A5005715979- Planetary Science and Exploration
- Astro and Planetary Science
- Space Science and Extraterrestrial Life
- Space Exploration and Technology
- Ionosphere and magnetosphere dynamics
- Space Satellite Systems and Control
- Laser-induced spectroscopy and plasma
- Space exploration and regulation
- Scientific Research and Discoveries
- Geomagnetism and Paleomagnetism Studies
- Science Education and Perceptions
- Innovative Teaching Methods
- Science Education and Pedagogy
- Methane Hydrates and Related Phenomena
- Atmospheric Ozone and Climate
Boston University
2011-2019
Laboratory for Atmospheric and Space Physics
2018
By examining electron density profiles from the Mars Express Radio Science Experiment MaRS, we show that vertical structure of dayside ionosphere is more variable and complex than previously thought. The top can be below 250 km (25% occurrence rate) or above 650 (1%); topside well‐described by a single scale height (10%) two/three regions with distinct heights 10%), where those range between tens hundreds kilometers; main layer have sharply pointed (5%), flat‐topped (6%), wavy (8%) shape, in...
Abstract The variations in peak properties of the M1 layer (the lower photochemical plasma layer) with solar zenith angle (SZA) are important relationships for understanding physical processes which control this region Mars ionosphere. behavior has been poorly characterized to date. Here we introduce an automated and repeatable method determining M2 layers simultaneously 5600 Global Surveyor radio occultation profiles dayside electron density. results support previous findings subsolar...
Electron densities in planetary ionospheres increase substantially during solar flares response to the increased irradiance at soft X‐ray and extreme ultraviolet wavelengths. Here we modify an existing model of ionosphere Mars incorporate time‐dependent irradiances use it simulate ionospheric conditions X14.4 M7.8 15 26 April 2001, respectively. Simulations were validated by comparison Global Surveyor radio occultation measurements vertical profiles electron density. Adjustments model's...
Abstract The peak electron density in the dayside Martian ionosphere is a valuable diagnostic of state ionosphere. Its dependence on factors like solar zenith angle, ionizing irradiance, neutral scale height, and temperature has been well studied. Mars Atmosphere Volatile EvolutioN spacecraft's September 2015 “deep dip” orbits, which orbital periapsis was lowered to ~125 km, provided first opportunity since Viking sample situ complete profile including main peak. Here we present measurements...
Abstract Increased soft X‐ray irradiance during solar flares produces increased electron densities in the lower ionosphere of Mars, and relative changes density a flare are greater for altitudes larger flares. However, this relationship has not been quantified. This impeded validation simulations ionospheric response to flares, which necessary developing accurate descriptions physical processes governing behavior under extreme conditions. Here we develop function, mathematical expression...
Observations of peak electron densities in the Mars ionosphere are well fit by a simplistic theory that assumes temperature, T e , at remains constant as solar zenith angle, χ changes. However, ought to vary with both altitude and . Here we use an existing numerical model ionospheric energetics, which includes vertical diurnal variations temperatures, predict is relatively independent This accurately predicts observed dependence density on whereas predictions using Viking‐based temperatures...
Abstract The M1 layer of the Mars ionosphere is one its most significant features, second only to M2 layer. Observations have shown how physical properties this depend on solar zenith angle (SZA) and irradiance, but these trends not yet been explored in detail by numerical simulations. Hence, full implications observational findings for layer's behavior established. Here we use Boston University Ionosphere Model simulate over a period 6 months. In order adequately reproduce SZA dependence...
Abstract The topside ionosphere of Mars is subject to dynamic interactions between the planet and surrounding space environment. Significant variations in its structure have been observed that not consistently investigated or explained. All 5,600 ionospheric profiles obtained by Global Surveyor Radio Science experiment are analyzed here systematically characterize a layer visible ~50% observations. For simplicity, we refer this plasma as M3 find it located, on average, ~ 40 km above main...
Abstract The ionospheres in our solar system vary not only their electron densities but also the dominance of atomic versus molecular ions at altitudes peak plasma density. With exception Earth's F layer composed oxygen and electrons, all other planets have ionospheric layers electrons embedded a dense neutral atmosphere. At Mars, both its ions, with M 1 lower altitude than more robust 2 above it. terrestrial ionosphere has prominent region (the E layer) below dominant layer. In this paper,...
Abstract Radio occultation electron densities measurements from the Mariner 9 and Viking spacecraft, which orbited Mars in 1970s, have recently become available a digital format. These data are highly complementary to radio density profiles Global Surveyor, were restricted solar zenith angle altitude. We compiled 9, Viking, Surveyor experiments for comparison made by Advanced Radar Subsurface Ionosphere Sounding (MARSIS), topside radar sounder on Express, MARSIS‐based empirical models. find...
Abstract The Martian crustal magnetic field modifies the structure of ionosphere, loss atmosphere to space, and interactions upper with solar wind. Mars Advanced Radar for Subsurface Ionosphere Sounding topside sounder on Express has regularly observed oblique echoes from magnetically controlled plasma structures in regions strong vertical fields. Here we present 11 observations unusually high densities compare them more common typical ionospheric densities. In two cases, density is at least...
Knowledge of Mars's ionosphere has been significantly advanced in recent years by observations from Mars Express (MEX) and lately MAVEN. A topic particular interest are the interactions between planet's ionospheric plasma its highly structured crustal magnetic fields, how these lead to redistribution affect propagation radio waves system. In this paper, we elucidate a possible relationship two anomalous radar signatures previously reported MARSIS instrument on MEX. Relatively uncommon...