EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Variation of Ionospheric O+ and H+ Outflow during Sawtooth Oscillations

Niloufar Nowrouzi1, Lynn Kistler1, Eric Lund1,3, and Kai Zhao2
Niloufar Nowrouzi et al.
  • 1University of New Hampshire, Space Science Senter, United States of America (
  • 2nstitute of Space Weather, Nanjing University of Information Science and Technology, Nanjing, China
  • 3College Brook Scientific, Durham, NH, USA

Sawtooth events are repeated injections of energetic particles at geosynchronous orbit. Although studies have shown that 94% of sawtooth events occur during  magnetic storm times, the main factor that causes a sawtooth event is unknown. Simulations have suggested that heavy ions like O+ may play a role in driving the sawtooth mode by increasing the magnetotail pressure and causing the magnetic tail to stretch. O+ ions located in the nightside auroral region have a direct access to the near-earth plasma-sheet. O+ in the dayside cusp can reach to the midtail plasma-sheet when the convection velocity is sufficiently strong. Whether the dayside or nightside source is more important is not known.

We show results of a statistical study of the variation of the O+ and H+ outflow flux during sawtooth events for SIR and ICME sawtooth events. We perform a superposed epoch analysis of the ion outflow using the TEAMS (Time-of-Flight Energy Angle Mass Spectrograph) instrument on the FAST spacecraft. TEAMS measures the ion composition over the energy range of 1 eV e-1 to 12 keV e-1.  We have done major corrections and calibrations (producing 3D data set, anode calibration, mass classification, removing ram effect and incorporating dead time corrections) on TEAMS data and produced a data set for four data species (H+, O+, and He+). From 1996 to 2007, we have data for 133 orbits of CME-driven and for 103 orbits of SIR-driven sawtooth events with an altitude above 1500 km. We found that:

  • the averaged O+ outflow flux is more intense in the cusp dayside than in the nightside, before and after onset time.
  • Before onset, an intense averaged outflow flux in the dawnside of CME events is seen. This outflow decreases after onset time.
  • In both CME-driven and SIR-driven, the averaged O+ outflow increases after onset time, in the nightside, cusp dayside. This increase is greater on the nightside than in the cusp.

We will develop this study by performing a similar statistical study for H+ outflow and finally will compare the H+ result with the O+ result.

How to cite: Nowrouzi, N., Kistler, L., Lund, E., and Zhao, K.: The Variation of Ionospheric O+ and H+ Outflow during Sawtooth Oscillations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13991,, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.