835 research outputs found
ULF vlny/fluktuace ve forešoku: Statistický přístup
No full textTitle: ULF waves/fluctuations in the foreshock: Statistical approach Author: Anna Mita Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Jana Šafránková, DrSc., Department of Surface and Plasma Science Abstract: The thesis deals with ultra-low frequency (ULF) wave activity in the terrestrial foreshock, a turbulent region upstream of the bow shock that plays a crucial role in the interaction of the solar wind with the magnetosphere. In the thesis, we analyze some aspects of the behavior of ULF waves/fluctuations of the magnetic field, using a statistical point of view. We focused (i) on the boundary between the pure solar wind and wave activity region represented by enhanced ULF fluctuations, and on the changes of the boundary position with solar wind conditions and interplanetary magnetic field orientation; and (ii) on growth rates of foreshock ULF fluctuations at different distances from the bow shock with a special highlight on a region close to the Moon. In both statistical studies, we use THEMIS/ARTEMIS data and describe the behavior of fluctuations by the standard deviations in the ULF range of 0.0017-0.17 Hz. We present a novel coordinate system, determine so-called "foreshock ULF boundary" and report its realistic shape that is consistent with the theory of the foreshock...Název práce: ULF vlny/fluktuace ve forešoku: Statistický přístup Autor: Anna Mita Katedra: Katedra fyziky povrchů a plazmatu Vedoucí disertační práce: Prof. RNDr. Jana Šafránková, DrSc., Katedra fyziky povrchů a plazmatu Abstrakt: Předložená práce se zabývá ULF (Ultra Low Frequency) fluktuacemi v turbulentní oblasti před rázovou vlnou (forešok), která hraje klíčovou roli v interakci slunečního větru s magnetosférou Země. V práci analyzujeme některé aspekty chování ULF vln/fluktuací magnetického pole s využitím statistického zpracování dat naměřených dvěma družicemi projektu THEMIS/ARTEMIS. Zaměřili jsme se (i) na hranici mezi neporušeným slunečním větrem a oblastí charakterizovanou vysokými ULF fluktuacemi a na změny polohy této hranice v závislosti na podmínkách ve slunečním větru a na orientaci meziplanetárního magnetického pole; a (ii) na rychlost růstu nebo tlumení ULF vln/fluktuací v různých vzdálenostech od rázové vlny se zvláštním zřetelem na oblast blízko Měsíce. Ve statistických studiích popisujeme chování fluktuací pomocí směrodatných odchylek v rozsahu 0,0017-0,17 Hz. V práci představujeme nový souřadnicový systém umožňující určit tzv. "foreshock ULF boundary", diskutujeme nalezený tvar a ukazujeme, že je v souladu s teorií formování forešoku. Ve druhé studii se soustřeďujeme na růst (případně...Katedra fyziky povrchů a plazmatuDepartment of Surface and Plasma ScienceFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult
ULF waves/fluctuations in the foreshock: Statistical approach
No full textTitle: ULF waves/fluctuations in the foreshock: Statistical approach Author: Anna Mita Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Jana Šafránková, DrSc., Department of Surface and Plasma Science Abstract: The thesis deals with ultra-low frequency (ULF) wave activity in the terrestrial foreshock, a turbulent region upstream of the bow shock that plays a crucial role in the interaction of the solar wind with the magnetosphere. In the thesis, we analyze some aspects of the behavior of ULF waves/fluctuations of the magnetic field, using a statistical point of view. We focused (i) on the boundary between the pure solar wind and wave activity region represented by enhanced ULF fluctuations, and on the changes of the boundary position with solar wind conditions and interplanetary magnetic field orientation; and (ii) on growth rates of foreshock ULF fluctuations at different distances from the bow shock with a special highlight on a region close to the Moon. In both statistical studies, we use THEMIS/ARTEMIS data and describe the behavior of fluctuations by the standard deviations in the ULF range of 0.0017-0.17 Hz. We present a novel coordinate system, determine so-called "foreshock ULF boundary" and report its realistic shape that is consistent with the theory of the foreshock..
