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"Interplanetary space"
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A magnetic reconnection X-line extending more than 390 Earth radii in the solar wind
Feel the Force
Magnetic reconnection is a process in which pairs of magnetic field lines merge to convert magnetic energy into particle energy. Kinks formed in the merged field lines produce a slingshot effect that accelerates high-speed plasma jets away from the merger site. The process supplies energy to solar flares and the space storms near Earth that interfere with electric power grids and telecommunications. Space physicists have long debated whether reconnection occurs over great distances, or randomly in localized patches. On 2 February 2002, the Cluster, ACE and Wind spacecraft, widely separated in interplanetary space, all detected similar plasma jets within the same passing current sheet. It was direct evidence of a 2.5-million-kilometre reconnection region, confirming that magnetic reconnection can occur on a very large scale over long periods. On the cover, kinked magnetic field lines accelerate a pair of particle jets.
Magnetic reconnection in a current sheet converts magnetic energy into particle energy, a process that is important in many laboratory
1
, space
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,
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and astrophysical contexts
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,
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,
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. It is not known at present whether reconnection is fundamentally a process that can occur over an extended region in space or whether it is patchy and unpredictable in nature
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. Frequent reports of small-scale flux ropes and flow channels associated with reconnection
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,
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,
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,
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,
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,
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in the Earth's magnetosphere raise the possibility that reconnection is intrinsically patchy, with each reconnection X-line (the line along which oppositely directed magnetic field lines reconnect) extending at most a few Earth radii (
R
E
), even though the associated current sheets span many tens or hundreds of
R
E
. Here we report three-spacecraft observations of accelerated flow associated with reconnection in a current sheet embedded in the solar wind flow, where the reconnection X-line extended at least 390
R
E
(or 2.5 × 10
6
km). Observations of this and 27 similar events imply that reconnection is fundamentally a large-scale process. Patchy reconnection observed in the Earth's magnetosphere is therefore likely to be a geophysical effect associated with fluctuating boundary conditions, rather than a fundamental property of reconnection. Our observations also reveal, surprisingly, that reconnection can operate in a quasi-steady-state manner even when undriven by the external flow.
Journal Article
Whistler waves associated with weak interplanetary shocks
We analyze the properties of 98 weak interplanetary shocks measured by the dual STEREO spacecraft over approximately 3 years during the past solar minimum. We study the occurrence of whistler waves associated with these shocks, which on average are high beta shocks (0.2 < β< 10). We have compared the waves properties upstream and downstream of the shocks. In the upstream region the waves are mainly circularly polarized, and in most of the cases (∼75%) they propagate almost parallel to the ambient magnetic field (<30°). In contrast, the propagation angle with respect to the shock normal varies in a broad range of values (20° to 90°), suggesting that they are not phase standing. We find that the whistler waves can extend up to 100,000 km in the upstream region but in most cases (88%) are contained in a distance within 30,000 km from the shock. This corresponds to a larger region with upstream whistlers associated with IP shocks than previously reported in the literature. The maximum amplitudes of the waves are observed next to the shock interface, and they decrease as the distance to the shock increases. In most cases the wave propagation direction becomes more aligned with the magnetic field as the distance to the shock increases. These two facts suggest that most of the waves in the upstream region are Landau damping as they move away from the shock. From the analysis we also conclude that it is likely that the generation mechanism of the upstream whistler waves is taking place at the shock interface. In the downstream region, the waves are irregularly polarized, and the fluctuations are very compressive; that is, the compressive component of the wave clearly dominates over the transverse one. The majority of waves in the downstream region (95%) propagate at oblique angles with respect to the ambient magnetic field (>60°). The wave propagation with respect to the shock‐normal direction has no preferred direction and varies similarly to the upstream case. It is possible that downstream fluctuations are generated by ion relaxation as suggested in previous hybrid simulation shocks. Key Points Full description of the whistler wave properties in interplanetary shocks First comparison between downstream and upstream whistler waves Study of the plasma properties associated with the interplanetary shocks
Journal Article
Leviathan wakes
When Captain Jim Holden's ice miner stumbles across a derelict, abandoned ship, he uncovers a secret that threatens to throw the entire system into war. Attacked by a stealth ship belonging to the Mars fleet, Holden must find a way to uncover the motives behind the attack, stop a war and find the truth behind a vast conspiracy that threatens the entire human race.
