Effects of cosmic rays on the Earth's environment

Bazilevskaya, G. A.; Крайнев, М. Б.; Махмутов, В. С.

doi:10.1016/s1364-6826(00)00113-9

Cited by 62 publications

(56 citation statements)

References 32 publications

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“…This range of average periods refers to IMFs relevant for the QBOs. The interval is wider than the commonly accepted QBO range of 1.5-3.5 yr (e.g., Bazilevskaya et al 2000), considering that the IMF period is not constant and it is calculated through an average operation (see Section 3). In fact, the limits 1 and 4.5 yr reconcile the intention of isolating the QBOs and the need that the selection of the EMD modes is clear and unambiguous.…”

Section: Results For the Radial Componentmentioning

confidence: 99%

“…The most prominently recognized periods are the quasi-biennial oscillations (QBOs) at timescales around 2 yr. This component of the cycle, although weaker than the main component, has been identified in many activity indices (Rao 1973;Valdés-Galicia et al 1996;Bazilevskaya et al 2000;Kudela et al 2002;Bai 2003;Knaack & Stenflo 2005;Vecchio & Carbone 2008, 2009). The QBO origin is still unknown even if it could be related to the dynamo action in the inner solar layers (Benevolenskaya 1998), being also detected in phenomena directly connected with the solar interior.…”

Section: Introductionmentioning

confidence: 85%

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The Dynamics of the Solar Magnetic Field: Polarity Reversals, Butterfly Diagram, and Quasi-Biennial Oscillations

Vecchio

Laurenza

Meduri

et al. 2012

ApJ

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The spatio-temporal dynamics of the solar magnetic field has been investigated by using NSO/Kitt Peak magnetic synoptic maps covering the period 1976 August-2003 September. The field radial component, for each heliographic latitude, has been decomposed in intrinsic mode functions through the Empirical Mode Decomposition in order to investigate the time evolution of the various characteristic oscillating modes at different latitudes. The same technique has also been applied on synoptic maps of the meridional and east-west components, which were derived from the observed line-of-sight projection of the field by using the differential rotation. Results obtained for the ∼22 yr cycle, related to the polarity inversions of the large-scale dipolar field, show an antisymmetric behavior with respect to the equator in all the field components and a marked poleward flux migration in the radial and meridional components (from about −35 • and +35 • in the southern and northern hemispheres, respectively). The quasi-biennial oscillations (QBOs) are also identified as a fundamental timescale of variability of the magnetic field and associated with poleward magnetic flux migration from low latitudes around the maximum and descending phase of the solar cycle. Moreover, signs of an equatorward drift, at a ∼2 yr rate, seem to appear in the radial and toroidal components. Hence, the QBO patterns suggest a link to a dynamo action. Finally, the high-frequency component of the magnetic field, at timescales less than 1 yr, provides the most energetic contribution and it is associated with the outbreaks of the bipolar regions on the solar surface.

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Section: Results For the Radial Componentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 85%

The Dynamics of the Solar Magnetic Field: Polarity Reversals, Butterfly Diagram, and Quasi-Biennial Oscillations

Vecchio

Laurenza

Meduri

et al. 2012

ApJ

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“…Indeed, this periodicity represents the highest amplitude mode (j = 8, τ 8 = 21 ± 7 yr) in the HMF magnitude. The CLI mode j = 7 (τ 7 = 6.5 ± 0.5 yr) is found to be the third most prominent mode, while IMFs with τ j at the typical QBOs timescales (Benevolenskaya 1998;Bazilevskaya et al 2000Bazilevskaya et al , 2006 have lower amplitudes (j = 4, j = 5, and j = 6 with periods τ 4 = 1.31±0.04 yr, τ 5 = 2.19 ± 0.09 yr, and τ 6 = 3.5 ± 0.3, respectively). Mode j = 10, with τ 10 ∼ 40 yr, shows only one oscillation, whose τ j cannot be considered as reliable, given the limited time extent of the data set.…”

Section: Data Used and Methods Of Investigationmentioning

confidence: 91%

“…We remark that, when computing p over the whole time period and in the above frequency ranges, we obtain the same results computed through Equation (5) listed in the first and third column of Table 2. The parameter p has been computed in selected time intervals where there is no well defined HMF polarity, as has been reported in the literature (Makarov & Sivaraman 1986;Bazilevskaya et al 2000;Gopalswamy et al 2003). Values are listed in Table 3, which also indicates the sign (plus or minus) of the mean drift-associated mode in the considered time interval.…”

Section: Estimation Of Drift Effectsmentioning

confidence: 99%

“…As a consequence, the CR intensity shows a pronounced 11 yr variation, with the intensity maximum corresponding almost with the solar activity minimum and vice versa. In addition, many manifestations of solar magnetism, as well as some interplanetary phenomena, show quasi-biennial oscillations (QBOs; see Bazilevskaya et al 2000;Vecchio et al 2012a and references therein), which are also present in CR measurements (e.g., Laurenza et al 2012 and references therein). In particular, it has been shown that the main features of solar activity can be essentially described by superposing QBOs to the ∼11 yr mode (e.g., Vecchio et al 2010;Laurenza et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Drift Effects on the Galactic Cosmic Ray Modulation

Laurenza

Vecchio

Storini

et al. 2014

ApJ

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Cosmic ray (CR) modulation is driven by both solar activity and drift effects in the heliosphere, although their role is only qualitatively understood as it is difficult to connect the CR variations to their sources. In order to address this problem, the Empirical Mode Decomposition technique has been applied to the CR intensity, recorded by three neutron monitors at different rigidities (Climax, Rome, and Huancayo-Haleakala (HH)), the sunspot area, as a proxy for solar activity, the heliospheric magnetic field magnitude, directly related to CR propagation, and the tilt angle (TA) of the heliospheric current sheet (HCS), which characterizes drift effects on CRs. A prominent periodicity at ∼six years is detected in all the analyzed CR data sets and it is found to be highly correlated with changes in the HCS inclination at the same timescale. In addition, this variation is found to be responsible for the main features of the CR modulation during periods of low solar activity, such as the flat (peaked) maximum in even (odd) solar cycles. The contribution of the drift effects to the global Galactic CR modulation has been estimated to be between 30% and 35%, depending on the CR particle energy. Nevertheless, the importance of the drift contribution is generally reduced in periods nearing the sunspot maximum. Finally, threshold values of ∼40 • , ∼45 • , and >55 • have been derived for the TA, critical for the CR modulation at the Climax, Rome, and HH rigidity thresholds, respectively.

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