Near-equatorial Pi2 and Pc3 waves observed by CHAMP and on SAMBA/MAGDAS stations

Abstract

We have examined simultaneous ULF activity in the Pi2 and Pc3 bands at the near-equatorial magnetic stations in South America from SAMBA and MAGDAS arrays and low-orbiting CHAMP satellite during its passage over this meridional network. At the nighttime, both Pi2 and Pc3 waves in the upper ionosphere and on the ground are nearly of the same magnitude and in-phase. At the same time, the daytime Pc3 pulsations on the ground and in space are nearly out-of-phase. Comparison of observational results with the theoretical notions on the MHD wave interaction with the system ionosphere-atmosphere-ground suggests that nighttime low-latitude Pi2 and Pc3 wave signatures are produced by magnetospheric fast compressional mode. The daytime near-equatorial Pc3 waves still resist a quantative interpretation. These waves may be produced by a combination of two mechanisms: compressional mode leakage through the ionosphere, and by oscillatory ionospheric current spreading towards equatorial latitudes.

Low‐latitude Pi2 oscillations observed by polar Low Earth Orbiting satellite

“…These percentage values are found to be 25, 8, and 43 in the frequency bands 6-10 mHz, 10-15 mHz, and 15-25 mHz, respectively (average~25%), indicating that~75% of nighttime events have higher amplitude at satellite. The coherent in-phase oscillations observed in the compressional component at satellite and H at the ground are in accordance with previous satellite-based studies suggesting cavity-mode oscillations during nighttime [Takahashi et al, 1995;Sutcliffe and Lühr, 2003;Sutcliffe and Lühr, 2010;Han et al, 2004;Cuturrufo et al, 2014]. If Pi2 pulsations are generated by the cavity-mode resonance, then those Pi2 signatures should appear in the poloidal component as well [Takahashi et al, 1995;Sutcliffe and Lühr, 2010].…”

New opportunities offered by Cubesats for space research in Latin America: The SUCHAI project case

“…Since 2002 Chilean scientists, led by Dr. Stepanova, have been collaborating with the University of California Los Angeles and the Air Force Research Lab in the SAMBA international project financed by NSF and AFRL (P.I., E. Zesta). The magnetometer array and in particular SAMBA array can study multiple phenomena such as: (1) Equatorial density variation and the connection to the equatorial electrojet (Yizengaw et al, 2013), (2) The plasmasphere mass density distribution and its effect on radiation belt fluxes (Boudouridis and Zesta, 2007), (3) ULF wave propagation and magnetosphere-ionosphere coupling (Cuturrufo et al, 2015) and (4) Dynamics of auroral electrojects during strong geomagnetic storms (Vassiliadis et al, 2000). The magnetometers used by SAMBA are fluxgate magnetometers similar to those used in the NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, which study aurora formation.…”

Nighttime Pc3 pulsations: MM100 and MAGDAS observations

“…However, parameters and eigenfrequencies of this cavity are known very approximately, and it is unclear whether they may comprise the Pc3 band. Coordinated observations at low-orbiting CHAMP satellite and on the ground (Cuturrufo et al 2015) indeed confirmed that nighttime Pc3 pulsations at low latitudes are fast mode waves directly transmitted to the ground. Upon propagation into the inner magnetosphere, in contrast to Pi2 transients, fast mode waves in the Pc3 band emitted from the magnetotail region can be partially converted into Alfven waves at midlatitudes (L ≈ 2).…”

“…These variations followed the variations of the IMF magnetic field magnitude and cone angle, indicating the upstream wave origin of the observed nighttime wave event. Compressional mode Pc3 waves were detected simultaneously at low latitudes at nightside by low-orbiting satellite and ground stations (Cuturrufo et al 2015). Thus, these case studies indicated that dayside and nightside Pc3-4 waves are coupled.…”