Noise Storms Research Articles

Characteristics of Type III Radio Bursts.

view Abstract Citations (56) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Characteristics of Type III Radio Bursts. Malville, J. M. Abstract Observations of the drift rate, duration, and frequency range of type III bursts between 580 and 8 Mc/s are discussed. The drift rate below 40 Mc/s is systematically lower than expected from the interferometric measurements in the 6O45-Mc/s range. A lower density gradient than that of Newkirk's streamer model is indicated. The upper frequencies of simultaneous noise storms and type III bursts are found generally to coincide. The duration of type III bursts can be related to the electron-proton collision time An observed mean duration of 5 seconds at 25 Mc/s indicates a temperature of 2.7 x 106 K. If the electron waves associated with type III bursts are excited by the double-beam instability, the small natural band width of the waves results in a time constant for Landau damping that is always negligible compared with the collision frequency. Moreover, electron scattering is apparently more important than Landau damping for establishing a minimum drift rate. The band width of the bursts should be determined primarily by the radial extent of the exciting agent and by thermal density fluctuations in the corona. Publication: The Astrophysical Journal Pub Date: July 1962 DOI: 10.1086/147371 Bibcode: 1962ApJ...136..266M full text sources ADS |

On the association between noise storms and solar flares

The association between noise storms and flares was studied for the period of the IGY. These phenomena were considered to be associated only when a noise storm, type 1 radio burst, or continuum, occurred within 15 minutes after the start of a flare. Only a small fraction of flares appear to be truly associated with noise storms; similarly, only a small percentage of noise storms can be said to really follow flares. The association improves with increasing flare importance and more especially with increasing flare brightness. Certain plage regions have higher flare noise storm association than normal.

Characteristics of Type III Bursts.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Characteristics of Type III Bursts. Malville, J. M. Abstract Observations of the drift rate, 4uration, and frequency range of type III bursts between 5~0-8 Me/sec are discussed. The drift rate below 40 Me/sec is systematically lower than expected from the interferometric measurements in the 60~5 Me/sec range. A lower density gradient than that of Newkirk's streamer model is indicated. The upper frequencies of simultaneous noise storms and type III bursts generally coincide. The two phenomena may be similar, differing primarily in the growth rate of the instabilities. The duration of type III bursts can be related to the electron-proton collision time in the corona. An observed mean duration of 5 see at 25 Me/sec indicates a temperature of 2.7 X 106 0K. It should be possible to test models of the temperature and density structure of the outer corona by observations of type III bursts at very low frequencies. On the basis of Chamberlain's hydrodynamic model of the corona (Astrophys. J. 133, 675, 1961), the duration and bandwidth of type III bursts are predicted down to a plasma frequency of 700 ke/sec. Landau damping appears to be of little significance for type III bursts. The natural bandwidth of the oscillations may be so small that the Landau damping rate is negligible compared to the collision frequency. Electron scattering may be more important than Landau damping for establishing a minimum drift rate for the bursts. Publication: The Astronomical Journal Pub Date: March 1962 DOI: 10.1086/108821 Bibcode: 1962AJ.....67Q.276M full text sources ADS |

Presence and Correlation of Fine Structure in Jovian Decametric Radiation

JUPITER'S non-thermal emission in the decameter region of the spectrum takes the form of sporadic radio noise storms having durations ranging from minutes to several hours1. Observers agree that the storms show fine structure, in part composed of bursts which typically have durations ranging from several tenths of a second to several seconds. However, there has not been agreement as to the presence of still finer structure or the intrinsic origin of any of the fine structure.

High-Energy X Rays During Solar Flares

X-radiation was measured coincidently with other cosmic radiation from solar flares observed on Oct. 12, 1960. Measurements were taken from a baloon that reached a peak altitude of 1.2 x 10/sup 5/ ft. Two events were recorded on the x-ray scintillation counter, one at 1730 UT and the other at 1747 UT. Sudden enhancements of atmospherics, sudden cosmic noise absorptions, and radio noise storms that occurred during this time period were described. (T.F.H.)

Observations of 26.3 Mc/s solar radio noise during August 1959

Decameter wavelength observations of the solar noise storm during the latter portion of August 1959 were obtained at this laboratory. These data displayed several characteristics not apparent in the observations at shorter wavelengths. First, we observed decameter wavelength emission before the meter wavelength emission was observed. Second, intense decameter wave emission ended on August 25, whereas intense meter wavelength emission persisted until September 3. Third, our observations indicate quite uniform emission. We did not observe the intense amplitude scintillations found by other observers. Our observations tend to confirm the identification of this disturbance as a type I noise storm. Even at decameter wavelengths, the emission region appeared to be of small angular diameter, and low in the corona.

