One‐Hertz Waves at Mars: MAVEN Observations

Suranga Ruhunusiri; J. S Halekas; J. R Espley; F Eparvier; D Brain; C Mazelle; Y Harada; G. A DiBraccio; E. M. B Thiemann; D. E Larson; D. L Mitchell; B. M Jakosky; A. H Sulaiman

doi:10.1029/2017JA024618

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One‐Hertz Waves at Mars: MAVEN Observations

Journal article

Peer reviewed

One‐Hertz Waves at Mars: MAVEN Observations

Suranga Ruhunusiri, J. S Halekas, J. R Espley, F Eparvier, D Brain, C Mazelle, Y Harada, G. A DiBraccio, E. M. B Thiemann, D. E Larson, …

Journal of geophysical research. Space physics, Vol.123(5), pp.3460-3476

05/2018

DOI: 10.1029/2017JA024618

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Abstract

We perform a survey of 1‐Hz waves at Mars utilizing Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft observations for a Martian year. We find that the 1‐Hz wave occurrence rate shows an apparent variation caused by masking of the waves by background turbulence during the times when the background turbulence levels are high. To correct for this turbulence masking, we select waves that occur in time intervals where the background turbulence levels are low. We find that the extreme ultraviolet flux does not affect the wave occurrence rate significantly, suggesting that the newly born pickup ions originating in the Mars's exosphere contribute minimally to the 1‐Hz wave generation. We find that the wave occurrence rates are higher for low Mach numbers and low beta values than for high Mach numbers and high beta values. Further, we find that a high percentage of 1‐Hz waves satisfy the group‐standing condition, which suggests that a high percentage of the waves seen as monochromatic waves in the spacecraft frame can be broadband waves in the solar wind frame that have group velocities nearly equal and opposite to the solar wind velocity. We infer that the wave occurrence rate trends with the Mach number and proton beta are a consequence of how the Mach numbers and beta values influence the wave generation and damping or how those parameters affect the group‐standing condition. Finally, we find that the 1‐Hz waves are equally likely to be found in both the quasi‐parallel and the quasi‐perpendicular foreshock regions. Key Points One‐hertz waves at Mars show an apparent occurrence rate variation due to masking of the waves during times of high background turbulence levels The wave occurrence rates vary significantly with Mach numbers and proton beta values but do not vary significantly with EUV flux levels The 1‐Hz waves are observed in both the quasi‐parallel and quasi‐perpendicular foreshock regions with comparable occurrence rates

1‐Hz waves

group‐standing waves

low‐frequency whistler waves

Mars

MAVEN

Details

Title: Subtitle: One‐Hertz Waves at Mars: MAVEN Observations
Creators: Suranga Ruhunusiri - University of Iowa
J. S Halekas - University of Iowa
J. R Espley - Goddard Space Flight Center
F Eparvier - University of Colorado Boulder
D Brain - University of Colorado Boulder
C Mazelle - Université de Toulouse
Y Harada - University of Iowa
G. A DiBraccio - Goddard Space Flight Center
E. M. B Thiemann - University of Colorado Boulder
D. E Larson - University of California, Berkeley
D. L Mitchell - University of California, Berkeley
B. M Jakosky - University of Colorado Boulder
A. H Sulaiman - University of Iowa
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.123(5), pp.3460-3476
DOI: 10.1029/2017JA024618
ISSN: 2169-9380
eISSN: 2169-9402
Number of pages: 17
Grant note: NASA CNES
Language: English
Date published: 05/2018
Academic Unit: Physics and Astronomy
Record Identifier: 9984199668402771

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