Physics - Space Physics Publications (50)


Physics - Space Physics Publications

Whether Turbulence-induced anomalous resistivity (AR) can facilitate a fast magnetic reconnection in collisionless plasma is a subject of active debate for decades. A particularly difficult problem in experimental and numerical simulation studies of the problem is how to distinguish the effects of AR from those originating from Hall-effect and other non-turbulent processes in the generalized Ohm's. In this paper, using particle-in-cell simulations, we present a case study of how AR produced by Buneman Instability accelerates magnetic reconnection. Read More

An asteroid impact is a low probability event with potentially devastating consequences. The Asteroid Risk Mitigation Optimization and Research (ARMOR) software tool calculates whether a colliding asteroid experiences an airburst or surface impact and calculates effect severity as well as reach on the global map. To calculate the consequences of an impact in terms of loss of human life, new vulnerability models are derived that connect the severity of seven impact effects (strong winds, overpressure shockwave, thermal radiation, seismic shaking, ejecta deposition, cratering and tsunamis) with lethality to human populations. Read More

The Principle of Maximum Entropy, a powerful and general method for inferring the distribution function given a set of constraints, is applied to deduce the overall distribution of plasmoids (flux ropes/tubes). The analysis is undertaken for the general 3D case, with mass, total flux and (3D) velocity serving as the variables of interest, on account of their physical and observational relevance. The distribution functions for the mass, width, total flux and helicity exhibit a power-law behavior with exponents of $-4/3$, $-2$, $-3$ and $-2$ respectively for small values, whilst all of them display an exponential falloff for large values. Read More

A simple physical model for calculation of the ion-induced soft error rate in space environment has been proposed, based on the phenomenological cross section notion. Proposed numerical procedure is adapted to the multiple cell upset characterization in highly scaled memories. Nonlocality of the ion impact has been revealed as the key concept determining the difference between physical processes in low scaled and highly scaled memories. Read More

Authors: T. Laitinen1
Affiliations: 1Jeremiah Horrocks Institute, University of Central Lancashire, Preston, UK

Solar and heliospheric cosmic rays provide a unique perspective in cosmic ray research: we can observe not only the particles, but also the properties of the plasmas in which the they are accelerated and propagate, using in situ and high-resolution remote sensing instruments. The heliospheric cosmic ray observations typically require space missions, which face stern competition against planetary and astrophysics missions, and it can take up to decades from the initial concept proposal until the actual observing of the cosmic rays can commence. Therefore it is important to have continuity in the cosmic ray mission timeline. Read More

Shock acceleration is considered one of the most important mechanisms of astrophysical energetic particles' acceleration. In this work, we calculate large amount of test charged particles' trajectories accurately in a parallel shock with magnetic turbulence. We investigate energetic particles' acceleration mechanisms by calculating particles' energy and flux evolution with time. Read More

Propagation of coronal mass ejections (CMEs) from the Sun far into interplanetary space is not well understood due to limited observations. In this study we examine the propagation characteristics of two geo-effective CMEs, which occurred on 2005 May 6 and 13, respectively. Significant heliospheric consequences associated with the two CMEs are observed, including interplanetary CMEs (ICMEs) at the Earth and Ulysses, interplanetary shocks, a long-duration type II radio burst, and intense geomagnetic storms. Read More

We address the important question of whether the newly discovered exoplanet, Proxima Centauri b (PCb), is capable of retaining an atmosphere over long periods of time. This is done by adapting a sophisticated multi-species MHD model originally developed for Venus and Mars, and computing the ion escape losses from PCb. The results suggest that the ion escape rates are about two orders of magnitude higher than the terrestrial planets of our Solar system if PCb is unmagnetized. Read More

Many magnetic structures in the solar atmosphere evolve rather slowly so that they can be assumed as (quasi-)static or (quasi-)stationary and represented via magneto-hydrostatic (MHS) or stationary magneto-hydrodynamic (MHD) equilibria, respectively. While exact 3D solutions would be desired, they are extremely difficult to find in stationary MHD. We construct solutions with magnetic and flow vector fields that have three components depending on all three coordinates. Read More

