Ghost images of auroral X ray sources observed by directional balloon‐borne detectors

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Quantitative contributions of the ghost images associated with aurora! X-ray image formings at balloon altitudes have been investigated by a Monte Carlo simulation. Contour maps of the ratios of the ghost peak count to real images are shown as functions of the detectors' specifications, collimation angle, the zenith angle of the collimator axis and threshold energy and balloon altitude. As a result, the count ratio decreases for smaller collimation angle and zenith angle, but is occasionally beyond unity even at a conventional balloon altitude of 10 g/cm2.

Section: Discussionmentioning

confidence: 99%

“…OGURA and KODAMA (1989) first pointed out the possibility of ghost images being superposed on the real image when using a directional X-ray detector at balloon altitudes.…”

Section: Introductionmentioning

confidence: 99%

Ghost image simulation of auroral X-ray sources at balloon altitudes.

Yoneda

Kodama

1990

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“…Such spurious images vary with the collimation angle and the zenith angle of the collimation axis. Details of these interesting features are given in a separate paper (OGURA and KODAMA, 1989). image with mono-energy at depths less than 10 g/cm2 are found to be as small as 1…”

Section: Dependence Of Defocusing On Detector Specificationsmentioning

confidence: 99%

“…Although the collimation device for the balloon-born detector is effective for making the defocusing smaller, it is occasionally accompanied by a kind of spurious ghost image relevant to the defocusing, when the inclined directional telescope is used. Details of this ghost image will be reported in a separate paper (OGURA and KODAMA, 1989).…”

Section: Introductionmentioning

confidence: 99%

Defocusing characteristics of auroral X-ray images observed at balloon altitudes.

Kodama

1989

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The purpose of the present paper is to estimate defocusing characteristics of auroral X-ray images observed at balloon altitudes, on the basis of propagation properties of photons from the top to deep in the atmosphere. A Monte Carlo simulation of the X-ray propagation down to a selected atmospheric depth between 6 and 14 gf cm2 was carried out to deduce the spatial dispersion of the initial source photons with different functions of energy and incident direction. The simulation results obtained can be summarized as follows: 1) the horizontal dispersion at a depth is amplified with increasing energy and incident zenith angle of source photons; 2) a fractional contribution of the upward scattering photons amounts to about one-third of the downward moving photons;3) the omni-directional X-ray spectral type of isotropic photon; and 4) the collimated detector with a angle, to about one-third of case 3. An example demonstrates defocused images of a ring-shaped photon source, as functions of incident direction, collimation angle and atmospheric depth.

“…If the field line is connected to an observation point, some of the protons can be observed. In our actual calculation, the procedure registering the coordinate of proton is inverse by referring Ogura and Kodama (1989). That is, neutrons are emitted as a= 0, and decay into protons on the Sun-Earth line, where angle a is measured from the Sun-Earth line.…”

Section: Modelmentioning

confidence: 99%

Propagation of Solar Neutron-Decay Protons near the Earth.

Sakai

Kato

Muraki

1997

A Monte Carlo simulation of solar neutron-decay protons is performed using a simple interplanetary magnetic field (slab model) in interplanetary space. The time profile of solar neutron-decay protons obtained by our simulation is compared with observations. It is shown that the simple model can predict coherent pulses at the start of events. Magnetic field parameters used in the comparison can suggest the mean free path of protons near the Earth. The values are discussed in relation to other published results. Also, the comparisons show that it is difficult to determine the angular distribution of solar neutrons emitted at a flare site as long as the presently available solar neutron-decay protons are used.