H. J. Fahr

University of Bonn | Uni Bonn · Argelander-Institute of Astronomy

We present a review of Anomalous Cosmic Rays (ACRs), including the history of their discovery and recent insights into their acceleration and transport in the heliosphere. We focus on a few selected topics including a discussion of mechanisms of their acceleration, escape from the heliosphere, their effects on the dynamics of the heliosheath, trans...

The standard (nonrelativistic) κ -distribution is widely used to fit data and to describe macroscopic thermodynamical behavior, e.g., the pressure (temperature) as the second moment of the distribution function. By contrast to a Maxwellian distribution, for small relevant values κ < 2 there exists a significant, but unphysical contribution to the p...

We study the behaviour of shocked wind-electrons leaving wind-driving stars after undergoing the outer wind termination shock. As an example, we describe the evolution of the keV-energetic electron distribution function downstream of the heliospheric termination shock. We start from a kinetic transport equation in the bulk frame of the heliosheath...

In classical thermodynamics the entropy is an extensive quantity, i.e., the sum of the entropies of two subsystems in equilibrium with each other is equal to the entropy of the full system consisting of the two subsystems. The extensitivity of entropy has been questioned in the context of a theoretical foundation for the so-called κ distributions,...

In classical thermodynamics the entropy is an extensive quantity, i.e.\ the sum of the entropies of two subsystems in equilibrium with each other is equal to the entropy of the full system consisting of the two subsystems. The extensitivity of entropy has been questioned in the context of a theoretical foundation for the so-called $\kappa$-distribu...

The Interstellar Mapping and Acceleration Probe (IMAP) is a revolutionary mission that simultaneously investigates two of the most important overarching issues in Heliophysics today: the acceleration of energetic particles and interaction of the solar wind with the local interstellar medium. While seemingly disparate, these are intimately coupled b...

In a most recent paper by Qin and Waldrop (2016), it had been found that the scale height of hydrogen in the upper exosphere of the Earth, especially during solar minimum conditions, appears to be surprisingly large. This indicates that during minimum conditions when exobasic temperatures should be small, large exospheric H-scale heights predominat...

The study addresses the question of the origin of low-energy electrons measured by Voyager 1 in the multi-keV range in the inner heliosheath. It intends to demonstrate that the observed keV-fluxes of electrons are consistent with their transmission through the termination shock under the influence of the associated electrostatic field. A power-law...

Circumterrestrial Lyman-α column brightness observations from 3–8 Earth radii (Re) have been used to study temporal density variations in the exospheric neutral hydrogen as response to geomagnetic disturbances of different strength, i.e., Dst peak values between -26 and -147 nT. The data used were measured by the two Lyman-α detectors (LAD1/2) onbo...

The study aims at a derivation of generalized Rankine-Hugonoit relations, especially that for the entropy, for the case of different upstream/downstream polytropic indices and their implications. We discuss the solar/stellar wind interaction with the interstellar medium for different polytropic indices and concentrate on the case when the polytropi...

According to present cosmological views the energy density of CMB (Cosmic Microwave Background) photons, freely propagating through the expanding cosmos, varies proportional to 1/S^4 with S being the scale factor of the universe. This behavior is expected, because General Theory of Relativity, in application to FLRW- (Friedmann-Lemaitre-Robertson-W...

Wie wir schon im ersten Kapitel des Buches herausgestellt haben, sieht sich die heutige Kosmologie insbesondere mit zwei sehr plagenden und irritierenden Problemen konfrontiert. Sowohl durch die Rotverschiebung der fernsten Supernovae (Perlmutter et al. 1999) als auch durch die Versuche einer Simulation der Struktur im heutigen Universum (Springel...

Wie vollzieht sich ein Denken an anderer Stelle im Kosmos oder gar am Rande des Universums im Vergleich zu dem unseren hier auf der Erde? Denkt man anderswo wohl anders als bei uns? Und wenn ja, dann wäre jede Theorie über die Entstehung und die Natur unseres Universums nur eben unsere hausbackene, geomorphe oder anthropomorphe Theorie, die mehr mi...

