Reidy_et_al-2018-Journal_of_Geophysical_Research__Space_Physics.pdf (16.69 MB)
Interhemispheric Survey of Polar Cap Aurora
journal contributionposted on 2019-08-20, 14:38 authored by JA Reidy, RC Fear, DK Whiter, B Lanchester, AJ Kavanagh, SE Milan, JA Carter, LJ Paxton, Y Zhang
This study investigates the interhemispheric nature of polar cap auroras via ultraviolet imaging, combined with particle data, to determine whether they occur on open or closed field lines. Data from the SSUSI (Special Sensor Ultraviolet Spectrographic Imager) instrument on board the DMSP (Defence Meteorological Satellite Program) spacecraft are examined. The DMSP spacecraft are in 90‐min orbits; hence, images of each hemisphere are separated by 45 min providing a good opportunity for interhemispheric study. 21 polar cap arc (PCA) events are recorded in December 2015 which have particle data from the SSJ/4 particle spectrometer associated with an arc in at least one hemisphere. Nine events are found to contain "arcs" consistent with a closed field line mechanism, that is, arcs associated with an ion signature present in both hemispheres. Six events contained arcs that were consistent with an "open field line" mechanism, that is, they were associated with electron‐only precipitation. Events containing arcs that were not consistent with either of these expectations are also explored, including an example of a "non‐conjugate" theta aurora and an interesting example of auroral morphology similar to a PCA which is associated with a geomagnetic storm. Seasonal effects are also investigated through a statistical analysis of PCAs over 4 months in 2015. It is found that PCAs are visible in the SSUSI data at least 20% of the time and that it is likely some are missed due to the spacecraft field of view and poor sensitivity in the summer hemisphere due to increased solar illumination.
This work was supported by the Natural Environmental Research Council (NERC) studentship number NE/L002531/1. R.C.F. was supported by the United Kingdom's Science and Technology Facilities Council (STFC) Ernest Rutherford Fellowship ST/K004298/2. D.K.W. and B.S.L. are supported by NERC Grant NE/N004051/1. S.E.M. and J.A.C. are supported by the STFC consolidated Grant ST/N000749/1. S.E.M is also supported by the Research Council of Norway under contract 223252/F50. The SSUSI data were obtained from http://ssusi.jhuapl.edu/. The DMSP particle detectors were designed by D. Hardy of Air Force Research Laboratory, and data were obtained from the Johns Hopkins University Applied Physics Laboratory. OMNI and ARTEMIS data were obtained from https://omniweb.gsfc.nasa.gov/ and https://sscweb.gsfc.nasa.gov/, respectively. For the Iridium‐derived AMPERE data (http://ampere.jhuapl.edu/), we acknowledge the AMPERE Science Center. The authors would also like to thank Stephen Browett and John Coxon for their help during this study.
CitationJournal of Geophysical Research: Space Physics, 2018, 123 (9), pp. 7283-7306 (24)
Author affiliation/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy
- VoR (Version of Record)