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1. EMIC wave events during the four GEM QARBM challenge intervals

   https://doi.org/10.1002/2018JA025505  

   Engebretson, M. J. ; Posch, J. L. ; Braun, D. J. ; Li, W. ; Ma, Q. ; Kellerman, A. C. ; Huang, C.-L. ; Kanekal, S. G. ; Kletzing, C. A. ; Wygant, J. R. ; et al ( August 2018 , Journal of geophysical research. Space physics)

   This paper presents observations of electromagnetic ion cyclotron (EMIC) waves from multiple data sources during the four Geospace Environment Modeling challenge events in 2013 selected by the Geospace Environment Modeling Quantitative Assessment of Radiation Belt Modeling focus group: 17 and 18 March (stormtime enhancement), 31 May to 2 June (stormtime dropout), 19 and 20 September (nonstorm enhancement), and 23–25 September (nonstorm dropout). Observations include EMIC wave data from the Van Allen Probes, Geostationary Operational Environmental Satellite, and Time History of Events and Macroscale Interactions during Substorms spacecraft in the near-equatorial magnetosphere and from several arrays of ground-based search coil magnetometersmore »worldwide, as well as localized ring current proton precipitation data from low-altitude Polar Operational Environmental Satellite spacecraft. Each of these data sets provides only limited spatial coverage, but their combination shows consistent occurrence patterns and reveals some events that would not be identified as significant using near-equatorial spacecraft alone. Relativistic and ultrarelativistic electron flux observations, phase space density data, and pitch angle distributions based on data from the Relativistic Electron-Proton Telescope and Magnetic Electron Ion Spectrometer instruments on the Van Allen Probes during these events show two cases during which EMIC waves are likely to have played an important role in causing major flux dropouts of ultrarelativistic electrons, particularly near L* ~4.0. In three other cases, identifiable smaller and more short-lived dropouts appeared, and in five other cases, these waves evidently had little or no effect.« less
2. ELFIN observations of energetic electron precipitation and backscatter: implication for losses, atmospheric effects, and magnetospheric populations.

   Angelopoulos, V. ( December 2020 , Fall AGU 2020)

   We report on the behavior of precipitating and backscattered energetic electrons as function of latitude, energy and pitch-angle across a wide range of local times. ELFIN’s two spinning satellites from a 450km altitude, near-polar orbit, permit excellent resolution of pitch-angles (22.5deg) well within the loss cone, and allow clear discrimination of locally trapped and field-aligned electrons between 50keV and 5MeV (dE/E ~ 40%). We find that at times of low precipitation (fluxes <10% of trapped) both precipitating and backscattered electrons are present and their ratio is close to 1. This is likely because atmospheric scattering contributes to loss-cone filling, bothmore »up and down the field line. When precipitation is significant (flux >10% of trapped, up to an energy Epmax) it dominates the upward-to-downward flux ratio at energies as low as 0.2 times Epmax, rendering that ratio very low (<10%). However, below ~0.2Epmax, as well as above Epmax, backscattering is a significant fraction of precipitation. We discuss the possible reasons for this backscatter. We also discuss the implications of our findings for electron losses from the radiation belts, for modeling atmospheric effects of energetic electron precipitation and for populating the magnetosphere with field-aligned energetic electrons.« less
3. Distinguishing Convective-Transition Moisture-Temperature Relationships with a Constellation of Polarimetric Radio Occultation Observations in and near Convection

   https://doi.org/10.3390/atmos13020259  

   Turk, F. Joseph ; Padullés, Ramon ; Morabito, David D. ; Emmenegger, Todd ; Neelin, J. David ( February 2022 , Atmosphere)

