Proton cyclotron waves occurrence rate upstream from Mars observed by MAVEN: Associated variability of the Martian upper atmosphere

Romanelli, Norberto; Mazelle, C.; Chaufray, Jean‐Yves; Meziane, K.; Lun, Shan; Ruhunusiri, S.; Connerney, J. E. P.; Espley, J. R.; Eparvier, F.; Thiemann, E.; Halekas, J. S.; Mitchell, David; McFadden, J. P.; Brain, David; Jakosky, B. M.

doi:10.1002/2016ja023270

Cited by 68 publications

(134 citation statements)

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“…In any case, SWIA observations indicate a remarkable level of seasonal variability in the exosphere, implying an order of magnitude variation in the column density that interacts with the solar wind outside of the bow shock during the time period surveyed. Other MAVEN observations of UV emission from the hydrogen corona, low‐frequency waves seen upstream near the proton cyclotron frequency [ Romanelli et al ., ], and pickup ions [ Rahmati et al ., ] confirm a seasonal variation in the corona during the MAVEN mission. This variation closely tracks the EUV flux, which primarily varies with heliocentric distance over this time period (solar cycle effects may play a secondary role).…”

Section: Solar Energy Inputs To the Martian Systemmentioning

confidence: 62%

Structure, dynamics, and seasonal variability of the Mars‐solar wind interaction: MAVEN Solar Wind Ion Analyzer in‐flight performance and science results

et al. 2017

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We report on the in‐flight performance of the Solar Wind Ion Analyzer (SWIA) and observations of the Mars‐solar wind interaction made during the Mars Atmosphere and Volatile EvolutioN (MAVEN) prime mission and a portion of its extended mission, covering 0.85 Martian years. We describe the data products returned by SWIA and discuss the proper handling of measurements made with different mechanical attenuator states and telemetry modes, and the effects of penetrating and scattered backgrounds, limited phase space coverage, and multi‐ion populations on SWIA observations. SWIA directly measures solar wind protons and alpha particles upstream from Mars. SWIA also provides proxy measurements of solar wind and neutral densities based on products of charge exchange between the solar wind and the hydrogen corona. Together, upstream and proxy observations provide a complete record of the solar wind experienced by Mars, enabling organization of the structure, dynamics, and ion escape from the magnetosphere. We observe an interaction that varies with season and solar wind conditions. Solar wind dynamic pressure, Mach number, and extreme ultraviolet flux all affect the bow shock location. We confirm the occurrence of order‐of‐magnitude seasonal variations of the hydrogen corona. We find that solar wind Alfvén waves, which provide an additional energy input to Mars, vary over the mission. At most times, only weak mass loading occurs upstream from the bow shock. However, during periods with near‐radial interplanetary magnetic fields, structures consistent with Short Large Amplitude Magnetic Structures and their wakes form upstream, dramatically reconfiguring the Martian bow shock and magnetosphere.

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Section: Solar Energy Inputs To the Martian Systemmentioning

confidence: 62%

Structure, dynamics, and seasonal variability of the Mars‐solar wind interaction: MAVEN Solar Wind Ion Analyzer in‐flight performance and science results

et al. 2017

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“…Yamauchi et al () found that pickup ions upstream from Mars are significantly enhanced around perihelion and suggested this was due to a seasonal enhancement in the underlying neutral exosphere. Romanelli et al () confirmed such a seasonal variation in the neutral exosphere, with neutral hydrogen densities (at altitides of 3 Mars Radii) at perihelion ≈4× denser than at aphelion. Romanelli et al () discovered that this coincided with a significant enhancement in the abundance of the ULF ("proton cyclotron") waves discussed in this study.…”

Section: A Search For More Eventsmentioning

confidence: 88%

“…The intensity of ULF waves upstream of Mars (Halekas et al, ) and Venus (Delva et al, ) is strongly dependent upon the orientation of the interplanetary magnetic field, with more intense waves being observed when the IMF is radial , for example, parallel to the Sun‐Planet line. At Mars, ULF waves exhibit a strong seasonal variation, with stronger waves closer to perihelion (Romanelli et al, ) due to the exospheric hydrogen that gets heated and enhanced at higher altitudes due to the brightening sunlight (Yamauchi et al, ). These waves attempt to propagate upstream (sunwards) but are blown backward toward the bow shock by the solar wind.…”

