29 research outputs found
Gossamer roadmap technology reference study for a solar polar mission
A technology reference study for a solar polar mission is presented. The study uses novel analytical methods to quantify the mission design space including the required sail performance to achieve a given solar polar observation angle within a given timeframe and thus to derive mass allocations for the remaining spacecraft sub-systems, that is excluding the solar sail sub-system. A parametric, bottom-up, system mass budget analysis is then used to establish the required sail technology to deliver a range of science payloads, and to establish where such payloads can be delivered to within a given timeframe. It is found that a solar polar mission requires a solar sail of side-length 100 â 125 m to deliver a âsufficient valueâ minimum science payload, and that a 2. 5ÎŒm sail film substrate is typically required, however the design is much less sensitive to the boom specific mass
The plasma universe: a coherent science theme for Voyage 2050
In review of the White Papers from the Voyage 2050 process1 and after the public presentation of a number of these papers in October 2019 in Madrid, we as White Paper lead authors have identified a coherent science theme that transcends the divisions around which the Topical Teams are structured. This note aims to highlight this synergistic science theme and to make the Topical Teams and the Voyage 2050 Senior Committee aware of the wide importance of these topics and the broad support that they have across the worldwide science community
Progressive transformation of a flux rope to an ICME
The solar wind conditions at one astronomical unit (AU) can be strongly
disturbed by the interplanetary coronal mass ejections (ICMEs). A subset,
called magnetic clouds (MCs), is formed by twisted flux ropes that transport an
important amount of magnetic flux and helicity which is released in CMEs. At 1
AU from the Sun, the magnetic structure of MCs is generally modeled neglecting
their expansion during the spacecraft crossing. However, in some cases, MCs
present a significant expansion. We present here an analysis of the huge and
significantly expanding MC observed by the Wind spacecraft during 9 and 10
November, 2004. After determining an approximated orientation for the flux rope
using the minimum variance method, we precise the orientation of the cloud axis
relating its front and rear magnetic discontinuities using a direct method.
This method takes into account the conservation of the azimuthal magnetic flux
between the in- and out-bound branches, and is valid for a finite impact
parameter (i.e., not necessarily a small distance between the spacecraft
trajectory and the cloud axis). Moreover, using the direct method, we find that
the ICME is formed by a flux rope (MC) followed by an extended coherent
magnetic region. These observations are interpreted considering the existence
of a previous larger flux rope, which partially reconnected with its
environment in the front. These findings imply that the ejected flux rope is
progressively peeled by reconnection and transformed to the observed ICME (with
a remnant flux rope in the front part).Comment: Solar Physics (in press
The Plasma and Suprathermal Ion Composition (PLASTIC) Investigation on the STEREO Observatories
The Heliospheric Plasma Sheet Observed in situ by Three Spacecraft over Four Solar Rotations
Measurements of radiation quality factor on Mars with the Mars Science Laboratory Radiation Assessment Detector
We report the first long-term measurements of the radiation quality factor of energetic charged particles on the
surface of Mars. The Radiation Assessment Detector (RAD) aboard the Mars Science Laboratory rover, also
known as Curiosity, has been operating on Mars since 2012. RAD contains thin silicon detectors that record the
ionization energy loss of energetic charged particles. The particles are dominantly galactic cosmic rays (GCRs)
and the products of their interactions in the Martian atmosphere, with occasional contributions from solar energetic particles (SEPs). The quality factor on the surface of Mars is influenced by two factors: variations in the
shielding provided by the atmosphere, and changes in the spectrum of the incident energetic particle flux due to
the 11-year solar cycle. The two cannot be easily disentangled using the data alone, but insights can be gained
from calculations and Monte Carlo simulations
First observations and performance of the RPW instrument on board the Solar Orbiter mission
Contains fulltext :
243987.pdf (Publisherâs version ) (Open Access
In Situ Observations of Solar Wind Stream Interface Evolution
The heliocentric orbits of the two STEREO satellites are similar in radius and ecliptic latitude, with separation in longitude increasing by about 45° per year. This arrangement provides a unique opportunity to study the evolution of stream interfaces near 1 AU over time scales of hours to a few days, much less than the period of a Carrington rotation. Assuming nonevolving solar wind sources that corotate with the Sun, we calculated the expected time and longitude of arrival of stream interfaces at the Ahead observatory based on the in situ solar wind speeds measured at the Behind observatory. We find agreement to within 5° between the expected and actual arrival longitude until the spacecraft are separated by more than 20° in heliocentric inertial longitude. This corresponds to about one day between the measurement times. Much larger deviations, up to 25° in longitude, are observed after 20° separation. Some of the deviations can be explained by a latitude difference between the spacecraft, but other deviations most likely result from evolution of the source region. Both remote and in situ measurements show that changes at the source boundary can occur on a time scale much shorter than one solar rotation. In 32 of 41 cases, the interface was observed earlier than expected at STEREO/Ahead
Irregular Proton Injection to High Energies at Interplanetary Shocks
How thermal particles are accelerated to suprathermal energies is an unsolved issue, crucial for many astrophysical systems. We report novel observations of irregular, dispersive enhancements of the suprathermal particle population upstream of a high-Mach-number interplanetary shock. We interpret the observed behavior as irregular âinjectionsâ of suprathermal particles resulting from shock front irregularities. Our findings, directly compared to self-consistent simulation results, provide important insights for the study of remote astrophysical systems where shock structuring is often neglected. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]