Observations of cosmic radio noise at 18 Mc/s in Hawaii

Abstract

Cosmic‐radio‐noise measurements at 18 Mc/s made in Hawaii during the period of November 1958 to December 1959 are reported. Diurnal attenuation curves are presented for the summer, winter, and equinoctial months that show a very pronounced resemblance to the F‐region critical frequency curves. It is shown that an important part of the total attenuation can be accounted for by an ionospheric window effect. The remaining attenuation is attributed to deviative absorption in the F region and nondeviative absorption in the D region. A nighttime component of attenuation is observed and it is suggested that this phenomenon is related to the cooling of the ionosphere. Finally, it is observed that on numerous occasions when the F‐region critical frequency exceeds the operating frequency, considerable flux continues to arrive at the antenna. It is suggested that this can be accounted for in terms of cosmic radio radiation trapped and propagated underneath the ionosphere. It is also possible that thermal radiation from the ionosphere plays a secondary role in this phenomenon.

A discussion about some aspects of the solar-terrestrial systems coupling with regard to space weather effects

“…), São Martinho da SerraBrazil. Its operation is based on determining the Quiet Day Curve (QDC), which methodology has been discussed extensively for several authors (Mitra and Shain, 1953;Lusignan, 1960;Fredriksen and Dyce, 1960;Steiger and Warwick, 1961;Heisler and Hower, 1967;Armstrong et al, 1977;Krishnaswamy et al, 1985;Tanaka et al, 2007).…”

A comparison of two different techniques for deriving the quiet day curve from SARINET riometer data

“…In the early studies, the techniques were to scale the daily charts for a sufficient period of time, transfer these values to the proper sidereal time (ST) and compare all values for a giving sidereal hour. The highest reliable values for each hour become point on the QDC (Mitra and Shain, 1953;Lusignan, 1960;Steiger and Warmick, 1961;Fredriksen and Dyce, 1967). These methodologies assume that the highest values correspond to a condition of zero absorption.…”

“…The methodology of determining the QDC has been discussed extensively by several authors (Mitra and Shain, 1953;Lusignan, 1960;Steiger and Warmick, 1961;Fredriksen and Dyce, 1967;Heisler and Hower, 1967;Armstrong et al, 1977;Krishnaswamy et al, 1985;Tanaka et al, 2007). Despite the many works on the subject since the 1960s, a reliable methodology to derive the QDC from riometer data is still a puzzling task.…”

Extension of cosmic noise absorption measurements to lower frequencies, using polarized antennas

“…Cosmic-noise observations on broad beam antennas are subject to deviative effects which become noticeable wb en the critical frequency is such that the ionosphere b egins to limit the area of sky viewed by the antenna (e.g., see Steiger and Warwick [1961]). In order to lninimize this effect, the antennas used for the present experiment were specifically designed to have low sensitivity at high zenith angles.…”