Temporal variations of strength and location of the South Atlantic Anomaly as measured by RXTE

Fürst, Felix; Wilms, J.; Rothschild, R. E.; Pottschmidt, K.; Smith, David M.; Lingenfelter, R. E.

doi:10.1016/j.epsl.2009.02.004

Cited by 47 publications

(53 citation statements)

References 36 publications

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“…The associated particle flux change however remains small when compared to the oscillations of the anomaly during the solar cycle and cannot be detected. In contradiction with Fürst et al (2009) we conclude that rapid changes of the main field cannot be detected in particle flux measurements.…”

Section: Discussioncontrasting

confidence: 91%

“…In fact, a westward drift of the anomaly of about 0.3 • /yr is retrieved from the movement of the eccentric dipole, which is consistent with estimates obtained directly from particle flux data (e.g. Fürst et al, 2009;Noel et al, 2014;Schaefer et al, 2016). It is enlightening to describe the anomaly in this way, the interaction of charged particles with the main field can be considered in a dipole field geometry (though tilted and displaced from the Earth's centre).…”

Section: Reference Framessupporting

confidence: 84%

“…Casadio and Arino, 2011;Qin et al, 2014). To account for an apparent West-East morphological asymmetry, Weibull and Gumbel functions have also been tested (Fürst et al, 2009;Hell, 2010). Here, we follow a different approach by making use of a statistical non-parametric method, i.e., that does not assume any particular spatial or temporal dependences for the data.…”

Section: Principal Component Analysis Applied To Saamentioning

confidence: 99%

“…The neutral atmosphere expands during the ascending phase of the solar cycle and, at altitudes above 100 km, its density increases (Solomon et al, 2013). As a result, in regions where mirror points are low enough, protons are removed from the inner belt through nuclear collisions with atmospheric neutral particles (Gledhill, 1976), explaining why the particle flux in the SAA region is anti-correlated with the solar activity as measured by the 10.7 cm radio flux of the Sun (Fürst et al, 2009;Casadio and Arino, 2011;Qin et al, 2014). This effect is maximized for the low values of L that correspond to the highest energy proton shells (Vacaresse et al, 1999).…”

Section: Introduction: the Particle Flux In The South Atlantic Anomalymentioning

confidence: 99%

“…Unlike most previous authors who chose either Gaussian (e.g. Konradi et al, 1994) or Weibull (Fürst et al, 2009) functions to describe the shape of the SAA, we do not assume a priori geometry of the anomaly. Spatial patterns emerge instead from the Principal Component Analysis (PCA) of either POES particle flux or CALIOP dark noise data, which are distributed on a geographical grid.…”

Section: Introduction: the Particle Flux In The South Atlantic Anomalymentioning

confidence: 99%

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The South Atlantic Anomaly throughout the solar cycle

Domingos

Jault

Pais

et al. 2017

Earth and Planetary Science Letters

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The Sun-Earth's interaction is characterized by a highly dynamic electromagnetic environment, in which the magnetic field produced in the Earth's core plays an important role. One of the striking characteristics of the present geomagnetic field is denoted the South Atlantic Anomaly (SAA) where the total field intensity is unusually low and the flux of charged particles, trapped in the inner Van Allen radiation belts, is maximum. Here, we use, on one hand, a recent geomagnetic field model, CHAOS-6, and on the other hand, data provided by different platforms (satellites orbiting the Earth -POES NOAA for 1998 and CALIPSO for 2006. Evolution of the SAA particle flux can be seen as the result of two main effects, the secular variation of the Earth's core magnetic field and the modulation of the density of the inner radiation belts during the solar cycle, as a function of the L value that characterises the drift shell, where charged particles are trapped. To study the evolution of the particle flux anomaly, we rely on a Principal Component Analysis (PCA) of either POES particle flux or CALIOP dark noise. Analysed data are distributed on a geographical grid at satellite altitude, based on a L-shell reference frame constructed from the moving eccentric dipole. Changes in the main magnetic field are responsible for the observed westward drift. Three PCA modes account for the time evolution related to solar effects. Both the first and second modes have a good correlation with the thermospheric density, which varies in response to the solar cycle. The first mode represents the total intensity variation of the particle flux in the SAA, and the second the movement of the anomaly between different L-shells. The proposed analysis allows us to well recover the westward drift rate, as well as the latitudinal and longitudinal solar cycle oscillations, although the analysed data do not cover a complete (Hale) magnetic solar cycle (around 22 yr). Moreover, the developments made here would enable us to forecast the impact of the South Atlantic Anomaly on space weather. A model of the evolution of the eccentric dipole field (magnitude, offset and tilt) would suffice, together with a model for the solar cycle evolution.