Book
Modulation of Galactic Cosmic Rays Due to Magnetic Clouds and Associated Structures in the Interplanetary Space: 1996-2018
We study the modulation of galactic cosmic rays due to magnetic clouds observed during solar cycles 23 and 24 (1996-2018). We utilize solar wind plasma and field data together with cosmic ray intensity (CRI) data during the passage of magnetic clouds and associated structures. We apply superposed epoch analysis to analyze these data. We study the relative importance of magnetic clouds and their associated structures in modulating the cosmic rays. We observe significant differences in the amplitudes and time profiles of transient depressions in cosmic ray intensity due to magnetic regimes of different field strengths and topologies. We discuss the observed results in light of differences in the simultaneous plasma and magnetic field properties.
Journal Article
The future of humanity : terraforming Mars, interstellar travel, immortality, and our destiny beyond Earth
\"Formerly the domain of fiction, moving human civilization to the stars is increasingly becoming a scientific possibility--and a necessity. Whether in the near future due to climate change and the depletion of finite resources, or in the distant future due to catastrophic cosmological events, we must face the reality that humans will one day need to leave planet Earth to survive as a species ... Kaku explores ... the process by which humanity may gradually move away from the planet and develop a sustainable civilization in outer space\"-- Provided by publisher.
Book
An Analytical Model of Turbulence in Parker Spiral Geometry and Associated Magnetic Field Line Lengths
Understanding the magnetic connections from the Sun to interplanetary space is crucial for linking in situ particle observations with the solar source regions of the particles. A simple connection along the large-scale Parker spiral magnetic field is made complex by the turbulent random walk of field lines. In this paper, we present the first analytical model of heliospheric magnetic fields where the dominant 2D component of the turbulence is transverse to the Parker spiral. The 2D wave field is supplemented with a minor wave field component that has asymptotic slab geometry at small and large heliocentric distances. We show that turbulence spreads field lines from a small source region at the Sun to a 60° heliolongitudinal and heliolatitudinal range at 1 au, with a standard deviation of the angular spread of the field lines of 14°. Small source regions map to an intermittent range of longitudes and latitudes at 1 au, consistent with dropouts in solar energetic particle intensities. The lengths of the field lines are significantly extended from the nominal Parker spiral length of 1.17 au up to 1.6 au, with field lines from sources at and behind the west limb considerably longer than those closer to the solar disk center. We discuss the implications of our findings for understanding charged particle propagation and the importance of understanding the turbulence properties close to the Sun.
Journal Article
The Width of Magnetic Ejecta Measured near 1 au: Lessons from STEREO-A Measurements in 2021–2022
Coronal mass ejections (CMEs) are large-scale eruptions with a typical radial size at 1 au of 0.21 au but their angular width in interplanetary space is still mostly unknown, especially for the magnetic ejecta (ME) part of the CME. We take advantage of STEREO-A angular separation of 20°–60° from the Sun–Earth line from 2020 October to 2022 August, and perform a two-part study to constrain the angular width of MEs in the ecliptic plane: (a) we study all CMEs that are observed remotely to propagate between the Sun–STEREO-A and the Sun–Earth lines and determine how many impact one or both spacecraft in situ, and (b) we investigate all in situ measurements at STEREO-A or at L1 of CMEs during the same time period to quantify how many are measured by the two spacecraft. A key finding is that out of 21 CMEs propagating within 30° of either spacecraft only four impacted both spacecraft and none provided clean magnetic cloud-like signatures at both spacecraft. Combining the two approaches, we conclude that the typical angular width of an ME at 1 au is ∼20°–30°, or 2–3 times less than often assumed and consistent with a 2:1 elliptical cross section of an ellipsoidal ME. We discuss the consequences of this finding for future multi-spacecraft mission designs and for the coherence of CMEs.
Journal Article