Savvas

Savvas

Space Plasma Physics & Machine Learning Applications

Publications

2025

Adaptive PCA-Based Outlier Detection for Multi-feature Time Series in Space Missions

Published in omputational Science – ICCS 2025. Lecture Notes in Computer Science, 2025

Ekelund, J., Raptis, S., Toy-Edens, V., Mo, W., Turner, D. L., Cohen, I. J., & Markidis, S. (2025). Adaptive PCA-Based Outlier Detection for Multi-feature Time Series in Space Missions. In: Lees, M.H., et al. Computational Science – ICCS 2025. ICCS 2025. Lecture Notes in Computer Science, vol 15903. Springer, Cham. https://doi.org/10.1007/978-3-031-97626-1_18

Control of Solar Wind on Magnetic Field Fluctuations in the Subsolar Magnetosheath

Published in Journal of Geophysical Research - Space Physics, 2025

Zou, Y., Walsh, B. M., Chen, Y., Zhou, H., & Raptis, S. (2025). Control of solar wind on magnetic field fluctuations in the subsolar magnetosheath. Journal of Geophysical Research: Space Physics, 130, e2025JA033856. https://doi.org/10. 1029/2025JA033856

Interplay between a foreshock bubble and a hot flow anomaly forming along the same rotational discontinuity

Published in Geophysical Research Letters (GRL), 2025

Turc, L., Archer, M. O., Zhou, H., Pfau-Kempf, Y., Suni, J., Kajdiˇc, P., Blanco-Cano, X., Dahani, S., Battarbee, M., Raptis, S. , Liu, T. Z., Zhang, H., Escoubet, P. C., LaMoury, A. T., Tao, S., Lipsanen, V., Hao, Yufei., & Palmroth, M., (2025). Interplay between a foreshock bubble and a hot flow anomaly forming along the same rotational discontinuity. Geophysical Research Letters, 52, e2025GL116473. https://doi.org/10.1029/ 2025GL116473

Ground magnetic response to an extraordinary IMF By flip during the May 2024 storm: Travel time from the magnetosheath to dayside high latitudes

Published in Journal of Geophysical Research - Space Physics, 2025

Ohtani, S., Zou, Y., Merkin, V. G., Wiltberger, M., Pham, K. H., Raptis, S., Friel, M., & Gjerloev, J. W., (2025). Ground magnetic response to an extraordinary IMF By flip during the May 2024 storm: Travel time from the magnetosheath to dayside high latitudes. Journal of Geophysical Research: Space Physics, 130, e2024JA033691. https://doi.org/10.1029/2024JA033691

Sunward Flows in the Magnetosheath Associated with Magnetic Pressure Gradient and Magnetosheath

Published in Frontiers in Astronomy and Space Sciences, 2025

Madanian, H., Pfau-Kemp, Y., Rachel, R., Liu, T. Z., Karlsson, T., Raptis, S., Turner, D.L. & Beedle, J., (2025). Sunward Flows in the Magnetosheath Associated with Magnetic Pressure Gradient and Magnetosheath. Front. Astron. Space Sci. - Space Physics, doi: 10.3389/fspas.2025.1574577

Magnetosheath Jet-Triggered ULF Waves: Energy Deposition in the Ionosphere

Published in Journal of Geophysical Research - Space Physics, 2025

Krämer, E., Hamrin, M., Gunell, H., Baddeley, L., Partamies, N., Raptis, S., Herlingshaw, K., & Schillings, A., (2025). Magnetosheath Jet-Triggered ULF Waves: Energy Deposition in the Ionosphere. Journal of Geophysical Research: Space Physics 130, e2025JA033792. https://doi.org/10.1029/ 2025JA033792

Multimission Observations of Relativistic Electrons and High-speed Jets Linked to Shock-generated Transients

Published in The Astrophysical Journal Letters (ApJL), 2025

Raptis, S., Lindberg, M., Liu, T.Z., Turner, D.L., Lalti, A., Zhou, Y., Kajdič, P., Kouloumvakos, A., Sibeck, D.G., Vuorinen, L., Michael, A., Shumko, M., Osmane, A., Krämer, E., Turc, L., Karlsson, T., Katsavrias, C., Wilson III, L.B., Madanian, H., Blanco-Cano, X., Cohen, I.J., & Escoubet C.P., (2025). Multimission Observations of Relativistic Electrons and High-speed Jets Linked to Shock-generated Transients.The Astrophysical Journal Letters 981(1) L10, https://dx.doi.org/10.3847/2041-8213/adb154

