The Heliosphere through the Solar Activity Cycle (Springer Praxis Books)
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During the weeklong European Planetary Science Congress Berlin, 18—22 September , sessions offered a broad range of science topics related to planetary science and planetary missions. This venue was an ideal environment for a session covering the topic of interplanetary space weather. The session consisted of two solicited talks, the first concerning solar energetic particles and the second concerning radiation risks to space travelers. Three contributing talks covered satellite anomalies and launch failures, galactic cosmic ray characteristics, and the ionosphere of Mars.
Following the oral presentations, the session continued with 2 hours of dynamic discussions regarding the scientific, technical, and biological issues surrounding interplanetary travel. In this report, the main results from the talks are summarized and conclusions from the discussions are given. Routine human missions to the Moon will doubtlessly be the predecessor for any further human interplanetary mission, especially one to Mars.
Only several days away from us in space, the Moon offers new opportunities for studying the space environment outside the terrestrial magnetosphere, as well as being a possible host for the first space colony in our solar system. Apart from the problems caused to spacecraft by the ultrahigh vacuum and extremes of heat and cold in space, spacecraft also have to survive very hostile environments that can severely limit space missions as well as pose threats to humans. In the case of a solar energetic particle SEP event, charged particles can propagate to remote sites e.
There was a general consensus throughout the workshop that the populations of energetic particles in various regions of the heliosphere, as well as transient solar particle events and cosmic rays, are the primary radiation hazards for current space missions and future interplanetary travel.
The different radiation environments for example, near Jupiter, on Mars, or even near the heliopause originate from different sources of particle populations, such as galactic and anomalous cosmic rays or solar energetic particles, accelerated through different physical processes in the heliosphere and interstellar medium. The particle populations listed in Table 1 are all a function of solar activity, though each in their own way.
For example, it is well known that the galactic cosmic ray GCR flux in the solar system is modulated by solar activity. During solar maximum when sunspot number is at its highest the increase in the interplanetary magnetic field strength, as well as its polarity and the level of solar wind turbulence, enhances shielding of the heliosphere against penetrating GCR particles. Therefore the GCR population is most intense during solar minimum. Therefore SEPs are most frequent and intense near solar maximum. Tendencies such as those mentioned here are readily illustrated in profile plots that vary with time.
Figure 1 shows how a systematic increase in energetic particle flux is observed at solar maximum when the sunspot number is at its highest. In the course of a solar cycle, the number of CMEs and their average speed increase with rising solar activity Figure 2. As evidenced by the number of factors that must be considered to prepare spacecraft for the space hazards, conference attendees agreed that understanding and predicting the perils of interplanetary travel are not simple tasks.
For example, planets such as Mars, which lack a substantial internal magnetic field, do not shield space travelers or equipment from energetic particles. The workshop's speakers discussed the perils of interplanetary space travel in more detail.
Bibliographic Codes, Conference Proceedings Abbreviations
This talk was a review of the current status of the origin of SEPs and their link to space weather. Both models use as a basis SEP event distributions over integrated proton fluxes with energies exceeding the given levels. One of the basic assumptions behind the MSU model is that the average rate of SEP events is proportional to solar activity [ Nymmik, ]. The MSU model and the previous two models were compared, and the results were presented as a function of flight duration.
This talk considered how mission designers face the difficult task of containing the overall health risk of astronauts within acceptable limits.
AMSCI ICON NAVIGATION:
The major message that came across during this talk was that radiation risk management striving to conform to predetermined radiation exposure limits—such as those set by government agencies for LEOs—is likely to be counterproductive since these limits control only the late cancer mortality risk, many years after the mission, rather than the immediate risks faced during the mission.
Instead, a new hazard measure or risk criterion is needed that—in addition to this late radiation risk—allows a unified quantitative treatment of all other nonradiation health and technical risks arising during the mission. Further, the major contribution to the healthy life span lost occurs during the mission. The radiation contribution to this loss stems from energetic solar particle events. The probability distribution function for a given mission scenario of acute dose levels due to such events is only poorly predictable.
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Finally, even if the levels of exposure could be predicted for a given mission scenario without uncertainty, a substantial uncertainty would remain for the prediction of associated health effects since—for both late and early effects—the uncertainties in the dose effect relations are still sizable and the extent to which these dose effect relations might be modified by other factors of the space environment such as weightlessness is essentially unknown.
For the analysis, various parameters particle type, particle energy, anomaly type were considered as a function of solar activity. Preliminary results obtained from a statistical analysis on the origin of launch crashes at Russia's space site Plesetsk reveal that in summertime, the crash frequency is 2 times larger compared with other seasons.
Energy spectra of cosmic ray nuclei and the composition of cosmic ray nuclei were shown based on data from various space missions. The heavy ion component is particularly important for space instrumentation and astronaut safety due to its high ionization density. Information about the radial variation of cosmic ray intensity in the heliosphere was given. It was also shown how studies of radioactive isotopes and nitrates preserved in polar ice deposits make it possible to extend the record of cosmic ray incidents on the Earth's surface back hundreds of years.
It is a difficult task for scientists to develop physical tools and models that can predict radiation levels in the various domains of space in order to help engineers to design suitable technologies for radiation mitigation for spacecraft and passengers. However, one of the key points discussed was that in order to avoid the obvious e.
The biological effect of a radiation dose received over the time period of a week is less dangerous than if the same dose is received instantaneously e. The ultimate goal is to minimize radiation together with all other health effects and technical hazards by optimizing orbit parameters and shielding. Just prior to this conference, NASA selected a dozen new research proposals focused on better understanding and reducing the risks that space crews of future Moon and Mars missions could face from space radiation.
Finally, one should not forget hazard assessment—learning from past failures—as forecasting, mitigation, and hazard assessment go hand in hand. Particle flux profile predictions are highly compromised when the target is on the opposite side of the Sun with respect to the Earth, a scenario that by default occurs for more than half of the mission's duration. While envisioned manned modules for future space missions to Mars are generally equipped with shielded astronaut shelters, adequate warning is necessary for these to be useful.
At the end of the discussions, it was emphasized that more exact space weather and space climate definitions need to be defined. Protecting astronauts from radiation is a key factor for future human space exploration and during the past years several meetings have been held [e. To achieve this knowledge, different scientific communities need to interact with each other.
The Heliosphere Through the Solar Activity Cycle Springer Praxis Books
This is possible through joint sessions at specific meetings. The authors of this meeting report would like to acknowledge Mark Wiedenbeck for participating in this workshop. Xenophon Moussas would like to express thanks to the University of Athens research committee. Natalia Romanova is a Ph. Xenophon Moussas is an associate professor of space physics and director of the Astrophysics Laboratory, University of Athens, Athens, Greece.
European Planetary Science Congress Space Weather: Physics and Effects, edited by V. Bothmer and I.
http://www.cantinesanpancrazio.it/components/dyhehot/335-come-spiare-telefonate.php Daglis, Springer Praxis Books, Volume 6 , Issue 1. If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account. If the address matches an existing account you will receive an email with instructions to retrieve your username. Open access. Space Weather Volume 6, Issue 1.
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