In this chapter we examine how our knowledge of present day Venus can inform terrestrial exoplanetary science and how exoplanetary science can inform our study of Venus. In a superficial way the contrasts in knowledge appear stark. We have been looking at Venus for millennia and studying it via telescopic observations for centuries. Spacecraft observations began with Mariner 2 in 1962 when we confirmed that Venus was a hothouse planet, rather than the tropical paradise science fiction pictured. As long as our level of exploration and understanding of Venus remains far below that of Mars, major questions will endure. On the other hand, exoplanetary science has grown leaps and bounds since the discovery of Pegasus 51b in 1995, not too long after the golden years of Venus spacecraft missions came to an end with the Magellan Mission in 1994. Multi-million to billion dollar/euro exoplanet focused spacecraft missions such as JWST, ARIEL and their successors will be flown in the coming decades. At the same time, excitement about Venus exploration is blooming again with a number of confirmed and proposed missions in the coming decades from India, Russia, Japan, the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). In this chapter, we review what is known and what we may discover tomorrow in complementary studies of Venus and its exoplanetary cousins.
We examine the wave coupling efficiency of solar wind to magnetospheric fluctuations in the ULF frequency range using an advanced full-wave simulation code, Petra-M. Earth’s magnetic field is tilted to the ecliptic plane; thus, compressional wave sources can be incident over a wide range of magnetic latitudes. When compressional waves are incident at a low latitude, very little wave power can reach the inner magnetosphere. On the other hand, waves incident from a high latitude source can propagate efficiently into the inner magnetosphere and reach the ground near the cusp region. The mode-conversion and polarization reversal at the crossover plays a critical role in compressional wave propagation. The mode-converted linearly polarized electromagnetic ion cyclotron waves also occur at the Alfvén and ion-ion hybrid resonances. Therefore, the results suggest that solar wind compression can drive the linearly polarized EMIC waves, and the wave occurrence can have seasonal and diurnal dependence.
We present a new open-source tool for magnetospheric computations, that is modelling of cosmic ray propagation in the geomagnetosphere, named the “Oulu - Open-source geomagneToSphere prOpagation tool” (OTSO). A tool of this nature is required in order to interpret experiments and study phenomena within the cosmic ray research field. Within this work OTSO is applied to the investigation several ground level enhancement events. Here, we demonstrated several applications of OTSO, namely computation of asymptotic directions of selected cosmic ray stations, effective rigidity cut-off across the globe at various conditions within the design, general properties, including the magnetospheric models employed. A comparison and validation of OTSO with older widely used tools such as MAGNETOCOSMICS was performed and good agreement was achieved. An application of OTSO for providing the necessary background for analysis of two notable ground level enhancements is demonstrated and the their spectral and angular characteristics are presented.
Due to the potential risks that space weather (SW) events associated with solar-wind disturbances pose on modern technology and infrastructure, there has been increasing interest in physics-based forecasts of the solar wind and related phenomena, such as coronal mass ejections. Computational models of heliospheric space plasmas and space weather are generally based on the equations of ideal magnetohydrodynamics (MHD) that describe the conservation of plasma mass, momentum, and energy, as well as the time evolution of the magnetic field. Over the last few decades significant effort has been devoted to the development of efficient numerical schemes for solving the ideal MHD equations, especially in the context of space plasmas. More recently, there has been increasing interest in incorporating observational data within SW simulations via data assimilation (DA) to produce improved space weather forecasts. While the use of DA methods is a mature field that has proved to be vastly successful in meteorological applications, its use has seen limited application in heliospheric space weather forecasting, or MHD modeling in general. In this study, the results of the assimilation of synthetic plasma observations in one-dimensional ideal MHD initial value problems are considered. DA methods are generally divided into two families of approaches: variational and sequential methods. Both categories of approaches are examined here with assimilation results presented for the 4DVar and Ensemble Kalman Filter (EnKF) methods, respectively. Observing system simulation experiments are performed and the simulation errors obtained using the 4DVar and EnKF methods, as well as, without the use of DA are compared. The sensitivity of error reduction to temporal and spatial observation availability is explored, and the computational costs of each method are reported. Finally, the challenges associated with extensions to 3D models are discussed.