High speed solar wind streams (HSSs) are very efficient drivers of geomagnetic activity at high latitudes. In this paper we use a recently developed $\Delta{H}$ parameter of geomagnetic activity, calculated from the night-side hourly magnetic field measurements of the Sodankyl\"a observatory, as a proxy for solar wind (SW) speed at monthly time resolution in 1914-2014 (solar cycles 15-24). The seasonal variation in the relation between monthly $\Delta{H}$ and solar wind speed is taken into account by calculating separate regressions between $\Delta{H}$ and SW speed for each month. Read More

MMS observations recently confirmed that crescent-shaped electron velocity distributions in the plane perpendicular to the magnetic field occur in the electron diffusion region near reconnection sites at Earth's magnetopause. In this paper, we re-examine the origin of the crescent-shaped distributions in the light of our new finding that ions and electrons are drifting in opposite directions when displayed in magnetopause boundary-normal coordinates. Therefore, ExB drifts cannot cause the crescent shapes. Read More

Observing nearby galaxies would facilitate the search for artificial radio signals by sampling many billions of stars simultaneously, but few efforts have been made to exploit this opportunity. An added attraction is that the Milky Way is the second-largest member of the Local Group, so our galaxy might be a probable target for hypothetical broadcasters in nearby galaxies. We present the first relatively high spectral resolution (<1 kHz) 21 cm band search for intelligent radio signals of complete galaxies in the Local Group with the Jansky VLA, observing the galaxies M31 (Andromeda) and M33 (Triangulum) - the first and third largest members of the group respectively - sampling more stars than any prior search of this kind. Read More

Alfv\'enic fluctuations in the solar wind display many properties reflecting an ongoing nonlinear cascade, e.g. a well-defined spectrum in frequency, together with some characteristics more commonly associated with the linear propagation of waves from the Sun, such as the variation of fluctuation amplitude with distance, dominated by solar wind expansion effects. Read More

We present the results of three-dimensional (3D) ideal magnetohydrodynamics (MHD) simulations on the dynamics of a perpendicularly inhomogeneous plasma disturbed by propagating Alfv\'enic waves. Simpler versions of this scenario have been extensively studied as the phenomenon of phase mixing. We show that, by generalizing the textbook version of phase mixing, interesting phenomena are obtained, such as turbulence-like behavior and complex current-sheet structure, a novelty in longitudinally homogeneous plasma excited by unidirectionally propagating waves. Read More

Affiliations: 1Yu. G. Shafer Institute of Cosmophysical Research and Aeronomy, SB RAS, Yakutsk, Russia, 2Yu. G. Shafer Institute of Cosmophysical Research and Aeronomy, SB RAS, Yakutsk, Russia, 3Yu. G. Shafer Institute of Cosmophysical Research and Aeronomy, SB RAS, Yakutsk, Russia, 4Yu. G. Shafer Institute of Cosmophysical Research and Aeronomy, SB RAS, Yakutsk, Russia

Solar energetic particles acceleration by a shock wave accompanying a coronal mass ejection (CME) is studied. The description of the accelerated particle spectrum evolution is based on the numerical calculation of the diffusive transport equation with a set of realistic parameters. The relation between the CME and the shock speeds, which depend on the initial CME radius, is determined. Read More

We present results of observation of Cygnus-A radiosource scintillation in the Earth's ionosphere in quiet and disturbed geomagnetic condition at Irkutsk incoherent scattering radar (IISR). Scintillation method applied for ionosphere testing at IISR confidently defines Fresnel frequency and power cutoff - the spectral characteristics usually related to the velocities and spatial spectra of ionospheric plasma irregularities. We also use IGFR magnetic field model in order to show relation between shape of discrete radio source scintillation spectra and direction to the radio source with respect to geomagnetic field. Read More

The misalignment of the solar rotation axis and the magnetic axis of the Sun produces a periodic reversal of the Parker spiral magnetic field and the sectored solar wind. The compression of the sectors is expected to lead to reconnection in the heliosheath (HS). We present particle-in-cell simulations of the sectored HS that reflect the plasma environment along the Voyager 1 and 2 trajectories, specifically including unequal positive and negative azimuthal magnetic flux as seen in the Voyager data \citep{Burlaga03}. Read More

The analysis of the Parker-Moffatt problem, recently revisited in Pezzi et al. (2016), is here extended by including the Hall magnetohydrodynamics and two hybrid kinetic Vlasov-Maxwell numerical models. The presence of dispersive and kinetic features is studied in detail and a comparison between the two kinetic codes is also reported. Read More