MMS highlighted summary : MMS highlighted summary

Revealing an unexpectedly low electron injection threshold via reinforced shock acceleration

Published in Nature Communications, 2025

Raptis, S., Lalti, A., Lindberg, M., Turner, D. L., Caprioli, D., & Burch, J. L. (2025). Revealing an unexpectedly low electron injection threshold via reinforced shock acceleration. Nature Communications, 16(1), 488 https://doi.org/10.1038/s41467-024-55641-9

MMS highlighted summary : MMS highlighted summary
ARTEMIS Science Nugget Highlight : ARTEMIS Science Nugget Highlight
Press Coverage: Northumbria University, phys.org, sciencedaily.com
Behind The Paper: Nature Portfolio

2024

Jets Downstream of Collisionless Shocks: Recent Discoveries and Challenges

Published in Space Science Reviews, 2024

Krämer, E., Koller, F., Suni, J., LaMoury T. A., Pöppelwerth, A., Glebe, G., Mohammed-Amin, T., Raptis, S. , Vuorinen, L., Weiss, S., Xirogiannopoulou, N., Archer, M., Bianco-Cano, X., Gunell. H., Hietala, H., Karlsson, T., Plaschke, F., Preisser, L., Roberts, O., Wedlund, S. C., Temmer, M., & Vörös , Z. (2025). ts Downstream of Collisionless Shocks: Recent Discoveries and Challenges. Space Science Reviews, 221(1), 1-59

The Effect of Fast Solar Wind on Ion Distribution Downstream of Earth’s Bow Shock

Published in The Astrophysical Journal (ApJ), 2024

Osmane, A., & Raptis, S. (2024). On the formation of super-Alfvénic flows downstream of collisionless shocks. The Astrophysical Journal, 976(1), 104.

Plasma Sheet Magnetic Flux Transport During Geomagnetic Storms

Published in Geophysical Research Letters (GRL), 2024

Raptis, S. , Merkin, V., Ohtani, S., Gkioulidou, M., & Regoli, L. H. (2024). Plasma sheet magnetic flux transport during geomagnetic storms. Geophysical Research Letters, 51, e2024GL110839. https://doi.org/10.1029/2024GL110839

MMS highlighted summary : MMS highlighted summary

Transient upstream mesoscale structures: drivers of solar-quiet space weather

Published in Frontiers in Astronomy and Space Sciences, 2024

Kajdič, P., Blanco-Cano, X., Turc, L., Archer, M., Raptis, S., Liu, TZ., Pfau-Kempf, Y., LaMoury, AT., Hao, Y., Escoubet, PC., Omidi, N., Sibeck, DG., Wang, B., Zhang, H., and Lin, Y. (2024) Transient upstream mesoscale structures: drivers of solar-quiet space weather. Front. Astron. Space Sci. 11:1436916. doi: 10.3389/fspas.2024.1436916

Classifying 8 Years of MMS Dayside Plasma Regions via Unsupervised Machine Learning

Published in Journal of Geophysical Research - Space Physics, 2024

Toy-Edens, V., Mo, W., Raptis, S., & Turner, D. L. (2024). Classifying 8 years of MMS dayside plasma regions via unsupervised machine learning. Journal of Geophysical Research: Space Physics, 129, e2024JA032431. https://doi.org/10.1029/2024JA032431

Temporal Evolution of O+ Population in the Near-Earth Plasma Sheet During Geomagnetic Storms as Observed by the Magnetospheric Multiscale Mission

Published in Journal of Geophysical Research - Space Physics, 2024

Regoli, L. H., Gkioulidou, M., Ohtani, S., Raptis, S., Mouikis, C. G., Kistler, L. M., et al. (2024). Temporal evolution of O+ population in the near-Earth plasma sheet during geomagnetic storms as observed by the magnetospheric multiscale mission. Journal of Geophysical Research: Space Physics, 129, e2023JA032203. https://doi.org/10.1029/2023JA032203

The Effect of Fast Solar Wind on Ion Distribution Downstream of Earth’s Bow Shock

Published in The Astrophysical Journal Letters (ApJL), 2024

Koller, F., Raptis, S., Temmer, M., & Karlsson, T. (2024). The Effect of Fast Solar Wind on Ion Distribution Downstream of Earth's Bow Shock. The Astrophysical Journal Letters 954(1) L5, https://dx.doi.org/10.3847/2041-8213/ad2ddf

Electron Acceleration at Earth’s Bow Shock Due to Stochastic Shock Drift Acceleration