Texas will be uniquely situated as the nexus of the “X” where the annular eclipse of October 14, 2023 and the total solar eclipse of April 8, 2024 cross. Everyone in the state of Texas will experience at least 84% solar coverage for one or both of these remarkable events, and over 8 million people will be within a 30 minute drive of totality, not counting the dramatic influx of visitors expected because of the favorable weather conditions. Texas is the fastest growing state, and one with the highest fraction (25%) of children under 18. In addition, it is one with a large population of ESL learners in the path of the dark skies. Our goals are three: 1. To bring information to all regions of the state so that every person has a safe experience of a partial and/or annular eclipse; 2. To maximize the number of Texans (residents and visitors) who can experience totality; and 3. To create a set of activities for schools, for groups, and for citizen scientists to collect data on the environment and on bird and animal behavior during these events. We have created two websites for information about the upcoming eclipses http://space.rice.edu/eclipse and http://texaseclipse.net; we have a mailing list for people and educators interested in eclipses http://eepurl.com/cv68Qj and we have seven eclipse animations already created for planetariums and schools: https://space.rice.edu/eclipse/eclipse_animations.html, plus a number of diagrams. We are creating two more animations describing annular eclipses which should be ready for the AGU meeting. We have developed a set of Powerpoint slides and animations to be used for eclipse training, and special “dome versions” using the fulldome animations, to be used in fixed and portable planetariums. We have already done trainings in South Texas (where the eclipses cross) and will work with AAS, NASA, and other groups to ensure the widest possible dissemination of eclipse information, particularly safety information. By the time of AGU we will have already used these materials in teacher trainings at the CAST conference and planetarium trainings for LIPS, and will post them for download. Educational and safety materials will be provided in both English and Spanish, and presentations for both flatscreen Powerpoint or fulldome planetarium programs will be made freely available, thanks to the NASA HEAT program.
The solar wind is a continuous outflow of plasma from the Sun, which expands into the space between the planets in our solar system and forms the heliosphere. The solar wind is inherently turbulent and characterised by kinetic micro-instabilities on a range of scales. The Sun also intermittently ejects mass (coronal mass ejections; CMEs) or solar energetic particles (SEPs) which change their trajectory or energy due to their interactions with the solar wind. When these violent particle events hit the Earth’s magnetosphere, they can cause “space weather” with both long- and short-term impacts on our natural and technological environment. This presentation investigates the behaviour and the effects of kinetic instabilities in a turbulent plasma with particular emphasis on energy transfer processes. We utilise the unprecedented observations from ESA’s Solar Orbiter spacecraft, launched in February 2020, to advance our understanding of the Sun, the solar wind, and space weather. Large-scale compressions (ubiquitous in solar-wind turbulence) create conditions for proton, alpha-particle and electron microinstabilities, which then transfer energy to small-scale fluctuations. These instability-driven small-scale fluctuations, including those driven by turbulence and other sources of free energy (e.g. particle beams, differential flows, heat fluxes, temperature anisotropies), make a significant contribution to the fluctuation spectrum at kinetic scales, where energy dissipation occurs. We consider instabilities driven by turbulence in the plasma by using statistical methods to analyse the Solar Orbiter data and characterise the turbulence at the relevant scales and amplitude. Specifically, we evaluate the processes by which turbulence combined with temperature anisotropy causes instability, comparing theoretical calculations with the high resolution data available from the Solar Orbiter MAG and SWA instruments.
