Article
Geosciences, Multidisciplinary
D. Nunn, X-J Zhang, D. Mourenas, A. Artemyev
Summary: Researchers analyzed statistics of lower-band chorus waves in the inner magnetosphere and found that moderately intense short wave packets can be formed by superposing two or more waves with a sufficiently large frequency difference near the magnetic equator.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geosciences, Multidisciplinary
C. C. Chaston
Summary: The transport of energetic electrons in Earth's outer radiation belt immersed in Alfvenic turbulence is studied. It is found that these electrons experience rapid transport across L-shells, pitch-angle and through momentum space due to the action of an empirically derived 3-D spectrum of Alfvenic field fluctuations. The timescales for radial transport and scattering at large pitch-angle are similar, while transport through momentum space occurs at a rate comparable to whistler mode chorus, especially below 100 keV. Bounce-averaged transport coefficients for these processes are consistent with quasi-linear estimates for drift-bounce resonances, but with enhanced values. A transition from super-diffusion to sub-diffusion with increasing energy is observed.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Multidisciplinary Sciences
Xiao-Jia Zhang, Anton Artemyev, Vassilis Angelopoulos, Ethan Tsai, Colin Wilkins, Satoshi Kasahara, Didier Mourenas, Shoichiro Yokota, Kunihiro Keika, Tomoaki Hori, Yoshizumi Miyoshi, Iku Shinohara, Ayako Matsuoka
Summary: Energetic electron precipitation from Earth's outer radiation belt affects the upper atmosphere and its chemical properties. Low-altitude satellite observations reveal that electron precipitation rates often exceed the conventional upper limit due to nonlinear electron interactions with intense plasma waves, which were not previously considered in radiation belt models.
NATURE COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
Hayley J. Allison, Yuri Y. Shprits, Irina S. Zhelayskaya, Dedong Wang, Artem G. Smirnov
Summary: The study reveals that under conditions of extremely low plasma density, electrons can be accelerated to ultra-high energies, a phenomenon that occurs only when the plasma number density is very low.
Article
Astronomy & Astrophysics
S. D. Walton, C. Forsyth, I. J. Rae, N. P. Meredith, J. K. Sandhu, M-T Walach, K. R. Murphy
Summary: The population of near-relativistic electrons in the outer Van Allen radiation belt is highly dynamic and influenced by geomagnetic activity. Through analyzing a 12-year data set, it is found that there is a proportional increase in trapped electrons entering the bounce loss cone during storm and early recovery phases.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
David M. Malaspina, Allison N. Jaynes, Scot Elkington, Anthony Chan, George Hospodarsky, John Wygant
Summary: This study investigates the spatial distribution characteristics of lower-band whistler-mode chorus wave power, finding that it is primarily determined by L-shell and largely independent of plasmapause location. The plasmapause acts as a boundary to Earthward lower-band whistler-mode chorus wave activity.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Viviane Pierrard, Jean-Francois Ripoll, Gregory Cunningham, Edith Botek, Ondrej Santolik, Scott Thaller, William S. Kurth, Melanie Cosmides
Summary: Comparing ESA PROBA-V and NASA Van Allen Probes observations of electron flux in October 2013, we found that dropouts occurred in all energy bands during storms, and equatorially trapped electron flux was higher than at LEO. The outer radiation belt showed isotropic structure during quiet times and exhibited pitch angle dependence of high energy injection. The Dst effect during geomagnetic storms explained the characteristics of outer radiation belt electron dropouts.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
T. P. O'Brien, C. L. Lemon, J. B. Blake
Summary: This study investigates the hypothesis that electron microbursts can generate electron precipitation curtains. The results suggest that the accumulation of drift-dispersed microburst electron byproducts in the drift loss cone can explain many of the observed curtains.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Lunjin Chen, Xiao-Jia Zhang, Anton Artemyev, Liheng Zheng, Zhiyang Xia, Aaron W. Breneman, Richard B. Horne
Summary: This study investigates the interaction of ducted and nonducted chorus waves with energetic electrons, revealing substantial differences in electron transport between the two scenarios and comparing resultant electron precipitation patterns. This comparison is valuable for interpreting low Earth-orbiting satellite observations of electron flux variation in response to the interaction with magnetospheric chorus waves.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2021)
Review
Astronomy & Astrophysics
Sadie. S. S. Elliott, Aaron Breneman, Christopher Colpitts, Jacob Bortnik, Allison Jaynes, Alexa Halford, Mykhaylo Shumko, Lauren Blum, Lunjin Chen, Ashley Greeley, Drew Turner
Summary: Microbursts are rapid injections of high-energy electrons into the Earth's atmosphere, which play a significant role in the loss of the outer radiation belt. Understanding the causes and consequences of microburst precipitation is crucial in the field of radiation belt physics and has implications for space weather and atmospheric chemistry. However, important questions regarding the dominant cause of microburst precipitation and its overall importance remain unanswered due to the lack of coordinated observations of causative waves and precipitating particles.
