INFERENCES FROM RADIO SIGNALS FROM THE SUN AND PLANETS

1957 ◽  
Vol 43 (1) ◽  
pp. 2-8 ◽  
Author(s):  
J. Firor
Keyword(s):  
The Sun ◽  
2002 ◽  
Vol 48 ◽  
pp. 167-178 ◽  
Author(s):  
Antony Hewish

Bearing in mind the dramatic impact of radioastronomy upon our knowledge of the Universe during the years after World War II, it is remarkable that the seminal discovery of radio emission from our galaxy by Karl Jansky in the USA in 1931 attracted so little attention from the astronomical community at that time. It was, in fact, the radio amateur Grote Reber, of Wheaton, Illinois, and not the professionals, who first followed up Jansky's discovery. Designing his own radio telescopes, the first of which were unsuitable because the wavelengths were too short, Reber persevered until, in 1941, he successfully performed surveys of the distribution of radio noise intensity across the sky that indicated a strong concentration towards the galactic centre. In this country the key figure was J.S. Hey, who was engaged in wartime operational research concerned with anti-aircraft radar when, in February 1942, radar stations along the south coast of England were seriously affected by radio interference of unknown origin. From the direction of the interfering signals Hey concluded that the Sun must be responsible, so he contacted the Royal Greenwich Observatory and was informed that a large sunspot group was near the centre of the solar disc. He correctly deduced that some kind of disturbance in the solar atmosphere must have generated the radio signals, but this remained a wartime secret until the cessation of hostilities. Returning to his discovery in 1946, when the Sun was again active, Hey and his team made more detailed observations and showed that the intense bursts of radiation were often associated with solar flares. In the same year, while following up the work of Jansky and Reber, Hey noticed that radiation from the direction of the constellation Cygnus often showed fluctuations of intensity on a time-scale of a few seconds. With his experience of solar radiation, Hey deduced that a discrete source must have been responsible and more were soon located by other groups. Initially called radio stars, but later found to be supernova remnants, normal galaxies and new types of galaxy located near, or beyond, the limits of optical telescopes, Hey's discovery initiated an era of research that transformed observational astronomy. Such was the pace and excitement of this period that the significance of Hey's pioneering contributions tended to be overlooked. He was not proposed for Fellowship of The Royal Society until 1978, and he was elected in the same year.


2019 ◽  
Author(s):  
Dyah Rahayu Martiningrum

About 40 km altitude, VLF radio waves are partially reflected and partially absorbed by the D-layer of the ionosphere. By measuring the amplitude of radio signals after they have reflected from the ionosphere, it is possible to detect kinds of ionospheric and space activity taking place. Recently, Division Ionosphere and Telecommunication, Space Science Center, National Institute of Aeronautics and Space (LAPAN) have installed VLF receiver to investigate effects of solar flare to ionosphere, mainly Sudden Ionospheric Disturbances (SIDs). By monitoring transmission from Earth-based beacons which are affected by variabilities in the ionosphere, giving an indirect indication of events on the Sun. The VLF receiver output is a voltage varying with time, which may be fed to any data logger or digital multimeter. In this paper, we discuss about system of UKRAA (United Kingdom Radio Astronomy Association) VLF receiver, our research plan related to this instrument, and preliminary result of installation of VLF receiver


1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.


1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.


1997 ◽  
Vol 161 ◽  
pp. 761-776 ◽  
Author(s):  
Claudio Maccone

AbstractSETI from space is currently envisaged in three ways: i) by large space antennas orbiting the Earth that could be used for both VLBI and SETI (VSOP and RadioAstron missions), ii) by a radiotelescope inside the Saha far side Moon crater and an Earth-link antenna on the Mare Smythii near side plain. Such SETIMOON mission would require no astronaut work since a Tether, deployed in Moon orbit until the two antennas landed softly, would also be the cable connecting them. Alternatively, a data relay satellite orbiting the Earth-Moon Lagrangian pointL2would avoid the Earthlink antenna, iii) by a large space antenna put at the foci of the Sun gravitational lens: 1) for electromagnetic waves, the minimal focal distance is 550 Astronomical Units (AU) or 14 times beyond Pluto. One could use the huge radio magnifications of sources aligned to the Sun and spacecraft; 2) for gravitational waves and neutrinos, the focus lies between 22.45 and 29.59 AU (Uranus and Neptune orbits), with a flight time of less than 30 years. Two new space missions, of SETI interest if ET’s use neutrinos for communications, are proposed.


1997 ◽  
Vol 161 ◽  
pp. 707-709 ◽  
Author(s):  
Jun Jugaku ◽  
Shiro Nishimura

AbstractWe continued our search for partial (incomplete) Dyson spheres associated with 50 solar-type stars (spectral classes F, G, and K) within 25 pc of the Sun. No candidate objects were found.


2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.


2000 ◽  
Vol 179 ◽  
pp. 193-196
Author(s):  
V. I. Makarov ◽  
A. G. Tlatov

AbstractA possible scenario of polar magnetic field reversal of the Sun during the Maunder Minimum (1645–1715) is discussed using data of magnetic field reversals of the Sun for 1880–1991 and the14Ccontent variations in the bi-annual rings of the pine-trees in 1600–1730 yrs.


Sign in / Sign up

Export Citation Format

Share Document