• Arecibo measurements of D-region electron densities during sunset and sunrise: implications for atmospheric composition 

      Baumann, Carsten; Kero, Antti; Raizada, Shikha; Rapp, Markus; Sulzer, Michael P.; Verronen, Pekka T.; Vierinen, Juha (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-02)
      Earth’s lower ionosphere is the region where terrestrial weather and space weather come together. Here, between 60 and 100 km altitude, solar radiation governs the diurnal cycle of the ionized species. This altitude range is also the place where nanometre-sized dust particles, recondensed from ablated meteoric material, exist and interact with free electrons and ions of the ionosphere. This ...
    • Auroral molecular-emission effects on the atomic oxygen line at 777.4 nm 

      Oyama, Shin-Ichiro; Tsuda, Takuo T.; Hosokawa, Keisuke; Ogawa, Yasunobu; Miyoshi, Yoshizumi; Kurita, Satoshi; Kero, Antti; Fujii, Ryochi; Tanaka, Yoshimasa; Mizuno, Akira; Kawabata, Tetsuya; Gustavsson, Björn Johan; Leyser, Thomas (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-16)
      One of the representative auroral emission lines that radiates from F-region heights and is measurable on the ground is the 777.4 nm line from excited atomic oxygen. This line has been adopted, along with another E-region emission line, for example 427.8 nm, to estimate the mean energy and total energy flux of precipitating auroral electrons. The influence of emissions from part of the molecular ...
    • Cosmic noise absorption during solar proton events in WACCM-D and riometer observations 

      Heino, Erkka Petteri; Verronen, Pekka T.; Kero, Antti; Kalakoski, Niilo; Partamies, Noora (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-18)
      Solar proton events (SPEs) cause large‐scale ionization in the middle atmosphere leading to ozone loss and changes in the energy budget of the middle atmosphere. The accurate implementation of SPEs and other particle ionization sources in climate models is necessary to understand the role of energetic particle precipitation in climate variability. We use riometer observations from 16 riometer stations ...
    • Electron Energy Spectrum and Auroral Power Estimation From Incoherent Scatter Radar Measurements 

      Virtanen, Ilkka I.; Gustavsson, Björn Johan; Aikio, Anita; Kero, Antti; Asamura, Kazushi; Ogawa, Yasunobu (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-23)
      Differential energy flux of electrons precipitating into the high‐latitude ionosphere can be estimated from incoherent scatter radar observations of the ionospheric electron density profile. We present a method called ELSPEC for electron spectrum estimation from incoherent scatter radar measurements, which is based on integration of the electron continuity equation and spectrum model selection by ...
    • On the determination of ionospheric electron density profiles using multi-frequency riometry 

      McKay, Derek; Vierinen, Juha; Kero, Antti; Partamies, Noora (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-27)
      Radio wave absorption in the ionosphere is a function of electron density, collision frequency, radio wave polarisation, magnetic field and radio wave frequency. Several studies have used multi-frequency measurements of cosmic radio noise absorption to determine electron density profiles. Using the framework of statistical inverse problems, we investigated if an electron density altitude profile ...
    • Radar—CubeSat Transionospheric HF Propagation Observations: Suomi 100 Satellite and EISCAT HF Facility 

      Kallio, Esa; Kero, Antti; Harri, Ari-Matti; Kestilä, Antti; Aikio, Anita; Fontell, Mathias; Jarvinen, Riku; Kauristie, Kirsti; Knuuttila, Olli; Koskimaa, Petri; Loyala, Jauaries; Lukkari, Juha-Matti; Modabberian, Amin; Niittyniemi, Joonas; Rynö, Jouni; Vanhamäki, Heikki; Varberg, Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-20)
      Radio waves provide a useful diagnostic tool to investigate the properties of the ionosphere because the ionosphere affects the transmission and properties of high frequency (HF) electromagnetic waves. We have conducted a transionospheric HF-propagation research campaign with a nanosatellite on a low-Earth polar orbit and the EISCAT HF transmitter facility in Tromsø, Norway, in December 2020. In ...
    • Review of Environmental Monitoring by Means of Radio Waves in the Polar Regions: From Atmosphere to Geospace 

      Alfonsi, Lucilla; Bergeot, Nicolas; Cilliers, Pierre J.; De Franceschi, Giorgiana; Baddeley, Lisa; Correia, Emilia; Di Mauro, Domenico; Enell, Carl-Fredrik; Engebretson, Mark; Ghoddousi-Fard, Reza; Häggström, Ingemar; Ham, Young-bae; Heygster, Georg; Jee, Geonhwa; Kero, Antti; Kosch, Michael; Kwon, Hyuck-Jin; Lee, Changsup; Lotz, Stefan; Macotela, Liliana; Marcucci, Maria Federica; Miloch, Wojciech Jacek; Morton, Y. Jade; Naoi, Takahiro; Negusini, Monia; Partamies, Noora; Petkov, Boyan H.; Pottiaux, Eric; Prikryl, Paul; Shreedevi, P.R.; Slapak, Rikard; Spogli, Luca; Stephenson, Judy; Triana-Gómez, Arantxa M.; Troshichev, Oleg A.; Van Malderen, Roeland; Weygand, James M.; Zou, Shasha (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-23)
      The Antarctic and Arctic regions are Earth's open windows to outer space. They provide unique opportunities for investigating the troposphere–thermosphere–ionosphere–plasmasphere system at high latitudes, which is not as well understood as the mid- and low-latitude regions mainly due to the paucity of experimental observations. In addition, different neutral and ionised atmospheric layers at high ...