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- Title
The Statistical Characteristics of Small‐Scale Ionospheric Irregularities Observed in the Martian Ionosphere.
- Authors
Fowler, C. M.; Bonnell, J. W.; Huba, J. D.; Andersson, L.; Espley, J.; Benna, M.; Ergun, R. E.
- Abstract
Small‐scale ionospheric irregularities in magnetic field strength and ionospheric density have recently been discovered at Mars by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Studying these irregularities provides insight into the interaction between the thermosphere and ionosphere and allows for comparative aeronomy between Mars, Earth, and other planets. This paper reports the first statistical study utilizing 3.5 years of MAVEN in situ measurements to characterize these irregularities and to provide maps of where these irregularities are most likely to be observed. Irregularities are most likely to be observed at dawn and dusk, between solar zenith angles of 90° and 150°, although events are observed all the way to midnight. Irregularities occur primarily outside of the crustal magnetic field regions, between altitudes of ∼130 and 160 km, when ionospheric dynamo conditions exist (magnetized electrons and unmagnetized ions). The irregularities appear to be MHD‐like in nature (an interesting difference to their electrostatic terrestrial counterparts), characterized by variations in absolute magnetic field strength of 5–15% of the background field and perpendicular to magnetic field length scales of 5–20 km. Although MAVEN cannot accurately resolve the associated density variations, we estimate these variations to typically be between 10% and 75% of the background ionospheric density. When present, irregularity events appear to occur with equal likelihood above and below the ionospheric peak. At Earth, the occurrence of irregularity events exhibits strong seasonal dependencies; the MAVEN data set is currently too small to identify any conclusive trends as a function of Mars season. Key Points: We present the first extensive statistical study of ionospheric density and magnetic field irregularities at Mars, using MAVEN in situ dataIonospheric irregularities are most likely to occur outside of crustal magnetic field regions, between SZA of 90° to 150°Irregularities are characterized by variations in magnetic field strength of 5–15%, and ionospheric density of 10–75%, of background values
- Subjects
MARTIAN ionosphere; MARS Atmosphere &; Volatile Evolution (Artificial satellite); MAGNETIC fields; UPPER atmosphere; IONOSPHERE
- Publication
Journal of Geophysical Research. Space Physics, 2019, Vol 124, Issue 7, p5874
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2019JA026677