Ein Schluss, der wohl gezogen werden muss: Selbst das Licht bleibt nicht ewig schnell und hell! Und das hat eine Menge Konsequenzen, wie wir zeigen wollen.Was schon vor Einstein galt, ist mit und nach Einstein geradezu zur Gralsweisheit der Naturwissenschaften geworden: Das Licht bewegt sich immer und überall gleichschnell, nämlich mit einer immer...

The evolution of the solar wind proton distribution function along the plasma flow downstream of the heliospheric termination shock is studied. Starting from a kinetic phase space transport equation valid in the bulk frame of the plasma flow that takes into account convective changes, cooling, velocity diffusion, and charge exchange-induced injecti...

As has been revealed in a number of more recent astrophysical papers, in most of the tenuous space plasmas Maxwellian distribution functions cannot be expected for ions or electrons because of the lack of efficient relaxation processes. Many of the classical characteristics of plasmas, such as plasma frequency or Debye length, are calculated on the...

We consider a fast magnetosonic multifluid shock as a representation of the solar-wind termination shock. We assume the action of the transition happens in a three-step process: In the first step, the upstream supersonic solar-wind plasma is subject to a strong electric field that flashes up on a small distance scale Δz ≃ U1/Ωe (first part of the t...

Wie jeder weiß, leben wir heute in einer anspruchsvollen Zeit; anspruchsvoll in jeder Hinsicht: im Ressourcenkonsum, im Komfortbedürfnis und gerade aber auch im Wissen: „Die Welt ist groß und rund“, das zu wissen, reicht heute nicht mehr. Es muss schon heißen: „Die Welt ist eine dynamische vierdimensionale Raum-Zeit-Gegebenheit mit inflationärer Ex...

Im Rahmen des Urknallbildes ist von George Gamov und Kollegen bereits 1950 die Existenz einer allgemeinen, isotropen kosmischen Hintergrundstrahlung im Mikrowellenbereich des elektromagnetischen Spektrums als Relikt der „heißen Kosmogenesis“ vorhergesagt worden, und danach, beginnend mit den Entdeckungen von Arno Penzias und David Wilson im Jahre 1...

Wenn die Teile der Welt ganz isoliert voneinander existierten, ohne jede Synchronisation mit dem Rest des Universums, dann gelte es nicht, die Welt als Ganze, sondern ihre Teile zu verstehen. Wenn also das Universum nichts anderes als ein kontingentes, physikalisch unzusammenhängendes Nebeneinander von Sternen, Galaxien und Galaxienhaufen wäre, die...

Über allen Gipfeln ist Ruh’, beginnt ein Gedicht von Johann Wolfgang von Goethe und es stützt die menschliche Zuversicht, dass über den Wipfeln des Irdischen die Welt der Ewigkeit und der Zeitlosigkeit beginnt. Alles dort oben ist in Ruhe gebettet, wie die Menschheit glauben will. Aber wo beginnt dieses System der Ruhe? Schon jenseits des Mondes? J...

In den vorangegangenen Abbildungen hatten wir, wie dort schon erklärt, materielle Häufungserscheinungen im Kosmos erkennen können, die sich in allen Richtungen des Universums immer wieder in ganz ähnlicher Form auffinden lassen. Diese Häufungen treten hier zunächst einmal als Häufungen auf einer Rotverschiebungsachse auf, und die Frage muss deswege...

Am Ende dieses Buches sollten wir uns nun abschließend einmal fragen, ob wir den Kosmos als Ganzen nach allen zuvor angestellten Überlegungen nun eigentlich besser verstanden haben. Kommen wir deswegen noch einmal auf die Ausgangsfrage des Buches zurück: Können wir nach allen Rätseln, die das Universum in Form seiner von uns beobachteten Eigenschaf...

Von größter Bedeutung für das Verständnis desjenigen Lichterphänomens, das sich an unserem Nachthimmel zeigt, also für das allnächtlich begeisternde Sternenfirmament, ist ganz ersichtlich die dahinterstehende räumliche Verteilung der leuchtenden Materie im Weltall, also der Sterne und Galaxien. Und dabei geht es ja, wie man sich klar machen muss, u...

