Christos Katsavrias

Christos Katsavrias
National and Kapodistrian University of Athens | uoa · Department of Astrophysics, Astronomy and Mechanics

PhD Space physics; MSc Astrophysics; BSc Physics

About

52
Publications
7,105
Reads
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350
Citations
Citations since 2016
36 Research Items
331 Citations
2016201720182019202020212022020406080
2016201720182019202020212022020406080
2016201720182019202020212022020406080
2016201720182019202020212022020406080
Introduction
Dr. Christos Katsavrias is a space physicist and postdoctoral fellow at the University of Athens. His interests lie in the field of magnetospheric physics and space weather with emphasis in energetic particles in the Van Allen radiation belts, wave-particle interactions and time-series analysis using wavelet-based methods. He has worked as a research associate for several research projects (ESA and EU funded).
Additional affiliations
February 2019 - December 2022
National and Kapodistrian University of Athens
Position
  • PostDoc Position
January 2015 - present
January 2015 - present
National and Kapodistrian University of Athens
Position
  • Laboratory Assistant
Description
  • Astrophysics
Education
April 2014 - January 2019
October 2011 - July 2013

Publications

Publications (52)
Article
Full-text available
In this paper, we present a new method to compute rapidly, wave particle interaction induced pitch angle and momentum diffusion coefficients. Those terms are normally obtained by the numerical solving of equations based on the quasi‐linear theory. However, this bulk resolution leads to a high computational cost, preventing the integration of plasma...
Article
Full-text available
During July to October of 2019, a sequence of isolated Corotating Interaction Regions (CIRs) impacted the magnetosphere, for four consecutive solar rotations, without any interposed Interplanetary Coronal Mass Ejections. Even though the series of CIRs resulted in relatively weak geomagnetic storms, the net effect of the outer radiation belt during...
Article
Full-text available
Radial diffusion has been established as one of the most important mechanisms contributing to both the acceleration and loss of relativistic electrons in the outer radiation belt, as well as to the supply of particles to the inner radiation belt. In the framework of the “SafeSpace” project, we have used 9 years (2011–2019) of multi-point magnetic a...
Article
Full-text available
Geospace disturbances refer collectively to the variations of the geomagnetic field and the trapped particle populations in the near-Earth space. These are the result of transient and recurrent solar activity, which consequently drives the variable solar wind. They may appear in multiple timescales, from sub-seconds to days, months and years. Wavel...
Article
Full-text available
The Earth's outer radiation belt response to geospace disturbances is extremely variable spanning from a few hours to several months. In addition, the numerous physical mechanisms, which control this response depend on the electron energy, the timescale, and the various types of geospace disturbances. As a consequence, various models that currently...
Preprint
Full-text available
Radial diffusion has been established as one of the most important mechanisms contributing to both the acceleration and loss of relativistic electrons in the outer radiation belt. In the framework of the SafeSpace project we have used 9 years (2011–2019) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to cr...
Article
Full-text available
We report observations of a magnetosheath jet followed by a period of decelerated background plasma. During this period, THEMIS‐A magnetometer showed abrupt disturbances which, in the wavelet spectrum, appeared as prominent and irregular pulsations in two frequency bands (7.6–9.2 and 12–17 mHz) within the Pi2 range. The observations suggest—for the...
Article
Full-text available
Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increases the accuracy of scientific studies and the reliability of data‐driven models th...
Article
Full-text available
Electron variability at geosynchronous orbit (GEO) plays a key role in satellite operations especially concerning the low energies which can lead to surface charging effects on spacecraft. In this work, we use 9 years (2011–2019) of electron measurements from GOES‐13, 14 and 15 satellites to study the evolution of electron fluxes with respect to va...
Article
Full-text available
p>The nature of the semi-Annual variation in the relativistic electron fluxes in the Earth's outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and Geostationary Operational Environmental Satellite Energetic Particle Sensor (GOES/EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad ene...
Preprint
Full-text available