Section: Introductionmentioning

confidence: 99%

Solar Wind Induced Waves in the Skies of Mars: Ionospheric Compression, Energization, and Escape Resulting From the Impact of Ultralow Frequency Magnetosonic Waves Generated Upstream of the Martian Bow Shock

et al. 2018

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Using data from the National Aeronautics and Space Administration Mars Atmosphere and Voltatile EvolutioN and the European Space Agency Mars Express spacecraft, we show that transient phenomena in the foreshock and solar wind can directly inject energy into the ionosphere of Mars. We demonstrate that the impact of compressive ultralow frequency waves in the solar wind on the induced magnetospheres drive compressional, linearly polarized, magnetosonic ultralow frequency waves in the ionosphere, and a localized electromagnetic "ringing" at the local proton gyrofrequency. The pulsations heat and energize ionospheric plasmas. A preliminary survey of events shows that no special upstream conditions are required in the interplanetary magnetic field or solar wind. Elevated ion densities and temperatures in the solar wind near to Mars are consistent with the presence of an additional population of Martian ions, leading to ion‐ion instablities, associated wave‐particle interactions, and heating of the solar wind. The phenomenon was found to be seasonal, occurring when Mars is near perihelion. Finally, we present simultaneous multipoint observations of the phenomenon, with the Mars Express observing the waves upstream, and Mars Atmosphere and Voltatile EvolutioN observing the response in the ionosphere. When these new observations are combined with decades of previous studies, they collectively provide strong evidence for a previously undemonstrated atmospheric loss process at unmagnetized planets: ionospheric escape driven by the direct impact of transient phenomena from the foreshock and solar wind.

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“…The absence of spectral indices with small positive values for L s ∼0 and L s ∼90 (see Figures b and c) indicates that this energy injection mechanism is not dominant for these latter time intervals. An investigation of proton cyclotron wave occurrence rate by Romanelli et al [], encompassing these same three time periods, revealed a high occurrence rate of proton cyclotron waves at L s ∼270 and a drastic diminishment at L s ∼0 and L s ∼90. Thus, we infer that the small positive values of spectral indices reveal the presence of proton cyclotron waves.…”

Section: Discussionmentioning

confidence: 99%

Characterization of turbulence in the Mars plasma environment with MAVEN observations

et al. 2017

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We characterize turbulence in the Mars plasma environment in a global scale for the first time by computing spectral indices for magnetic field fluctuations (slopes in the magnetic field power spectra) and determining how they vary with frequency and in different regions. In the magnetosheath, unlike in the solar wind, we find an absence of the inertial range which has a spectral index value equal to the Kolmogorov scaling value of −5/3. Instead, as observed in the magnetosheaths of other planets, we find that the spectral indices transition from low negative values close to −0.5 at low frequencies (< proton gyrofrequency) to values much lower than −5/3 at high frequencies (> proton gyrofrequency). This indicates that the pristine solar wind is modified at the Martian bow shock and that the fluctuations are dominated by locally generated fluctuations in the magnetosheath. The absence of spectral indices with the Kolmogorov scaling value indicates that the fluctuations in the magnetosheath do not have sufficient time to interact with one another leading to a fully developed energy cascade. Spectral index values near the Kolmogorov scaling value are observed for the low‐frequency range near the magnetic pileup boundary, and this indicates the presence of fully developed energy cascade. In the wake, we find that the spectral indices have approximately the same values, typically near −2, for both the low‐ and high‐frequency ranges. We observe seasonal variations of the spectral indices, mainly in the upstream region, which indicate the seasonal variations of the proton cyclotron waves.

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Proton cyclotron waves occurrence rate upstream from Mars observed by MAVEN: Associated variability of the Martian upper atmosphere

Cited by 68 publications

References 53 publications

Structure, dynamics, and seasonal variability of the Mars‐solar wind interaction: MAVEN Solar Wind Ion Analyzer in‐flight performance and science results

Structure, dynamics, and seasonal variability of the Mars‐solar wind interaction: MAVEN Solar Wind Ion Analyzer in‐flight performance and science results

Solar Wind Induced Waves in the Skies of Mars: Ionospheric Compression, Energization, and Escape Resulting From the Impact of Ultralow Frequency Magnetosonic Waves Generated Upstream of the Martian Bow Shock

Characterization of turbulence in the Mars plasma environment with MAVEN observations

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