Abstract
Stereo energetic neutral atom (ENA) images obtained by Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS) are analyzed to quantify the latitudinal anisotropy of ring current ENAs, and by implication, the system‐level pitch‐angle response during a moderate geomagnetic storm on 6 April 2010. During a 15‐min interval just after midday, TWINS 1 and 2 were at similar local times but different latitudes, and thus were able to simultaneously sample two different pitch angles from selected locations. The observations show a global dawn‐dusk asymmetry in the ring current ENA latitudinal anisotropy, the dusk side being ∼1–2 orders of magnitude more anisotropic than the dawn side. The latitudinal dependence of the ENAs implies a duskside ion distribution that is more equatorial than isotropic; this anisotropy becomes less pronounced with increasing energy. The observed dawn‐dusk ENA anisotropy may be caused by ring current ions drifting adiabatically in self‐consistently varying electric and (nondipolar) magnetic fields.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
