(s):  
Rajesh Mishra ◽  
Rekha Agarwal ◽  
Sharad Tiwari
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Cycle ◽  
Interplanetary Magnetic Field ◽  
Cosmic Ray ◽  
Solar Wind Plasma ◽  
Solar Cycles ◽  
Plasma Parameters ◽  
Solar Cycle Variation ◽  
Cosmic Ray Intensity

Solar Cycle Variation of Cosmic ray Intensity along with Interplanetary and Solar Wind Plasma ParametersGalactic cosmic rays are modulated at their propagation in the heliosphere by the effect of the large-scale structure of the interplanetary medium. A comparison of the variations in the cosmic ray intensity data obtained by neutron monitoring stations with those in geomagnetic disturbance, solar wind velocity (V), interplanetary magnetic field (B), and their product (V' B) near the Earth for the period 1964-2004 has been presented so as to establish a possible correlation between them. We used the hourly averaged cosmic ray counts observed with the neutron monitor in Moscow. It is noteworthy that a significant negative correlation has been observed between the interplanetary magnetic field, product (V' B) and cosmic ray intensity during the solar cycles 21 and 22. The solar wind velocity has a good positive correlation with cosmic ray intensity during solar cycle 21, whereas it shows a weak correlation during cycles 20, 22 and 23. The interplanetary magnetic field shows a weak negative correlation with cosmic rays for solar cycle 20, and a good anti-correlation for solar cycles 21-23 with the cosmic ray intensity, which, in turn, shows a good positive correlation with disturbance time index (Dst) during solar cycles 21 and 22, and a weak correlation for cycles 20 and 23.

scholarly journals Pulsars and Bubble Dynamics

1997 ◽  
Vol 166 ◽  
pp. 223-226
Author(s):  
Ramen Kumar Parui
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Bubble Dynamics ◽  
Recent Observation ◽  
Cosmic Ray ◽  
Activity Period ◽  
Cycle Period ◽  
Cosmic Ray Intensity

AbstractBased on recent observation of the dominance of the flare generated solar wind streams over the co-rotating streams and a significant lowering in the cosmic ray intensity in the abnormal year of the solar activity period, I have predicted the occurrence of discernible changes in magnetic field strength and the thickness of the shell of the local bubble during high sunspots years of the solar cycle period. In order to observe the variation, both in the magnetic field strength and in the thickness of the compressed shell, a proposal of continuous monitor of these two parameters through the observation of Faraday Rotation Measure has been proposed with an emphasize to the observations in the period of next abnormal year of the solar cycle in near future.

Cosmic-Ray Transport in Heliospheric Magnetic Structures. III. Implications of Solar Magnetograms for the Drifts of Cosmic Rays

2021 ◽  
Vol 922 (2) ◽  
pp. 124
Author(s):  
Andreas Kopp ◽  
Jan Louis Raath ◽  
Horst Fichtner ◽  
Marius S. Potgieter ◽  
Stefan E. S. Ferreira ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Cosmic Rays ◽  
Boundary Conditions ◽  
Large Scale ◽  
Cosmic Ray ◽  
Magnetic Polarity ◽  
Solar Observatory ◽  
Field Polarity ◽  
Heliospheric Magnetic Field

Abstract The transport of energetic particles in the heliosphere is reviewed regarding the treatment of their drifts over an entire solar cycle including the periods around solar maximum, when the tilt angles of the heliospheric current sheet increase to large values and the sign of the magnetic polarity changes. While gradient and curvature drifts are well-established elements of the propagation of cosmic rays in the heliospheric magnetic field, their perturbation by the solar-activity-induced large-scale distortions of dipole-like field configurations and by magnetic turbulence is an open problem. Various empirical or phenomenological approaches have been suggested, but either lack a theory-based motivation or have been shown to be incompatible with measurements. We propose a new approach of more closely investigating solar magnetograms obtained from GONG maps, leading to a new definition of (i) tilt angles that may exceed those provided by the Wilcox Solar Observatory during high activity and of (ii) a “noninteger sign” that can be used to reduce the drifts during these periods as well as to provide a refinement of the magnetic field polarity. The change of sign from A < 0 to A > 0 of solar cycle 24 can be in this way localized to occur between Carrington Rotations 2139 and 2140 in mid 2013. This treatment is fully consistent in the sense that the transport modeling uses the same input data to formulate the boundary conditions at the heliobase as do the magnetohydrodynamic models of the solar wind and the embedded heliospheric magnetic field that exploit solar magnetograms as inner boundary conditions.

