A5070156168- Planetary Science and Exploration
- Astro and Planetary Science
- Space Science and Extraterrestrial Life
- Space Exploration and Technology
- Geomagnetism and Paleomagnetism Studies
- Ionosphere and magnetosphere dynamics
- Space exploration and regulation
- Solar and Space Plasma Dynamics
- Spaceflight effects on biology
- Scientific Research and Discoveries
- Isotope Analysis in Ecology
- Space Satellite Systems and Control
- Geology and Paleoclimatology Research
- Particle accelerators and beam dynamics
- Graph Theory and Algorithms
- Electromagnetic Launch and Propulsion Technology
- IoT and Edge/Fog Computing
- Software-Defined Networks and 5G
- Nuclear Physics and Applications
United States Naval Observatory
2021-2024
University of Iowa
2007-2021
Broadband whistler‐mode emissions, commonly observed by the Cassini spacecraft at high latitudes in Saturn's magnetosphere frequencies below about 100 Hz, have characteristics very similar to auroral hiss Earth's magnetosphere. In contrast terrestrial hiss, which shows no obvious rotational modulation, Saturnian a pronounced modulation. We show that rotation period of is different northern and southern hemispheres, with 10.6 hours hemisphere 10.8 hemisphere. To within experimental error...
Radar soundings from the MARSIS instrument on board Mars Express spacecraft have shown that distinct layers can occur in topside ionosphere of Mars, well above main photo‐ionization layer. These appear as cusps, or sometimes steps, plots time delay a function frequency. Usually only one layer is observed, typically at altitudes 180 to 240 km. However, occasionally an additional occurs even higher altitudes. The are transient features and present about 60% near subsolar point, decreasing with...
Abstract The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Express, which operates between 0.1 5.5 MHz, suffered from a complete blackout 10 days in September 2017 when observing on the nightside (a rare occurrence). Moreover, Shallow (SHARAD) Reconnaissance Orbiter, at 20 also three operating both dayside nightside. We propose that these blackouts are caused by solar energetic particles of few tens keV above associated with an extreme space weather event 22...
Previous observations have shown that, during Martian dust storms, the peak of ionosphere rises in altitude. Observational studies this type, however, been extremely limited. Using 13 years ionospheric altitude data from Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on Express, we study how responded to storms six different Years (MY). The increased $\sim$10-15 km all events, which include a local storm (MY 33), three regional (MYs 27, 29, 32), two global 28...
Abstract We present topside ionospheric sounding on the nightside of Mars during September 2017 solar event by Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) board Express along with complementary dayside observations from Atmosphere Volatile EvolutioN (MAVEN). The MARSIS MAVEN suggest that (i) bottomside ionosphere was significantly enhanced energetic particles, (ii) peak electron density increased to unusually high values ∼1–2 ×10 4 cm −3 around 120 km altitudes owing...
We use Mars Atmosphere and Volatile EvolutioN observations of the upstream solar wind, Express ionospheric electron densities magnetic fields, to study how topside ionosphere ($>$ 320 km) is affected by variations in wind dynamic pressure. find that high pressures result being depleted plasma at all zenith angles, coincident with increased induced field strengths. The depletion response observed both weak strong crustal regions. Taken together, our results suggest lead compression, ion...
Abstract We study the seasonal and geographical variability of peak electron density altitude main ionospheric at Mars. For this purpose, we use data obtained by ESA Mars Express mission, namely radar MARSIS radio occultation experiment MaRS. The accumulation during long lifetime provides for first time an almost complete coverage. remove dominant factors affecting peak, effect changes in solar zenith angle (SZA), ultraviolet radiation output Sun. When averaging results all latitudes, find...
Abstract The Martian ionosphere originates from the ionization of planetary neutral atmosphere by solar radiation. This conductive layer is embedded within thermosphere and exosphere Mars where it forms a highly variable interaction region with wind. has been continuously observed three plasma instruments MaRS, MARSIS ASPERA-3 on Express for last 20 years ( >10 years). Those long-term observations laid solid foundation what we know today about ionosphere, provided numerous opportunities...
Here we report the discovery of a well‐defined plasma density boundary at high latitudes in Saturn's magnetosphere. The separates region relatively L less than about 8 to 15 from with densities nearly three orders magnitude lower higher values. Magnetic field measurements show that strong field‐aligned currents, probably associated aurora, are located just inside boundary. Analyses anisotropy energetic electrons magnetic lines usually closed and open outside boundary, although exceptions...
Over the last three years, Cassini spacecraft has been in a series of high inclination orbits, allowing investigation and measurements Saturnian auroral phenomena. During this time, Radio Plasma Wave Science (RPWS) Investigation on detected low frequency whistler mode emissions propagating upward along field lines, much like terrestrial hiss. Comparisons RPWS data with Spectrometer (CAPS) plasma during high‐latitude pass 17 October 2008, show that intense moving electron beams energies few...
Abstract The upper ionosphere of Mars contains a variety perturbations driven by solar wind forcing from above and upward propagating atmospheric waves below. Here we explore the global distribution variability ionospheric irregularities around exobase at analyzing topside sounding data Advanced Radar for Subsurface Ionosphere Sounding (MARSIS) instrument on board Express. As irregular structure gives rise to off‐vertical echoes with excess propagation time, diffuseness echo traces can be...