The Juno spacecraft’s polar orbits have enabled direct sampling of Jupiter’s low-altitude auroral field lines. While various datasets have identified unique features over Jupiter’s main aurora, they are yet to be analyzed altogether to determine how they can be reconciled and fit into the bigger picture of Jupiter’s auroral generation mechanisms. Jupiter’s main aurora has been classified into distinct “zones”, based on repeatable signatures found in energetic electron and proton spectra. We combine fields, particles, and plasma wave datasets to analyze Zone-I and Zone-II, which are suggested to carry the upward and downward field-aligned currents, respectively. We find Zone-I to have well-defined boundaries across all datasets. H+ and/or H3+ cyclotron waves are commonly observed in Zone-I in the presence of energetic upward H+ beams and downward energetic electron beams. Zone-II, on the other hand, does not have a clear poleward boundary with the polar cap, and its signatures are more sporadic. Large-amplitude solitary waves, which are reminiscent of those ubiquitous in Earth’s downward current region, are a key feature of Zone-II. Alfvénic fluctuations are most prominent in the diffuse aurora and are repeatedly found to diminish in Zone-I and Zone-II, likely due to dissipation, at higher altitudes, to energize auroral electrons. Finally, we identify sharp and well-defined electron density depletions, by up to two orders of magnitude, in Zone-I, and discuss their important implications for the development of parallel potentials, Alfvénic dissipation, and radio wave generation.
Ground-based VLF transmitters located around the 2 world generate signals that leak through the bottom side of the 3 ionosphere in the form of whistler mode waves. Wave and particle 4 measurements on satellites have observed that these man-made 5 VLF waves can be strong enough to scatter trapped energetic 6 electrons into low pitch angle orbits, causing loss by absorption in 7 the lower atmosphere. This precipitation loss process is greatly 8 enhanced by intentional amplification of the whistler waves using 9 a newly discovered process called Rocket Exhaust Driven 10 Amplification (REDA). Satellite measurements of REDA have 11 shown between 30-and 50-dB intensification of VLF waves in 12 space using a 60-second burn of the 150 g/s thruster on the Cygnus 13 satellite that services the International Space Station (ISS). This 14 controlled amplification process is adequate to deplete the 15 energetic particle population in the radiation belts in a few minutes 16 rather than the multi-day period it would take naturally. 17 Numerical simulations of the pitch angle diffusion for radiation 18 belt particles use the UCLA quasi-linear Fokker Planck model 19 (QLFP) to assess the impact of REDA on radiation belt 20 remediation (RBR) of newly injected energetic electrons. The 21 simulated precipitation fluxes of energetic electrons are applied to 22 models of D-region electron density and bremsstrahlung x-rays for 23 predictions of the modified environment that can be observed with 24 satellite and ground-based sensors. 25 26 Index Terms-Active Space Experiments, Parametric
We present simulations of the outer radiation belt electron flux during the March 2015 and March 2013 storms using a radial diffusion model. Despite differences in Dst intensity between the two storms the response of the ultra-relativistic electrons in the outer radiation belt was remarkably similar, both showing a sudden drop in the electron flux followed by a rapid enhancement in the outer belt flux to levels over an order of magnitude higher than those observed during the pre-storm interval. Simulations of the ultra-relativistic electron flux during the March 2015 storm show that outward radial diffusion can explain the flux dropout down to L*=4. However, in order to reproduce the observed flux dropout at L*<4 requires the addition of a loss process characterised by an electron lifetime of around one hour operating below L*~3.5 during the flux dropout interval. Nonetheless, during the pre-storm and recovery phase of both storms the radial diffusion simulation reproduces the observed flux dynamics. For the March 2013 storm the flux dropout across all L-shells is reproduced by outward radial diffusion activity alone. However, during the flux enhancement interval at relativistic energies there is evidence of a growing local peak in the electron phase space density at L*~3.8, consistent with local acceleration such as by VLF chorus waves. Overall the simulation results for both storms can accurately reproduce the observed electron flux only when event specific radial diffusion coefficients are used, instead of the empirical diffusion coefficients derived from ULF wave statistics.