Some statistics of solar radio bursts at sunspot maximum

This paper discusses the occurrence and intensity of solar radio bursts at four frequencies in the band 100 to 600 Mc/s. The observations cover 4010 hours during a 12-month period at sunspot maximum; the results refer essentially to bursts of intensity great than 10−1 mks unit and duration greater than 0.3 second; and the statistical information has been interpreted in terms of the spectral characteristics of the bursts. The experimental data were taken at Fort Davis, Texas, and the analysis shows that at 125 Mc/s burst radiation was recorded for 560 hours, of which 380 hours were of low intensity. At 200 Mc/s the burst radiation covered 350 hours, of which 240 hours were of low intensity. For these two frequencies the bursts occurred mainly in the form of noise storms (spectral type I). At 425 and 550 Mc/s the total times of the solar bursts were much less, being respectively 21 and 23 hours; for the most part, however, this radiation was of high intensity and appeared in the form of continuum radiation (spectral type IV) over a wide frequency range.

Some measurements of atmospheric noise levels at low and very low frequencies in Canada

Atmospheric noise levels at 11, 35, and 135 kc/s have been recorded at Ottawa and Churchill for a period of 1 year beginning September 1958. A statistical analysis of the noise as a function of frequency, time of day, and season of the year has shown the following: (1) The same noise storms determine the noise levels received at both locations (since the beginning of the midday maxima occurs at the same time, whereas local time differs by 1 hour, and the departures of the daily median from the monthly median varies in a regular way and is the same at both locations). (2) The noise level decreases with increase of frequency more rapidly than predicted by CCIR (especially in winter when the noise storm centers are most distant). (3) The morning decrease in noise level varies in a regular way over the year, as expected from the sunrise time, between the receiver and the location of the most active storm centers. (4) The equipment measures both rms and the average noise levels. Only at the highest frequency during the winter season is a regular daily variation obtained.

Geomagnetic disturbances and 5 kilocycles per second electromagnetic radiation

A comparison is made between variations of the geomagnetic field and bursts of 5-kc/s radio noise recorded at Camden, N. S. W., between June 1958 and October 1959. During this period 8 noise storms were recorded. All occurred during the main phase of a geomagnetic storm, beginning on the average 3 hours after the start of the main phase. Of 97 isolated noise bursts of less than 4 hours' duration, 43 were associated with positive bays in the record of the magnetic H component. No consistent delay between the noise burst and the bay was observed. Noise bursts were not in general associated with geomagnetic micropulsations of less than 1-minute period, although some correlation with quasi-sinusoidal magnetic variations with periods between 10 and 60 minutes was noted. During the period of the observations 30 magnetic sudden commencements were followed by noise bursts or storms after an average delay of 8.5 hours. On four occasions, a noise burst started immediately after a sudden commencement occurring between 1200 and 1800 hours GMT.

Observations of Radio Noise Storms on Jupiter During the 1960 Apparition.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of Radio Noise Storms on Jupiter During the 1960 Apparition. Carr, T. D. ; Smith, A. G. ; Chatterton, N. ; Six, F. Abstract The radio noise sporadically emitted by Jupiter was monitored at several frequencies between 10 and 27.6 Mc for approximately six months during the 1960 apparition. Observations were made at the University of Florida Radio Observatory and at the Maipu' Radio-astronomical Observatory of the University of Chile. Activity was found to be considerably greater than during the two previous apparitions. Activity was greatest in the vicinity of 18 Mc, and was slight at 27.6 Mc. The principal source is still centered at approximately the same System III longitude that it has occupied during the six previous years for which data are available. The polarization of the radiation at 22.2 Mc was almost always right- handed elliptical at both observatories. The fact that the same polarization sense was observed from stations above and below the geomagnetic equator apparently rules out the possibility that the polarization originates in the terrestrial ionosphere. A noise storm was usually confined to a frequency band a few megacycles wide, but the active band often drifted slowly up or down the spectrum. The spectrum of each pulse making up a storm was usually a few tenths of a megacycle wide. Simultaneous observations at 10 Mc and 20 Mc revealed that noise occurring at these harmonically related frequencies is not correlated. Striking differences in 18-Mc bursts observed simultaneously from Chile and Florida are attributed to scintillations arising in the terrestrial ionosphere. The theory that the radiation arises from the entry of solar particles into Jupiter's magnetic field is being tested by correlating the noise data obtained in Chile at Jovian opposition with the occurrence of solar flares and geomagnetic disturbances. This work is being sponsored by the National Science Foundation, the Office of Naval Research, and the U.S. Army Office of Ordnance Research. Publication: The Astronomical Journal Pub Date: 1960 DOI: 10.1086/108128 Bibcode: 1960AJ.....65R.485C full text sources ADS |

