Space weather, i.e. the conditions in space driven by the dynamic solar activity, is a terminology that has been traditionally used to refer to the Sun’s effects on the near-Earth environment. This is because of a rather obvious reason, namely that most of the technological systems susceptible to space weather conditions and all human beings are currently on Earth or in near-Earth space. Hence, space weather research and forecasting efforts have focussed for decades mainly on our own neighbourhood. Nevertheless, in more recent years there has been a paradigm shift, due to which the field of space weather science has been gradually evolving into a heliosphere-wide discipline. This has been motivated by two main factors: (1) a growing interest in human exploration outside the Earth–Luna system, with efforts centred especially on Mars, and (2) an increasing endeavour from the research community to view the solar system as a Sun–heliosphere–planets integrated environment.

In this presentation, we will first provide a brief overview of the more “traditional” approach of space weather science to studying the Sun and its transient phenomena—e.g., the structured solar wind, coronal mass ejections, and solar energetic particles. We will then showcase more recent efforts that have been centred on taking advantage of data from missions scattered throughout the solar system to analyse space weather events at multiple points in the heliosphere and their effects on different planetary environments. Finally, we will highlight current and future opportunities for advancing our knowledge of the Sun and space weather-driving phenomena across the heliosphere. Particular emphasis will be given to possible synergies between different subjects of solar system science—i.e. solar, heliospheric, and planetary—and to ideas for the future in terms of multi-disciplinary space missions that can improve our understanding of space weather phenomena from a fundamental physics standpoint and, at the same time, that can expand our knowledge of space weather drivers and effects at other locations than Earth.

How to cite: Palmerio, E.: Space weather today: From an Earth-centred discipline to a heliosphere-wide field of research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7037, https://doi.org/10.5194/egusphere-egu24-7037, 2024.

Open magnetic flux (OMF) emanating from the Sun permeates the entire interplanetary space and plays an important role in all physical processes throughout the heliosphere that involve magnetic fields. It has been a topic of investigation based on both observational and numerical model analysis. And yet, there are still unresolved debates surrounding the OMF, considered to be among the big open questions in the field of solar and space physics. One of these is the “missing” open flux problem, according to which photospheric open flux estimates do not match measurements made in situ at 1 au. These photospheric estimates are obtained based on two different methods. According to the first, extreme ultraviolet (EUV) observations of coronal holes (CHs), that are considered as primary sources of OMF, are overlaid over global magnetic maps (Carrington maps), and the magnetic flux they enclosed is summed up. The second method is based on areas of open flux determined by coronal models and the summation of the magnetic flux they enclose. However, regardless of the complexity of coronal models, current research has shown that modelled open flux strongly underestimates that determined by the first method, and both underestimate the flux measure in situ at 1 au, by at least a factor of 2. These comparisons with values measured at 1 au are based on the conclusion made by Ulysses’ observations of the latitudinal invariance of the magnitude of the radial interplanetary magnetic field, which lead to the consensus that the total heliospheric open flux can be calculated by a single point in situ measurements. The aforementioned discrepancies have raised many questions. Are observational limitations responsible for the missing open flux? Are model limitations, such as the complexity of the model, the numerical implementation, and uncertainties in input data, contributing to the problem? How can we constrain and validate coronal models? Do we fully understand the sources of open flux? During this presentation we will navigate through research contributing to answering these questions and the direction of current and future efforts both in modelling and observations.

How to cite: Asvestari, E.: Exploring the heliospheric open flux problem from multiple perspectives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7959, https://doi.org/10.5194/egusphere-egu24-7959, 2024.

How to cite: Rutala, M. J., Jackman, C. M., Fogg, A. R., Murray, S. A., Owens, M. J., and Tao, C.: The Balance of Internal and External Drivers in Gas Giant Magnetospheres, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19005, https://doi.org/10.5194/egusphere-egu24-19005, 2024.

Solar system missions studying the sun and the planets in the inner and outer heliosphere use gravity assists of the planets to reach the target orbit of the missions. If such a maneuver happens around Earth, these observations enable us a unique multipoint observation of the magnetosphere together with other existing geospace missions as was the case of the Bepicolombo in April 2020 and the Solar Orbiter in November 2021 and is expected for JUICE in August 2024. Although the spacecraft during flybys are usually not operated in a full science mode, a new constellation with other fleet of spacecraft in Geospace can provide important information in particular for studying large-scale magnetospheric dynamics.

