Bibliography

Total Electron Content Variations during an HSS/CIR driven storm at high and middle latitudes

Geethakumari, Gopika; Aikio, Anita; Cai, Lei; Vanhamaki, Heikki; Pedersen, Marcus; Coster, Anthea; Marchaudon, Aurélie; Blelly, Pierre-Louis; Haberle, Veronika; Maute, Astrid; Ellahouny, Nada; Virtanen, Ilkka; Norberg, Johannes; Soyama, Shin-Ichiro; Grandin, Maxime;

Published by:       Published on: mar

YEAR: 2022     DOI: 10.5194/egusphere-egu22-8194

Large-Scale Dune Aurora Event Investigation Combining Citizen Scientists Photographs and Spacecraft Observations

Recently, citizen scientist photographs led to the discovery of a new auroral form called “the dune aurora” which exhibits parallel stripes of brighter emission in the green diffuse aurora at about 100 km altitude. This discovery raised several questions, such as (i) whether the dunes are associated with particle precipitation, (ii) whether their structure arises from spatial inhomogeneities in the precipitating fluxes or in the underlying neutral atmosphere, and (iii) whether they are the auroral manifestation of an atmospheric wave called a mesospheric bore. This study investigates a large-scale dune aurora event on 20 January 2016 above Northern Europe. The dunes were observed from Finland to Scotland, spanning over 1,500 km for at least 4 h. Spacecraft observations indicate that the dunes are associated with particle precipitation and reveal the presence of a temperature inversion layer below the mesopause during the event, creating suitable conditions for mesospheric bore formation. The analysis of a time lapse of pictures by a citizen scientist from Scotland leads to the estimate that, during this event, the dunes propagate toward the west-southwest direction at about 200 m s−1, presumably indicating strong horizontal winds near the mesopause. These results show that citizen science and dune aurora studies can fill observational gaps and be powerful tools to investigate the least-known region of near-Earth space at altitudes near 100 km.

Grandin, Maxime; Palmroth, Minna; Whipps, Graeme; Kalliokoski, Milla; Ferrier, Mark; Paxton, Larry; Mlynczak, Martin; Hilska, Jukka; Holmseth, Knut; Vinorum, Kjetil; , others;

Published by: AGU Advances      Published on:

YEAR: 2021     DOI: https://doi.org/10.1029/2020AV000338

Hybrid-Vlasov simulation of auroral proton precipitation in the cusps: Comparison of northward and southward interplanetary magnetic field driving

Particle precipitation is a central aspect of space weather, as it strongly couples the magnetosphere and the ionosphere and can be responsible for radio signal disruption at high

Grandin, Maxime; Turc, Lucile; Battarbee, Markus; Ganse, Urs; Johlander, Andreas; Pfau-Kempf, Yann; Dubart, Maxime; Palmroth, Minna;

Published by: Journal of space weather and space climate      Published on:

YEAR: 2020     DOI: 10.1051/swsc/2020053

Hybrid-Vlasov modelling of nightside auroral proton precipitation during southward interplanetary magnetic field conditions

Particle precipitation plays a key role in the coupling of the terrestrial magnetosphere and ionosphere by modifying the upper atmospheric conductivity and chemistry, driving field-aligned currents, and producing aurora. Yet quantitative observations of precipitating fluxes are limited, since ground-based instruments can only provide indirect measurements of precipitation, while particle telescopes aboard spacecraft merely enable point-like in situ observations with an inherently coarse time resolution above a given location. Further, orbit timescales generally prevent the analysis of whole events. On the other hand, global magnetospheric simulations can provide estimations of particle precipitation with a global view and higher time resolution. We present the first results of auroral (∼1–30 keV) proton precipitation estimation using the Vlasiator global hybrid-Vlasov model in a noon–midnight meridional plane simulation driven by steady solar wind with a southward interplanetary magnetic field. We first calculate the bounce loss-cone angle value at selected locations in the simulated nightside magnetosphere. Then, using the velocity distribution function representation of the proton population at those selected points, we study the population inside the loss cone. This enables the estimation of differential precipitating number fluxes as would be measured by a particle detector aboard a low-Earth-orbiting (LEO) spacecraft. The obtained differential flux values are in agreement with a well-established empirical model in the midnight sector, as are the integral energy flux and mean precipitating energy. We discuss the time evolution of the precipitation parameters derived in this manner in the global context of nightside magnetospheric activity in this simulation, and we find in particular that precipitation bursts of <1 min duration can be self-consistently and unambiguously associated with dipolarising flux bundles generated by tail reconnection. We also find that the transition region seems to partly regulate the transmission of precipitating protons to the inner magnetosphere, suggesting that it has an active role in regulating ionospheric precipitation.

Grandin, Maxime; Battarbee, Markus; Osmane, Adnane; Ganse, Urs; Pfau-Kempf, Yann; Turc, Lucile; Brito, Thiago; Koskela, Tuomas; Dubart, Maxime; Palmroth, Minna;

Published by:       Published on:

YEAR: 2019     DOI: 10.5194/angeo-37-791-2019

IPIM Modeling of the Ionospheric F ₂ Layer Depletion at High Latitudes During a High-Speed Stream Event

Our aim is to understand the effect of high-speed stream events on the high-latitude ionosphere and more specifically the decrease of the f_oF₂ frequency during the entire day following the impact. First, we have selected one summertime event, for which a large data set was available: Super Dual Auroral Radar Network (SuperDARN) and European Incoherent SCATter (EISCAT) radars, Troms\o and Sodankylä ionosondes, and the CHAllenging Minisatellite Payload (CHAMP) satellite. We modeled with the IPIM model (IRAP Plasmasphere Ionosphere Model) the dynamics of the ionosphere at Troms\o and Sodankylä using inputs derived from the data. The simulations nicely match the measurements made by the EISCAT radar and the ionosondes, and we showed that the decrease of f_oF₂ is associated with a transition from F₂ to F₁ layer resulting from a decrease of neutral atomic oxygen concentration. Modeling showed that electrodynamics can explain short-term behavior on the scale of a few hours, but long-term behavior on the scale of a few days results from the perturbation induced in the atmosphere. Enhancement of convection is responsible for a sharp increase of the ion temperature by Joule heating, leading through chemistry to an immediate reduction of the F₂ layer. Then, ion drag on neutrals is responsible for a rapid heating and expansion of the thermosphere. This expansion affects atomic oxygen through nonthermal upward flow, which results in a decrease of its concentration and amplifies the decrease of [O]/[N₂] ratio. This thermospheric change explains long-term extinction of the F₂ layer.

Marchaudon, A.; Blelly, P.-L.; Grandin, M.; Aikio, A.; Kozlovsky, A.; Virtanen, I.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 08/2018

YEAR: 2018     DOI: 10.1029/2018JA025744

IPIM Modeling of the Ionospheric F 2 Layer Depletion at High Latitudes During a High-Speed Stream Event

Our aim is to understand the effect of high‐speed stream events on the high‐latitude ionosphere and more specifically the decrease of the f o F 2 frequency during the entire day

Marchaudon, A; Blelly, P-L; Grandin, M; Aikio, A; Kozlovsky, A; Virtanen, I;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2018     DOI: 10.1029/2018JA025744