FRONTIERS IN ASTRONOMY AND SPACE SCIENCES
(2022)
Article
Astronomy & Astrophysics
O. Agapitov, D. Mourenas, A. Artemyev, A. Breneman, J. W. Bonnell, G. Hospodarsky, J. Wygant
Summary: Based on multi-point wave measurements by two Van Allen Probes, the study reveals that the spatial scales and active region extents of chorus and hiss waves are influenced by their generation process, propagation, and damping, as well as the location inside or outside the radiation belts. The analysis shows that the source region scale and active region size of chorus waves differ significantly at different radial and azimuthal extents, with variations observed inside and outside the outer radiation belt.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Geosciences, Multidisciplinary
Nigel P. Meredith, Jacob Bortnik, Richard B. Horne, Wen Li, Xiao-Chen Shen
Summary: Utilizing data from eight satellites, this study examines the role of chorus waves in plasmaspheric hiss generation, finding that chorus waves of different frequency ranges have varying impacts on plasmaspheric hiss distribution.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geosciences, Multidisciplinary
S. Saito, Y. Miyoshi
Summary: Results from a test particle simulation indicate that electron scattering driven by lower band whistler chorus waves along a magnetic field line is crucial in producing the butterfly distribution of relativistic electrons. Two nonlinear scattering processes, phase trapping and dislocation, contribute to the formation of the butterfly distribution within a minute. Quasilinear diffusion alone is insufficient to reproduce this distribution. The simulation also reveals an upper limit for rapid electron acceleration, suggesting the role of phase trapping in relativistic electron acceleration in the outer radiation belt core.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Lunjin Chen, Xiao-Jia Zhang, Anton Artemyev, Vassilis Angelopoulos, Ethan Tsai, Colin Wilkins, Richard B. Horne
Summary: During magnetospheric storms, energetic electron microbursts are observed. It is found that these microbursts may be caused by ducted whistler-mode lower-band chorus waves.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Jinxing Li, Jacob Bortnik, Wen Li, Xin An, Larry R. Lyons, William S. Kurth, George B. Hospodarsky, David P. Hartley, Geoffrey D. Reeves, Herbert O. Funsten, J. Bernard Blake, Harlan Spence, Daniel N. Baker
Summary: This study addresses the formation mechanism of chorus spectral gaps in the Earth's magnetosphere. By analyzing data from Van Allen Probes, it is found that the gaps are observed in the source region of chorus waves, where the waves propagate in parallel and anti-parallel directions. Gaps below 0.5 f(ce) are associated with electron parallel acceleration at high energies. This finding is important for understanding the origin and evolution of chorus waves in the Earth's magnetosphere.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Meteorology & Atmospheric Sciences
I Kolmasova, S. Soula, O. Santolik, T. Farges, O. Bousquet, G. Diendorfer, R. Lan, L. Uhlir
Summary: This study combines electromagnetic measurements with meteorological and lightning detection data to explain the unusually strong preliminary breakdown produced by a thunderstorm system in Southern France. The research finds that the thunderstorm possesses temporary strong negatively charged pockets located above a strong positive charge region, which explains the observed phenomenon.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2022)
Article
Geosciences, Multidisciplinary
D. P. Hartley, L. Chen, I. W. Christopher, C. A. Kletzing, O. Santolik, W. Li, R. Shi
Summary: Plumes act as a pathway for chorus waves to enter the plasmasphere. This study parameterizes the properties of chorus waves based on their distance from the plume boundary. The results indicate that near the plume edge, the polar wave vector angle becomes more oblique. The distribution of theta(k) also exhibits different behavior between the Eastward and Westward boundaries, with an Eastwards skew reported near the Eastward plume boundary.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Ningyu Y. Liu, Olaf Scholten, Brian M. Hare, Joseph R. Dwyer, Christopher F. Sterpka, Ivana Kolmasova, Ondrej Santolik
Summary: This paper reports an observational study of lightning initial breakdown pulses (IBPs) using low-frequency array radio telescope and a broadband magnetic field sensor. The study reveals that the spatiotemporal evolution of the electrical breakdown causing an IBP is complex. It is found that bursts of very high frequency (VHF) electromagnetic radiation occur spatially and temporally separated in a volume on the order of 100(3) m(3), coincident with brief magnetic field pulses, indicating sudden changes in the location of the active breakdown region. Recurrent breakdown activity is observed, particularly at the location of VHF bursts. The study suggests that IBPs are likely generated through the involvement of multiple space stems/leaders and connections between them.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