Low-Frequency Solar Bursts and Noise Storms.

view Abstract Citations (21) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Low-Frequency Solar Bursts and Noise Storms. Boischot, A. ; Lee, R. H. ; Warwick, J. W. Abstract We report observations of fast-drift, or type III, bursts in the frequency range 15-38 Mc/s Such bursts account for most of the solar emission observed in this spectral range While fast-drift bursts last only a few seconds at metric wave lengths, they may persist for half a minute or more in the decametric region and show only a relatively small variation in frequency with time A physical interpretation of the duration of the bursts suggests that they occur in a region of steep temperature gradient Their breadth in frequency indicates excitation by quasi-relativistic particles leaving the sun At intervals of several weeks we also observe steady noise sources, generally persisting for several days. The spectrum of these sources is a continuum, crossed occasionally by a few bursts and ionospheric scintillations The sources often show discontinuous variations in position from day to day On one occasion, June 3, 1959, a source moved with a velocity of the order of 850 km/s Publication: The Astrophysical Journal Pub Date: January 1960 DOI: 10.1086/146807 Bibcode: 1960ApJ...131...61B full text sources ADS |

A Uniform Statistical Analysis of Jovian Decameter Radiation, 1950

view Abstract Citations (12) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Uniform Statistical Analysis of Jovian Decameter Radiation, 1950 Douglas, James N. Abstract 1960. JAMES N. DOUGLAS, Yale University -A permanent I B M -card catalogue has been initiated of all of the known Jupiter decameter radio noise storms, kindly made available by C. Shain, B. Burke, K. Franklin, R. Gallet, J. Kraus, G. Reber, A. Smith, and T. Carr, and supplemented with four years of multichannel observations at Yale. Uniform statistical analysis of this material establishes the radio (presumably also the solid-body) rotation period of Jupiter as 9h55rn298.37 *0S.16 s.d. A provisional definition of "radio longitude" follows as =Mi$0.2742 (t-2433339.5000), with )y the radio longitude, X23 the familiar System II longitude, and tin Julian days. Within the precision of the existing data, the period has been constant over the ten years of observation from 1950 to 1960, over the frequency range from 18 to 27 Mc, and for the three principal regions of emission whose radio longitudes are 760*13, 1780*7 and 2540*15. The width of the major, 1780, peak declines with frequency as noted by other observers, being 600 at 18 Mc, 470 at 20 Mc and 400 at 22.2 Mc. It is interesting to note that the two minor peaks are separated by 1800 in longitude. While the three peaks are usually well defined, there is evidence that they may not be completely independent. The shape of the occurrencefrequency histogram correlates significantly with the solar elongation of earth as seen from Jupiter. Also in the combined data there appears to be a significant correlation with solar activity, delayed three or four days, in general agreement with Warwick's findings. This work was made possible by Research Corporation, NSF, and NASA grants. Publication: The Astronomical Journal Pub Date: 1960 DOI: 10.1086/108158 Bibcode: 1960AJ.....65S.487D full text sources ADS |

Spaced Observations of Radio Noise from the Outer Atmosphere

IT has recently been suggested1 that during some types of radio noise storms generated in the Earth's outer atmosphere the source of the noise may remain almost constant in position in Right Ascension. If this were so, it would be expected that the arrival of the storm would be recorded at almost the same local time at places of different longitude, rather than simultaneously. To test this idea and more generally to investigate the extent to which observations of the noise are correlated at different places, recordings have been made during June and July 1959, at Camden N.S.W. (Latitude 34°03′S Longitude 150°42′E) and Adelaide (Latitude 34°56′S Longitude 138°53′E). The geomagnetic latitudes are 42°S and 45°S respectively. The noise level in a frequency band 1 kc./s. wide centred at 4.5 kc./s. was recorded using conventional techniques.

Observations of the Fine Structure of Enhanced Solar Radio Radiation with a Narrow-Band Spectrum Analyser

THE different components of the solar radio emission at metre wave-lengths were classified according to their spectral properties by Wild and McCready1 in 1950. In this classification the noise storm or type 1 radiation is characterized by a relatively steady enhancement over a wide range of frequencies, usually with short-lived, narrow-band bursts superposed (storm bursts, type 1 bursts). With equipment of high resolving power these bursts may be resolved into pips, each lasting for a fraction of a second only.