Ein früher oft verwendetes Sprichwort besagte: Wie man in den Wald hineinruft, so schallt es hinaus! Das will sagen, dass aus einer passiven Masse nur zurücktönen kann, was man von außen in sie hineingerufen hat. Ist nun der Kosmos mit seinen unzähligen Sternen und Sternsystemen im übertragenen Sinne auch nichts anderes als eine solche passive Mass...

Dieses Buch beschäftigt sich mit den aktuellen Themen der Kosmologie und der Entstehung des Universums und greift dabei insbesondere die Fragestellung auf, inwieweit sich die Welt als physikalisch zusammenhängendes Gesamtgebilde verstehen lässt. Der Autor erläutert dabei auf verständliche Weise die modernen Forschungsergebnisse und Aspekte der Urkn...

By three independent hints it will be demonstrated that still at present there is a substantial lack of theoretical understanding of the CMB phenomenon. One point, as we show, is that at the phase of the recombination era one cannot assume complete thermodynamic equilibrium conditions but has to face both deviations in the velocity distributions of...

In the majority of the literature on plasma shock waves until now, electrons have played the role of "ghost particles," since they contribute to mass- and momentum flows only negligibly and have been treated as taking care of the electric plasma neutrality. In some more recent papers, however, electrons play a new important role in the shock dynami...

In a series of earlier papers, we developed expressions for ion and electron velocity distribution functions and their velocity moments at the passage over the solar wind termination shock. As we have shown there, with the introduction of appropriate particle invariants and the use of Liouville's theorem one can get explicit solutions for the resul...

Circumterrestrial Lyman-α column brightness observations above 3 Earth radii (Re) have been used to derive separate 3-D neutral hydrogen density models of the Earth's exosphere for solar minimum (2008, 2010) and near-solar-maximum (2012) conditions. The data used were measured by Lyman-α detectors (LAD1/2) onboard each of the TWINS satellites from...

In the present days of modern cosmology it is assumed that the main ingredient to cosmic energy presently is vacuum energy with an energy density $\epsilon_\mathrm{vac}$ that is constant over the cosmic evolution. In this paper here we show, however, that this assumption of constant vacuum energy density is unphysical, since it conflicts with the r...

It is well known that (pick-up) ions in the inner heliosphere do not maintain Maxwellian distributions but tend to non-equilibrium distributions with extended suprathermal tails. Such states have been classified as quasi-equilibria which in many cases can well be described by so-called κ-distributions. With the present study we start out from a pha...

Ambient plasma electrons undergo strong heating in regions associated with compressive traveling interplanetary solar-wind bulk-velocity jumps due to their specific interactions with the jump-inherent electric fields. After thermalization of this energy gain per shock passage through the operation of the Buneman instability, strong electron heating...

In a series of earlier papers, we have developed expressions for ion and electron velocity distribution functions and theirvelocity moments at the passage over the solar wind termination shock. As we have shown there, with introduction of appropriate particle invariants and the use of Liouville`s theorem one can get explicit solutions for the resul...

Understanding the outer heliospheric interface is a major challenge, especially in the light of recent observations by the IBEX and Voyager missions. We present further details on a new required theoretical correction that has been identified as substantial in a recent paper, the so-called source depletion effect. These results complement and expan...

It is still a major challenge to understand the data of energetic neutral atoms (ENAs) that arrive from the outer heliosphere. These data are provided by the IBEX mission. With the most recent data covering three years of dynamical evolution, it is now possible to study temporal correlations with the solar cycle. We present in this paper for the fi...

We study the temperature of electrons advected with the solar wind to large solar distances far beyond 1 AU. Almost nothing is known about the thermodynamics of these electrons from in-situ plasma observations at these distances, and usually it is tacitly assumed that electrons, due to adiabatic behaviour and vanishing heat conduction, rapidly cool...

