The South Atlantic Anomaly throughout the solar cycle

Abstract

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.

South Atlantic Anomalyduring ascending and maximum phase of solar cycle 24

“…The research on the SAA throughout the solar cycle has been made by Domingos et al (2017). Evolution of the SAA particle flux can be seen as the result of two main effects, the secular variation of the Earth's magnetic field and the modulation of the protons density of the inner Van Allen radiation belt during the solar cycle (Domingos et al, 2017).…”

“…The research on the SAA throughout the solar cycle has been made by Domingos et al (2017). Evolution of the SAA particle flux can be seen as the result of two main effects, the secular variation of the Earth's magnetic field and the modulation of the protons density of the inner Van Allen radiation belt during the solar cycle (Domingos et al, 2017). In order to learn on the evolution of the particle flux anomaly, the method Principal Component Analysis (PCA) of either Polar Orbiting Environmental Satellites particle flux or Cloud-Aerosol Lidar with Orthogonal Polarization dark noise has been applied.…”

“…The SAA region can be describe as a low intensity magnetic field region. Study has been made by Domingos (2017) on the impact of SAA on the space weather. One of the dangers to spacecraft in orbit around the Earth is the presence of large doses of radiation encountered in space (Schaefer et al, 2016).…”

South Atlantic Anomaly, Ionospheric Signals from Seismic Events

“…Figure 3 displays the distribution of the world magnetic field, comparing the regions with high magnetic fields and lower magnetic fields. Domingos et al have found that the eccentric dipole is currently offset from the Earth's center by about 550 km in a direction approximately 220N, 1400E [5].…”

CALIPSO Lidar Calibration at 532 nm: Version 4 Nighttime Algorithm

“…Anomaly (SAA), where high energy charged particles from the sun and cosmic rays trapped in the Van Allen belts come down to relatively low altitudes (Noel et al, 2014;Domingos et al, 2017). Because the CALIOP 10 photomultipliers (PMTs) are not shielded against cosmic radiation, when these charged particles strike the PMT dynode chain they can generate large noise excursions (i.e., "spikes") that appear at arbitrary altitudes throughout the measured profiles ).…”