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Ionospheric outflow supplies nearly all of the heavy ions observed within the magnetosphere, as well as a significant fraction of the proton density. While much is known about upflow and outflow energization processes, the full global pattern of outflow and its evolution is only known statistically or through numerical modeling. Because of the dominant role of heavy ions in several key physical processes, this unknown nature of the full outflow pattern leads to significant uncertainty in understanding geospace dynamics, especially surrounding storm intervals. That is, global models risk not accurately reproducing the main features of intense space storms because the amount of ionospheric outflow is poorly specified and thus magnetospheric composition and mass loading could be ill‐defined. This study defines a potential mission to observe ionospheric outflow from several platforms, allowing for a reasonable and sufficient reconstruction of the full outflow pattern on an orbital cadence. An observing system simulation experiment is conducted, revealing that four well‐placed satellites are sufficient for reasonably accurate outflow reconstructions. The science scope of this mission could include the following: reveal the global structure of ionospheric outflow; relate outflow patterns to geomagnetic activity level; and determine the spatial and temporal nature of outflow composition. The science objectives could be focused to be achieved with minimal instrumentation (only a low‐energy ion spectrometer to obtain outflow reconstructions) or with a larger scientific scope by including contextual instrumentation. Plain Language Summary: Earth's upper atmosphere above 500 km altitude constantly loses charged particles to outer space in a process called ionospheric outflow. This outflow is important for the dynamics of the near‐Earth space environment ("space weather") yet is poorly understood on a global scale. A mission is needed to observe the global patterns of ionospheric outflow and its relation to space weather driving conditions. The science objectives of such a mission could include not only the reconstruction of global outflow patterns but also the relation of these patterns to geomagnetic activity and the spatial and temporal nature of outflow composition. A study is presented to show that four well‐placed spacecraft would be sufficient for reasonable outflow reconstructions. Key Points: A simulation study is conducted to determine the number of spacecraft needed for accurate reconstruction of 2D ionospheric outflow patternsDetermining the global pattern of ionospheric outflow is needed to understand the geospace system, especially during geomagnetic stormsA potential ionospheric outflow mission concept is defined that could address this unresolved key issue of space physics and space weather [ABSTRACT FROM AUTHOR]

Solar wind‐magnetosphere interaction and the injection of large quantity of plasma particles into the Earth's magnetosphere are the primary reasons behind geomagnetic storm, auroral effects, and, in general, all the fluctuations observed in the terrestrial magnetic field. In this paper, we analyzed the perturbed magnetosphere as a sandpile‐like cellular automata model based on the concept of self‐organized criticality and many‐body interactive system and proposed a solar wind‐magnetosphere energy coupling function in terms of interplanetary magnetic field BZ, the zth component of interplanetary magnetic field. The function determines the cusp width W depending on the intensity of (−BZ − BTh) where BTh is the threshold value. The model generates two output series, which are the numerical representation of the real‐time Dst index and AE index series, respectively. For our study, the range of years 1997–2007 of the 23rd solar cycle had been considered here. The threshold value BTh plays a significant role in the analysis and exhibits a proportional relationship with the yearly mean total number of sunspots for each year of the range 1997–2007 of the 23rd solar cycle. For each year, the two resultant output time series of the model display high‐correlation coefficients with the real‐time Dst and AE indexes, respectively, which denotes the acceptability of the proposed energy coupling function and its relation with the solar activities. Key Points: The solar wind‐magnetosphere coupling has been analyzed using a cellular automata model based on the concept of self‐organized criticalityA new coupling function is introduced to determine the cusp widthA threshold value of BZ, the zth component of the interplanetary magnetic field related to the yearly mean total number of sunspots, is introduced [ABSTRACT FROM AUTHOR]

Abstract: A model is described for the transport of magnetospheric oxygen ions with low charge state and energies up to several MeV/nucleon (MeV/u) as they precipitate into Jupiter's polar atmosphere. A revised and updated hybrid Monte Carlo model originally developed by Ozak et al. (2010, https://doi.org/10.1029/2010JA015635) is used to model the Jovian X‐ray aurora. The current model uses a wide range of incident oxygen ion energies (10 keV/u to 5 MeV/u) and the most up‐to‐date collision cross sections. In addition, the effects of the secondary electrons generated from the heavy ion precipitation are included using a two‐stream transport model that computes the secondary electron fluxes and their escape from the atmosphere. The model also determines H2 Lyman‐Werner band emission intensities, including a predicted spectrum and the associated color ratio. Implications of the new model results for interpretation of data from National Aeronautics and Space Administration's Juno mission are discussed. In particular, the model predicts that for a 2 MeV/u oxygen ion energy input of 10 mW/m2: (1) escaping electrons are produced with an energy range from 1 eV to 4 keV, which is a smaller range than previous models by Ozak et al. (2013, https://doi.org/10.1002/2013GL50812) predicted, (2) H2 band emission rates of 75 kR are generated, similar to previous estimates, and (3) a newly calculated Lyman and Werner band color ratio of 10 is expected. The color ratios are put into a context of various methane number density distributions. [ABSTRACT FROM AUTHOR]