Neue Messungen der Plasmaeigenschaften in der Umgebung von Voyager 1 belegen, dass die Raumsonde die Heliosphäre verlassen und den interstellaren Raum erreicht hat. Insbesondere Messungen der Ionendichten, Elektronenplasma-Schwingungen und Magnetfelder entsprechen den Vorhersagen für den Übergang in das interstellare Medium.

In the heliosphere, especially in the inner heliosheath, mass-, momentum-, and energy loading induced by the ionization of neutral interstellar species plays an important, but for some species, especially Helium, an underestimated role. We discuss the implementation of charge exchange and electron impact processes for interstellar neutral Hydrogen...

In this paper we consider a multi-fluid plasma that describes the upstream solar wind at its passage over the solar wind termination shock. In one respect, the plasma at the shock reacts like a joint fluid that is described by a single compression ratio. This ratio depends on all upstream and downstream pressures of the magnetohydrodynamic (MHD) pl...

In this paper we study the temperatures of electrons convected with the solar wind to large solar distances and finally transported over the solar wind termination shock. Nearly nothing, unless at high energies in the cosmic ray regime, is known about the thermodynamical behaviour of these distant electrons from in~situ plasma observations. Hence i...

Voyager 2 plasma observations have recently revealed that, as predicted by theory, there exists a solar wind termination shock at 87 au. However, it is evidently different from classical expectations, for instance revealing the downstream solar wind protons still to be in a supersonic mode. In this paper we show that in order to explain the non-cla...

The magnetic moment is one of the most fundamental, nontrivial particle properties known in plasma physics. Also known as the first adiabatic invariant, it is conserved under a broad range of microphysical processes and plasma boundary conditions. However, especially in modern numerical simulations, the conservation of this property, which in princ...

Though the solar wind termination shock in more recent studies is described as a multi-fluid MHD Rankine-Hugoniot structure, electrons are generally not treated in this context as an individual, separate fluid, instead they are normally described as simply being in thermodynamic equilibrium with solar wind protons, i.e. with equal densities and tem...

For more than three years now, the IBEX mission monitors fluxes of energetic neutral atoms (ENAs) in the range between 0.1 to 6 keV from all directions of the sky. During this extended observation period, it could be confirmed that an outstanding ENA emission feature, called the "ribbon", has been continuously found over the past years. In addition...

The Lyman-α Detectors (LAD) on board the two TWINS 1/2-satellites allow for the simultaneous stereo imaging of the resonant emission glow of the H-geocorona from very different orbital positions. Terrestrial exospheric atomic hydrogen (H) resonantly scatters solar Lyman-α (121.567 nm) radiation. During the past solar minimum, relevant solar paramet...

Das Sonnensystem befindet sich im Inneren einer ausgedehnten Plasmablase, der Heliosphäre. Ursache hierfür ist der Sonnenwind. Bislang ließen sich die physikalischen Zustände und Prozesse an der Grenze von der Heliosphäre zum interstellaren Medium nicht beobachten. Dies änderte sich jetzt mit dem Satelliten IBEX. Er registriert energiereiche Wasser...

We study the physics of a multi-ion MHD shock, i.e. an MHD shock feature that forms when a supersonic flow of mixed ion populations is forced to adapt itself to a pressure obstacle further downstream. We shall describe this situation by using a multi-fluid approach for a mixture of ion populations with different specific masses and charges per ion...

The discussion of exactly which process is causing the preferred build-up of v −5 -power law tails of the veloc-ity distribution of suprathermal particles in the solar wind is still ongoing. Criteria allowing one to discriminate between the various suggestions that have been made would be useful in order to clarify the physics behind these tails. W...

Most of the large-scale models of the heliosphere include for the coupling of the neutral hydrogen gas and the proton plasma the charge exchange process and the photoionization, but only a few also consider explicitly the electron impact process. Here we will briefly review the characteristics of all of these ionization processes and will especiall...

It has recently been discussed that two of the paradigms in modeling the transport of galactic cosmic rays -- namely that the modulation boundary is identical with the heliopause and that the local interstellar spectra are identical to the galactic cosmic ray spectra -- have to be revised. Theoretical findings imply that the modulation is, due to t...