At the Earth’s magnetopause, the Kelvin-Helmholtz (KH) instability, driven by the persistent velocity shear between the magnetosheath and the magnetosphere, has been frequently observed during northward interplanetary magnetic field (IMF) periods and considered as one of the most important candidates for transporting and mixing plasmas across the magnetopause. However, how this process interacts with magnetic field fluctuations, which persistently exist near the magnetopause, has been less discussed. Here we perform a series of 2-D fully kinetic simulations of the KH instability at the magnetopause considering a power-law spectrum of initial fluctuations in the magnetic field. The simulations demonstrate that when the amplitude level of the initial fluctuations is sufficiently large, the KH instability evolves faster, leading to a more efficient plasma mixing within the vortex layer. In addition, when the spectral index of the initial fluctuations is sufficiently small, the modes whose wavelength is longer than the theoretical fastest growing mode grow dominantly. The fluctuating magnetic field also results in the formation of the well-matured turbulent spectrum with a -5/3 index within the vortex layer even in the early non-linear growth phase of the KH instability. The obtained spectral features in the simulations are in reasonable agreement with the features in KH waves events at the magnetopause observed by the Magntospheric Multiscale (MMS) mission and conjunctively by the Geotail and Cluster spacecraft. These results indicate that the magnetic field fluctuations may really contribute to enhancing the wave activities especially for longer wavelength modes and the associated mixing at the magnetopause.
Several studies suggest that magnetic reconnection plays an essential role to generate and accelerate most of the erupting coronal magnetic flux ropes such as coronal mass ejections (CMEs). We explore the connection between magnetic properties (magnetic flux and helicity) of interplanetary coronal mass ejection (ICME) flux-ropes (magnetic clouds [MCs]) and those of associated near-sun CME flux-ropes formed in situ by low corona magnetic reconnection. We identify the progenitor CMEs and their solar sources and derive the source region reconnection flux using the post-eruption arcade (PEA) method. Combining the reconnection flux and the geometrical properties of associated CMEs obtained by forward-modeling, we extract the magnetic properties of CME flux ropes at their source. To measure the magnetic properties of 1 AU ICME we use constant-α force-free cylindrical flux rope model fit to in situ observations and directly from the observed magnetic time series rotated to the cloud frame. We investigate whether a significant difference exists in magnetic properties of ICMEs if their solar source is composed of pre-existing flux-ropes (filaments). This study has significant implications in finding the role of reconnection in the formation of twisted flux ropes during a solar eruptive process that transport solar magnetic flux and helicity into interplanetary space.
The MHD with embedded PIC (MHD-EPIC) model makes it feasible to incorporate kinetic physics into a global simulation. Still, this requires a large enough box-shaped PIC domain to accommodate the movement and changes of the magnetic reconnection regions over time. This wastes computational resources on simulating regions with the expensive PIC model where MHD would be sufficient to describe the physics. We have developed a new MHD with Adaptively Embedded PIC (MHD-AEPIC) algorithm that couples the BATS-R-US MHD model with the new FLexible Exascale Kinetic Simulator (FLEKS) PIC code. In the new coupled model the PIC domains can move with the magnetic reconnection regions and adapt to them with an arbitrary shape. In this work, we will first introduce the algorithms for selecting the reconnection regions in the MHD model that need to be resolved with the kinetic PIC model. Then we will compare simulations obtained with MHD-EPIC using fixed PIC regions versus MHD-AEPIC employing adaptive PIC regions to verify that the new model generates reliable results. Finally, we will apply the MHD-AEPIC model to a global magnetic storm simulation and demonstrate the improved efficiency.
The Interstellar Boundary Explorer (IBEX) mission has shown that variations in the ENA flux from the outer heliosphere are associated with the solar cycle and longer-term variations in the solar wind. In particular, there is a good correlation between the dynamic pressure of the outbound solar wind and variations in the later-observed IBEX ENA flux. The time difference between observations of the outbound solar wind and the heliospheric ENAs with which they correlate ranges from approximately two to six years or more, depending on ENA energy and look direction. This time difference can be used as a means of “sounding” the heliosheath, that is, finding the average distance to the ENA source region in a particular direction. We apply this method to build a three-dimensional map of the heliosphere. We use IBEX ENA data collected over a complete solar cycle, from 2009 through 2019, corrected for survival probability to the inner heliosphere. We divide the data into 56 “macro-pixels” covering the entire sky, and as each point in the sky is sampled once every six months, this gives us a time series of 22 points per macro-pixel on which to time-correlate. Consistent with prior studies and heliospheric models, we find that the shortest distance to the heliopause dHP is slightly south of the nose direction (dHP ~ 110 – 120 au), with a flaring toward the flanks and poles (dHP ~ 160 – 180 au). The heliosphere extends at least ~350 au tailward, which is the distance limit of the technique.