Published in Geophysical Research Letters (GRL), 2024

Lindberg, M., Vaivads, A., Amano, T., Raptis, S. , & Joshi, S. (2024). Electron Acceleration at Earth's Bow Shock Due to Stochastic Shock Drift Acceleration Geophysical Research Letters, 51, e2023GL106612. https://doi.org/10.1029/2023GL106612

Magnetosheath jets at Jupiter and across the solar system

Published in Nature Communications, 2024

Zhou, Y., Raptis, S. , Wang, S., Shen, C., Ren., N., & Ma, L. (2024). Magnetosheath jets at Jupiter and across the solar system. Nature Communications., 15, 4, https://doi.org/10.1038/s41467-023-43942-4

Press Coverage: phys.org, Astronomy Magazine

2023

Shocklets and Short Large Amplitude Magnetic Structures (SLAMS) in the High Mach Foreshock of Venus

Published in Geophysical Research Letters (GRL), 2023

Collinson, G., Hietala, H., Plaschke, F., Karlsson, T., Wilson, B. L., Archer, M., Battarbee, M., Bianco-Cano, X., Bertucci, C., Long, D., Opher, M., Sergis, N., Gasque, C., Liu, T., Raptis, S., Burne, S., Frahm, R., Zhang, T., & Futaana, Y. (2023). Shocklets and Short Large Amplitude Magnetic Structures (SLAMS) in the high Mach foreshock of Venus. Geophysical Research Letters, 50, e2023GL104610, https://doi.org/10.1029/2023GL104610

Velocity of magnetic holes in the solar wind from Cluster multipoint measurements

Published in Annales Geophysicae (ANGEO), 2023

Trollvik, H., Karlsson, T., Raptis, S. (2023). Velocity of magnetic holes in the solar wind from Cluster multipoint measurements. Ann. Geophys., 41, 327–337, https://doi.org/10.5194/angeo-41-327-2023

MMS observation of two-step electron acceleration at Earth’s bow shock

Published in Geophysical Research Letters (GRL), 2023

Lindberg, M., Vaivads, A., Raptis, S., & Karlsson, T. (2023). MMS observation of two-step electron acceleration at Earth’s bow shock. Geophysical Research Letters, 50, e2023GL104714. https://doi.org/10.1029/2023GL104714

2022

Solar wind magnetic holes can cross the bow shock and enter the magnetosheath

Published in Annales Geophysicae (ANGEO), 2022

Karlsson, T., Trollvik, H., Raptis, S., Nilsson, H., & Madanian, H. (2022). Solar wind magnetic holes can cross the bow shock and enter the magnetosheath. Ann. Geophys., 40, 687–699, doi:10.5194/angeo-40-687-2022

Dynamics of Earth’s bow shock under near-radial interplanetary magnetic field conditions

Published in Physics of Plasmas, 2022

Pollock, C., Chen, L-J., Schwartz, S., Wang, S., Avanov, L. A., Burch, J. L., Gershman, D. J., Giles, B. L., Raptis, S., & Russell, C. T. (2022). Dynamics of Earth’s bow shock under near-radial interplanetary magnetic field conditions, Physics of Plasmas 29, 112902 (2022) https://doi.org/10.1063/5.0089937

On Magnetosheath Jet Kinetic Structure and Plasma Properties

Published in Geophysical Research Letters (GRL), 2022

Raptis, S., Karlsson, T., Vaivads, A., Lindberg, M., Johlander, A., & Trollvik, H. (2022). On magnetosheath jet kinetic structure and plasma properties. Geophysical Research Letters, 49, e2022GL100678. https://doi.org/10.1029/2022GL100678

MMS highlighted summary : MMS highlighted summary

Electron kinetic entropy across quasi-perpendicular shocks

Published in Entropy, 2022

Lindberg, M., Vaivads, A., Raptis, S., Lindqvist, P.-A., Giles, B. L., & Gershman, D. J. (2021). Electron kinetic entropy across quasi-perpendicular shocks. Entropy 24, 745. https://doi.org/10.3390/e24060745

Downstream high-speed plasma jet generation as a direct consequence of shock reformation ☆

Published in Nature Communications, 2022

Raptis, S., Karlsson, T., Vaivads, A., Pollock, C., Plaschke, F., Johlander, A., Trollvik, H., & Lindqvist, P.-A. (2022). Downstream high-speed plasma jet generation as a direct consequence of shock reformation. Nature Communications. 13, 598 https://doi.org/10.1038/s41467-022-28110-4