Confronted with microwave background observations by WMAP and with consternating supernova locations in the magnitude–redshift diagram modern cosmology feels enforced to call for cosmic vacuum energy as a necessary cosmological ingredient. Most often this vacuum energy is associated with Einstein’s cosmological constant Λ or with so-called “dark en...

As the Sun moves through the local interstellar medium, its supersonic, ionized solar wind carves out a cavity called the heliosphere. Recent observations from the Interstellar Boundary Explorer (IBEX) spacecraft show that the relative motion of the Sun with respect to the interstellar medium is slower and in a somewhat different direction than pre...

As an example for the solar wind termination shock the physics of a multi-ion plasma passing over an MHD shock is studied. As we can show the different upstream plasma species, different in energy, electric charge and mass, undergo different specific reactions when being convected from upstream to downstream of the shock structure. Conserving typic...

At large solar distances beyond 10 AU MHD turbulence amplitudes are decreasing and even selfgenerated turbulences by pick-up ions will not support effectively enough energy diffusion processes driven by nonlinear wave-particle interactions. This should suppress the evolution of suprathermal ion tails beyond the pick-up ion injection border, though...

Fluxes of energetic neutral atoms (ENAs) that have been recently observed by the IBEX mission exhibit several unexpected properties, including a previously unmodeled region of increased intensities in the approximate shape of a ribbon, dominating energy regions above 1 keV. We present latest results from a model that produces a very similar feature...

A stellar wind passing through the reverse shock is deflected into the astrospheric tail and leaves the stellar system either as a sub-Alfvenic or as a super-Alfvenic tail flow. An example is our own heliosphere and its heliotail. We present an analytical method of calculating stationary, incompressible, and field-aligned plasma flows in the astrot...

Context. The "IBEX ribbon" feature provides significant challenges to theoretical modeling attempts of the outer heliosphere. Classical ENA production by shock-processed nonthermal tails results in no relevant ENA signatures, mainly due to the downstream solar wind proton temperature observed by the Voyagers being one order of magnitude smaller tha...

From most in-situ plasma observations made in the outer heliosphere it became evident that above the injection border of pick-up ions (≃1 keV), an extended suprathermal ion tail is found which in most cases can be fitted by a power law with velocity power indices of (-6) ≤ γv ≤ (-4). As has been shown by theory such energetic ion tails cannot be ex...

Two of the paradigms in modeling the transport of galactic cosmic rays are that the modulation boundary is the heliopause and that the local interstellar spectra are identical to the galactic cosmic ray spectra. Here we demonstrate, that the proton spectrum is already modulated, due to an altered interstellar diffusion coefficient in the outer heli...

Terrestrial exospheric atomic hydrogen (H) resonantly scatters solar Lyman-α (121.567 nm) radiation, observed as the glow of the H-geocorona. The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) satellites are equiped with two Lyman-α line-of-sight Detectors (LADs) each. Since during the past solar minimum conditions the relevant solar con...

Context. The phase space transport of pick-up ions (PUIs) in the heliosphere has been studied for the cases that these particles are experiencing a second-order Fermi process, i.e. velocity diffusion, a convection with the solar wind, and adiabatic or "magnetic" cooling, i.e. cooling connected with the conservation of the magnetic moment. Aims: The...

Context. Up to now, three succesive full-sky maps of heliospheric fluxes of KeV-energetic neutral H-atoms have been registered with the satellite IBEX. The most outstanding feature persisting in these maps is the so-called ribbon which appears as an arc around the upwind direction with unexpectedly high fluxes. This radiation feature was not predic...

Two of the paradigms in modeling the transport of galactic cosmic rays are that the modulation boundary is the heliopause and that the local interstellar spectra are identical to the galactic cosmic ray spectra. Here we demonstrate that the proton spectrum is already modulated due to an altered interstellar diffusion in the outer heliosheath as a c...

In this paper we start from the most recently observed fact that the solar wind plasma after passage over the termination shock is still supersonic with a Mach number of about 2. To explain this unexpected phenomenon and to predict the evolution of properties of the downstream plasma flow we here consider a two-fluid proton plasma with pick-up prot...

