Browsing by Author "Kilpua, E."

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Investigating Mercury’s Environment with the Two-Spacecraft BepiColombo Mission
(2020-08-01) Milillo, A.; Fujimoto, M.; Murakami, G.; Benkhoff, J.; Zender, J.; Aizawa, S.; Dósa, M.; Griton, L.; Heyner, D.; Ho, G.; Imber, S. M.; Jia, X.; Karlsson, T.; Killen, R. M.; Laurenza, M.; Lindsay, S. T.; McKenna-Lawlor, S.; Mura, A.; Raines, J. M.; Rothery, D. A.; André, N.; Baumjohann, W.; Berezhnoy, A.; Bourdin, P. A.; Bunce, E. J.; Califano, F.; Deca, J.; de la Fuente, S.; Dong, C.; Grava, C.; Fatemi, S.; Henri, P.; Ivanovski, S. L.; Jackson, B. V.; James, M.; Kallio, E.; Kasaba, Y.; Kilpua, E.; Kobayashi, M.; Langlais, B.; Leblanc, F.; Lhotka, C.; Mangano, V.; Martindale, A.; Massetti, S.; Masters, A.; Morooka, M.; Narita, Y.; Oliveira, J. S.; Odstrcil, D.; Orsini, S.; Pelizzo, M. G.; Plainaki, C.; Plaschke, F.; Sahraoui, F.; Seki, K.; Slavin, J. A.; Vainio, R.; Wurz, P.; Barabash, S.; Carr, C. M.; Delcourt, D.; Glassmeier, K. H.; Grande, M.; Hirahara, M.; Huovelin, J.; Korablev, O.; Kojima, H.; Lichtenegger, H.; Livi, S.; Matsuoka, A.; Moissl, R.; Moncuquet, M.; Muinonen, K.; Quèmerais, E.; Saito, Yoshifumi; Yagitani, S.; Yoshikawa, I.; Wahlund, J. E.
A2 Katsausartikkeli tieteellisessä aikakauslehdessä
The ESA-JAXA BepiColombo mission will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric dynamics at Mercury as well as their interactions with the solar wind, radiation, and interplanetary dust. Many scientific instruments onboard the two spacecraft will be completely, or partially devoted to study the near-space environment of Mercury as well as the complex processes that govern it. Many issues remain unsolved even after the MESSENGER mission that ended in 2015. The specific orbits of the two spacecraft, MPO and Mio, and the comprehensive scientific payload allow a wider range of scientific questions to be addressed than those that could be achieved by the individual instruments acting alone, or by previous missions. These joint observations are of key importance because many phenomena in Mercury’s environment are highly temporally and spatially variable. Examples of possible coordinated observations are described in this article, analysing the required geometrical conditions, pointing, resolutions and operation timing of different BepiColombo instruments sensors.
Magnetosheath control of solar wind-magnetosphere coupling efficiency
(2016-09-01) Pulkkinen, T. I.; Dimmock, A. P.; Lakka, A.; Osmane, A.; Kilpua, E.; Myllys, M.; Tanskanen, E. I.; Viljanen, A.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We examine the role of the magnetosheath in solar wind-magnetosphere-ionosphere coupling using the Time History of Events and Macroscale Interactions during Substorms plasma and magnetic field observations in the magnetosheath together with OMNI solar wind data and auroral electrojet recordings from the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer chain. We demonstrate that the electric field and Poynting flux reaching the magnetopause are not linear functions of the electric field and Poynting flux observed in the solar wind: the electric field and Poynting flux at the magnetopause during higher driving conditions are lower than those predicted from a linear function. We also show that the Poynting flux normal to the magnetopause is linearly correlated with the directly driven part of the auroral electrojets in the ionosphere. This indicates that the energy entering the magnetosphere in the form of the Poynting flux is directly responsible for driving the electrojets. Furthermore, we argue that the polar cap potential saturation discussed in the literature is associated with the way solar wind plasma gets processed during the bow shock crossing and motion within the magnetosheath.
The Response of the Venusian Plasma Environment to the Passage of an ICME: Hybrid Simulation Results and Venus Express Observations
(2018-05) Dimmock, A. P.; Alho, M.; Kallio, E.; Pope, S. A.; Zhang, T. L.; Kilpua, E.; Pulkkinen, T. I.; Futaana, Y.; Coates, A. J.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Owing to the heritage of previous missions such as the Pioneer Venus Orbiter and Venus Express, the typical global plasma environment of Venus is relatively well understood. On the other hand, this is not true for more extreme driving conditions such as during passages of interplanetary coronal mass ejections (ICMEs). One of the outstanding questions is how do ICMEs, either the ejecta or sheath portions, impact (1) the Venusian magnetic topology and (2) escape rates of planetary ions? One of the main issues encountered when addressing these problems is the difficulty of inferring global dynamics from single spacecraft obits; this is where the benefits of simulations become apparent. In the present study, we present a detailed case study of an ICME interaction with Venus on 5 November 2011 in which the magnetic barrier reached over 250 nT. We use both Venus Express observations and hybrid simulation runs to study the impact on the field draping pattern and the escape rates of planetary O+ ions. The simulation showed that the magnetic field line draping pattern around Venus during the ICME is similar to that during typical solar wind conditions and that O+ ion escape rates are increased by approximately 30% due to the ICME. Moreover, the atypically large magnetic barrier appears to manifest from a number of factors such as the flux pileup, dayside compression, and the driving time from the ICME ejecta.
