Mapping pitch angle distribution of electrons and protons in the South Atlantic Anomaly between 2002 and 2018

NASA Reuven Ramaty High Energy Solar Spectroscopic Imager RHESSI and ESA PROBA-1 satellites, both flying the Low Earth Orbit, and equipped with small radiation monitors were used in this study. Proba-1 was launched on Oct 22nd, 2001 in the sun-synchronous orbit and is still in operation.  It is a small autonomous satellite developed for Technology Demonstration Program of ESA. Its primary goal was to test satellite autonomy. Its secondary objective was space environment investigation with Standard Radiation Environment Monitor SREM. Its three Si-diode detectors are optimized to measure electrons and protons encountered in the Earth Radiation Belts. Level 2 SREM data provide time resolved particle spectra along Proba-1 orbit. RHESSI was launched into space on February 5th, 2002 as NASA Small Explorer and operated until August 2018. Its Ge-spectrometer provided first ever permanent images of the Sun at wide range of X-ray energies. RHESSI small radiation monitor measured electrons with energies from about 65 keV and protons from above 28 MeV using well shielded Si-diode. The monitor, looking perpendicularly from the spacecraft rotation axis, allowed for sampling angular distribution of incoming particles. Inside the South Atlantic Anomaly SAA, the pointing direction of RHESSI nearly aligns with the geomagnetic field vector. This way angular distributions over the full range of pitch angles along the magnetic field line were measured. We discuss evolution of electron and proton pitch angles inside the SAA during the second half of solar cycle 23 and almost the whole solar cycle 24. Specific examples of observed features including anisotropies related to particle loss are provided. Impact of directionality distribution on radiation models is given, based on cross-comparison with Proba-1 observations.