In this presentation we discuss the three-dimensional evolution of the magnetotail current of a substorm on April 10, 2020 that took place during the Earth-flyby interval of Bepicolombo. Magnetotail disturbances are observed by GOES 17 and Cluster in the midnight region, while BepiColombo spacecraft traversed the premidnight region duskward at 9-11 RE downtail. The four Cluster satellites, which were separated mainly in north-south direction, crossed the inner magnetosphere successively from north to south. They enable us to monitor the vertical (latitudinal) structure and the sequential changes of the magnetotail current sheet until the end of the recovery phase of the substorm. Multiple dipolarizations and multiple transient field-aligned currents (FAC) were observed by Cluster. Using the unique dataset from these multi-point observations, we examine the structure of the large-scale current sheet and analyze the embedded transient intense field-aligned current disturbances. By also comparing the observations with an empirical magnetic field model, we obtain the changes of the near-Earth magnetotail structure during the multiple dipolarization event.

How to cite: Nakamura, R., Slavin, J., Schmid, D., and Sun, W. and the Bepicolombo Earth-Flyby Interval Substorm Study Team: Study of magnetosphere dynamics combing geospace and planetary missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5907, https://doi.org/10.5194/egusphere-egu24-5907, 2024.

Earth’s magnetosheath, particularly its region downstream of the quasi-parallel bow shock, is permeated by plasma jets. These are local enhancements in the dynamic pressure, bubbles of plasma that are typically faster and denser in comparison to the ambient plasma. While jets emanate from the patchy and rippled quasi-parallel bow shock or upstream foreshock region, they are able to cross the entire magnetosheath and impact on the magnetopause. There, they may trigger magnetic reconnection and magnetopause surface waves, thereby coupling into large-scale magnetospheric dynamics. Consequently, the effects of jets can be observed inside the magnetosphere and also from ground. Jets are conceptually highly interesting phenomena as they can be interpreted as coupling elements between different regions and vastly different scales. Interdisciplinary research has led to significant advances in our understanding of jets over the past decade. However, despite all the efforts, many basic and fundamental questions remain unanswered. We review some latest results and open questions in jet research, emphasizing the benefit of interdisciplinary approaches.

How to cite: Plaschke, F.: Magnetosheath jets: an interdisciplinary perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10912, https://doi.org/10.5194/egusphere-egu24-10912, 2024.

Auroral emissions have been observed throughout the Solar System. They are the photo-manifestation of the interaction of energetic, extra-atmospheric particles (typically electrons or ions) with an atmosphere. As the source of energy comes from the space environment (e.g., solar wind or magnetosphere if applicable), the auroral emissions are a tracer of plasma bombardments in an atmosphere. They are also a fingerprint of plasma source and atmospheric species. They are an invaluable, remote-sensing probe of plasma interaction in the Solar System.

Through a multi-instrument analysis of gas, particle and spectroscopic dataset from Rosetta, we have established that the atomic emissions observed in the coma of comet 67P at large heliocentric distances (> 2 astronomical units) are of auroral origin [Galand et al., Nature Astronomy, https://doi.org/10.1038/s41550-020-1171-7, 2020; Stephenson et al.., A&A, https://doi.org/10.1051/0004-6361/202039155, 2021]. We will discuss the source of the energetic particles responsible for the Far UltraViolet (FUV) emissions and will highlight the relevance of observing some of them from Earth. We will contrast these emissions with those observed at comets in the soft X-rays and extreme ultraviolet and with the FUV emissions observed at Earth, Mars and Ganymede.

How to cite: Galand, M.: Far Ultraviolet atomic emissions at comet 67P: What have we learned? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16001, https://doi.org/10.5194/egusphere-egu24-16001, 2024.

Aurora has been detected on a few occasions on the Venus nightside with the Pioneer Venus UltraViolet Spectrometer (PVO-UVS). The main characteristics are the presence of the OI 130 and 136 nm emissions, a lack of discrete structure (diffuse aurora) and correlation with interplanetary shocks. Ground-based observations in the visible have shown that the [OI] green line at 557.7 nm is also observed following periods of the solar wind intensification. Although no concurrent measurement of auroral particle precipitation has been made, numerical simulations of the UV emissions have indicated that precipitation of soft auroral electrons (15-20 eV) and low energy fluxes is a likely candidate.

