Localized Heating of the Martian Topside Ionosphere Through the Combined Effects of Magnetic Pumping by Large‐Scale Magnetosonic Waves and Pitch Angle Diffusion by Whistler Waves. Issue 5 (3rd March 2020)

• Record Type: Journal Article
• Authors: Fowler, C. M.; Agapitov, O. V.; Xu, S.; Mitchell, D. L.; Andersson, L.; Artemyev, A.; Espley, J.; Ergun, R. E.; Mazelle, C.
• Is Part Of: Geophysical research letters. Volume 47:Issue 5(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-03-03
• Subjects: magnetic pumping -- Mars ionosphere -- wave‐particle interactions -- whistler waves -- pitch angle diffusion; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2019GL086408
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We present Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of periodic ( ∼ 25 s) large‐scale (hundreds of km) magnetosonic waves propagating into the Martian dayside upper ionosphere. These waves adiabatically modulate the superthermal electron distribution function, and the induced electron temperature anisotropies drive the generation of observed electromagnetic whistler waves. The localized (in altitude) minimum in the ratio f pe / f ce provides conditions favorable for the local enhancement of efficient wave‐particle interactions, so that the induced whistlers act back on the superthermal electron population to isotropize the plasma through pitch angle scattering. These wave‐particle interactions break the adiabaticity of the large‐scale magnetosonic wave compressions, leading to local heating of the superthermal electrons during compressive wave "troughs." Further evidence of this heating is observed as the subsequent phase shift between the observed perpendicular‐to‐parallel superthermal electron temperatures and compressive wave fronts. This heating mechanism may be important at other unmagnetized bodies. Key Points: Large‐scale magnetosonic waves heat ionospheric electrons via the generation of whistler waves and subsequent wave‐particle interactions The observed heating mechanism demonstrates energy transfer from the solar wind to the Mars upper ionosphere Such a heating mechanism may be important at other unmagnetized bodies such as Venus and comets