Continuous plasma coherent emission is maintained by repetitive Langmuir collapse driven by the nonlinear evolution of a strong electron two-stream instability. The Langmuir waves are modulated by solitary waves in the linear stage, and by electrostatic whistler waves in the nonlinear stage. Modulational instability leads to Langmuir collapse and electron heating that fills in cavitons. Read More

We simulate decaying turbulence in a homogeneous pair plasma using three dimensional electromagnetic particle-in-cell (PIC) method. A uniform background magnetic field permeates the plasma such that the magnetic pressure is three times larger than the thermal pressure and the turbulence is generated by counter-propagating shear Alfv\'en waves. The energy predominately cascades transverse to the background magnetic field, rendering the turbulence anisotropic at smaller scales. Read More

We develop a simple one-zone model of the steady-state Crab nebula spectrum encompassing both the radio/soft $X$-ray and the GeV/multi-TeV observations. We determine analytically the photon differential energy spectrum as originated by an electron distribution evolved from a log-parabola injection spectrum: we find an impressive agreement with the synchrotron region observations whereas synchrotron self-Compton accommodates the previously unsolved origin of the broad $200$ GeV peak that matches the Fermi/LAT data beyond $1$ GeV with the MAGIC data. We determine the parameters of the log-parabola electron distribution, ruling out a simple power-law. Read More

A phenomenological model is presented for the quantitative description of the evolution of solar cycles in terms of the number of M-class flares. The determining factor of the model is based on the relative ecliptic longitude of the planets Jupiter and Saturn. Using as input the temporal distribution of flares during cycle 21, results in notable agreement with the observations are obtained for cycles 22-24 and predictions are provided for the evolution of solar activity in the next years. Read More

The remoteness of the Sun and the harsh conditions prevailing in the solar corona have so far limited the observational data used in the study of solar physics to remote-sensing observations taken either from the ground or from space. In contrast, the `solar wind laboratory' is directly measured in situ by a fleet of spacecraft measuring the properties of the plasma and magnetic fields at specific points in space. Since 2007, the solar-terrestrial relations observatory (STEREO) has been providing images of the solar wind that flows between the solar corona and spacecraft making in-situ measurements. Read More

On 2010 August 14, a wide-angled coronal mass ejection (CME) was observed. This solar eruption originated from a destabilized filament that connected two active regions and the unwinding of this filament gave the eruption an untwisting motion that drew the attention of many observers. In addition to the erupting filament and the associated CME, several other low-coronal signatures that typically indicate the occurrence of a solar eruption were associated to this event. Read More

A major challenge in solar and heliospheric physics is understanding how highly localized regions, far smaller than 1 degree at the Sun, are the source of solar-wind structures spanning more than 20 degrees near Earth. The Sun's atmosphere is divided into magnetically open regions, coronal holes, where solar-wind plasma streams out freely and fills the solar system, and closed regions, where the plasma is confined to coronal loops. The boundary between these regions extends outward as the heliospheric current sheet (HCS). Read More

Planar magnetic structures (PMSs) are periods in the solar wind during which interplanetary magnetic field vectors are nearly parallel to a single plane. One of the specific regions where PMSs have been reported are coronal mass ejection (CME)-driven sheaths. We use here an automated method to identify PMSs in 95 CME sheath regions observed in-situ by the Wind and ACE spacecraft between 1997 and 2015. Read More

A vast wealth of literature exists on the topic of rocket trajectory optimisation, particularly in the area of interplanetary trajectories due to its relevance today. Studies on optimising interstellar and intergalactic trajectories are usually performed in flat spacetime using an analytical approach, with very little focus on optimising interstellar trajectories in a general relativistic framework. This paper examines the use of low-acceleration rockets to reach galactic destinations in the least possible time, with a genetic algorithm being employed for the optimisation process. Read More

CubeSats and small satellites are emerging as low-cost tools to perform astronomy, exoplanet searches and earth observation. These satellites can be dedicated to pointing at targets for weeks or months at a time. This is typically not possible on larger missions where usage is shared. Read More

The flow of material from Io's volcanoes into the Io plasma torus, out into the magnetosphere, and along field lines into Jupiter's upper atmosphere is not adequately understood. The lack of observations of spatial and temporal variations in the Io plasma torus impedes attempts to understand the system as a whole. Here we propose that radio occultations of the Io plasma torus by the Juno spacecraft can measure plasma densities in the Io plasma torus. Read More