Solar Intensity X-Ray and Particle Spectrometer SIXS: Instrument Design and First Results
(2020-08-01) Huovelin, J.; Vainio, R.; Lehtolainen, A.; Kilpua, E.; Korpela, S.; Esko, Eero; Muinonen, K.; Bunce, E.; Martindale, A.; Grande, M.; Andersson, H.; Nenonen, S.; Lehti, Jussi; Schmidt, W.; Genzer, M.; Vihavainen, T.; Saari, J.; Peltonen, J.; Valtonen, E.; Talvioja, M.; Portin, P.; Narendranath, S.; Järvinen, Riku; Okada, T.; Milillo, A.; Laurenza, M.; Heino, E.; Oleynik, P.
A2 Katsausartikkeli tieteellisessä aikakauslehdessä
The Solar Intensity X-ray and particle Spectrometer (SIXS) on the BepiColombo Mercury Planetary Orbiter (“Bepi”) measures the direct solar X-rays, energetic protons, and electrons that bombard, and interact with, the Hermean surface. The interactions result in X-ray fluorescence and scattering, and particle induced X-ray emission (PIXE), i.e. “glow” of the surface in X-rays. Simultaneous monitoring of the incident and emitted radiation enables derivation of the abundances of some chemical elements and scattering properties of the outermost surface layer of the planet, and it may reveal other sources of X-ray emission, due to, for example, weak aurora-like phenomena in Mercury’s exosphere. Mapping of the Hermean X-ray emission is the main task of the MIXS instrument onboard BepiColombo. SIXS data will also be used for investigations of the solar X-ray corona and solar energetic particles (SEP), both in the cruise phase and the passes of the Earth, Venus and Mercury before the arrival at Mercury’s orbit, and the final science phase at Mercury’s orbit. These observations provide the first-ever opportunity for in-situ measurements of the propagation of SEPs, their interactions with the interplanetary magnetic field, and space weather phenomena in multiple locations throughout the inner solar system far away from the Earth, and more extensively at Mercury’s orbit. In this paper we describe the scientific objectives, design and calibrations, operational principles, and scientific performance of the final SIXS instrument launched to the mission to planet Mercury onboard BepiColombo. We also provide the first analysis results of science observations with SIXS, that were made during the Near-Earth Commissioning Phase and early cruise phase operations in 2018–19, including the background X-ray sky observations and “first light” observations of the Sun with the SIXS X-ray detection system (SIXS-X), and in-situ energetic electron and proton observations with the SIXS Particle detection system (SIXS-P).
Solar-wind control of plasma sheet dynamics
(2015) Myllys, M.; Kilpua, E.; Pulkkinen, T.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The purpose of this study is to quantify how solar-wind conditions affect the energy and plasma transport in the geomagnetic tail and its large-scale configuration. To identify the role of various effects, the magnetospheric data were sorted according to different solar-wind plasma and interplanetary magnetic field (IMF) parameters: speed, dynamic pressure, IMF north-south component, epsilon parameter, Auroral Electrojet (AE) index and IMF ultra low-frequency (ULF) fluctuation power. We study variations in the average flow speed pattern and the occurrence rate of fast flow bursts in the magnetotail during different solar-wind conditions using magnetospheric data from five Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission spacecraft and solar-wind data from NASA's OM-NIWeb. The time interval covers the years from 2008 to 2011 during the deep solar minimum between cycles 23 and 24 and the relatively quiet rising phase of cycle 24. Hence, we investigate magnetospheric processes and solar-wind-magnetospheric coupling during a relatively quiet state of the magnetosphere. We show that the occurrence rate of the fast (vertical bar V-tail vertical bar > 100 km s(-1)) sunward flows varies under different solar-wind conditions more than the occurrence of the fast tailward flows. The occurrence frequency of the fast tailward flows does not change much with the solar-wind conditions. We also note that the sign of the IMF B-Z has the most visible effect on the occurrence rate and pattern of the fast sunward flows. High-speed flow bursts are more common during the slow than fast solar-wind conditions.