Ducted electromagnetic waves in the Martian ionosphere detected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding radar

Zhang, Zhenfei; Orosei, R.; Huang, Qian; Zhang, Jie

doi:10.1002/2016gl069591

Cited by 3 publications

(27 citation statements)

References 42 publications

(89 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We indicate the extension of the interval for which a trace associated with the epsilon signature is visible by the red hatched region in Figure . Significantly, this leads to a clear connection between the epsilon signature reported by Zhang et al () and the peak density enhancements reported by Nielsen et al (), with the final reflection site of the T2 branch of the epsilon trace (the ionospheric footprint of the ducting field line) being colocated with the peak density enhancement.…”

Section: Observationssupporting

confidence: 66%

“…This is in addition to more complex signatures simultaneously detected resulting from ducted propagation of the sounder pulses along the field‐aligned irregularities, including a long‐distance duct that leads to reflections from the ionospheric peak, close to the region sampled by the nadir case from the first sounding. The most obvious signature of these ducted traces is the epsilon noted by Zhang et al (). We note the apparent lack of the isolated corresponding T1 trace in Figure d, which is expected at delays smaller than that of the nadir reflection on the basis of the properties of the T2 and T1+T2 traces (from which the expected T1 trace can be uniquely determined).…”

Section: Summary and Discussionmentioning

confidence: 88%

“…The final ionogram shown in Figure d depicts one of the epsilon signatures, reported first in the Martian ionosphere by Zhang et al (). In addition to a more typical ionospheric reflection similar to that seen in Figure a, three connected traces are also visible over much larger delays of ∼3–4.4 ms.…”

Section: Observationsmentioning

confidence: 81%

“…Furthermore, Andrews et al () have demonstrated that the echoes associated with ionospheric upwellings are highly repeatable, being detectable in all orbits that cross over the same region. Their relative stability and repeatability is in contrast to these peak density enhancements, which are only very rarely observed (Zhang et al, ).…”

Section: Observationsmentioning

confidence: 97%

“…Throughout the interval shown, the spacecraft moved to progressively lower SZAs, and periapsis was reached at 06:15. Vertical red dashed lines and shading through each panel span the period in which the epsilon signature was reported by Zhang et al (2016), while vertical black dashed lines and gray shading show the three peak density increases noted by Nielsen et al (2007) on this orbit. The time variation of the peak frequency of the ionospheric reflection can be discerned by examining the highest frequency signals in Figure 2a, which rise above the dark blue background intensity.…”

Section: Observationsmentioning

confidence: 99%

See 4 more Smart Citations

MARSIS Observations of Field‐Aligned Irregularities and Ducted Radio Propagation in the Martian Ionosphere

et al. 2018

View full text Add to dashboard Cite

Knowledge of Mars's ionosphere has been significantly advanced in recent years by observations from Mars Express and lately Mars Atmosphere and Volatile EvolutioN. A topic of particular interest are the interactions between the planet's ionospheric plasma and its highly structured crustal magnetic fields and how these lead to the redistribution of plasma and affect the propagation of radio waves in the system. In this paper, we elucidate a possible relationship between two anomalous radar signatures previously reported in observations from the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on Mars Express. Relatively uncommon observations of localized, extreme increases in the ionospheric peak density in regions of radial (cusp‐like) magnetic fields and spread echo radar signatures are shown to be coincident with ducting of the same radar pulses at higher altitudes on the same field lines. We suggest that these two observations are both caused by a high electric field (perpendicular to B) having distinctly different effects in two altitude regimes. At lower altitudes, where ions are demagnetized and electrons magnetized, and recombination dominantes, a high electric field causes irregularities, plasma turbulence, electron heating, slower recombination, and ultimately enhanced plasma densities. However, at higher altitudes, where both ions and electrons are magnetized and atomic oxygen ions cannot recombine directly, the high electric field instead causes frictional heating, a faster production of molecular ions by charge exchange, and so a density decrease. The latter enables ducting of radar pulses on closed field lines, in an analogous fashion to interhemispheric ducting in the Earth's ionosphere.