A discrete aurora was first observed in the middle ultraviolet on the Martian nightside limb from the Mars Express orbiter in a region of strong crustal field in the southern hemisphere. Prominent emissions included the CO Cameron bands and the CO₂⁺ UV doublet.  Limb observations have been made from Mars Express and MAVEN during the last 10 years. Recently, global auroral images have been collected with the UltraViolet Spectrometer (EMUS) on board the Emirates Mars Mission (EMM). These observations reveal a wide variety of auroral morphologies including discrete, diffuse, proton and sinuous aurora, each one bearing the signature of the interaction between the solar wind, the induced (or crustal) magnetic field and the atmosphere.

In this presentation, we compare the characteristics of the Venus and Mars diffuse aurora observed by Pioneer Venus and MAVEN respectively. We focus on the determination of the charged particles characteristics (mean energy, flux, energy distribution) based on the brightness and intensity ratio of spectral emissions. Following recent laboratory measurement of the efficiency of the Cameron bands excitation by electron impact, we re-examine the dependence of the Cameron/CO₂⁺ UVD intensity ratio on the auroral electron energy. Similarly, the different shapes of the electron excitation cross sections of the OI emissions at 130 and 136 nm induces an intensity ratio that depends on the energy of the precipitation. This dependence can be used to map the mean electron energy, based on FUV spectral observations with the EMUS. Finally, we discuss the expected brightness of the Mars visible aurora and set an upper limit on the intensity of the OI green line based on attempts to detect it with the UVIS spectrometer on board the Trace Gas Orbiter. We show that global observations with the M-AC visible camera on board the M-MATISSE orbiters will generate considerable progress in our understanding of the morphology, time variations and energetics of the Martian aurora.

How to cite: Gérard, J.-C. and Soret, L.: Spectroscopy of Mars and Venus aurora: a remote sensing tool for similarities and differences, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9791, https://doi.org/10.5194/egusphere-egu24-9791, 2024.

Mars' lack of a global magnetic field led to initial expectations of minimal auroral activity. Mars Express's SPICAM instrument nonetheless discovered an unusual form of aurora in 2005. The ultraviolet emissions were confined near Mars' strong crustal field region, showing that even weak magnetic fields can be responsible for aurora. These discrete aurora emissions were identified in 19 observations over SPICAM's decade of observations. 

The MAVEN spacecraft arrived at Mars in 2014 carrying the Imaging UltraViolet Spectrograph (IUVS). Thanks to its high sensitivity and observing cadence, IUVS increased detections of discrete aurora twenty-fold. IUVS also discovered two new widespread forms of aurora. Diffuse aurora is a planet-engulfing phenomenon, caused by solar energetic protons and electrons directly impacting the entire unshielded planet. Proton aurora is caused by solar wind protons charge-exchanging into the atmosphere and causing Lyman alpha emission across the dayside. IUVS studies the aurora at mid- and far-UV wavelengths in both limb scans and nadir imaging.

The Emirates Mars Mission (EMM) arrived in 2021 carrying the Emirates Mission UltraViolet Spectrometer (EMUS). EMUS quickly added to the menagerie of auroral phenomena thanks to its high far-UV sensitivity. Discrete aurora emissions were seen in a substantial fraction of nightside observations, and appear to take on new forms not seen by IUVS (sinuous, "non-crustal field", among others). Furthermore, EMUS detected a spatially-variable form of proton aurora called patchy proton aurora. EMUS studies the aurora through nadir imaging at far- and extreme-UV wavelengths.

The net result of the tremendous influx of new observations is a lag in cataloguing and cross-comparing the types of observations made with different instruments at different wavelength ranges in different observing modes. We now have the perspective to identify the causes of these auroral phenomena, which gives a more physics-based nomenclature:

• suprathermal electron aurora: hot electrons from the Mars environment appear to be responsible for most forms of discrete aurora
• solar energetic particle aurora: SEP electrons and protons from the Sun cause the planet-wide diffuse aurora 
• solar wind aurora: solar wind protons charged-exchange into the atmosphere to cause dayside aurora

This presentation seeks to give that broader context, highlighting

• what phenomena IUVS and EMUS observe, depending on their distinct instrumental capabilities
• whether they’re actually seeing the same phenomena or different ones, 
• how can one type of observation can complement the other, 
• where one’s capabilities are unique, and 
• what are the best directions for collaboration;
• how in situ measurements of particles and fields can contribute to the next stage of understanding of the conditions for particle precipitation

A more coherent observational perspective, as outlined above, may grant a framework for developing a deeper physical understanding of Mars unexpected diverse auroral processes.

