scholarly journals Observing the magnetosphere through global auroral imaging: 2. Observing techniques

2016 ◽  
Vol 121 (10) ◽  
Author(s):  
Stephen B. Mende
Keyword(s):  
Auroral Imaging ◽  
Observing Techniques

scholarly journals High time resolution PFISR and optical observations of naturally enhanced ion acoustic lines

2009 ◽  
Vol 27 (4) ◽  
pp. 1457-1467 ◽  
Author(s):  
R. G. Michell ◽  
K. A. Lynch ◽  
C. J. Heinselman ◽  
H. C. Stenbaek-Nielsen
Keyword(s):  
High Resolution ◽  
Time Resolution ◽  
Acoustic Waves ◽  
Fast Moving ◽  
High Time ◽  
High Time Resolution ◽  
Ion Acoustic Waves ◽  
Raw Data ◽  
Ion Acoustic ◽  
Auroral Imaging

Abstract. Observations of naturally enhanced ion acoustic lines (NEIALs) taken with the Poker Flat Incoherent Scatter Radar (PFISR) using a mode with very high time resolution are presented. The auroral event took place over Poker Flat, Alaska on 8 February 2007 at 09:35 UT (~22:00 MLT), and the radar data are complemented by common-volume high-resolution auroral imaging. The NEIALs occurred during only one of the standard 15-s integration periods. The raw data of this time show very intermittent NEIALs which occur only during a few very short time intervals (≤1 s) within the 15-s period. The time sampling of the raw data, ~19 ms on average, allows study of the time development of the NEIALs, though there are indications that even finer time resolution would be of interest. The analysis is based on the assumption that the NEIAL returns are the result of Bragg scattering from ion-acoustic waves that have been enhanced significantly above thermal levels. The spectra of the raw data indicate that although the up- and down-shifted shoulders can both become enhanced at the same time, (within 19 ms), they are most often enhanced individually. The overall power in the up-and down-shifted shoulders is approximately equal throughout the event, with the exception of one time, when very large up-shifted power was observed with no corresponding down-shifted power. This indicates that during the 480 μs pulse, the strongly enhanced ion-acoustic waves were only traveling downward and not upward. The exact time that the NEIALs occurred was when the radar beam was on the boundary of a fast-moving (~10 km/s), bright auroral structure, as seen in the high resolution auroral imaging of the magnetic zenith. When viewed with high time resolution, the occurrence of NEIALs is associated with rapid changes in auroral luminosity within the radar field of view due to fast-moving auroral fine structures.

scholarly journals Observing techniques for astronomical laser guide star adaptive optics

1998 ◽  
Author(s):  
Claire E. Max ◽  
Bruce A. Macintosh ◽  
Scot S. Olivier ◽  
Donald T. Gavel ◽  
Herbert W. Friedman
Keyword(s):  
Adaptive Optics ◽  
Laser Guide Star ◽  
Guide Star ◽  
Laser Guide ◽  
Observing Techniques

Application of Visible Monochromatic Auroral Imaging Data for Modeling Infrared Earth-Limb Morphology.

1981 ◽  
Author(s):  
J. B. Kumer ◽  
R. D. Sears ◽  
J. E. Evans ◽  
S. E. Harris ◽  
R. M. Nadile
Keyword(s):  
Imaging Data ◽  
Auroral Imaging ◽  
Limb Morphology

scholarly journals The eclipses of the black widow pulsar J1810+1744 at low radio frequencies

2017 ◽  
Vol 13 (S337) ◽  
pp. 396-397
Author(s):  
Elliott J. Polzin ◽  
Rene P. Breton ◽  
Ben W. Stappers ◽  
Keyword(s):  
Orbital Period ◽  
Line Of Sight ◽  
Dispersion Measure ◽  
Interferometric Imaging ◽  
Black Widow ◽  
Low Frequencies ◽  
Small Deviations ◽  
Imaging Mode ◽  
High Band ◽  
Observing Techniques

AbstractHere we present a study of the radio frequency eclipses of the black widow pulsar J1810+1744 at low frequencies, where we are most sensitive to small deviations in the effects of material along the line of sight. Utilising the simultaneous dual beamforming and interferometric (imaging) mode of LOFAR High Band Antenna, pulsar flux variations throughout the orbit are compared for the two observing techniques to test for the presence of scattering and absorption at eclipse orbital phases. Dispersion measure and scattering variations are used as a sensitive probe into outermost edges of the eclipsing material surrounding the companion star. We find the eclipsing medium to be variable on timescales shorter than the 3.6 hr orbital period, and propose cyclotron-synchrotron absorption as the most likely primary eclipse mechanism.

scholarly journals Dispersion of Interstellar Polarization

1965 ◽  
Vol 7 ◽  
pp. 57-64
Author(s):  
Thomas Gehrels
Keyword(s):  
Data Processing ◽  
High Altitude ◽  
Wavelength Range ◽  
Wavelength Dependence ◽  
Probable Error ◽  
Percentage Polarization ◽  
University Of Arizona ◽  
The University ◽  
Observing Techniques

The Wavelength Dependence of Polarization as observed in 32 stars, for which the Henry Draper numbers are given, is shown in figure 1. Details of some of these observations are presented in reference 1.The equipment is now being used with the new 154-cm Catalina reflector of the Lunar and Planetary Laboratory at the University of Arizona. The instrumental polarizations are nearly zero. The data processing and observing techniques have been further improved; the precision is mainly determined by statistics such that the internal probable error in the percentage polarization is ±0.03 percent (±0.0006 magnitude) for a half-hour observation per filter on objects brighter than about 7 magnitudes. The wavelength λ ranges from 0.33 to 0.95 μ covered by seven filters of bandwidth of about 0.05 μ. The wavelength range is being extended to 1.2, 1.6, and 2.2 μ and, with high-altitude ballooning, to 0.28 and 0.22 μ.

scholarly journals Focal Reducer Techniques for Direct Imaging and Field Spectroscopy with Large Telescopes

1984 ◽  
Vol 79 ◽  
pp. 575-583 ◽  
Author(s):  
Edward H. Geyer ◽  
Bruno Nelles
Keyword(s):  
Radial Velocity ◽  
Direct Imaging ◽  
Field Spectroscopy ◽  
Large Telescopes ◽  
Observing Techniques

AbstractTo exploit the full effectiveness of large ground based telescopes, the focal reducer technique can be applied very adequately. We review recent Hoher List observatory developments of observing techniques for direct imaging, field spectroscopy with multi-slit and masking methods for background supression and double-grism arrangements (heliometer principle)for absolute radial velocity determinations with a focal reducer field spectrograph.

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