Satellite in-situ electron density observations of the storm enhanced density 2 and the polar Tongue of Ionization on the noon meridional plane in the F 3 region during the The first report on satellite in-situ electron density measurements of the storm enhanced 15 density at the noon meridian plane 16 The lifecycle of ionospheric storm enhanced densities is mainly controlled by variations 17 of the dayside prompt penetration electric fields 18 The key methodologies include a comparison of TIEGCM modeling with satellite in-situ 19 electron density observations and a correlation analysis 20 21 22 Abstract 23 Ionospheric storm enhanced density (SED) has been extensively investigated using Total 24 Electron Content (TEC) deduced from GPS ground and satellite-borne receivers. However, in-25 situ electron density measurements have not been reported for SEDs yet. We report in-situ 26 electron density measurements of a SED event and its associated polar tongue of ionization 27 (TOI) at the noon meridian plane measured by the CHAMP polar-orbiting satellite at about 390 28 km altitude during the 20 November 2003 magnetic storm. The measurements provided rare 29 evidence about the SED’s life cycle at a fixed magnetic local time. CHAMP detected the SED 30 onset right after the arrival of an interplanetary coronal mass ejection shock front. The SED 31 electron density enhancement extended from the equatorial ionization anomaly to the noon cusp, 32 through which plasmas entered into the polar cap as polar plasma clouds/TOI. For several 33 satellite-ground conjunction passes, CHAMP measured the electron density of plasma clouds 34 comparable to the TOI density measured by the Tromso ISR, establishing that the plasma clouds 35 were related to the TOI. The SED plume in the NH retreated gradually to lower latitudes six 36 hours after the SED onset. We conducted TIEGCM modeling to demonstrate that the SED 37 density enhancement was likely due to the vertical transport of plasmas. The observed mid-38 latitude electron density varied with the cross-polar cap electric fields, suggesting that prompt 39 penetration electric fields (PPEFs) in the zonal direction played a dominant role. The 40 implication is that variations of the dayside PPEFs largely control the SED lifecycle. 41 42 Plain Language Summary 43 Ground radar and GPS stations have frequently detected enhancement of ionospheric electron 44 density at mid-latitudes and in the polar cap during the magnetic storm recovery phase. We 45 report in-situ satellite observations near 400 km at the noon meridian plane during an intense 46 magnetic storm. It provides for the first time clear evidence about the life cycle of ionospheric 47 electron density enhancement, starting from its onset at mid-latitudes, entry into the polar cap, 48 and retreat to lower latitudes. The mid-latitude ionospheric electron density was mainly 49 enhanced in the northern hemisphere, triggered by the passage of a solar wind dynamic pressure 50 shock front. Global circulation modeling suggests that the vertical transport of ionospheric 51 plasmas probably produced the enhancement. The dayside prompt-penetration electric fields in 52 the zonal direction likely drove the vertical plasma uplift. Thus, it appears that the SED lifecycle 53 is mainly controlled by variations of the dayside prompt electric field. 54
Next year marks the 50th anniversary of the detection of Coronal Mass Ejections from space. The discovery and subsequent observations of thousands of events from a stream of coronagraph telescopes marked a paradigm shift of our view of the corona, from a physical system changing gradually over a solar cycle, to a system marked with explosive transient activity on timescales from seconds to days to months. Thanks to coronagraphs, and more recently EUV imagers, Space Weather forecasting and research have become strong research areas within the Heliophysics discipline. adding to that, the transients and even the more quiescent background wind can now be imaged directly in the inner heliosphere thanks to the advent of heliospheric imaging since the mid-2000s. The recent deployment of the Parker Solar Probe and Solar Orbiter missions ushers a new era of coronal/heliospheric imaging from widely varying vantage points along with future missions, such as PUNCH, and operational mission at the L1 and L5 point. It is, therefore, an appropriate time to take stock of the lessons learned from the decades of imaging of the solar wind, both quiescent and transient. In this talk, I review those lessons/learned and discuss where to go next.
