Segmentation of extreme ultraviolet solar images via multichannel fuzzy clustering

The study of the variability of the solar corona and the monitoring of its traditional regions (Coronal Holes, Quiet Sun and Active Regions) are of great importance in astrophysics as well as in view of the Space Weather and Space Climate applications. Here we propose a multichannel unsupervised spatially constrained fuzzy clustering algorithm that automatically segments EUV solar images into Coronal Holes, Quiet Sun and Active Regions. Fuzzy logic allows to manage the various noises present in the images and the imprecision in the definition of the above regions. The process is fast and automatic. It is applied to SoHO–EIT images taken from February 1997 till May 2005, i.e. along almost a full solar cycle. Results in terms of areas and intensity estimations are consistent with previous knowledge. The method reveal the rotational and other mid-term periodicities in the extracted time series across solar cycle 23. Further, such an approach paves the way to bridging observations between spatially resolved data from imaging telescopes and time series from radiometers. Time series resulting form the segmentation of EUV coronal images can indeed provide an essential component in the process of reconstructing the solar spectrum.     

高超声速锥体表面凸起物分离干扰区气动力/热关联计算方法

针对高超声速锥体表面凸起物周围的分离干扰流动产生的气动力/热提供了关联计算方法,包括凸起物周围分离干扰区压力分布计算方法、分离干扰区几何特征的计算方法、分离干扰区附加气动力计算方法、分离干扰区气动热计算方法.对典型的钝锥加凸起物外形进行了计算,计算分析了由于凸起物周围分离干扰区压力升高引起的附加气动力、凸起物表面及干扰区的气动热,对气动热计算结果与激波风洞实验结果进行了比较,本文关联方法计算结果与实验结果符合较好.     

Early history of cosmic rays and solar wind – Some personal remembrances

The early history of solar wind was replete with prejudices and strong opposition to Parker’s formulation. It was only after conclusive evidence from satellite data was obtained that the idea of solar wind was accepted. Some personal experiences of mine during my stay at the University of Chicago in 1953–1954, including the encounter of Dr. Simpson with Dr. Biermann and the inconclusive discussion between them about a possible perpetual solar outflow of particles are presented and further developments when Parker came to Chicago in 1956 and formulated his idea of solar wind, as narrated to me later by Dr. Simpson, are described.     

Human and robotic repair of a solar array wing during ISS assembly mission 10A

With the installation of a new module and the relocation of three other modules, including multiple hand-offs from the station arm (SSRMS) to the shuttle arm (SRMS), International Space Station (ISS) assembly mission 10A/STS-120 was anticipated to be one of the most complicated ISS assembly missions ever attempted. The assembly operations became even more complex when a solar array wing (SAW) on the relocated Port-6 (P6) truss segment ripped while being extended. Repairing the torn SAW became the single most important objective for the remainder of STS-120, with future ISS assembly missions threatened by reduced power generation capacity if the SAW could not be repaired. Precise coordination between the space shuttle and ISS robotics teams led to an operational concept that combined the capabilities of the SRMS and SSRMS robotic systems in ways far beyond their original design capacities. Benefits of consistent standards for ISS robotic interfaces have been previously identified, but the advantages of having two such versatile and compatible robotic systems have never been quite so spectacular. This paper describes the role of robotics in the emergency SAW repair and highlights how versatility within space robotics systems can allow operations far beyond the intended design scenarios.     

Interplanetary medium – A dusty plasma

The average mass of dust per volume in space equals that of the solar wind so that the interplanetary medium should provide an obvious region to study dust plasma interactions. While dust collective behavior is typically not observed in the interplanetary medium, the dust component rather consists of isolated grains screened by and interacting with the plasma. Space measurements have revealed several phenomena possibly resulting from dust plasma interactions, but most of the dust plasma interactions are at present not quantified. Examples are the production of neutrals and pick-up ions from the dust, dust impact generated field variations at spacecraft and magnetic field variations possibly caused by solar wind interacting with dust trails. Since dust particles carry a surface charge, they are exposed to the Lorentz force in the interplanetary magnetic field and for grains of sub-micrometer sizes acceleration can be substantial.     

