Statistical observations of spatial characteristics of Pi1B pulsations |
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| Affiliation: | 1. Department of Physics, Augsburg College, Minneapolis, MN, USA;2. Space Sciences Laboratory, University of California, Berkeley, CA, USA;3. Space Science Center, University of New Hampshire, Durham, NH, USA;4. Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ, USA;5. Danish Meteorological Institute, Copenhagen, Denmark;6. Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, CA, USA;7. School of Mathematical and Physical Sciences, University of Newcastle, NSW, Australia;1. Skobelstyn Institute of Nuclear Physics, Lomonosov Moscow State University, Russia;2. Space Research Institute, RAS, Russia;3. Departmento de Física, Universidad de Santiago de Chile (USACH), Chile;4. Polar Geophysical Institute, Apatity, Murmansk Region, Russia;1. Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic, Bocni II, 14131 Prague, Czech Republic;2. George Mason University, School of Physics, Astronomy and Computational Science, 4400 University Drive, Fairfax, VA 22030, USA;3. NASA Goddard Space Flight Center, Heliospheric Physics Laboratory, Greenbelt, MD 20771, USA;1. Astronautical Engineering Department, Istanbul Technical University, Istanbul, Turkey;2. Meteorological Engineering Department, Faculty of Aeronautics and Astronautics, Istanbul Technical University, Istanbul, Turkey;3. Aeronautical Engineering Department, Faculty of Aeronautics and Astronautics, Istanbul Technical University, Istanbul, Turkey |
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| Abstract: | We have examined the spatial and temporal correlation of high-latitude Pi1B and Pi2 pulsations, mid-latitude Pi2 pulsations, and auroral substorm onsets identified in the IMAGE far ultraviolet imager (FUV) data. Numerous search coil and fluxgate magnetometers at high latitudes (65–80° in Antarctica and Greenland) and mid-latitude fluxgate magnetometers are used. We find that Pi1B onset times agree well with onset times of intense isolated auroral substorms identified by the IMAGE FUV instrument: Pi1B onsets occurred within the 2 min cadence of the imager. For any given event, we find that Pi1B are localized to approximately 4 h of local time and 7° of magnetic latitude relative to the initial auroral brightening location as observed by IMAGE FUV. Not surprisingly, we also find that Pi1B pulsations occur typically between 2100 and 0200 MLT. Comparison to Pi2 records from these and other lower-latitude stations shows that in almost all cases Pi1B activity coincides within ±2 min with Pi2 activity. Power law fits showed that Pi1B amplitude fell off with distance−2.9 for two strong events (i.e., similar to the r−3 falloff of the signal from a dipolar source), and only slightly more rapidly than the falloff of Pi2 activity (d−2.8). Given the global nature of Pi2 pulsations versus the localized nature of Pi1B events in this study, we conclude that the mechanism that drives Pi1B pulsations is likely different from that responsible for Pi2 pulsations. |
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