Evidence of Dayside Asymmetries in High-Latitude Magnetic Perturbations Measured By ST5 and DMSP

Tuesday, 16 December 2014: 2:52 PM
Delores J Knipp1, Liam M Kilcommons1, James A Slavin2, Guan Le3, Jesper W Gjerloev4 and Robert J Redmon5, (1)University of Colorado at Boulder, Boulder, CO, United States, (2)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (3)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (4)Johns Hopkins University - Applied Physics Laboratory, Laurel, MD, United States, (5)Natl Geophysical Data Ctr, Boulder, CO, United States
Magnetometer data from the three-spacecraft Space Technology 5 (ST5) mission and from two Defense Meteorological Spacecraft Program (DMSP) spacecraft are available during the 90-day ST5 mission (late March – late June, 2006). The ST5 spacecraft were in a 300 km x 4500 km orbit while the DMSP spacecraft were in near circular orbit at ~ 850 km. We removed gain jumps from the ST5 data and improved a high-latitude background removal method for DMSP. All data were processed through the Modified Apex Coordinate transformation and mapped to 110 km. Agreement between different spacecraft observations was verified by computing magnetic conjunctions and extracting data from a small region around each ST5-DMSP conjunction. We found excellent agreement between the magnetic perturbations at 277 conjunctions between DMSP and ST5. With these data we show: 1) a global view of storm-time field aligned current (FAC) perturbations; 2) a global view of calm-before-the-storm FAC events; and 3) clear evidence of hemispheric asymmetries in cusp region magnetic perturbation strength during the equinox season. Our methods provide a ‘path forward’ in terms of comparing on-orbit electric and magnetic field data from multiple spacecraft.