A new Arts/Lab Student Residence program was developed that brings artists into a research lab. Science and Engineering undergraduate and graduate students working in the lab describe their research and allow the artists to shadow them to learn more about the work. The Arts/Lab Student Residencies are designed to be unique and fun, while encouraging interdisciplinary learning and creative production by exposing students to life and work in an alternate discipline’s maker space - i.e. the artist in the engineering lab, the engineer in the artist’s studio or performance space. Each residency comes with a cash prize and the expectation that a work of some kind will be produced as a response to experience. The Moldwin Prize is designed for an undergraduate student currently enrolled in the Penny W. Stamps School of Art & Design, the Taubman School of Architecture and Urban Planning or the School of Music, Theatre and Dance who is interested in exchange and collaboration with students engaged in research practice in an engineering lab. No previous science or engineering experience is required, although curiosity and a willingness to explore are essential! Students receiving the residency spend 20 hours over 8 weeks (February-April) participating with the undergraduate research team in the lab of Professor Mark Moldwin, which is currently doing work in the areas of space weather (how the Sun influences the space environment of Earth and society) and magnetic sensor development. The resident student artist will gain a greater understanding of research methodologies in the space and climate fields, data visualization and communication techniques, and how the collision of disciplinary knowledge in the arts, engineering and sciences deepens the creative practice and production of each discipline. The student is expected to produce a final work of some kind within their discipline that reflects, builds on, explores, integrates or traces their experience in the residency. This talk will describe the program, the inaugural year’s outcomes, and plans to expand the program to other research labs.
We present partial ring distributions of solar wind protons observed by the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. The formation of ring distributions is usually associated with high activity comets, where the spatial scales are larger than multiple ion gyroradii. Our observations are made at a low-activity comet at a heliocentric distance of 2.8 AU on April 19th, 2016, and the partial rings occur at a spatial scale comparable to the ion gyroradius. We use a new visualisation method to simultaneously show the angular distribution of median energy and differential flux. A fitting procedure extracts the bulk speed of the solar wind protons, separated into components parallel and perpendicular to the gyration plane, as well as the gyration velocity. The results are compared with models and put into context of the global comet environment. We find that the formation mechanism of these partial rings of solar wind protons is entirely different from the well-known partial rings of cometary pickup ions at high-activity comets. A density enhancement layer of solar wind protons around the comet is a focal point for proton trajectories originating from different regions of the upstream solar wind. If the spacecraft location coincides with this density enhancement layer, the different trajectories are observed as an energy-angle dispersion and manifest as partial rings in velocity space.
Surface charging properties of a non-conducting surface that has a deep cavity and is in contact with the solar wind plasma are investigated by means of the particle-in-cell plasma simulations. The modeled topography is intended with a portion of irregular surfaces found on solid planetary bodies. The simulations have revealed unconventional charging features in that the cavity bottom is charged up to positive values even without any electron emission processes such as photoemission, provided that the surface location is accessible to a portion of incoming solar wind ions. The major driver of the positive charging is identified as drifting ions of the solar wind plasma, and an uncommon current ordering where ion currents exceed electron currents is established at the innermost part of the deep cavity. This also implies that the cavity bottom surface may have a positive potential of several hundred volts, corresponding to the kinetic energy of the ions. The present study also clarifies the role of photoelectrons in developing the distinctive charging environment inside the cavity. The photoemitted electrons can no longer trigger positive charging at the cavity bottom, but rather exhibit the effect of relaxing positive potentials caused by the solar wind ions. The identified charging process, which are primarily due to the solar wind ions, are localized at the depths of the cavity and may be one possible scenario for generating intense electric fields inside the cavity.