Aircraft Radiation Research Articles

The limitations of using vertical cutoff rigidities determined from the IGRF magnetic field models for computing aircraft radiation dose

Vertical cutoff rigidities derived from the International Geomagnetic Reference Fields (IGRF) are normally used to compute the radiation dose at a specific location and to organize the radiation dose measurements acquired at aircraft altitudes. This paper presents some of the usually ignored limits on the accuracy of the vertical cutoff rigidity models and describes some of the computational artifacts present in these models. It is noted that recent aircraft surveys of the radiation dose experienced along specific flight paths is sufficiently precise that the secular variation of the geomagnetic field is observable.

Monte Carlo calculations of the influence on aircraft radiation environments of structures and solar particle events

Radiation transport codes are applied to calculate the influence of aircraft structure and loads on the internal environment from galactic cosmic rays. Significant shielding effects are predicted, while thermalization of the neutron flux can lead to enhanced single-event upset rates in devices containing boron. The enhanced environments due to large solar particle events are calculated and shown to be very important for both single-event effects in electronics and dose to crew and passengers.

No evidence for solar absorption anomaly by marine water clouds through collocated aircraft radiation measurements

No observational evidence was found for the so‐called anomalous solar absorption by maritime water clouds through collocated aircraft measurements taken during the Japanese Cloud‐Climate Study (JACCS) program. The aircraft experiment has been carried out by using two aircraft equipped with various instruments for wintertime stratocumulus clouds over an area centered at (29°N, 129°E) in the East China Sea. Here we have carefully analyzed solar absorption by the water stratocumulus clouds observed on February 2, 1998. The visible‐band net fluxes measured above and below the cloud layer were almost the same within measurement accuracy; this means no substantial absorption in the visible spectral region. On the other hand, there were significant differences as much as 50–80 W m−2 between the near‐infrared‐band net fluxes measured above and below the cloud layer; this difference corresponds to absorptance of 6–10% of the total‐band solar irradiance above the cloud layer. Without cloud particles, water vapor absorption was estimated to be about 4% of the total‐band irradiance for the layer. Distributions along the flight legs of the measured visible‐band and near‐infrared‐band absorptance were in phase in their positions with zero mean visible‐band absorptance. The measured radiation budget averaged over long distances along the flight legs for the inhomogeneous cloud layers agreed well with theoretical counterparts calculated for plane‐parallel, homogeneous cloud models based on the observed microphysical parameters.