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Section: Discussioncontrasting

confidence: 91%

Section: Reference Framessupporting

confidence: 84%

Section: Principal Component Analysis Applied To Saamentioning

confidence: 99%

Section: Introduction: the Particle Flux In The South Atlantic Anomalymentioning

confidence: 99%

Section: Introduction: the Particle Flux In The South Atlantic Anomalymentioning

confidence: 99%

See 3 more Smart Citations

The South Atlantic Anomaly throughout the solar cycle

Domingos

Jault

Pais

et al. 2017

Earth and Planetary Science Letters

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Solar cycle variations of trapped proton flux in the inner radiation belt

Qin

Zhang

et al. 2014

JGR Space Physics

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Trapped proton population in the inner radiation belt is highly dense, posing a potential danger to astronauts and man-made space assets traversing through this region. While being significantly stable within timescales up to hundreds of days, inner zone proton fluxes can exhibit considerable solar cycle variations, which has not been investigated comprehensively yet. To analyze the long-term variation of the South Atlantic Anomaly (SAA), we adopt the proton flux data measured by NOAA 15 from 1999 through 2009 and perform statistical analyses on the basis of reasonable Gaussian fits. We report that the variation of the peak proton flux in the SAA is anticorrelated with that of F 10.7 during a solar cycle. There also exists a phase lag of 685 days between the solar F 10.7 flux and the proton flux. Similar features are seen for changes of the SAA distribution area, which in addition shows a rapid decrease during the solar maximum and a slow increase during the solar minimum. We also find that the region where the proton flux peaks drifts westward year by year with larger drift rates during the solar minimum. The peak region shifts southward during the solar maximum but in the opposite direction during the solar minimum with higher shift speed. Enhancements in solar wind dynamic pressure can favor the north-south drift of the SAA.

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Short‐term variations of the inner radiation belt in the South Atlantic anomaly

Zou

Zong

et al. 2015

JGR Space Physics

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Long‐term variations of South Atlantic anomaly (SAA) are generally derived by fitting a Gaussian‐like function to an averaged distribution of the proton flux at a certain altitude accumulated over time periods for a month or longer. These data do not show the short‐term variation of SAA arising from geomagnetic storm effects whose time scale is less than a month. To investigate the short‐term variations, the features of SAA for the high‐energy protons detected by NOAA Polar Orbiting Environmental Satellites during 1998–2008 have been investigated with a 5 day running average method. It is found that the two SAA parameters for three proton channels reflect the maximal proton flux in SAA and the extension of SAA decreases several percent during geomagnetic storms. Possible reasons for the decreases of the two SAA parameters for high‐energy protons are discussed. Proton losses at the outer boundary of the inner radiation belt can be explained by the field line curvature scattering mechanism, while the decrease of the proton flux near the center of SAA is probably caused by the enhanced neutral atmospheric density during geomagnetic storms. The study of the behavior of high‐energy protons in SAA is useful for understanding of storm time and long‐term variations of the radiation environment near Earth and for constructing dynamic radiation belt models.

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Temporal variations of strength and location of the South Atlantic Anomaly as measured by RXTE

Cited by 47 publications

References 36 publications

The South Atlantic Anomaly throughout the solar cycle

The South Atlantic Anomaly throughout the solar cycle

Solar cycle variations of trapped proton flux in the inner radiation belt

Short‐term variations of the inner radiation belt in the South Atlantic anomaly

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