Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
2,456
result(s) for
"Interplanetary space"
Sort by:
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
2
,
3
and astrophysical contexts
4
,
5
,
6
. 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
7
. Frequent reports of small-scale flux ropes and flow channels associated with reconnection
8
,
9
,
10
,
11
,
12
,
13
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
Episodes of particle ejection from the surface of the active asteroid (101955) Bennu
Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.
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
Origins of the Ambient Solar Wind: Implications for Space Weather
The Sun’s outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind. We also discuss where the community stands in its ability to forecast how variations in the solar wind (i.e., fast and slow wind streams) impact the Earth. Although the last few decades have seen significant progress in observations and modeling, we still do not have a complete understanding of the relevant physical processes, nor do we have a quantitatively precise census of which coronal structures contribute to specific types of solar wind. Fast streams are known to be connected to the central regions of large coronal holes. Slow streams, however, appear to come from a wide range of sources, including streamers, pseudostreamers, coronal loops, active regions, and coronal hole boundaries. Complicating our understanding even more is the fact that processes such as turbulence, stream-stream interactions, and Coulomb collisions can make it difficult to unambiguously map a parcel measured at 1 AU back down to its coronal source. We also review recent progress—in theoretical modeling, observational data analysis, and forecasting techniques that sit at the interface between data and theory—that gives us hope that the above problems are indeed solvable.
Journal Article
Acceleration and Propagation of Solar Energetic Particles
Solar Energetic Particles (SEPs) are an important component of Space Weather, including radiation hazard to humans and electronic equipment, and the ionisation of the Earth’s atmosphere. We review the key observations of SEPs, our current understanding of their acceleration and transport, and discuss how this knowledge is incorporated within Space Weather forecasting tools. Mechanisms for acceleration during solar flares and at shocks driven by Coronal Mass Ejections (CMEs) are discussed, as well as the timing relationships between signatures of solar eruptive events and the detection of SEPs in interplanetary space. Evidence on how the parameters of SEP events are related to those of the parent solar activity is reviewed and transport effects influencing SEP propagation to near-Earth locations are examined. Finally, the approaches to forecasting Space Weather SEP effects are discussed. We conclude that both flare and CME shock acceleration contribute to Space Weather relevant SEP populations and need to be considered within forecasting tools.
Journal Article