Dream on, but with your eyes open: An obituary for Ulf Kadritzke (1943-2020)
No full textUlf Kadritzke war der PROKLA als Autor und Mitglied des Redaktionsbeirats viele Jahre eng verbunden. Mit seinen Ideen und seinem Engagement hat er nicht nur die PROKLA bereichert und geprägt. Am 14. November 2020 verstarb Ulf Kadritzke überraschend.Ulf Kadritzke was closely associated with PROKLA for many years as an author and a member of the editorial advisory board. With his ideas and commitment, he enriched and shaped not only PROKLA. Ulf Kadritzke passed away unexpectedly on November 14, 2020
Ulf eta Cornelia: Berlingo maitasun istorio bat
No full text“Ulf and Cornelia: A Berlin love story” is part of the PhD thesis Berlin fin de millenium: An Experiment in Corporeal Ethnography, carried out between 1998 and 2003. In this article, the author puts into practice his investigative endeavor as a discovery process, narrating his encounters with Ulf and Cornelia, two bodies in transit in a Berlin characterized by its dramatic urban transformation. The focus of the ethnography is Ulf’s enamored experience. Using wonder as a knowledge technique, we will dive in the realm previous to the formation of stable identities, meaning the domain of corporeal stimulus and unconscious impulses. The subjects that appear in the scenes of this article, the author himself and the city where they live are in construction.“Ulf y Cornelia: una historia de amor berlinesa” es un apartado que pertenece a la tesis Berlín fin de milenio: un experimento en la etnografía corporal, realizada entre 1998 y 2003. En este artículo, el autor lleva a cabo una labor de investigación puesta en práctica como un proceso de descubrimientos, relatando sus encuentros con Ulf y Cornelia, dos cuerpos en tránsito en un Berlín sumido en una dramática transformación urbana. La etnografía está enfocada particularmente en la experiencia de enamoramiento de Ulf. Utilizando la capacidad de asombro como técnica para el conocimiento, nos sumergiremos en el ámbito anterior a la formación de identidades estables, es decir, en el dominio de estímulos corporales e impulsos inconscientes. Se trata, pues, de un artículo donde tanto los sujetos en escena como el propio autor y la ciudad en la que viven están en proceso de construcción.“Ulf eta Cornelia: maitasun istorio bat Berlinen”, 1999-2003 urteen artean garatutako Berlin fin de millenium: gorputz etnografíaren gaineko esperimentu bat tesiaren ataletako bat da. Artikulu honetan, autoreak, Ulfekin eta Corneliarekin, Berlin behin behineko bizilekutzat duten bi gorputzekin, bizitako uneak kontatzen dizkigu. Zehazki, Ulfen maitemintzea izango da etengabeko aurkikuntza prozesuan oinarritutako etnografía honen ardatza. Lilurarako gaitasuna ezagutzarako teknika bezala erabiliaz, nortasun egonkorrak eratu aurretiko eremura eramango gaitu, hau da, gorputz-estimulu eta bulkada inkontzienteen mundura. Azpimarratu behar da, artikulu honetan protagonista diren pertsonak, autorea bera eta bizi diren hiria eraikuntza prozesuan daudela
Simulation of Bounce Resonance ULF Wave-Particle Interactions
No full textPoloidal mode ultra-low-frequency (ULF) waves with high azimuthal mode number (high-m) are common throughout Earth's magnetosphere. The electric fields in these waves are on the order of tens of millivolts per meter, and are large enough to energize ions and electrons via drift- and drift-bounce wave-particle resonance. In this article, we present full orbit test-particle simulations of drift-bounce resonance using a numerical model of ULF waves. The model uses a dipole magnetic field and can accommodate a realistic ionosphere with height-resolved Pedersen and Hall conductivity. It is demonstrated that second-harmonic poloidal mode waves can energize ions to tens of keV depending on the wave amplitude. The test-particle simulations also predict ion flux oscillations that have energy dispersion similar to many satellite observations. It will be shown that features in the energy dispersion are in agreement with theoretical considerations.CPCI-S(ISTP)[email protected]; [email protected]
THEMIS observations of ULF wave excitation in the nightside plasma sheet during sudden impulse events
No full textSudden impulses (SIs) are an important source of ultra low frequency (ULF) wave activity throughout the Earth's magnetosphere. Most SI-induced ULF wave events have been reported in the dayside magnetosphere; it is not clear when and how SIs drive ULF wave activity in the nightside plasma sheet. We examined the ULF response of the nightside plasma sheet to SIs using an ensemble of 13 SI events observed by THEMIS (Timed History of Events and Macroscale Interactions during Substorms) satellites (probes). Only three of these events resulted in ULF wave activity. The periods of the waves are found to be 3.3, 6.0, and 7.6 min. East-west magnetic and radial electric field perturbations, which typically indicate the toroidal mode, are found to be stronger and can have phase relationships consistent with standing waves. Our results suggest that the two largest-amplitude ULF responses to SIs in the nightside plasma sheet are tailward-moving vortices, which have previously been reported, and the dynamic response of cross-tail currents in the magnetotail to maintain force balance with the solar wind, which has not previously been reported as a ULF wave driver. Both mechanisms could potentially drive standing Alfven waves (toroidal modes) observed via the field-line resonance mechanism. Furthermore, both involve frequency selection and a preference for certain driving conditions that can explain the small number of ULF wave events associated with SIs in the nightside plasma sheet. Citation: Shi, Q. Q., et al. (2013), THEMIS observations of ULF wave excitation in the nightside plasma sheet during sudden impulse events, J. Geophys. Res. Space Physics, 118, 284-298, doi:10.1029/2012JA017984.Astronomy & AstrophysicsSCI(E)10ARTICLE1284-29811