Abstract: Sudden impulses of the magnetospheric and geomagnetic field are caused by sudden increases in the dynamic pressure of the solar wind, generally associated with the Earth’s arrival of interplanetary shock waves or discontinuities. We compared the observed field jumps, at geosynchronous orbit and at ground, with those predicted by a theoretical model (T04, Tsyganenko and Sitnov, 2005) for transitions between two steady states representations of the magnetosphere under different solar wind conditions. The geosynchronous response (mostly along the northward component, B z) in the dayside hemisphere is basically consistent with the magnetic field jump expected for changes of the magnetopause current alone. A similar conclusion holds for the positive changes observed in the nightside hemisphere; by contrast, the competing contributions of several current systems (from the magnetopause, cross-tail current, ring current, field aligned currents) determine in this time sector a large variety of small amplitude and negative responses that cannot be univocally interpreted. A different situation emerges in ground observations, at low latitudes. Here the observed responses along the northward component, H, in the dawn sector are consistent with changes of the magnetopause current; by contrast, in the entire postnoon hemisphere, they are greater than expected. The H variations are also typically accompanied by a significant change of the eastward component, D. These aspects reveal additional ionospheric contributions which determine a negative change of the D component through the entire day and a remarkable enhancement (≈50%) of the H component in the postnoon sector. The comparison between observations and model representations in several cases allows to discriminate between the roles of the current systems which compete in determining the field variations. Occasionally, SI manifestations are accompanied by trains of ULF fluctuations (f≈1–100mHz); we present a case in which the experimental observations suggest evidence for a cavity/waveguide oscillation at f≈3.2mHz. [Copyright &y& Elsevier]

Abstract: This study seeks to establish a new system characteristic describing dayside convective flows in the coupled magnetosphere–ionosphere: the low-pass filter function through which interplanetary magnetic field (IMF) fluctuations are processed as they are communicated from the magnetopause to the high-latitude ionosphere near local noon. In doing so, this study confirms that variations in the ionospheric flows at high-latitudes near local noon are well correlated with variations in the IMF orientation and magnitude on short timescales. We construct the filter function by comparing time series of the ionospheric equivalent flows at a fixed location at magnetic local noon and 80° latitude with time series of the IMF. The coherence spectra of these two parameters—averaged over 330h of comparison—indicate that there is a low-pass cutoff in the ionospheric response to IMF driving at a periods shorter than 20min (frequencies higher than 0.8mHz). When there is sufficient power in the IMF fluctuations, this cutoff is relatively sharp—the coherence drops by roughly a factor of three between the periods 32 and 21min (0.5 and 0.8mHz). The results also show that on average the coherence between the east–west component of the equivalent flows and IMF By tends to be less than the coherence between the north–south component of the equivalent flows and IMF Bz . [Copyright &y& Elsevier]

Abstract: In the first place, this work will demonstrate that there are at least several cases for which the magnetosphere–ionosphere system “does not behave as a low-pass filter”, or better it transmits high frequencies. In one selected case study, a monochromatic solar wind pressure wave in the Pc5 band directly excites the same frequency of ground pulsations. The other two case studies are composed of repetitive solar wind pressure pulses, like quasi-periodic solar wind pressure waves, which are associated to ionospheric currents in a one-to-one correspondence. Our most interesting case shows that the magnetosphere sometimes has the ability to respond in such small timescales as 2.7min. The same case provides strong evidence that the successive solar wind pressure pulses excite a global mode wave in the magnetosphere. We further discuss these events under the perspective established by the three recent papers of Sarafopoulos (2004a. Distinct solar wind pressure pulses producing convection twin-vortex systems in the ionosphere. Annales Geophysicae 22, 2201–2211; 2004b. Repetitive X-line Hall current structures over the dawnside ionosphere induced by successive exo-magnetosphere pressure pulses. Annales Geophysicae 22, 4153–4163; 2005. Pseudo-field line resonances in ground Pc5 pulsation events. Annales Geophysicae 23, 593–608) that the solar wind pressure pulses produce pseudo-field-line resonances on the ground station data; and this result certainly do not support the cavity mode model. Previously, many researchers have suggested that the magnetosphere acts as low-pass filter with a threshold separating the driven from the loading–unloading processes that are based on the inherent system dynamics. Essentially, their works are based on the AE (or AL) index. Our suggestion here is that the methodology whereby the AE index was introduced may eliminate the power density in high frequencies. The AE index may fail to carry the high-frequency part of input information. Neighboring ground stations with a phase-shift in their recorded waveforms may produce a no fluctuating AE index. The research efforts using AE may result in an error estimate of the cutoff frequency for the magnetosphere considered as a low-pass filter. Additionally, these works are not able to capture high-frequency couplings between the solar wind and the magnetosphere because they use low-resolution measurements. The presented high-frequency couplings emphasize the complementary character of this work. We shall not search special mechanisms or conditions permitting or preventing the direct entry of Pc5 frequency activity on Earth and any statistical approach is beyond the scope of this paper. [Copyright &y& Elsevier]