☆ Springer 2022 Highlight : Breakthrough Research Highlights: Astronomy
☆ Editor Highlighted : Focus : Astronomy and planetary science
Press Coverage: KTH, phys.org, spacedaily.com
Behind The Paper: Nature Portfolio

2021

Solar Energetic Particle Event occurrence prediction using Solar Flare Soft X-ray measurements and Machine Learning

Published in Journal of Space Weather and Space Climate (JSWSC), 2021

Sigiava, A-G., Raptis, S., Anastasiadis, A. A., Tsigkanos, A., Sandberg, I., Papaioannou, A., Papadimitrioy, C., Jiggens, P., Aran, A., & Daglis, I.A. (2021). Solar Energetic Particle Event occurrence prediction using Solar Flare Soft X-ray measurements with Machine Learning. Journal of Space Weather and Space Climate (2021) doi: 10.1051/swsc/2021043

Classifying the magnetosheath behind the quasi-parallel and quasi-perpendicular bow shock by local measurements

Published in Journal of Geophysical Research - Space Physics, 2021

Karlsson, T., Raptis, S., Trollvik, H., & Nilsson, H. (2021). Classifying the magnetosheath behind the quasi-parallel and quasi-perpendicular bow shock by local measurements. Journal of Geophysical Research: Space Physics, 126, e2021JA029269. https://doi.org/10.1029/2021JA029269

On the generation of Pi2 pulsations due to plasma flow patterns around magnetosheath jets

Published in Geophysical Research Letters (GRL), 2021

Katsavrias, C., Raptis, S., Daglis, I. A., Karlsson, T., Georgiou, M., & Balasis, G. (2021). On the generation of Pi2 pulsations due to plasma flow patterns around magnetosheath jets. Geophysical Research Letters, 48, e2021GL093611. doi:10.1029/2021GL093611

Causes of jets in the quasi-perpendicular magnetosheath

Published in Geophysical Research Letters (GRL), 2021

Kajdič, P., Raptis, S., Blanco-Cano, X., & Karlsson, T. (2021). Causes of jets in the quasi-perpendicular magnetosheath. Geophysical Research Letters, 48, e2021GL093173. doi:10.1029/2021GL093173

Magnetosheath jet evolution as a function of lifetime: global hybrid-Vlasov simulations compared to MMS observations

Published in Annales Geophysicae (ANGEO), 2021

Palmroth, M., Raptis, S., Suni, J., Karlsson, T., Turc, L., Johlander, A., Ganse, U., Pfau-Kempf, Y., Blanco-Cano, X., Akhavan-Tafti, M., Battarbee, M., Dubart, M., Grandin, M., Tarvus, V., & Osmane, A. (2021). Magnetosheath jet evolution as a function of lifetime: global hybrid-Vlasov simulations compared to MMS observations, Ann. Geophys., 39, 289–308, doi:10.5194/angeo-39-289-2021

2020

Helium in the Earth’s foreshock: a global Vlasiator survey

Published in Annales Geophysicae (ANGEO), 2020

Battarbee, M., Blanco-Cano, X., Turc, L., Kajdič, P., Johlander, A., Tarvus, V., Fuselier, S., Trattner, K., Alho, M., Brito, T., Ganse, U., Pfau-Kempf, Y., Akhavan-Tafti, M., Karlsson, T., Raptis, S., Dubart, M., Grandin, M., Suni, J., and Palmroth, M. (2020). Helium in the Earth's foreshock: a global Vlasiator survey, Ann. Geophys., 38, 1081–1099, doi:10.5194/angeo-38-1081-2020

Classifying Magnetosheath Jets Using MMS: Statistical Properties

Published in Journal of Geophysical Research - Space Physics, 2020

Raptis, S., Karlsson, T., Plaschke, F., Kullen, A., & Lindqvist, P.-A. (2020). Classifying magnetosheath jets using MMS: Statistical properties. Journal of Geophysical Research: Space Physics, 125, e2019JA027754. doi:10.1029/2019JA027754

Classification of Magnetosheath Jets Using Neural Networks and High Resolution OMNI (HRO) Data

Published in Frontiers in Astronomy and Space Sciences, 2020

Raptis. S., Aminalragia-Giamini. S., Karlsson. T., & Lindberg. M. (2020) Classification of Magnetosheath Jets Using Neural Networks and High Resolution OMNI (HRO) Data. Front. Astron. Space Sci. 7:24. doi: 10.3389/fspas.2020.00024

Editorial E-book : Research Topic: Machine Learning in Heliophysics