Poloidal ULF wave observed in the plasmasphere boundary layer
No full textWe report on a rare ultra‐low‐frequency (ULF) wave generation event associated with the formation of a plasmasphere boundary layer (PBL), which was well observed by one of the THEMIS satellites, TH‐D, during subsequent outbound passes. On 13 September 2011, TH‐D observed a sharp plasmapause at L = 3.4. The plasmasphere started to expand and continued to be refilled on 14 September. On 15 September, a PBL was formed with two density gradients at L = 4.4 and 6.5, respectively. Within the two density gradients, strong radial magnetic field and azimuthal electric field oscillations were observed, suggesting poloidal ULF waves. Based on the phase delay between magnetic and electric field signals, as well as the comparison between the observed wave frequency and predicted harmonic eigenfrequency, we find that the observed oscillations are second harmonic poloidal waves. Further investigation shows that the observed waves are likely generated by drift‐bounce resonance with “bump‐on‐tail” plasma distributions at ~10 keV. We demonstrate that the waves are excited within the PBL where the eigenfrequency is close to the bounce frequency of these hot protons, but not outside the PBL where the eigenfrequency deviates from the bounce frequency. Finally, we suggest that cold plasma density seems to be a controlling factor for ULF wave generation as well, in addition to the bump‐on‐tail energy source, by altering eigenfrequency of the local field lines. Key Points A rare ULF wave event associated with the formation of a PBL is reported. The wave is second harmonic poloidal mode generated by drift bounce resonance. Cold plasma density plays an important role in regulating ULF wave generation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99699/1/jgra50427.pd
An initial ULF wave index derived from 2 years of Swarm observations
No full textThe ongoing Swarm satellite mission provides an opportunity for better knowledge of the near-Earth electromagnetic environment. Herein, we use a new methodological approach for the detection and classification of ultra low-frequency (ULF) wave events observed by Swarm based on an existing time-frequency analysis (TFA) tool and utilizing a state-of-the-art high-resolution magnetic field model and Swarm Level 2 products (i.e., field-aligned currents-FACs-and the Ionospheric Bubble Index-IBI). We present maps of the dependence of ULF wave power with magnetic latitude and magnetic local time (MLT) as well as geographic latitude and longitude from the three satellites at their different locations in low-Earth orbit (LEO) for a period spanning 2 years after the constellation's final configuration. We show that the inclusion of the Swarm single-spacecraft FAC product in our analysis eliminates all the wave activity at high altitudes, which is physically unrealistic. Moreover, we derive a Swarm orbit-by-orbit Pc3 wave (20-100 MHz) index for the topside ionosphere and compare its values with the corresponding variations of solar wind variables and geomagnetic activity indices. This is the first attempt, to our knowledge, to derive a ULF wave index from LEO satellite data. The technique can be potentially used to define a new Level 2 product from the mission, the Swarm ULF wave index, which would be suitable for space weather applications. © 2018 Author(s)
The interaction between ULF waves and thermal plasma ions at the plasmaspheric boundary layer during substorm activity
No full textDuring a substorm on 27 January 2004, energetic particle injections associated with ULF waves have been detected when Cluster fleet was traveling inbound in the Southern Hemisphere. Substorm-injected energetic particles are strong and clearly modulated by these ULF waves. The ULF waves with the period of 1 min are probably the third harmonic mode. The periodic pitch angle dispersion signatures at 5.2-6.9 keV energy channel were detected by Cluster satellite. These thermal plasma have high coherence with the electric field of the third harmonic poloidal mode and satisfy the drift-bounce resonant condition of N = 2. In addition, ion outflows from the Earth's ionosphere (tens to hundreds of eV) are also observed to be modulated by these ULF waves. To the best of our knowledge, this is the first report to show that ULF waves can simultaneously interact with both substorm-injected hot particles from the magnetotail and cold outflow ions from the Earth's ionosphere.Astronomy & AstrophysicsSCI(E)[email protected]
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