The nature of the semi-annual variation in the relativistic electron fluxes in the Earth's outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and GOES (EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad energy and spatial range of electron fluxes and examine their phase relationship...
Article
We perform a superposed epoch analysis on two groups of selected geospace disturbance events, emerging from single and isolated interplanetary drivers, and resulting in either the enhancement or the depletion of the average relativistic electron Phase Space Density (PSD). We investigate the occurrence of behavioural/temporal patterns of solar wind...
Preprint
Full-text available
We perform a superposed epoch analysis on two groups of selected geospace disturbance events, emerging from single and isolated interplanetary drivers, and resulting in either the enhancement or the depletion of the average relativistic electron Phase Space Density (PSD). We investigate the occurrence of behavioural/temporal patterns of solar wind...
Article
Full-text available
Electrons in the outer Van Allen (radiation) belt occasionally reach relativistic energies, turning them into a potential hazard for spacecraft operating in geospace. Such electrons have secured the reputation of satellite killers and play a prominent role in space weather. The flux of these electrons can vary over time scales of years (related to...
Article
Full-text available
We report observations of energetic electron flux and Phase Space Density (PSD) to show that a relatively weak magnetic storm with $Sym-H_{min} \approx -50 $nT, resulted in a relativistic and ultra--relativistic electron enhancement of two orders of magnitude similar to the St. Patrick's event of 2015, an extreme storm with $Sym-H_{min} \approx -23...
Article
We investigate the response of the outer Van Allen belt electrons to various types of solar wind and magnetospheric disturbances. We use electron phase space density calculations as well as concurrent Pc5 and chorus wave activity observations in the outer belt during the Van Allen Probes era to compare 20 electron enhancement and 8 depletion events...
Preprint
Full-text available
We report observations of energetic electron flux and Phase Space Density (PSD) to show that a relatively weak magnetic storm with $Sym-H_{min} \approx -50 $nT, resulted in a relativistic and ultra--relativistic electron enhancement of two orders of magnitude similar to the St. Patrick's event of 2015, an extreme storm with $Sym-H_{min} \approx -23...
Preprint
Full-text available
We investigate the response of the outer Van Allen belt electrons to various types of solar wind and magnetospheric disturbances. We use electron phase space density (PSD) calculations as well as concurrent Pc5 and chorus wave activity observations in the outer belt during the Van Allen Probes era to compare 20 electron enhancement and 8 depletion...
Preprint
Full-text available
Key Points: • Long-lasting multi-MeV electron enhancement during a period of a relatively weak geomagnetic storm not recorded in GEO. • Electron seed population was accelerated to relativistic energies by the enhanced chorus waves. • Relativistic electrons were further accelerated up to 10 MeV by inward diffusion Abstract We report observations of...
Preprint
Full-text available
Key Points: • The number of events with PSD enhancements is L and µ-dependent. • Loss, as a combined effect of magnetopause shadowing and outward diffusion, is a common feature in both depletion and enhancement events. • The synergy of enhanced seed population and chorus activity is what distinguishes relativistic electrons enhancements from deplet...
Preprint
Full-text available
Electrons in the outer Van Allen (radiation) belt occasionally reach relativistic energies, turning them into a potential hazard for spacecraft operating in geospace. Such electrons have secured the reputation of satellite killers and thus a prominent role in space weather. The flux of these electrons can vary over timescales of years (related to t...
Article
Full-text available
Transient and recurrent solar activity drive geomagnetic disturbances; these are quantified (among others) by DST, AE indices time-series. Transient disturbances are related to the Interplanetary Coronal Mass Ejections (ICMEs) while recurrent disturbances are related to co-rotating interaction regions (CIR). We study the relationship of the geomagn...
Article
Full-text available
We investigate the effect of magnetic disturbances on the ring current buildup and the dynamics of the current systems in the inner geospace by means of numerical simulations of ion orbits during enhanced magnetospheric activity. For this purpose, we developed a particle-tracing model that solves for the ion motion in a dynamic geomagnetic field an...
Article
Full-text available
During the interval 2012 March 7–11 the geospace experienced a barrage of intense space weather phenomena including the second largest geomagnetic storm of solar cycle 24 so far. Significant ultra-low-frequency wave enhancements and relativistic-electron dropouts in the radiation belts, as well as strong energetic-electron injection events in the m...