How to cite: Schneider, N., Lillis, R., Jain, S., Deighan, J., Cessna, J., Chaffin, M., Hughes, A., Chirakkil, K., Gérard, J.-C., and Soret, L.: Mars Aurora: A Comparison of MAVEN/IUVS and EMM/EMUS Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13384, https://doi.org/10.5194/egusphere-egu24-13384, 2024.

Benefiting from a large orbit and high sensitivity, the Emirates Mars mission EMUS instrument has provided the first opportunity to synoptically and regularly image Mars’ discrete FUV auroral oxygen emission at 130.4 and 135.6 nm.  Over 15-20 minutes, EMUS produces a) images by slewing its aperture slit across the disk or b) “movies” of narrow regions by staring continuously.

Discrete aurora are observed primarily where the magnetic topology is open (i.e. connected to the collisional atmosphere at one end), which occurs where Mars’ crustal magnetic fields are either very weak or primarily vertical.  Discrete aurora show a strong local time dependence, with occurrence % decreasing with increasing solar zenith angle.  The highest occurrences are generally found in the post-dusk sector, before 10 PM SLT, though a few regions (e.g. 60°-70° S, 120°-150° E) are brightest between midnight and 3 AM.   

Sinuous discrete auroras (SDA) are enigmatic, sharply-defined filamentary emissions identified in approximately 3% of observations. These emissions intersect Mars' UV terminator, aligning generally away from the Sun, tending to cluster into groups oriented to the north, south, east, and west. The occurrence of SDAs increases with higher solar wind pressure. SDAs have a tendency to form toward the direction of the solar wind convection electric field (i.e., forming in the +E hemisphere). Depending on whether they originate near dusk or dawn, there is a moderate clockwise or counterclockwise "twist" observed in the average orientation of SDAs, respectively. Based on these characteristics, we infer a connection between SDAs and Mars' magnetotail current sheet, suggesting that the emission may be a result of energized electrons within this sheet.

Lastly, near the dawn and dusk terminators, discrete aurora often display a preference for formation in regions of either positive or negative crustal magnetic field, depending on IMF direction.  This preference can be used to determine whether a dayside (magnetosheath or photoelectron) or nightside (magnetotail) source of electrons is dominant.  Overall, nightside sources dominate over dayside by 20-40%, although individual radial crustal fields can show strong preferences for day or night sources.  This tells us that local magnetic geometry plays a role in global precipitation patterns.

With more than 3000 nightside images and 400 aurora movies collected (totaling more than 12 million pixels) since April 2021, we now have a powerful tool to understand Martian aurora morphologies, variability, and dependence on internal and external drivers. 

How to cite: Lillis, R., Chirakkil, K., Deighan, J., Fillingim, M., Jain, S., Chaffin, M., Raghuram, S., Holsclaw, G., Almazmi, H., Brain, D., Schneider, N., Xu, S., Halekas, J., Espley, J., Gruesbeck, J., and Curry, S.: Exploring Mars discrete aurora with synoptic images and movies from EMM EMUS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13610, https://doi.org/10.5194/egusphere-egu24-13610, 2024.

Auroras on Mars are known since their first discovery in 2005 by Mars Express and subsequently have been observed by Mars Atmosphere and Volatile Evolution (MAVEN) since 2014. Since 2021, Emirates UV spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) has been observing Martian auroras with an unprecedented frequency. These auroras are seen as FUV and EUV emissions of H, O, CO, and CO2 and are categorized based on their morphologies and the particles that are responsible for these emissions. Electron precipitation on the nightside causes discrete and diffuse auroras whereas solar wind protons penetrating the Mars atmosphere cause proton auroras on the dayside. EMUS also detected new discrete auroras extending thousands of km into the nightside with a sinuous morphology. The variety and abundance of Mars aurora occurrences make them an important tool for gaining new insights into solar wind interaction with Mars's magnetosphere. Mars aurora research therefore involves characterizing aurora occurences in terms of solar activity, seasonal variability, IMF orientation, crustal magnetic fields, and energies of precipitating particles. In this work, we present applications of machine learning for modeling proton auroras as well as automatically detecting discrete electron auroras, leveraging a plethora of MAVEN and EMUS observations. We also focus on explainability of these ML models, commonly perceived as “black-boxes”, and approaches to analyze and validate correlations learned by these models. We discuss in detail the characteristics of proton and electron auroras thus revealed by these models and present future directions for such applications on Mars and other planets.

How to cite: Dhuri, D., Atri, D., and Hseih, S.: Application of machine learning for modeling and characterizing electron and proton auroras on Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14121, https://doi.org/10.5194/egusphere-egu24-14121, 2024.