The electromagnetic induction equation (Helmholtz equation) for the electrically conducting Earth is generalised to the inclusion of a spatially fluctuating internal conductivity spectrum that is superimposed on a one-dimensional large-scale conductivity reference-profile which depends solely on the vertical coordinate z>0. This large-scale profile is assumed to be known. The distribution of the fluctuations is allowed to be arbitrary. Read More

Reconnection in strong current-aligned magnetic guide fields allows for the excitation of the electron-cyclotron-maser instability and emission of electromagnetic radiationfrom the electron exhaust at the {\sf X} point. The electrons in the guide field remain magnetized, with reconnection barely affected. The guide field is responsible for the asymmetric properties of the {\sf X} point and exhaust. Read More

Gravity assist manoeuvres are one of the most succesful techniques in astrodynamics. In these trajectories the spacecraft comes very close to the surface of the Earth, or other Solar system planets or moons, and, as a consequence, it experiences the effect of atmospheric friction by the outer layers of the Earth's atmosphere or ionosphere. In this paper we analyze a standard atmospheric model to estimate the density profile during the two Galileo flybys, the NEAR and the Juno flyby. Read More

This study examines the impact that solar activity has on model results during geomagnetic quiet time for the ionosphere/thermosphere models: the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics Model (CTIPe) and the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). Using varying F10.7 flux values as a measurement of solar activity, the models were run over a two-day period with the constant parameters Kp= 2, n= 3 cm^3, and v= 400 km/s. Read More

Recently, Ciufolini et al. reported on a test of the general relativistic gravitomagnetic Lense-Thirring effect by analyzing about 3.5 years of laser ranging data to the LAGEOS, LAGEOS II, LARES geodetic satellites orbiting the Earth. Read More

In this paper, we present observations of cold (0-70 eV) plasma density in the magnetotail lobes. The observations and results are based on 16 years of Cluster observation of spacecraft potential measurements converted into local plasma densities. Measurements from all four Cluster spacecraft have been used, and the survey indicates a persistent asymmetry in lobe density, with consistently higher cold plasma densities in the northern lobe. Read More

The Atmospheric Drag, Occultation 'N' Ionospheric Scintillation mission (ADONIS) studies the dynamics of the terrestrial thermosphere and ionosphere in dependency of solar events over a full solar cycle in Low Earth Orbit (LEO). The objectives are to investigate satellite drag with in-situ measurements and the ionospheric electron density profiles with radio occultation and scintillation measurements. A constellation of two satellites provides the possibility to gain near real-time data (NRT) about ionospheric conditions over the Arctic region where current coverage is insufficient. Read More

Magnetic turbulence in the solar wind is treated from the point of view of electrodynamics. This can be done based on the use of Poynting's theorem attributing all turbulent dynamics to the spectrum of turbulent conductivity. For two directions of propagation of the turbulent fluctuations of the electromagnetic field with respect to the mean plus external magnetic fields an expression is constructed for the spectrum of turbulent dissipation. Read More

We perform the first statistical study of the effects of the interaction of suprathermal electrons with narrow-band whistler mode waves in the solar wind. We show that this interaction does occur and that it is associated with enhanced widths of the so called strahl component. The latter is directed along the inter- planetary magnetic field away from the Sun. Read More

Electric currents flowing through near-Earth space ($\textit{R}$ $\leq$12 $\mathit{R}_{E}$) can support a highly distorted magnetic field topology, changing particle drift paths and therefore having a nonlinear feedback on the currents themselves. A number of current systems exist in the magnetosphere, most commonly defined as (1) the dayside magnetopause Chapman-Ferraro currents, (2) the Birkeland field-aligned currents with high latitude "region 1" and lower-latitude "region 2" currents connected to the partial ring current, (3) the magnetotail currents, and (4) the symmetric ring current. In the near-Earth nightside region, however, several of these current systems flow in close proximity to each other. Read More

The MEPED instruments on board the NOAA POES andMetOp satellites have been continuously measuring energetic particles in the magnetosphere since 1978. However, degradation of the proton detectors over time leads to an increase in the energy thresholds of the instrument and imposes great challenges to studies of long-term variability in the near-Earth space environment as well as a general quantification of the proton fluxes. By comparing monthly mean accumulated integral flux from a new and an old satellite at the same magnetic local time (MLT) and time period, we estimate the change in energy thresholds. Read More

