A5001057531- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Geophysics and Gravity Measurements
- Solar Radiation and Photovoltaics
- Stellar, planetary, and galactic studies
- Global Energy and Sustainability Research
- Radioactive contamination and transfer
- Advancements in Solid Oxide Fuel Cells
- Statistical and numerical algorithms
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Spacecraft and Cryogenic Technologies
- Education, Psychology, and Social Research
- Atmospheric and Environmental Gas Dynamics
- Inertial Sensor and Navigation
- Radiation Therapy and Dosimetry
- Photocathodes and Microchannel Plates
- Adaptive optics and wavefront sensing
- Catalysts for Methane Reforming
- Radiation Detection and Scintillator Technologies
- Geophysics and Sensor Technology
- Spacecraft Design and Technology
- Scientific Measurement and Uncertainty Evaluation
Charles University
2017-2023
Smithsonian Astrophysical Observatory
2020
We present a technique for deriving the temperature anisotropy of solar wind protons observed by Parker Solar Probe (PSP) mission in near-Sun wind. The radial proton measured Wind Electrons, Alphas, and Protons (SWEAP) Cup is compared with orientation local magnetic field FIELDS fluxgate magnetometer, temperatures parallel perpendicular to are extracted. This procedure applied different data products, results optimum timescales selection trends uncertainty method identified. find that...
Previous statistical studies revealed that the tangential component of solar wind velocity is positive (co-rotating) in vicinity Sun but it turns its sign at about 0.2 AU. After it, this negative value increases toward 0.3 AU and gradually relaxes to zero distances excess 10 Since intervals a large exhibit also enhanced cross-helicity, outward propagating Alfven waves generated outer corona were suggested as most probable source observed deviation. However, weak point conclusion would...
Many in-situ solar wind observations show a clear correlation between the proton temperature and bulk speed. Different authors use various formulas to describe this behavior, but one relation over speed range covering both slow fast winds is usually sufficient for measurements made at 1 AU. Moreover, relationship observed throughout cycle no significant variations were measured. Therefore, it commonly used predict expected given The ratio measured also serves as of ICME identifiers since...
One of the commonly observed features solar wind is simultaneous streaming two different proton populations, one which dominant denser core, and other less dense faster-propagating, minor population called beam. The beam relative abundance typically 10-20%, moves to core along interplanetary magnetic field at about 1.2 local Alfven speed. origin evolution not yet fully understood.  A previous study based on data from Helios mission suggests that seed forms close Sun, leading...
Abstract Various solar wind ion species move with different speeds and theoretical considerations as well limited observations in a region close to the Sun show that heavy ions tend flow faster than protons, at least less-aged fast streams. The carries frozen-in interplanetary magnetic field (IMF) this situation evokes three related questions: (i) what is proper speed, (ii) speed equal of dominant component, whatever may be, (iii) field? We simple based on MHD approximation dynamics charged...
The paper reviews the interaction of collisionless interplanetary (IP) shocks with turbulent solar wind. coexistence and turbulence plays an important role in understanding acceleration particles via Fermi mechanisms, geoeffectiveness highly disturbed sheaths following IP and, among others, nature fluctuations themselves. Although our knowledge physics upstream downstream shock regions has been greatly improved recent years, many aspects IP-shock/turbulence are still poorly known, for...
Abstract Relative properties of solar wind protons and α particles are often used as indicators a source region on the surface, analysis their evolution along path tests our understanding physics multicomponent magnetized plasma. The paper deals with comprehensive difference between proton particle bulk velocities at 1 au special emphasis interplanetary coronal mass ejections (ICMEs). A comparison about 20 years Wind observations Helios measurements closer to Sun (0.3–0.7 au) generally...
Abstract A corotating interaction region (CIR) develops between the solar wind streams with different bulk speeds emanating from distinct coronal sources. The arising pressure perturbations redistribute momentum adjacent forming regions of compressed around stream interface. We focus on properties α -particles respect to protons in CIRs using measurements Wind and Helios spacecraft. In slow front CIRs, relative helium abundance He is usually low (about 1%) -proton differential drift, V αp...
Abstract We study the polarization properties of velocity fluctuations in solar wind turbulence using high-resolution data from Spektr-R spacecraft. The ratio perpendicular to parallel inertial range is smaller than equivalent for magnetic fluctuations, but gradually increases throughout this range. In kinetic range, there a large decrease ratio, similar fluctuations. compare measurements numerical solutions combination Alfvén waves and slow waves, finding that both increase sharp are...