show abstract

Section: Observationssupporting

confidence: 66%

Section: Summary and Discussionmentioning

confidence: 88%

Section: Observationsmentioning

confidence: 81%

Section: Observationsmentioning

confidence: 97%

Section: Observationsmentioning

confidence: 99%

See 3 more Smart Citations

MARSIS Observations of Field‐Aligned Irregularities and Ducted Radio Propagation in the Martian Ionosphere

et al. 2018

View full text Add to dashboard Cite

show abstract

Electron Densities and Temperatures in the Martian Ionosphere: MAVEN LPW Observations of Control by Crustal Fields

et al. 2023

View full text Add to dashboard Cite

The electrically conducting Martian ionosphere extends from the upper atmosphere of the planet out into space, where it forms an obstacle to the motion of the solar wind in its flow through and around the near-Mars space environment (see e.g., Witasse et al., 2008). Owing to its formation primarily by ionization by solar ultra violet radiation, Mars's ionosphere varies principally with solar zenith angle (SZA) and altitude, h, (or, more accurately neutral atmospheric density). In contrast to the Venus solar wind interaction, which may well be considered somewhat more straightforward, the Mars-solar wind interaction is complicated by two significant factors. First, the larger extent of the Martian exosphere and subsequent ionization of oxygen and hydrogen well outside the ionosphere gives rise to a pronounced pickup ion plume (e.g., Dong et al., 2015), and moreover reduces the extent to which well-defined plasma boundaries can be said to be present separating the solar wind from the ionosphere Abstract Mars Express and Mars Atmosphere and Volatile Evolution (MAVEN) observations have demonstrated the influence of Mars's spatially variable crustal magnetic fields upon the configuration of the plasma in the ionosphere. This influence furthermore leads to variations in ionospheric escape, conceivably in part through the modification of the plasma density and electron temperature in the upper ionosphere. In this study, we examine MAVEN Langmuir Probe and Waves data, finding a clear correspondence between the structure of the crustal fields and both the measured electron temperatures and densities, by first constructing an "average" profile from which departures can be quantified. Electron temperatures are shown to be lower in regions of strong crustal fields over a wide altitude range. We extend previous analyses to cover the nightside ionosphere, finding the same effects present to a lesser degree, in contrast to previous studies where the opposite relationship was found between densities and crustal fields. We further determine the altitude range over which this coupling between both plasma density (and temperature) and crustal fields is effective and use measurements made by MAVEN in the solar wind to explore the dependence of this crustal field control on the coupling to the solar wind and the interplanetary magnetic field (IMF). Based on this, there is some suggestion that variations in the solar wind dynamic pressure are associated with modulation of the effects of the crustal fields on plasma density, whereas the strength of the IMF modulates the crustal fields effects on both electron densities and temperatures.Plain Language Summary Mars's atmosphere is exposed to ultra-violet light from the Sun, forming a layer of plasma at high altitudes around the planet. This plasma layer, termed the ionosphere, is strongly affected in terms of its density and temperature, both by external factors like the solar wind and the interplanetary magnetic field (IMF), and internal factors, like Mars's crustal magnetic field. Here...

show abstract

On the Formation Mechanism of Martian Dayside Ionospheric Plasma Depletion Events

Basuvaraj,

Němec,

Fowler

et al. 2024

JGR Planets

View full text Add to dashboard Cite

Plasma Depletion Events (PDEs) are characterized by abrupt, localized reductions in ionospheric plasma density at least by an order of magnitude decrease. These events are observed over a limited range of altitudes, typically spanning a few tens of kilometers. We use Mars Atmosphere and Volatile Evolution spacecraft data to investigate the properties and possible formation mechanism of daytime PDEs, typically observed at altitudes above 250 km. We show, using two example events and statistical analysis, that the depletion events are associated with electrostatic fluctuations and increased electron temperatures. The events are further accompanied by enhanced fluxes of suprathermal electrons and light energetic ions. These are indicative of local plasma heating, possibly mediated by the electrostatic fluctuations. The heated plasma may eventually escape from the depletion region through the ambipolar diffusion.

show abstract

Ducted electromagnetic waves in the Martian ionosphere detected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding radar

Cited by 3 publications

References 42 publications

MARSIS Observations of Field‐Aligned Irregularities and Ducted Radio Propagation in the Martian Ionosphere

MARSIS Observations of Field‐Aligned Irregularities and Ducted Radio Propagation in the Martian Ionosphere

Electron Densities and Temperatures in the Martian Ionosphere: MAVEN LPW Observations of Control by Crustal Fields

On the Formation Mechanism of Martian Dayside Ionospheric Plasma Depletion Events

Contact Info

Product

Resources

About