A5043489156- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Solar Radiation and Photovoltaics
- Geophysics and Gravity Measurements
- Stellar, planetary, and galactic studies
- Earthquake Detection and Analysis
- Radiation Therapy and Dosimetry
- Nuclear Physics and Applications
- Atmospheric Ozone and Climate
- Atomic and Molecular Physics
- Atomic and Subatomic Physics Research
- Global Energy and Sustainability Research
- Laser-Plasma Interactions and Diagnostics
- Dark Matter and Cosmic Phenomena
- Spacecraft and Cryogenic Technologies
- Scientific Research and Discoveries
- Geomagnetism and Paleomagnetism Studies
- Pulsars and Gravitational Waves Research
- Neutrino Physics Research
- Energetic Materials and Combustion
- Impact of Light on Environment and Health
- Radioactivity and Radon Measurements
University of Oulu
2013-2023
Moscow Engineering Physics Institute
2021
Helsinki Institute of Physics
2012
University of Helsinki
2011-2012
University of Turku
2001-2011
National Oceanic and Atmospheric Administration
2008-2009
NOAA Space Weather Prediction Center
2009
Goddard Space Flight Center
1999
California Institute of Technology
1994-1995
Peter the Great St. Petersburg Polytechnic University
1992-1994
Abstract The first ground-level enhancement of the current Solar Cycle 25 occurred on 28 October 2021. It was observed by several space-borne and ground-based instruments, specifically neutron monitors. A moderate count-rate increase over background high-altitude polar stations South Pole Dome C at Antarctic plateau. Most monitors registered only marginal increases. Using detrended records employing a method verified direct measurements, we derive rigidity spectra angular distributions...
Abstract We have analyzed the data of world neutron monitor network for first ground level enhancement solar cycle 24, (GLE) on 17 May 2012. A newly computed yield function and an inverse method are applied to estimate energy spectrum, anisotropy axis direction, pitch angle distribution high‐energy particles in interplanetary space. The includes determination asymptotic viewing cones stations through computations trajectories cosmic rays a model magnetosphere. ray particle determined with...
Abstract We analyze the high-energy particle emission from Sun in two extreme solar events which protons are accelerated to relativistic energies and can cause a significant signal even ground-based detectors. Analysis of proton event is based on modeling transport interaction, near-Sun source through wind Earth’s magnetosphere atmosphere detector ground. This allows us deduce time profile at compare it with observed electromagnetic emissions. The 1998 May 2 associated flare coronal mass...
Abstract During Solar Cycle 23 16 ground-level enhancement events were registered by the global neutron monitor network. In this work we focus on period with increased solar activity during late October – early November 2003 producing a sequence of three events, specifically GLE 67 2 2003. On basis an analysis and space-borne data derived spectra pitch-angle distribution high-energy particles their dynamical evolution throughout event. According to our analysis, best fit spectral angular...
Abstract During the 24th solar cycle, Fermi Large Area Telescope (LAT) has observed a total of 27 flares possessing delayed γ -ray emission, including exceptionally well-observed flare and coronal mass ejection (CME) on 2017 September 10. Based Fermi/LAT data, we plot, for first time, maps possible sources >100 MeV emission 10 event. The long-lasting is localized under CME core. spectrum exhibits intermittent changes in implying that more than one source high-energy protons was formed...
Using the Energetic and Relativistic Nuclei Electron (ERNE) instrument on Solar Heliospheric Observatory (SOHO), we have measured 17-22 MeV proton flux anisotropy during 1998 May 2-3 solar energetic particle (SEP) event, when SOHO was inside a magnetic cloud associated with previous coronal mass ejection (CME). The ability of SOHO/ERNE to measure fluxes high angular resolution makes it unique for observing SEPs under weak scattering conditions. During most first 4 hr SEP event that started...
Abstract We analyze the relativistic proton emission from Sun during eruptive event on 2017 September 10, which caused a ground-level enhancement (GLE 72) registered by worldwide network of neutron monitors. Using monitor data and interplanetary transport modeling both along across magnetic field (IMF) lines, we deduce parameters injection into medium. The inferred profile protons is compared with >100 MeV γ -ray observed Fermi Large Area Telescope, attributed to pion production...