Dawn-dusk asymmetries are ubiquitous features of the coupled solar-wind-magnetosphere-ionosphere system. During the last decades, increasing availability of satellite and ground-based measurements has made it possible to study these phenomena in more detail. Numerous publications have documented the existence of persistent asymmetries in processes, properties and topology of plasma structures in various regions of geospace. Read More

Magnetic reconnection, as a fundamental energy conversion mechanism, can explosively convert energy contained in a magnetic field into ionised particles in solar system, astrophysical plasmas and laboratory plasmas. Planetary magnetic reconnection can be driven by solar wind energy or planetary internal energy. Externally driven processes, from the solar wind, have been extensively investigated at Earth and Mercury. Read More

The antiproton-to-proton ratio in the cosmic-ray spectrum is a sensitive probe of new physics. Using recent measurements of the cosmic-ray antiproton and proton fluxes in the energy range of 1-1000 GeV, we study the contribution to the $\bar{p}/p$ ratio from secondary antiprotons that are produced and subsequently accelerated within individual supernova remnants. We consider several well-motivated models for cosmic-ray propagation in the interstellar medium and marginalize our results over the uncertainties related to the antiproton production cross section and the time-, charge-, and energy-dependent effects of solar modulation. Read More

Recently, Hoang et al. (arXiv:1608.05284) reported analysis of the interaction of relativistic spacecrafts with interstellar medium (ISM, i. Read More

Solar Energetic Particles (SEPs), a major component of space weather, propagate through the interplanetary medium strongly guided by the Interplanetary Magnetic Field (IMF). In this work, we analyse the implications a flat Heliospheric Current Sheet (HCS) has on proton propagation from SEP release sites to the Earth. We simulate proton propagation by integrating fully 3-D trajectories near an analytically defined flat current sheet, collecting comprehensive statistics into histograms, fluence maps and virtual observer time profiles within an energy range of 1--800 MeV. Read More

Orbital experiment ARINA on the board of Russian satellite Resurs-DK1 launched in 2006 developed to study charged particle flux (electrons E ~ 3 - 30MeV , protons E ~ 30 - 100MeV ) in near-Earth space, especially high-energy electron precipitation from the inner radiation belt caused by various geophysical and solar-magnetospheric phenomena. Precipitated electrons under certain conditions (energy, LB-coordinate) drifts around the Earth and can be detected as fast increase in count rate of satellite spectrometer (so called bursts). High-energy electron bursts can be caused by local geophysical phenomena (like earthquakes or thunderstorms). Read More

Solar Orbiter is a joint ESA-NASA mission planed for launch in October 2018. The science payload includes remote-sensing and in-situ instrumentation designed with the primary goal of understanding how the Sun creates and controls the heliosphere. The spacecraft will follow an elliptical orbit around the Sun, with perihelion as close as 0. Read More

The results of observation of short-term variations of high-energy electron flux in the outer radiation belt, obtained in ARINA satellite experiment (2006 - 2016), are presented. Scintillation spectrometer ARINA on board the Resurs-DK1 Russian satellite has been developed in MEPhI. The instrument carried out continuous measurements of high-energy electron flux and its energy spectrum in low-Earth orbits in the range 3-30 MeV with 10 15% energy resolution. Read More

A recently proposed technique correlating electric fields and particle velocity distributions is applied to single-point time series extracted from linearly unstable, electrostatic numerical simulations. The form of the correlation, which measures the transfer of phase-space energy density between the electric field and plasma distributions and had previously been applied to damped electrostatic systems, is modified to include the effects of drifting equilibrium distributions of the type that drive counter-streaming and bump-on-tail instabilities. By using single-point time series, the correlation is ideal for diagnosing dynamics in systems where access to integrated quantities, such as energy, is observationally infeasible. Read More

Using two-dimensional hybrid expanding box simulations we study the competition between the continuously driven parallel proton temperature anisotropy and fire hose instabilities in collisionless homogeneous plasmas. For quasi radial ambient magnetic field the expansion drives $T_{\mathrm{p}\|}>T_{\mathrm{p}\perp}$ and the system becomes eventually unstable with respect to the dominant parallel fire hose instability. This instability is generally unable to counteract the induced anisotropization and the system typically becomes unstable with respect to the oblique fire hose instability later on. Read More