Abstract We report the detection of a dense ionized layer in upper atmosphere Mars caused by impact dust from comet Siding Spring. The observations were made ionospheric radar sounder on Express spacecraft during two low‐altitude passes approximately 7 h and 14 after closest approach to Mars. During these an unusual transient ionization was detected at altitudes about 80 100 km with peak electron densities (1.5 2.5) × 10 5 cm −3 , much higher than normally observed Martian ionosphere. From...
We study the ionopause of Mars using a database 6,893 detections obtained over 11 years by MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) experiment. The ionopause, in this work, is defined as steep density gradient that appears remote sounding ionograms horizontal line at frequencies below 0.4 MHz. find located on average an altitude $363 \pm 65$ km. also has weak dependence solar zenith angle varies with extreme ultraviolet (EUV) flux annual cycle time scales....
The objective of this White Paper, submitted to ESA's Voyage 2050 call, is get a more holistic knowledge the dynamics Martian plasma system, from its surface up undisturbed solar wind outside induced magnetosphere. This can only be achieved with coordinated multi-point observations high temporal resolution as they have scientific potential track whole system (from small large scales), and constitute next generation exploration Mars analogous what happened at Earth few decades ago. Paper...
Abstract Multipoint observations from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on board Express Atmosphere Volatile EvolutioN (MAVEN) mission reveal a dynamic response of Martian ionosphere to abrupt variations in upstream solar wind plasma. On 2 February 2017, MAVEN, located bow shock, encountered corotating interaction region‐related interplanetary shock with sudden enhancement pressure. MARSIS, operating upper at ∼478 km altitudes ∼78° zenith...
Abstract Nonhorizontal localized electron density structures associated with regions of near‐radial crustal magnetic fields are routinely detected via radar oblique echoes on the dayside Mars ionospheric sounding mode Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard Express. Previous studies mostly investigated these at a fixed plasma frequency assumed that larger apparent altitude compared to normal surrounding ionosphere implied they bulges. However, signal is...
Abstract The Martian ionopause boundary detected as steep gradients in the local electron density profiles from Mars Advanced Radar for Subsurface and Ionospheric Sounder on Express is studied individually statistically compared to photoelectron identified by drop of signature due CO 2 O molecules. In ~90% cases where we have energy flux data, coincides with boundary. form at border region above. observed a wide range latitude, longitude, altitude. According remote sounding investigations,...
Abstract The Mars Initial Reference Ionosphere (MIRI) model is a semiempirical formulation designed to provide climatological estimates of key parameters the Martian ionosphere. For new MIRI‐2018 version, an expanded database used from Express/Mars Advanced Radar for Subsurface and Sounding/Active Ionospheric Sounding (MEX/MARSIS/AIS) instrument, consisting 215,818 values maximum electron density M2‐layer (N m M 2 ) years 2005–2015. These data are organized by photochemical‐equilibrium...
Abstract We use more than 10 years of the Martian topside ionospheric data measured by Mars Advanced Radar for Subsurface and Ionosphere Sounding radar sounder on board Express spacecraft to derive an empirical model electron densities from peak altitude up 325 km. Altogether, 16,044 density profiles obtained at altitudes lower 425 km solar zenith angles 80° are included in analysis. Each is accurately characterized density, altitude, three additional parameters describing profile shape...
Abstract Due to the lower ionospheric thermal pressure and existence of crustal magnetism at Mars, Martian ionopause is expected behave differently from Venus. We study solar wind interaction balance Mars using both in situ remote sounding measurements Advanced Radar for Subsurface Ionosphere Sounding instrument on Express orbiter. show that magnetic usually dominates hold off with only 13% cases where plays a more important role balance. This percentage Venus, however, up 65%. also find...
Abstract Radar soundings from the Mars Advanced for Subsurface and Ionosphere Sounding (MARSIS) instrument on board Express spacecraft have shown that transient layers exist in dayside upper ionosphere of Mars. The most prominent these features is a second layer at an altitude near 200 km, well above main photoionization layer. While general properties this been studied previously, inner workings layer, mechanisms drive it, are only now becoming clear. With addition solar wind, particle,...
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...
Abstract The ion sensor of the Analyzer Space Plasmas and Energetic Atoms (ASPERA‐3) experiment detects accelerated ions during pulses radio emissions from powerful topside sounder: Mars Advanced Radar for Subsurface Ionosphere Sounding (MARSIS) onboard Express. Accelerated (O , O + lighter ions) are observed in an energy range up to 800 eV when MARSIS transmits at a frequency close plasma frequency. Individual observations consist almost monoenergetic beams aligned with antenna or lying...
Abstract We present the first direct comparison of Martian ionospheric electron densities measured by Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) topside radar sounder on board Express spacecraft Langmuir Probe Waves (LPW) instrument Atmosphere Volatile Evolution Mission (MAVEN) spacecraft. As low are not MARSIS due to power radiated at sounding frequencies, density profiles between local data point from (≈10 4 cm −3 ) rely an empirical profile shape. use LPW...