Relative fluxes of shock and prompt peaks in SEP event time profiles

Peak fluxes are an important property of gradual solar energetic particle (SEP) event time profiles from both astro/heliophysical and applications perspectives. However, the peak flux in an event may occur at the event onset, or at the time of the interplanetary shock arrival (the ESP or energetic storm particles). This makes an important difference in the interpretation of the peak flux, and in any attempts to characterize or model it. This paper describes a study of SEP data sets from ACE, IMP-8 and GOES toward determining the relative properties of these peak fluxes for protons with energies near 1, 10, and 50 MeV. The results suggest that for gradual events with both peaks, the ESP peak often dominates at 1 MeV energies and is dominant about half the time at 10 MeV. Moreover, the prompt peak fluxes can be used to estimate the shock peak (ESP event) up to days ahead, especially in the lower energy range.     

Properties of solar X-ray flares and proton event forecasting

X-ray flares and acceleration processes are in one complex of sporadic solar events (together with CMEs, radio bursts, magnetic field dissipation and reconnection). This supposes the connection (if not physical, but at least statistical) between characteristics of the solar energetic proton events and flares. The statistical analysis indicates that probability and magnitude of the near-Earth proton enhancement depends heavily on the flare importance and their heliolongitude. These relations may be used for elaboration of the forecasting models, which allow us to calculate probability of the solar proton events from the X-ray observations.     

Effect of “Noisy” sun conditions on aircrew radiation exposure

In computer codes used to estimate the aircrew radiation exposure from galactic cosmic radiation, a quiet sun model is usually assumed. A revised computer code (PCAIRE ver. 8.0f) is used to calculate the impact of noisy sun conditions on aircrew radiation exposure. The revised code incorporates the effect of solar storm activity, which can perturb the geomagnetic field lines, altering cutoff rigidities and hence the shielding capability of the Earth’s magnetic field. The effect of typical solar storm conditions on aircrew radiation exposure is shown to be minimal justifying the usual assumptions.     

Sensitivity studies of the deployment of a square inflatable solar sail with vanes

This paper summarizes the results of numerical experiments to determine the sensitivity of the final attitude of an inflatable solar sail with vanes after deployment to various parameters affecting the deployment process. These parameters are: in- and out-of-plane asymmetries during deployment, length inflation profile, and vane deployment failures. We show how robust the sail deployment is to geometric asymmetries before a 35° off-Sun angle is reached. Differential delays in the time to inflate the booms and a boom sweep-back angle affect the stability favorably. Adjacent vane failures to deploy affect the stability unfavorably, while the failure of opposing vanes is acceptable. Realistic boom length rate profiles obtained during ground tests are used in the simulation showing that failing adjacent vanes in conjunction with initial inflation delays in adjacent booms represent the worst case. We also demonstrate that by feeding back attitude and attitude rate measurements so that a corrective action is taken during the deployment, the final attitude can be maintained very close to the initial attitude, thus mitigating the attitude changes incurred during deployment.     

Study of the 27-day variations of the galactic cosmic ray intensity and anisotropy

We demonstrate that the general features of the radial and azimuthal components of the anisotropy of galactic cosmic rays can be studied by the harmonic analysis method using data from an individual neutron monitor with cut off rigidity <5 GV. In particular, we study the characteristics of the 27-day (solar rotation period) variations of the galactic cosmic ray intensity and anisotropy, solar wind velocity, interplanetary magnetic field strength and sunspot number. The amplitudes of the 27-day variations of the galactic cosmic ray anisotropy are greater, and the phases more clearly established, in A > 0 polarity periods than in A < 0 polarity periods at times of minimum solar activity. The phases of the 27-day variations of the galactic cosmic rays intensity and anisotropy are opposite with respect to the similar changes of the solar wind velocity in A > 0 polarity periods. No significant dependence of the amplitude of the 27-day variation of the galactic cosmic ray anisotropy on the tilt angle of the heliospheric neutral sheet is found. Daily epicyclegrams obtained by Chree’s method show that the 27-day variations of the galactic cosmic ray anisotropy during A > 0 polarity periods follow elliptical paths with the major axes oriented approximately along the interplanetary magnetic field. The paths are more irregular during A < 0 polarity periods.