Observation of a time lag in solar modulation of cosmic rays in the heliosphere

Orcinha, M.; Tomassetti, Nicola; Barão, F.; Bertucci, B.

doi:10.1088/1742-6596/1181/1/012013

Cited by 4 publications

(4 citation statements)

References 46 publications

(80 reference statements)

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“…Firstly, there is a delay in the modulation of cosmic rays, and therefore of the CRAND process that fills in the inner belts with protons, by the Sun. It takes a few months for the effects of the Sun's high activity and hence intense magnetic field to be felt at the heliopause (Orcinha et al., 2019; Tomassetti et al., 2017). Another thing is that depending on the satellite altitude and the energy of the measured proton, its lifetime against absorption by the atmosphere is shorter or longer.…”

Section: Resultsmentioning

confidence: 99%

South Atlantic Anomaly Evolution Seen by the Proton Flux

Ginisty,

Wrobel,

Ecoffet

et al. 2024

JGR Space Physics

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The SEM‐2 (Space Environment Monitor‐2) instrument embedded on the NOAA‐15 Low Earth Orbit satellite provides measurements of trapped protons in the Van Allen inner belt from 1998 to nowadays. This continuous set of measurements enables us to study the dynamics of the South Atlantic Anomaly (SAA) over more than two solar cycles, particularly, its temporal evolution. We observe that the area of the SAA is anti‐correlated with the solar activity. Two physical processes explain this anticorrelation. First, the more the Sun is active the more it disables the cosmic rays to reach the Earth's magnetosphere and fill in the inner radiation belt with protons. Then, when the Sun is more active, the upper atmosphere is warmer and therefore absorbs more protons from the radiation belt. Then, we investigate the protons flux centroid of the SAA. The temporal evolution of its position, latitude and, longitude is studied over the same time interval (1998–2022). We notice that the latitude of the centroid is also anti‐correlated with the solar activity whereas the longitude seems absolutely independent. The temporal evolution of the position of the centroid shows a drift of the SAA. Indeed from 1998 to 2022 the SAA drifted of about 7° West. The SEM‐2 instrument measures flux for protons of different energies (16, 36, 70, and, 140 MeV). For each energy, the SAA dynamic has a similar trend but with different values. These differences are investigated and the results are discussed.

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Section: Resultsmentioning

confidence: 99%

South Atlantic Anomaly Evolution Seen by the Proton Flux

Ginisty,

Wrobel,

Ecoffet

et al. 2024

JGR Space Physics

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“…The value of B 0 is provided by the Advanced Composition Explorer (ACE), while the tilt angle and polarity are provided by the Wilcox Solar Observatory (WSO), represented by solid lines in the two top panels. It takes time for the change in the magnetic field that embedded in the solar wind to affect the motion of GCR, typically around nine months, which is referred to as the time lag Tomassetti et al (2017); Orcinha et al (2019). Considering that, we calculate the average field and tilt angle encountered by GCR particles during their journey from heliopause to Earth, as represented by the square symbol.…”

Section: The Model Parametersmentioning

confidence: 99%

A New Scenario of Solar Modulation Model during the Polarity Reversing

Jiang¹,

Lin²,

Yang³

2023

Preprint

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When the Galactic Cosmic Rays (GCRs) entering the heliosphere, they encounter the solar wind plasma, and their intensity is reduced, so called solar modulation. The modulation is caused by the combination of a few factors, such as the particle energies, solar activity and solar disturbance. In this work, a 2D numerical method is adopted to simulate the propagation of GCRs in the heliosphere with SOLARPROP, and to overcome the time consuming issue, the machine learning technique is also applied. With the obtained proton local interstellar spectra (LIS) based on the observation from Voyager 1 and AMS-02, the solar modulation parameters during the solar maximum activity of cycle 24 have been found. It shows the normalization and index of diffusion coefficient indeed reach a maximal value in February 2014. However after taking into account the travel time of particles with different energies, the peak time found postponed to November 2014 as expected. The nine-month late is so called time lag.

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“…The change in the magnetic field that is embedded in the solar wind typically takes about 9 months to affect the motion of GCRs. This delay is referred to as the time lag (Tomassetti et al 2017;Orcinha et al 2019). Considering that, we calculate the average field and tilt angle encountered by GCR particles during their journey from HP to Earth, as represented by the square symbol.…”

Section: The Model Parametersmentioning

confidence: 99%

A New Scenario of Solar Modulation Model during the Polarity Reversing

Jiang,

Lin,

Yang

2023

ApJ

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When entering the heliosphere, galactic cosmic rays (GCRs) will encounter the solar wind plasma, reducing their intensity. This solar modulation effect is strongly affected by the structure of the solar wind and the heliospheric magnetic field (HMF). To address the effect during the solar maximum of cycle 24, we study the solar modulation under a scenario in which the weights for A = ±1 are determined by the structure of HMF, and the traveling time of GCRs simulated by SOLARPROP is taken into account. We then fit the cosmic-ray proton data provided by AMS-02 and Voyager in the energy range 4 MeV–30 GeV, and confirm that the modulation time lag in this model is about 9 months, which is consistent with the previous studies. This model incorporates a more realistic description of the polarity reversing and provides a more reliable estimation of the solar modulation effect during the maximum activity period.

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Observation of a time lag in solar modulation of cosmic rays in the heliosphere

Cited by 4 publications

References 46 publications

South Atlantic Anomaly Evolution Seen by the Proton Flux

South Atlantic Anomaly Evolution Seen by the Proton Flux

A New Scenario of Solar Modulation Model during the Polarity Reversing

A New Scenario of Solar Modulation Model during the Polarity Reversing

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