We report extreme-UV observations of the coronal Moreton wave and concurrent ~10-100 MeV protons. Observations are carried out with Extreme-UV Imaging Telescope Energetic Relativistic Nuclei Electron instrument on board SOHO spacecraft. study proton events associated mass ejections (CMEs) centered near central meridian. reveal initial injection ≳10 protons during period when was traversing western hemisphere Sun, this being an early signature CME launch. Acceleration CME-associated starts...
Abstract Intense solar activity was observed in May 2012. A notable ground level enhancement (GLE) registered on 17 2012 by several space‐borne instruments as well neutron monitors (NMs). This event is known GLE # 71. Here, we derived the spectral and angular characteristics, apparent source position of protons during 71, employing verified newly computed NM yield function sophisticated unfolding procedure. We considerably improved previously information about spectra distribution, namely,...
We present a test-particle model of diffusive shock acceleration on open coronal field lines based one-dimensional diffusion-convection equation with finite upstream and downstream diffusion regions. calculate the energy spectrum protons escaping into interplanetary space that interacting subcoronal material producing observable secondary emissions. Our can account for observed power-law broken spectra as well values order unity ratio to protons. compare our Monte Carlo simulations parallel...
During the period from January through mid‐May, 1997, four large Earth‐directed CMEs were observed by Large Angle Spectroscopic Coronograph (LASCO). These associated with long‐lasting fluxes of >1.6 MeV protons detected Energetic and Relativistic Nuclei Electron instrument (ERNE). However, magnitudes energetic proton events differed dramatically on different occasions. In strong events, production 10‐50 started during expansion coronal Moreton wave in western hemisphere Sun. The new SOHO...
The energy spectra of particles in gradual solar energetic particle (SEP) events do not always have a power-law form attributed to the diffusive shock acceleration mechanism. In particular, observed major SEP can take broken (double) power law. this paper, we study effect process that modify spectral produced by acceleration: stochastic re-acceleration protons enhanced Alfvenic turbulence downstream region wave. There are arguments suggesting be important when propagates corona. We consider...
With the first observations of solar γ-rays from decay pions, relationship protons producing ground level enhancements (GLEs) on Earth to those similar energies Sun has been debated. These two populations may be either independent and simply coincident in large flares, or they be, fact, same population stemming a single accelerating agent jointly distributed at also space. Assuming latter, we model scenario which particles are accelerated near shock wave with fraction transported back...
A model of stochastic acceleration heavy ions by Alfvén wave turbulence has been developed. It takes into account spatial diffusion, Coulomb losses, and the possibility charge changes for during acceleration. The main processes influencing ionic states are stripping thermal electrons protons as constituents a surrounding medium dielectronic radiative recombination. We have calculated energy spectra distributions nonthermal Fe sample species. dependence iron on parameters plasma (temperature...
Abstract Emission of relativistic protons and helium responsible for extreme solar particle events (ground level enhancements (GLEs)) is often structured. We investigate its organization depending on the eruption stage characterized by heliocentric height associated coronal mass ejections (CMEs). Seven GLEs are considered: 1997 November 6, 1998 May 2, 2000 July 14, 2001 December 26, 2003 2006 13, 2012 17, which half SOlar Heliospheric Observatory ( SOHO ) -era GLEs, excluding very weak...
We examine the energy-dependent rates of charge-changing processes energetic Fe ions in hot plasma solar corona. For ionization Fe-ion projectile collisions with ambient protons, three different methods estimating corresponding cross sections are presented and compared. Proton-impact is found to be significant irrespective particular method used. Differences proton-impact sections' estimates shown have little effect calculating highly nonequilibrium charge states during acceleration, whereas...
The onset of the >10‐MeV proton event August 13–14, 1996, revealed a velocity dispersion, which is signature its solar origin, but no associated soft X ray flare was observed. LASCO CME observations, presence AR 7981 beyond west limb, and type II IV radio burst timing with respect to indicate that parent eruption may be centered on back side Sun, at ∼150°W. In such case, expanding CME‐associated wave can reach Earth‐connected interplanetary magnetic field line in ∼1 hour so give rise...