Context. Throughout the heliosphere, ion power spectra have been found in observations to exhibit suprathermal tails that follow power laws. Ion power-law spectra, though having a broad range of spectral indices 4.4 ≤ γv = 6.6, perhaps favourably seem to have velocity power indices of γv ≃ (-5), a phenomenon that can more or less ubiquitously be fo...

In recent years one could witness tremendous progress regarding the physics of the transport of cosmic rays (CRs) in the heliosphere. This progress derives from both theoretical advances and new measurements from the outer boundary region of the heliosphere. At the same time theory and observations give new constraints on the local interstellar CR...

We study the plasma passage over astrophysical MHD shocks with frozen-in magnetic fields in arbitrary inclinations with respect to the bulk plasma motion. As a function of the compression ratio at the shock, we aim at the prediction of ion plasma properties downstream of the shock, especially the resulting downstream temperatures, pressures and pre...

We investigated the impact of three different modifications of Newtonian gravity on motions of Keplerian objects within the Solar System. These objects are located at distances of the order of the distance to the Oort cloud. With these three modifications we took into account a heliocentric Dark-Matter halo as was indicated by Diemand et al, Modifi...

Based on Ly-α-line-of-sight measurements taken with two Ly-α detectors onboard of the satellite TWINS1 (Two Wide-angle Imaging Neutral-atom Spectrometers) density profiles of the exospheric, neutral geocoronal hydrogen were derived for the time period between summer solstice and fall equinox 2008. With the help of specifically developed inversion p...

The recent Interstellar Boundary EXplorer (IBEX) observations have placed great doubt on up-to-now theoretical models of the source of these particles. Presently all existing models assume that the ENA source is located in the outer heliosheath, or beyond the heliopause, lacking any indication of the distinctive ribbon feature clearly emerging from...

Many observations of suprathermal and energetic particles in the solar wind and the inner heliosheath show that distribution functions scale approximately with the inverse of particle speed (v) to the fifth power. Although there are exceptions to this behavior, there is a growing need to understand why this type of distribution function appears so...

The Voyager‐2 observations at the recent crossing of the solar wind termination shock show that the downstream thermal protons still move with supersonic speed. Obviously it is due to their inefficient shock‐heating and that the surpathermal ions absorb most of the upstream kinetic solar wind energy. In this paper we present a three‐fluid approach...

Context. Observations by Voyager-2 at the crossing of the solar wind termination shock have led to unexpected discoveries, such as the downstream solar wind protons still having Mach numbers higher than 1 and temperatures, though increased by a factor of about 30, nevertheless being much lower than those expected from classical MHD shock theory. Th...

The solar wind plasma beyond 30 AU represents a multi-fluid phenomenon with different ion populations centered around typical energies of a few eV (solar wind protons), KeV (pick-up ions) and MeV (anomalous cosmic ray ions).To treat the passage of such a mixture of plasma fluids we use a hydrodynamic three-fluid model describing solar wind ions, pi...

The Voyager-2 observations at the recent crossing of the solar wind termination shock show that the downstream thermal protons still move with supersonic speed. This effect is due to their inefficient shock-heating and that the surpathermal ions absorb most of the upstream kinetic solar wind energy. However, when a parcel of the solar wind moves aw...

Interstellar Boundary Explorer (IBEX) mission gives us a unique opportunity to analyze global, three-dimensional and time-dependent, structure of the outer heliosphere. Charge exchange between interstellar neutral atoms and ions and interstellar magnetic field, through the heliopause draping, can significantly affect the topology of the heliospheri...

The Cosmic Microwave Background (CMB) is taken today as reflecting the thermodynamical state of the universe at these early cosmic times. Based on this assumption and standard cosmological principles meanwhile many fundamental cosmological facts have been deduced from the CMB state which, however, to some surprise reveal that the universe should be...