Article
Full-text available
We report observations of electron Phase Space Density (PSD) dropout and evidence that supports the loss mechanism of magnetopause shadowing and outward radial diffusion during a nonstorm period characterized by persistently positive values of the SYM-H index. On 14 April 2013 an electron PSD dropout of 2 orders of magnitude was observed at the nig...
Article
Geospace magnetic storms, driven by the solar wind, are associated with increases or decreases in the fluxes of relativistic electrons in the outer radiation belt. We examine the response of relativistic electrons to four intense magnetic storms, during which the minimum of the Dst index ranged from −105 to −387 nT, and compare these with concurren...
Article
Full-text available
We present electron phase space density (PSD) calculations as well as concurrent Pc5 and chorus wave activity observations during two intense geomagnetic storms caused by interplanetary coronal mass ejections (ICMEs) resulting in contradicting net effect. We show that, during the 17 March 2013 storm, the coincident observation of chorus and relativ...
Article
Full-text available
Broad Absorption Line Regions - BALR are composed of a number of successive independent absorbing density layers. Using the GR model, we analyze the UV Si IV ({\lambda}{\lambda}1393.755 - 1402.770), O IV ({\lambda}1401.156) and C IV ({\lambda}{\lambda}1548.187 - 1550.772) resonance lines in the spectra of a certain QSO and discuss the results conce...
Article
Full-text available
Boad Absorption Line Regions - BALR are composed of a number of successive independent absorbing density layers. Using the GR model, we analyze the UV Si IV (1393.755 - 1402.770), O IV (1401.156) and C IV (1548.187 - 1550.772) resonance lines in the spectra of a certain QSO and discuss the results concerning its kinematic properties (rotational, ra...
Article
The effects of the energetic phenomena of the Sun, flares and coronal mass ejections (CMEs) on the Earth’s ionosphere–magnetosphere, through the solar wind, are the sources of the geomagnetic disturbances and storms collectively known as Space Weather. The research on the influence of Space Weather on biological and physiological systems is open. I...
Article
Full-text available
The sun as an oscillator produces frequencies which propagate in the heliosphere, via solar wind, to the terrestrial magnetosphere. We searched for those frequencies in the parameters of the near Earth solar plasma and the geomagnetic indices for the past four solar cycles. The solar wind parameters used in this work are the interplanetary magnetic...
Article
Study of the solar and geomagnetic activity influence on the emergency proceedings in Greece, for selected months of solar cycle 23 and especially for the year 2005 is presented. We examined the time association between the magnetic storms (Dst geomagnetic index), daily numbers of solar flares and Coronal Mass Ejections (CMEs) with the emergency p...
Article
We present the time distribution of a large number (7798) of Myocardial Infractions (MI) recorded at the General Hospital ‘St. Panteleimon’ of the city of Nikea (in Piraeus, Greece), during time interval 1997–2007. This data set consisted of 5160 NON‐STEACS (non‐ST) and 2638 STEACS (ST) infractions are examined along with the monthly numbers of sol...
Article
In this paper we study the solar wind parameters during the 23rd solar cycle and the possible correlation between them. Those parameters’ data, which are Alfven Mach number, plasma beta, flow speed, proton density and temperature, dynamic pressure, average magnetic field, Bx and By, has been taken from OMNI 2. The first part of this project is ab...
Article
Eruptive solar events as flares and coronal mass ejections (CMEs) occur during solar activ-ity periods. Energetic particles, fast solar wind plasma and electromagnetic radiation pass through interplanetary space, arrive on Earth's ionosphere-magnetosphere and produce various disturbances. It is well known the negative influence of geomagnetic subst...
Data
Full-text available
Cosmological views of Democritus have been analyzed. Анализиран е космологичният светоглед на Демокрит.
Article
Full-text available
Cosmological views of Democritus have been analyzed.
Article
The purpose of this project is to study the behaviour of the solar wind parameters during the 23rd solar cycle and the possible correlation between them. The presented parameters are Alfven Mach number, plasma beta, flow speed, proton density and temperature, dynamic pressure, average magnetic field, Bx and By, and all data has been taken from OMNI...

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Projects

Projects (4)
Project
Modelling of the near-Earth radiation environment and forecasting of the electron population