Space weather drivers in the ACE era

Abstract

[1] We examine ACE observations of interplanetary disturbances and energetic particle activity for the period of solar maximum during solar cycle 23 and compare these measurements to the historical record as represented by the National Space Science Data Center Omnitape of near-Earth observations. Magnetospheric response parameters, Dst and Kp, are similarly compared for the two epochs. We find that ACE observed an unexpectedly large number of the strongest transient events with the strength of magnetospheric drivers exceeding the historical record for the space flight era. This is not entirely true of the magnetospheric response, which demonstrates that the magnetospheric response is an integrated effect that is more subtle than examination of single hourly averages would indicate. For these and other reasons, we argue that satellites at L1 orbit, such as ACE, provide an excellent database for the study of magnetospheric storm drivers and their associated energetic particle populations from which space weather models may be refined. We also compare and contrast energetic particle measurements. While protons are a large space weather concern, heavy ions are also a radiation hazard for hardware in particular. We argue that heavy ion radiation predictions based on the measurements of protons are not reliable and that only by measuring the actual composition of the solar energetic particle population can we hope to understand and address the threat posed by these particles to machines and to obtain a more complete view of the radiation environment.

NGC 2401: a template of the young population of the Norma–Cygnus arm in the Third Galactic Quadrant

“…The distance and age of NGC 2401 (see Section 3.3) indicate this object belongs to the innermost side young population of the probable extension of the Norma-Cygnus spiral arm in the Third Galactic Quadrant. This outer spiral structure was already suggested by Vogt (1976) using Luminous Stars and, more recently, by Kaltcheva & Hildilch (2000) studying OB stars. Star forming regions were found by Russeil (2003), though an inspection of his fig.…”

ASAS LIGHT CURVES OF INTERMEDIATE-MASS ECLIPSING BINARY STARS AND THE PARAMETERS OF HI Mon

“…Combining this angular diameter with the physical radius for the primary from Table 6, we estimate the distance to HI Mon to be 2.26 ± 0.04 kpc. By contrast, this value is not consistent with previous photometric distance estimates for HI Mon of 3.89 kpc (Eggen 1978) and 3.98 kpc (Vogt 1976).…”

“…This fit of the SED results in a limb-darkened angular diameter for the primary of θ LD = 21.5 ± 0.7 µas and a reddening of E(B − V ) = 0.35 ± 0.02 mag and a ratio of total-to-selective extinction of R = 3.2 ± 0.1. This reddening value matches reasonably well with the values in the literature of 0.30 (Eggen 1978) and 0.38 (Vogt 1976). Combining this angular diameter with the physical radius for the primary from Table 6, we estimate the distance to HI Mon to be 2.26 ± 0.04 kpc.…”

“…We can also estimate the distance to the system by fitting a spectral energy distribution (SED) to photometric measurements from the literature (since our spectra were not flux calibrated). We used measurements from Vogt (1976) for U, B, and V values, noting that the V -band measurement of maximum light from the ASAS light curve is consistent with these measures, meaning they were likely not taken during eclipse. In addition, we used 2MASS (Skrutskie et al 2006) measurements to constrain the near-IR part of the SED.…”

“…This system's variability was first noted in Wachmann (1968). The system was classified as an "OB" type system in Vogt (1976) and has been listed as an early B-type system since Eggen (1978), although no spectra for the system have been published. Spectroscopic investigations of such binaries with hot components are a critical part of any parametric analysis since the photometric colors are similar for all hot stars and are influenced by interstellar reddening.…”