The Cosmic Microwave Background (CMB) is taken today as reflecting the thermodynamical state of the universe at these early cosmic times. Based on this assumption and standard cosmological principles meanwhile many fundamental cosmological facts have been deduced from the CMB state which, however, to some surprise reveal that the universe should be...

Simulations of energetic neutral atom (ENA) maps predict flux magnitudes that are, in some cases, similar to those observed by the Interstellar Boundary Explorer (IBEX) spacecraft, but they miss the ribbon. Our model of the heliosphere indicates that the local interstellar medium (LISM) magnetic field (B(LISM)) is transverse to the line of sight (L...

The Sun moves through the local interstellar medium, continuously emitting ionized, supersonic solar wind plasma and carving out a cavity in interstellar space called the heliosphere. The recently launched Interstellar Boundary Explorer (IBEX) spacecraft has completed its first all-sky maps of the interstellar interaction at the edge of the heliosp...

We investigate the well accepted idea that anomalous cosmic ray (ACR) ions originate from suprathermal halo ions by means of diffusive shock acceleration. Usually the seed ions are taken to be the interplanetary pick-up ions, but here we want to enlarge this idea by taking in addition as seed candidates also into account normal solar wind ions whic...

This chapter covers the theory of physical processes in the outer heliosphere that are particularly important for the IBEX Mission, excluding global magnetohydrodynamic/Boltzmann modeling of the entire heliosphere. Topics addressed include the structure and parameters of the solar wind termination shock, the transmission of ions through the termina...

The Interstellar Boundary Explorer (IBEX) is one of five Small Explorer (SMEX) missions undergoing Phase A study for NASA's Office of Space Science. Around November 2004, NASA expects to select at least one of missions for development and flight. If selected, IBEX will provide the first global views of the Sun's interstellar boundaries by taking a...

Aims: We reinvestigate the parallel pressure-anisotropic MHD shock with an emphasis on the downstream stability of the plasma with respect to the firehose instability. Methods: Aiming to close the underdetermined jump conditions, we take advantage of a kinetic model of the shock transit, based on the Boltzman-Vlasow equation with CGL invariants. In...

Our recent kinetic model for the parallel solar wind termination shock describes the ion shock transit under the influence of a decelerating electrostatic potential and the turbulent wave-particle interaction with electrostatic plasma waves. Due to this diffusive interaction, a certain number of ions are reflected at the shock. These ions propagate...

Two satellites, TWINS-1 and TWINS-2, are presently orbiting the Earth on highly elliptic high-apogee orbits. In addition to energetic neutral atom (ENA) imagers, both satellites carry Lyman-alpha detectors (LAD). These broadband photon-counting sensors measure the line-of-sight integrated Lyman-alpha (121.6 nm) flux of solar photons resonantly scat...

We develop a kinetic model to describe the termination shock transition of anisotropic plasmas, which compliments the classical MHD approach to this problem. Using this model, we derive a condition under which upstream conditions wave generation is triggered, and how much classical MHD energy is transfered into the wave field degrees of freedom. As...

With the observations made at the more recent crossings of the Voyager space probes over the solar wind termination shock, up-to-date knowledge of the physics at astrophysical shocks has been deeply challenged in many respects. In this paper, we mainly address the associated facts that the ion plasma downstream of the shock appears to be supercriti...

Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) is a NASA Explorer Mission-of-Opportunity to stereoscopically image the Earth’s magnetosphere for the first time. TWINS extends our understanding of magnetospheric structure and processes by providing simultaneous Energetic Neutral Atom (ENA) imaging from two widely separated locations. TWIN...

Context. Anomalous cosmic rays are thought to be generated from pick-up ions that undergo Fermi-1 acceleration in the region close to the solar wind termination shock. This selective acceleration process depends on the efficiency at which upstream pick-up ions are injected into the first reflection mode, from where acceleration into higher energy a...

Though pick-up ions are well known in the inner heliosphere, their phase-space distribution nevertheless is a theoretically unsettled problem till now. Especially the question why pick-up ions form suprathermal tails, extending to far above their primary injection energy, is not satifactorily answered. Fermi-2 velocity diffusion theories indicate t...