F. Nemec, O. Santolik, G. B. Hospodarsky, W. S. Kurth, C. Kletzing
Summary: This article presents a systematic analysis of Power Line Harmonic Radiation (PLHR) electromagnetic wave events observed by the Van Allen Probes spacecraft from 2012 to 2019. The analysis shows that wave intensities at frequencies corresponding to the first few harmonics are significantly enhanced when the spacecraft is located above industrialized areas. Frequency spectra analysis reveals increased wave intensities at the frequencies corresponding to the first and third harmonics, especially during nighttime. The polarization and propagation properties of the events are also analyzed, showing that the waves are typically right-handed elliptically or nearly circularly polarized, and they propagate with oblique wave normal angles from low latitude sources and more field-aligned wave vectors from high latitude sources.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
D. P. Hartley, I. W. Christopher, C. A. Kletzing, W. S. Kurth, O. Santolik, I Kolmasova, J. R. Wygant, J. W. Bonnell
Summary: This study develops a method to determine the variable coupling impedance of spherical double probe electric field sensors with magnetospheric plasma in different measurement directions. By comparing electric field observations with magnetic field measurements and plasma theory, the response of the instrument can be evaluated under different plasma densities. A sheath model is also developed to describe the variations in sheath resistance, sheath capacitance, and relative effective length with plasma density.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Geosciences, Multidisciplinary
F. Nemec, O. Santolik, G. B. Hospodarsky, W. S. Kurth
Summary: The interaction between very low frequency transmitter signals and radiation belt electrons depends on their wave normal angles. Distinguishing between ducted and nonducted modes of propagation and evaluating their relative importance can be achieved using spacecraft data.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
B. Bezdekova, F. Nemec, J. Manninen, O. Santolik, G. B. Hospodarsky, W. S. Kurth
Summary: This study analyzes events with significant intensity enhancements in the 1.5-4 kHz frequency range measured by the ground-based Kannuslehto station in Finland. A total of 465 events are identified in the data collected between December 2012 and October 2019. It is found that these events usually last for several hours and preferentially occur on the dawn side during geomagnetically active periods. Simultaneous measurements from the Van Allen Probes spacecraft are used to determine the L-shells and magnetic local times associated with the intensity increase in space.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Geosciences, Multidisciplinary
I. Kolmasova, O. Scholten, O. Santolik, B. M. Hare, P. Zacharov, R. Lan, N. Liu, J. R. Dwyer
Summary: We present the first observations of negative intracloud (IC) dart-stepped leaders accompanied by regular trains of microsecond-scale pulses. These pulse trains were detected simultaneously using shielded broadband magnetic loop antennas and the radio telescope Low Frequency Array (LOFAR). The pulses within the trains are unipolar, a few microseconds wide, and exhibit an average inter-pulse interval of 5-7 μs. The broadband pulses correlate well with energetic bursts of very high frequency sources localized by LOFAR. All observed trains were generated by negative dart-stepped leaders propagating at a lower speed than usual dart leaders, following channels of previous leaders within the same flash.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geosciences, Multidisciplinary
D. P. Hartley, I. W. Christopher, C. A. Kletzing, W. S. Kurth, O. Santolik, I. Kolmasova, M. R. Argall, N. Ahmadi
Summary: A new sheath impedance model is developed to explain the effect of variable coupling impedance between Van Allen Probes instruments and ambient plasma on electric field wave measurements. The study quantifies the impact of this sheath correction on measured chorus wave properties and finds that the sheath-corrected electric field wave power is typically 2 to 9 times larger than the uncorrected measurement. The sheath correction also affects the Poynting vector, increasing the Poynting flux by a factor of 2 and changing the propagation direction in 2% of cases.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Review
Geochemistry & Geophysics
Miroslav Hanzelka, Ondrej Santolik
Summary: The significant role of nonlinear wave-particle interactions in the Earth's outer radiation belt is discussed, particularly in relation to electron dropouts, microbursts, and pulsating auroras. The formation mechanism of the whistler-mode chorus, a structured electromagnetic emission, remains uncertain despite decades of research. Different theories and observational challenges are discussed, including the interplay between nonlinear growth and microscale propagation effects.
