Study of Auroral VLF Hiss Observed at Syowa Station, Antarctica

Observations of polarization, incident angle and arriving direction of auroral hiss were carried out at Syowa Station during the period of 1967 to 1970. The present paper consists of two parts. In Part I, we describe the equipment used for the measurement of polarization, incident and azimuthal angles and show the obtained results. The direction finding (DE) system used is based on the analysis of Lissajous\u27 figures of electric and magnetic fields displayed on cathode ray tubes. The individual polarization of the received signal is also measured. Moreover, auroral hiss is decomposed into right-and left-handed polarized components, and these two components are continuously recorded. From the discussion of the observed results, it is found that auroral hiss has propagated downward in the azimuthal direction from a not so broad range around the magnetic meridian plane and its incident angle is also not so large. Additionally, in most cases, auroral hiss is known to consist of wave components downcoming from multiple directions in the azimuthal and incident planes. The DF system used was found to be effective in a few cases of isolated and sharp auroral hiss. However, this system should be re-examined because it is, strictly speaking, useful only for monochromatic waves, while the auroral hiss seems to have a noise-like nature. Therefore, a new DF system applying the correlation method is being planned to study, with more accuracy, the azimuthal and incident angles of noisy signals such as auroral hiss. The polarization of auroral hiss received on the ground seems to be almost right-handed circular, at VLF and LF, which is theoretically confirmed by the full wave calculation of the polarization using the realistic model of the auroral ionosphere. On the other hand, the observed polarization of ELF hiss is slightly right-handed circular, which can be reasonably accepted, taking into consideration the result of the full, wave calculation. In Part II, the morphological characteristics of auroral hiss are discussed in comparison with those of low-latitude hiss using the VLF data observed at Syowa Station and at Moshiri in Japan. Auroral hiss, considered to be a manifestation of polar substorms, is a local phenomenon and its frequency extends from a few kHz to more than 100 kHz. Low-latitude hiss, however, is closely correlated with worldwide geomagnetic storms and it is a narrow band VLF phenomenon. Together with other differences between them, it is concluded that auroral hiss is completely different from low-latitude hiss. Although the morphological features of auroral hiss have been well known, a complete understanding of its generation mechanism has not yet been obtained. There are unsolved problems such as about two orders shortening of the calculated intensity below the observations and the existence of the threshold low-energy electron flux below which VLF hiss is not observed. These facts may suggest that a coherent plasma instability mechanism is partially involved in the generation of auroral hiss. Therefore, the investigation of the coherency of auroral hiss being planned by us may give a better understanding of the generation processes of auroral hiss

Ten years\u27 progress of Syowa Station, Antarctica, as a global geodesy network site

Progress of geodesy programs at Syowa Station since our former review in 1933 is summarized.As for Very Long Baseline Interferometry (VLBI),Global Positioning System (GPS),and Doppler Orbitography Radiopositioning Integrated by Satellites(DORIS),Syowa Station isa participating station in an international network and hasobtained an International Earth Rotation Service (IERS)dome number.Time series of about /years show change of position by plate motion. Detection of vertical motion by glacial isostatic adjustment is still under investigation. More than 20000 synthetic aperture radar (SAR) scenes have been received from the European Remote Sensing satellite-1 and -2 (ERS-1/-2) and the Japan Earth Resources satellite-1 (JERS-1) by the Syowa 11-m multipurpose antenna. Several case studies by interferometric SAR analyses have shown characteristic features of the ice grounding zones,ice dynamics and Digital Elevation Model (DEM)estimates.As for absolute gravimeter (AG) measurements, Syowa Station is registered as the International Absolute Gravity Basestation Network (IAGBN)0417 point. Observa tionswith an FG5 gravimeter were made for two summer seasons 5 years apart, and they showed consistent results within 2μGal difference. The superconducting gravimeter (SG) observations with a TT70 (#016 ) produced many scientific results in the two streamlines of tidal bands and normal mode bands.Especially, the first evidence of incessant excitation of the Earth \u27s free oscillations (background free oscillations)is noted as an important contribution from the Syowa SG observations.The Gravity Recovery And Climate Experiment (GRACE) satellite will bring an important advance for the study of ice-water-air mass circulation and its interaction with the solid-earth.The local potential fields calibrated by connecting to the station observatory data should give appropriate ground-truth information for the regional-scale satellite data,which reflects the continuing important role of Syow

Japanese MAGSAT team

Construction of a model of the regional magnetic field and investigation of the local magnetic anomalies and their origin were approaches used in attempts to study the crustal structure near Japan and its Antarctic bases. Spatial properties of the regional magnetic field and comparison of the regional model with that derived from MAGSAT data are discussed. Possible causes of the magnetic anomalies, and results of aeromagnetic surveys incorporating gravity and seismic data are explored. Ionospheric and magnetospheric contributions to geomagnetic variations, field-aligned currents, magnetic geomagnetic pulsations, and hydromagnetic waves by analysis of MAGSAT data are also examined

Handbook for MAP, volume 32. Part 1: MAP summary. Part 2: MAPSC minutes, reading, August 1989. MAP summaries from nations. Part 3: MAP data catalogue

Extended abstracts from the fourth workshop on the technical and scientific aspects of mesosphere stratosphere troposphere (MST) radar are presented. Individual sessions addressed the following topics: meteorological applications of MST and ST radars, networks, and campaigns; the dynamics of the equatorial middle atmosphere; interpretation of radar returns from clear air; techniques for studying gravity waves and turbulence, intercomparison and calibration of wind and wave measurements at various frequencies; progress in existing and planned MST and ST radars; hardware design for MST and ST radars and boundary layer/lower troposphere profilers; signal processing; and data management

Ground-based detection of sprites and their parent lightning flashes over Africa during the 2006 AMMA campaign

Sprites have been detected in video camera observations from Niger over mesoscale convective systems in Nigeria during the 2006 AMMA (African Monsoon Multidisciplinary Analysis) campaign. The parent lightning flashes have been detected by multiple Extremely Low Frequency (ELF) receiving stations worldwide. The recorded charge moments of the parent lightning flashes are often in excellent agreement between different receiving sites, and are furthermore consistent with conventional dielectric breakdown in the mesosphere as the origin of the sprites. Analysis of the polarization of the horizontal magnetic field at the distant receivers provides evidence that the departure from linear magnetic polarization at ELF is caused primarily by the day–night asymmetry of the Earth–ionosphere cavity. Copyright © 2009 Royal Meteorological SocietyPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69175/1/489_ftp.pd

国立極地研究所 要覧 2019-2020

国立極地研究