Magnetosphere-Ionosphere Coupling of Global Pi2 Pulsations
Tuesday, 2 September 2014
Regency Ballroom (Hyatt Regency)
Andreas Keiling1, Octav Marghitu2, Joachim Vogt3, Olaf Amm4, Costel Bunescu2, Vlad Constantinescu2, Harald U Frey5, Maria Hamrin6, Tomas Karlsson7, Rumi Nakamura8, Hans Nilsson9, Joshua L Semeter10 and Eugen Sorbalo11, (1)Space Sciences Laboratory, Berkeley, CA, United States, (2)Institute for Space Sciences, Bucharest-Magurele, Romania, (3)Jacobs University Bremen gGmbH, Bremen, Germany, (4)Finnish Meteorological Institute, Helsinki, Finland, (5)Univ California Berkeley, Berkeley, CA, United States, (6)Umea Univ, Umea, Sweden, (7)KTH Royal Institute of Technology, Stockholm, Sweden, (8)Austrian Academy of Sciences, Graz, Austria, (9)IRF Swedish Institute of Space Physics Kiruna, Kiruna, Sweden, (10)Boston Univ, Boston, MA, United States, (11)Jacobs University Bremen, Bremen, Germany
Abstract:
Global Pi2 pulsations have mainly been associated with either low/middle latitudes or middle/high latitudes and, as a result, have been treated as two different types of Pi2 pulsations, either the plasmaspheric cavity resonance or the transient response of the substorm current wedge, respectively. However, in some reports global Pi2 pulsations have a single period spanning low/middle/high latitudes. This "super" global type has not yet been satisfactorily explained. In particular, it has been a major challenge to identify the coupling between the source region and the ground. In this presentation, we report two consecutive super global Pi2 events which were observed over a wide latitudinal and longitudinal range, using the THEMIS and McMAC magnetometer networks. Using in-situ data from THEMIS, GOES and Geotail, it was possible to follow the Pi2 signal along various paths with time delays from the magnetotail to the ground. Furthermore, it was found that the global pulsations were a combination of various modes including the transient Alfven and fast modes, field line resonance, and possibly a forced cavity-type resonance. As for the source of the Pi2 periodicity, oscillatory plasma flow inside the plasma sheet during flow braking is a possible candidate. Such flow modulations, resembling the ground Pi2 pulsations, were recorded for both events.