SURVEYS IN GEOPHYSICS
(2023)
Article
Multidisciplinary Sciences
Ivana Kolmasova, Ondrej Santolik, Masafumi Imai, William S. Kurth, George B. Hospodarsky, John E. P. Connerney, Scott J. Bolton, Radek Lan
Summary: Our understanding of lightning processes at Jupiter was limited by previous measurements. However, recent observations from the Juno mission have provided new insights. The Juno Waves instrument collected data at a resolution of 125 microseconds over a period of 5 years, revealing step-like extensions of lightning channels and indicating similarities between Jovian and intracloud lightning initiation processes on Earth.
NATURE COMMUNICATIONS
(2023)
Article
Astronomy & Astrophysics
M. Hajos, F. Nemec, A. Demekhov, O. Santolik, M. Parrot, T. Raita, B. Bezdekova
Summary: We compared quasiperiodic (QP) extra low frequency/very low frequency emissions observed by the DEMETER spacecraft with ultralow frequency geomagnetic field pulsations measured on the ground. We analyzed 398 QP events and found good agreement between the modulation periods and peak frequencies of certain types of geomagnetic pulsations. Some QP emissions were closely associated with geomagnetic pulsations (QP1 type) while others were not (QP2 type). The intensity of QP1 events did not correlate with the intensity of geomagnetic field pulsations, while the intensity of QP2 events did increase with the integral intensity of geomagnetic field pulsations. The radial distance of the generation region of QP1 emissions was estimated to be about L = 7.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
A. Brunet, N. Dahmen, C. Katsavrias, O. Santolik, G. Bernoux, V. Pierrard, E. Botek, F. Darrouzet, A. Nasi, S. Aminalragia-Giamini, C. Papadimitriou, S. Bourdarie, I. A. Daglis
Summary: The H2020 SafeSpace project aims to implement a space weather safety prototype, with a particular focus on predicting deep charging hazards. This paper presents the inner magnetosphere section of the SafeSpace pipeline, which relies on solar wind-driven and hourly updated models to describe the trapped electron environment and the physical processes they undergo. The forecasting performance of this new modeling pipeline was compared to a reference model during the St. Patrick's Day storm in 2015, showing that the new SafeSpace implementation has closer results to observations and a better forecast within the prediction horizon.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2023)
Article
Astronomy & Astrophysics
O. Scholten, B. M. Hare, J. Dwyer, N. Liu, C. Sterpka, I Kolmasova, O. Santolik, R. Lan, L. Uhlir, S. Buitink, T. Huege, A. Nelles, S. ter Veen
Summary: A new propagation mode for negative leaders in lightning was observed, emitting significantly more VHF and broadband radiation compared to normal negative leaders. Measurements with the LOFAR radio telescope showed an ionization front with a diameter over 500 meters during an intensely radiating negative leader, indicating a dense charge pocket.
Article
Environmental Sciences
Ivana Kolmasova, Ondrej Santolik, Katerina Rosicka
Summary: This study investigated lightning strokes in northern Europe during an unusually stormy winter in 2014/15 using data from the World Wide Lightning Location Network. The frequency of thunderstorm days and the number of individual lightning strokes were significantly higher than the long-term averages. The energy of detected strokes in the colder months was much larger than the global mean. Winter superbolts with high electromagnetic energies were observed mainly at night and in the morning hours. These lightning characteristics suggest anomalously efficient thundercloud charging in the eastern North Atlantic, possibly influenced by climatic events like the positive phase of the North Atlantic Oscillation and El Nino.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2022)