Observations of low-energy solar cosmic rays from the flare of 22 August 1958

Observations were made of protons at balloon altitudes in the energy range 100 to 300 Mev following a solar sequence of optical flare, r-f noise bursts, and long enduring noise storm. Other particles are shown to have low upper limits to their abundance. The flare particles continue to be observed for at least 2 days and arguments are given to show that their storage and emission takes place in the solar atmosphere. The differential energy spectrum is derived from ionization versus atmospheric depth data and is found to be E/sup -5/ dE. Observations by riometer and VHF scatter propagation paths over the polar regions indicate that solar acceleration of protons up to roughly 100 Mev energy is rather frequent. (auth)

The instantaneous position and diameter of short duration bursts of solar radio emission

It is known that the regions responsible for solar noise storms are associated with visible sunspot groups and that the diameter of such radio sources is not less than 7 minutes of arc at a wavelength of 3.7 m. Little, however, is known of the size and location of the individual short-lived bursts (duration ~1 second). Two interferometric systems have been set up at 3.7 m to measure these quantities, and some preliminary results have been obtained:(a) The diameters of single bursts. To measure the diameters of individual bursts an interferometer of spacing 270λ was connected to three receivers. Receivers 2 and 3 gave records corresponding to total power interferometers in antiphase, while receiver 1 was arranged as a phase-switching interferometer in quadrature with the other two. From the relative sizes of an individual burst on the three records it is possible to determine the burst intensity, its angular size and position in one coordinate. Measurements carried out during a noise storm on 1958 March 21 gave an angular diameter of 6 ± 1 minutes of arc for about 25 individual bursts.(b) The location of single bursts in two dimensions. In order to determine the instantaneous position of individual bursts, two phase-switching interferometers of spacing 135λ were aligned in E-W and N-S directions. A third aerial was used with a total power receiver to measure the burst intensity. Preliminary results indicate that the positions of the individual bursts during a noise storm show a scatter of less than 3 minutes of arc.

Solar radio bright spots at 88-cm wavelength

During 1957 we studied the solar radio radiation at a wavelength intermediate between the centimeter region with its slowly varying bright spots and the meter-wavelength region with its noise storms. At this intermediate wavelength (88 cm) the slowly varying bright-spot and the noise-storm producing regions merge into two aspects of the same persistent, bright, solar radio regions.

Some characteristics of dynamic spectra of solar bursts

The sun has been observed daily at the University of Michigan during the last year with three sweep-frequency receivers covering the 100 to 580 Mc/s band three times a second. The output is displayed as an intensity-modulated line on a precision cathode-ray tube that is photographed on a 35-mm film moving about one centimeter per minute, thereby producing a frequency-time record with solar intensities recorded as variations in photographic density. The combination of the film characteristic and the logarithmic response of the IF amplifier permits the recording of a wide range of intensities in greater detail than before. A number of typical radio events associated with solar flares have been obtained; a typical sequence is a short group of intense type III bursts (fast drifts) followed within minutes by a type II burst (slow drifts) lasting 10 to 30 minutes, and followed by a type I noise storm, with or without a continuum increase, continuing for hours or days. The type I event is usually confined to frequencies below about 200 Mc/s, whereas the type III and type II (bursts) have been recorded up to 580 Mc/s.

Frequency drift and fine structure of 200-Mc/s solar bursts

In 1957 high-speed records were obtained at a frequency of 200 Mc/s during solar radio noise storms at the Solar Observatory at Harestua. For the registrations a receiver of bandwidth 0.3 Mc/s and time constant 0.01 seconds was used in connection with a Brush recorder. Most records were secured at a paper speed of 25 mm/second.

Ionizing Radiation Associated with Solar Radio Noise Storm

Beginning at 1525 U.T. on August 22, 1958, ionizing radiation appeared at an atmospheric depth of 10 g/cm/sup 2/ in time association with a great solar radio noise storm. The response of three balloon-borne detectcrs, single counter, counter telescope, and ion chamber, is shown. The rates of the ion chamber and counter telescope rose by as much as a factor of ten above the cosmicray level while the single counter increased by a much smaller factor. The relative responses of the three detectors are given, and it is deduced that these ratios are wholly consistent with protons having an energy loss no greater than 4.5 times minimum ionization as was determnined by comparing their ion chamber to single counter ratio with that for cosmic rays and using data on average specific ionization. (W.D.M.)