Physics Department Seminar University of Alaska Fairbanks

J O U R N A L    C L U B


Space Plasma Science with Active Satellite Encounters

Paul Bernhardt
Geophysical Institute, UAF



Satellites in Low Earth Orbit, (LEO) can produce disturbances in the ionosphere that are recorded with other satellites using plasma wave and particle detectors. This process is useful for determining the plasma wave excitation around a satellite and determining the environmental impact of spacecraft rocket engine burns in space. For the past 20 years, rocket engines have been fired in the ionosphere with the specific purpose of making neutral exhaust clouds for investigation with in situ diagnostic instruments on satellites. For instance, in July 2009, the OMS engines on the Space Shuttle Endeavour (STS-127) were ignited for 12 seconds to produce a water vapor and carbon dioxide cloud to impact the AFLR C/NOFS satellite located at a range of 220 km [Bernhardt et al., 2012]. This satellite to satellite encounter produced a wide range of plasma waves that were recorded by the VEFI instrument on C/NOFS. The plasma disturbances excited by the STS-127 burn were (1) Compressional or Fast Alfven Wave Pulse, (2) Whistlers, (3) Ion Acoustic Turbulence, and (4) Lower Hybrid Turbulence. More recently, in July 2018, the BT-4 rocket motor on the Cygnus Spacecraft was fired for 30 seconds to yield a hypersonic exhaust cloud intersected 50 km away by the SWARM-E satellite with the Radio Receiver Instrument (RRI). Measurements of low frequency (10 Hz to 32 kHz) plasma waves [Bernhardt et al. 2021], show a frequency shift in the Strong Plasma Wave Emission (SWPE) of lower-hybrid waves that lasted for 20 seconds of the Cygnus burn. The next Cygnus burn experiment occurred in May 2020 when the BT-4 engine at 500 km altitude was fired over a ground VLF transmitter when the SWARM-E RRI was above the burn at 1000 km altitude on the same magnetic field line. This experiment produced 30 to 50 dB amplifications coherent VLF waves from ground sources [Bernhardt, 2021]. Recently, on 4 March 2022, the SWARE-E satellite passed by the Starlink-2521 satellite with a range of 400 meters. The RRI instrument detected a strong burst of waves near the lower hybrid frequency with that “near collision”. The implications of these measurements will be discussed.


Friday, 18 March 2022

Globe Room, Elvey Building and on Zoom :