Found 7 results
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Filters: Keyword is Heliosphere  [Clear All Filters]
2020
Authors: Hanneson Cedar, Johnson Catherine L., Mittelholz Anna, Asad Manar M. Al, and Goldblatt Colin
Title: Dependence of the Interplanetary Magnetic Field on Heliocentric Distance at 0.3–1.7 AU: A Six‐Spacecraft Study
Abstract:

We use magnetometer data taken simultaneously by MESSENGER, VEX, STEREO and ACE to characterize the variation of the interplanetary magnetic field (IMF) with heliocentric distance, rh, for rh≲ 1 AU. Power law fits (a rh b) to the individual IMF components and magnitude indicate that, on average, the IMF is more tightly wound and its strength decreases less rapidly with rh than the Parker spiral prediction. During Solar Cycle 24, temporal changes in b were insignificant, but changes in amplitude, a, were correlated with sunspot number, up to sunspot number ∼84. MAVEN data taken at 1.4-1.7 AU since late 2014 broadly confirm and extend these results in space and time. Our study demonstrates the importance of simultaneous observations from multiple spacecraft to separate heliocentric di. . .
Date: 03/2020 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA027139 Available at: https://onlinelibrary.wiley.com/doi/abs/10.1029/2019JA027139
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Authors: Scolini C., Chané E., Pomoell J., Rodriguez L., and Poedts S.
Title: Improving Predictions of High‐Latitude Coronal Mass Ejections Throughout the Heliosphere
Abstract:

Predictions of the impact of coronal mass ejections (CMEs) in the heliosphere mostly rely on cone CME models, whose performances are optimized for locations in the ecliptic plane and at 1 AU (e.g., at Earth). Progresses in the exploration of the inner heliosphere, however, advocate the need to assess their performances at both higher latitudes and smaller heliocentric distances. In this work, we perform 3-D magnetohydrodynamics simulations of artificial cone CMEs using the EUropean Heliospheric FORecasting Information Asset (EUHFORIA), investigating the performances of cone models in the case of CMEs launched at high latitudes. We compare results obtained initializing CMEs using a commonly applied approximated (Euclidean) distance relation and using a proper (great circle) distance rela. . .
Date: 03/2020 Publisher: Space Weather DOI: 10.1029/2019SW002246 Available at: https://onlinelibrary.wiley.com/doi/abs/10.1029/2019SW002246
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2019
Authors: Pacheco D., Agueda N., Aran A., Heber B., and Lario D.
Title: Full inversion of solar relativistic electron events measured by the Helios spacecraft
Abstract:

Context. The Parker Solar Probe and the incoming Solar Orbiter mission will provide measurements of solar energetic particle (SEP) events at close heliocentric distances from the Sun. Up to present, the largest data set of SEP events in the inner heliosphere are the observations by the two Helios spacecraft.

Aims. We re-visit a sample of 15 solar relativistic electron events measured by the Helios mission with the goal of better characterising the injection histories of solar energetic particles and their interplanetary transport conditions at heliocentric distances <1 AU.

Methods. The measurements provided by the E6 instrument on board Helios provide us with the electron directional distributions in eight different sectors that we use t. . .
Date: 01/2019 Publisher: Astronomy & Astrophysics Pages: A3 DOI: 10.1051/0004-6361/201834520 Available at: https://www.aanda.org/10.1051/0004-6361/201834520/pdf
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Authors: Parashar T. N., Cuesta M., and Matthaeus W. H.
Title: Reynolds Number and Intermittency in the Expanding Solar Wind: Predictions Based on Voyager Observations
Abstract:

The large-scale features of the solar wind are examined in order to predict small-scale features of turbulence in unexplored regions of the heliosphere. The strategy is to examine how system size, or effective Reynolds number Re, varies, and then how this quantity influences observable statistical properties, including intermittency properties of solar wind turbulence. The expectation based on similar hydrodynamics scalings is that the kurtosis, of the small-scale magnetic field increments, will increase with increasing Re. Simple theoretical arguments as well as Voyager observations indicate that effective interplanetary turbulence Re decreases with increasing heliocentric distance. The decrease of scale-dependent magnetic increment kurtosis with increasing heliocentric distance is ver. . .
Date: 10/2019 Publisher: The Astrophysical Journal Pages: L57 DOI: 10.3847/2041-8213/ab4a82 Available at: https://iopscience.iop.org/article/10.3847/2041-8213/ab4a82
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2018
Authors: Stansby David, Salem Chadi, Matteini Lorenzo, and Horbury Timothy
Title: A New Inner Heliosphere Proton Parameter Dataset from the Helios Mission
Abstract:

In the near future, Parker Solar Probe and Solar Orbiter will provide the first comprehensive in-situ measurements of the solar wind in the inner heliosphere since the Helios mission in the 1970s. We describe a reprocessing of the original Helios ion distribution functions to provide reliable and reproducible data to characterise the proton core population of the solar wind in the inner heliosphere. A systematic fitting of bi-Maxwellian distribution functions was performed to the raw Helios ion distribution function data to extract the proton core number density, velocity, and temperatures parallel and perpendicular to the magnetic field. We present radial trends of these derived proton parameters, forming a benchmark to which new measurements in the inner heliosphere will be compared. . . .
Date: 11/2018 Publisher: Solar Physics DOI: 10.1007/s11207-018-1377-3 Available at: http://link.springer.com/10.1007/s11207-018-1377-3http://link.springer.com/content/pdf/10.1007/s11207-018-1377-3.pdfhttp://link.springer.com/article/10.1007/s11207-018-1377-3/fulltext.htmlhttp://link.springer.com/content/pdf/10.1007/s11207-018-1377-3.pdf
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2015
Authors: Kuznetsov V.D.
Title: Solar and heliospheric space missions
Abstract:

The paper provides a review of the state of the art and prospects of space research in heliophysics, in which a pivotal role belongs to magnetic measurements in the Sun and heliosphere. New space missions, such as the Interhelioprobe, Solar Orbiter, Solar Probe Plus, etc., will follow the currently operating ones (Hinode, SDO, STEREO, etc.) to observe the Sun from short distances and from out-of-ecliptic positions, as well as to conduct in situ measurements in the vicinity of the Sun and outside the ecliptic. The planned coordinated observations within the framework of these missions will allow us to explore the structure and dynamics of magnetic fields in the polar regions of the Sun, to study the mechanisms of the solar dynamo and solar cycle, to gain a deeper insight into the process. . .
Date: 02/2015 Publisher: Advances in Space Research Pages: 879 - 885 DOI: 10.1016/j.asr.2014.07.034 Available at: https://linkinghub.elsevier.com/retrieve/pii/S0273117714004906https://api.elsevier.com/content/article/PII:S0273117714004906?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0273117714004906?httpAccept=text/plain
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2014
Authors: Vainio Rami, önni Arttu, Battarbee Markus, Koskinen Hannu E. J., Afanasiev Alexandr, et al.
Title: A semi-analytical foreshock model for energetic storm particle events inside 1 AU
Abstract:

We have constructed a semi-analytical model of the energetic-ion foreshock of a CME-driven coronal/interplanetary shock wave responsible for the acceleration of large solar energetic particle (SEP) events. The model is based on the analytical model of diffusive shock acceleration of Bell (1978), appended with a temporal dependence of the cut-off momentum of the energetic particles accelerated at the shock, derived from the theory. Parameters of the model are re-calibrated using a fully time-dependent self-consistent simulation model of the coupled particle acceleration and Alfvén-wave generation upstream of the shock. Our results show that analytical estimates of the cut-off energy resulting from the simplified theory and frequently used in SEP modelling are overestimating the cut-off . . .
Date: 02/2014 Publisher: Journal of Space Weather and Space Climate Pages: A08 DOI: 10.1051/swsc/2014005 Available at: http://www.swsc-journal.org/10.1051/swsc/2014005http://www.swsc-journal.org/10.1051/swsc/2014005/pdf
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