   Convective transition statistics serve as diagnostics for the parameterization of convection in climate and weather forecast models by characterizing the dependence of convection on the humidity-temperature environment. The observed strong pickup of precipitation as a function of layer-averaged water vapor and temperature is captured in models with varying accuracy. For independent observational verification, a low-Earth orbiting satellite constellation of Global Navigation Satellite System (GNSS) polarimetric radio occultation (PRO) measurements would be spaced such that adjacent RO would capture different profiles within and immediately adjacent to convection. Here, the number of profile observations needed to distinguish between convective transition relations bymore »different tropospheric temperature ranges is determined, over different tropical oceanic basins. To obtain these, orbit simulations were performed by flying different satellite constellations over global precipitation from the Global Precipitation Measurement (GPM) mission, varying the numbers of satellites, orbit altitude, and inclination. A 45-degree orbit inclination was found to be a good tradeoff between maximizing the number of observations collected per day, and the desired 50–150-km spacing between individual RO ray paths. Assuming a set of reasonable assumptions for net data yield, three tropospheric temperatures can be distinguished by 1 K with a six-month on-orbit duration from a constellation of at least three satellites.« less
4. Preliminary Design of a Distributed Telescope CubeSat Formation for Coronal Observations

   https://doi.org/10.2514/6.2021-0422  

   Gundamraj, Athreya ; Thatavarthi, Rohan ; Carter, Christopher ; Lightsey, E Glenn ; Koenig, Adam ; D'Amico, Simone ( January 2021 , AIAA Scitech 2021 Forum)

   This paper presents the preliminary system design of the Virtual Super-resolution Optics with Reconfigurable Swarms (VISORS) mission, a multi-CubeSat distributed telescope which will image the solar corona to investigate the existence of underlying energy release mechanisms. VISORS was conceived in the National Science Foundation (NSF) CubeSat Innovations Ideas Lab Workshop held in 2019 to address NSF science goals with innovative technologies. This mission will gather imagery that directly pertains to theories of coronal heating. In the paper, novel technologies are described that enable the VISORS mission to meet its challenging requirements and achieve the mission and science goals. The VISORSmore »formation is composed of two 6U CubeSats that fly 40 meters apart during science imaging as a distributed space telescope, with the lead spacecraft containing the optics and the trailing spacecraft containing the detector. An orbit maneuver planner utilizes GNSS carrier-phase measurements to provide a high-precision navigation solution, and a series of ceramic antenna arrays employ a novel 5.8 GHz inter-satellite crosslink. A 3 degrees-of-freedom (3DOF) propulsion system provides the capability for formation adjustments and active collision avoidance. The remaining spacecraft functions are handled by a spacecraft bus supplied by a commercial vendor, and the system integration is conducted by the VISORS mission team. Careful analysis of the system design and concept of operations led to the development of a safety plan which significantly reduces the risk of collision in a large subset of off-nominal scenarios. With a completed preliminary design review in Q4 2020 and a projected launch date in late 2023, this collaboration among 10 different universities, NASA, and a commercial partner is an upcoming mission that will demonstrate a new assembly of highly equipped CubeSats and their ability to conduct a state-of-the-art science mission in a cost and time effective manner.« less
5. On the relationship between energy input to the ionosphere and the ion outflow flux under different solar zenith angles

   https://doi.org/10.1186/s40623-021-01532-y  

   Kitamura, Naritoshi ; Seki, Kanako ; Keika, Kunihiro ; Nishimura, Yukitoshi ; Hori, Tomoaki ; Hirahara, Masafumi ; Lund, Eric J. ; Kistler, Lynn M. ; Strangeway, Robert J. ( November 2021 , Earth, Planets and Space)

   The ionosphere is one of the important sources for magnetospheric plasma, particularly for heavy ions with low charge states. We investigate the effect of solar illumination on the number flux of ion outflow using data obtained by the Fast Auroral SnapshoT (FAST) satellite at 3000–4150 km altitude from 7 January 1998 to 5 February 1999. We derive empirical formulas between energy inputs and outflowing ion number fluxes for various solar zenith angle ranges. We found that the outflowing ion number flux under sunlit conditions increases more steeply with increasing electron density in the loss cone or with increasing precipitating electronmore »density (> 50 eV), compared to the ion flux under dark conditions. Under ionospheric dark conditions, weak electron precipitation can drive ion outflow with small averaged fluxes (~ 10⁷ cm⁻² s⁻¹). The slopes of relations between the Poynting fluxes and outflowing ion number fluxes show no clear dependence on the solar zenith angle. Intense ion outflow events (> 10⁸ cm⁻² s⁻¹) occur mostly under sunlit conditions (solar zenith angle < 90°). Thus, it is presumably difficult to drive intense ion outflows under dark conditions, because of a lack of the solar illumination (low ionospheric density and/or small scale height owing to low plasma temperature).

   Graphical abstract

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