Instabilities described by linear theory characterize an important form of wave-particle interaction in the solar wind. We diagnose unstable behavior wind plasma between 0.3 and 1 au via Nyquist criterion, applying it to fits $\sim1.5$M proton $\alpha$ particle Velocity Distribution Functions (VDFs) observed \emph{Helios I} \emph{II}. The variation fraction intervals with radial distance from Sun is linear, signaling a gradual decline activity modes. When calculated as functions velocity...
Context. Rapid polarity reversals of the radial heliospheric magnetic field were discovered by Ulysses and they are now frequently observed as a common near-Sun phenomenon NASA’s Parker Solar Probe (PSP). Other solar wind missions, including ESA-NASA Orbiter (SolO), also observe similar phenomena. The nature these fluctuations is unclear, relation between “switchbacks” near Sun events at 1 AU unknown. Aims. We make detailed case study SolO plasma data obtained in region that magnetically...
Abstract The solar wind nonradial velocity components observed beyond the Alfvén point are usually attributed to waves, interaction of different streams, or other transient phenomena. However, Earth-orbiting spacecraft as well monitors at L1 indicate systematic deviations from radial direction. Since these order several degrees, calibration instruments is often questioned. This paper investigates for first time evolution flow along path ≈0.17 10 au. A comparison observations 1 au with those...
Abstract Less abundant but still dynamically important solar wind components are the proton beam and alpha particles, which usually contribute similarly to total ion momentum. The main characteristics of particles determined by source region, origin its properties not fully explained. We use plasma data measured in situ on path from 0.3 1 au (Helios 2) focus development with an increasing radial distance as well connection between particle properties. found that relative abundance increases...
Abstract We present a large statistical study of the fluctuation anisotropy in minimum variance (MV) frames magnetic field and solar wind velocity. use 2, 10, 20, 40 minute intervals simultaneous (the Wind spacecraft) velocity Spektr-R observations. Our confirms that turbulence is composite fluctuations varying along mean those changing direction perpendicular to field. Regardless length scale within studied range spacecraft-frame frequencies, ≈90% observed exhibit an MV aligned with field,...
Turbulent cascade transferring the free energy contained within large scale fluctuations of magnetic field, velocity and density into smaller ones is probably one most important mechanisms responsible for heating solar corona wind, thus turbulent behavior these quantities intensively studied. The temperature also highly fluctuating quantity but its variations are studied only rarely. There two reasons, first tensor and, second, an experimental determination requires knowledge full...
As the solar wind streams propagate with different speeds through interplanetary space, they meet and interact. This leads to formation of large interaction regions, one which is rarefaction regions (RRs). RRs develop at trailing edge fast stream come from an area small longitudinal extent on Sun. They exhibit a fine complex structure, interface position usually unclear. Superposed epoch analysis proton alpha parameters for within reveals gradual transitions in many them. Moreover, majority...
The HEliospheric pioNeer for sOlar and interplanetary threats defeNce (HENON) mission funded by the Italian Space Agency has recently advanced to implementation (Phase C). HENON 12U cubesat is expected reach a Distant Retrograde Orbit (DRO) of Sun–Earth system before end this decade. For several months it will stay about ≈ 0.1 AU in front Earth, providing thus unique vantage point in-situ solar wind monitoring allowing send space weather alerts hours related causal...
Abstract A rarefaction region (RR) occurs at the trailing edge of fast solar wind stream. It comes from an area small longitudinal extent on surface and exhibits a fine complex structure. In our study, we did superposed epoch analysis proton α parameters across RR observed their gradual evolution. We not find any clear boundary between slow winds inside because majority observations show that most plasma corresponds to wind; only –proton drift velocity decreases beginning RR. investigate...
Switchbacks are a striking phenomenon in near-Sun coronal hole flows, but their origins, evolution, and relation to the broadband fluctuations seen farther from Sun unclear. We use near-radial lineup of Solar Orbiter Parker Probe during September 2020 when both spacecraft were wind Sun's Southern polar investigate if switchback variability is related large scale properties near 1 au. Using measured solar speed, we map measurements source surface consider variations with Carrington longitude....
The slow solar wind is typically characterized as having low Alfv\'enicity. However, Parker Solar Probe (PSP) observed predominately Alfv\'enic during several of its initial encounters. From first encounter observations, about 55.3\% the inside 0.25 au highly ($|\sigma_C| > 0.7$) at current minimum, which much higher than fraction quiet-Sun-associated maximum 1 au. Intervals with different Alfv\'enicities seem to show similar plasma characteristics and temperature anisotropy distributions....
Importance of solar wind monitoring for space weather applications increases with expansion power networks and oils or gas pipelines to larger geomagnetic latitudes development new communication networks. Instruments based on Faraday cups are an ideal solution these purposes because they robust their light weight low consumption facilitate a small spacecraft. Another important feature is capability detection impacts interplanetary dust. Such instruments currently part two planned ESA...