scholarly journals Features of the Galactic Cosmic Ray Anisotropy in Solar Cycle 24 and Solar Minima 23/24 and 24/25

Solar Physics ◽  
2019 ◽  
Vol 294 (10) ◽  
Author(s):  
R. Modzelewska ◽  
K. Iskra ◽  
W. Wozniak ◽  
M. Siluszyk ◽  
M. V. Alania
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Radial Component ◽  
Galactic Cosmic Rays ◽  
Positive Polarity ◽  
Heliospheric Magnetic Field ◽  
Solar Cycle 24 ◽  
Cycle 24

Abstract We study the role of the drift effect in the temporal changes of the anisotropy of galactic cosmic rays (GCRs) and the influence of the sector structure of the heliospheric magnetic field on it. We analyze the GCR anisotropy in Solar Cycle 24 and solar minimum 23/24 with negative polarity ($qA<0$qA<0) for the period of 2007 – 2009 and near minimum 24/25 with positive polarity ($qA>0$qA>0) in 2017 – 2018 using data of the global network of Neutron Monitors. We use the harmonic analysis method to calculate the radial and tangential components of the anisotropy of GCRs for different sectors (‘+’ corresponds to the positive and ‘−’ to the negative directions) of the heliospheric magnetic field. We compare the analysis of GCR anisotropy using different evaluations of the mean GCRs rigidity related to Neutron Monitor observations. Then the radial and tangential components are used for characterizing the GCR modulation in the heliosphere. We show that in the solar minimum 23/24 in 2007 – 2009 when $qA<0$qA<0, the drift effect is not visibly evident in the changes of the radial component, i.e. the drift effect is found to produce $\approx 4$≈4% change in the radial component of the GCR anisotropy for 2007 – 2009. Hence the diffusion dominated model of GCR transport is more acceptable in 2007 – 2009. In turn, near the solar minimum 24/25 in 2017 – 2018 when $qA>0$qA>0, the drift effect is evidently visible and produces ≈40% change in the radial component of the GCR anisotropy for 2017 – 2018. So in the period of 2017 – 2018 a diffusion model with noticeably manifested drift is acceptable. The results of this work are in good agreement with the drift theory of GCR modulation, according to which, during negative (positive) polarity cycles, a drift stream of GCRs is directed toward (away from) the Sun, thus giving rise to a 22-year cycle variation of the radial GCR anisotropy.

Study of Cosmic Ray Intensity in Relation to the Interplanetary Magnetic Field and Geomagnetic Storms for Solar Cycle 23

Solar Physics ◽  
2016 ◽  
Vol 291 (2) ◽  
pp. 603-611 ◽  
Author(s):  
Hema Kharayat ◽  
Lalan Prasad ◽  
Rajesh Mathpal ◽  
Suman Garia ◽  
Beena Bhatt
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Storms ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity ◽  
Solar Cycle 23

scholarly journals Experimental spectrum of the cosmic ray variations within rigidity range of 1-20 GV in the Earth’s orbit by the data of AMS-02

2021 ◽  
pp. 31-38
Author(s):  
Anatoly V. Belov ◽  
Raisa T. Gushchina ◽  
Victor Yanke ◽  
Liudmila Trefilova ◽  
Pavel G. Kobelev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Solar Cycle ◽  
Cosmic Rays ◽  
Solar Magnetic Field ◽  
Cosmic Ray ◽  
Experimental Spectrum ◽  
Negative Polarity ◽  
Neutron Monitors ◽  
First Time

For the first time, based on the experimental data of AMS-02, a three-parameter spectrum of variations of ga - lactic cosmic rays was obtained in the range of rigidity 1- 20 GV, to which neutron monitors are most sensitive. It was found that during the period of negative polarity of the solar magnetic field, a power-law spectrum of va - riations is observed with a strong exponential decay in the region of high rigidity. When the polarity changes to positive at the beginning of the new 24th solar cycle, the spectrum of cosmic ray variations becomes purely po- wer-law. The transition to the experimentally obtained spectrum of variations will make it possible to remove a number of uncertainties and increase the accuracy of the analysis of data from the ground network of detectors. This will make it possible to retrospectively obtain fluxes of galactic protons with an average monthly resolution for the period of the space era based on ground-based monitoring.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

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