scholarly journals Some results on solar activity at 408 MHz

1968 ◽  
Vol 35 ◽  
pp. 556-564 ◽  
Author(s):  
B. Clavelier
Keyword(s):  
Solar Activity ◽  
Active Regions ◽  
Optical Observations ◽  
Noise Storm ◽  
First Results ◽  
Active Zones

We present the first results obtained with the 408 MHz interferometer of Nançay. The typical activity observed at 408 MHz is the ‘noise storm’. Undoubtedly with this apparatus we could distinguish multiple centres, generally double.The comparison with corresponding optical observations and with Nançay observations at frequency 169 MHz allowed us to associate the centres of noise storm at 408 MHz with eruptive centres lying in ‘Anomalous Active Regions’ and to describe the schematical structure of active zones.

Influence of Magnetic Fields on Solar Hydrodynamics: Experimental Results

1977 ◽  
Vol 36 ◽  
pp. 143-180 ◽  
Author(s):  
J.O. Stenflo
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
General Problem ◽  
Solar Rotation ◽  
Active Regions ◽  
Physical Conditions ◽  
Dynamic Phenomena

It is well-known that solar activity is basically caused by the Interaction of magnetic fields with convection and solar rotation, resulting in a great variety of dynamic phenomena, like flares, surges, sunspots, prominences, etc. Many conferences have been devoted to solar activity, including the role of magnetic fields. Similar attention has not been paid to the role of magnetic fields for the overall dynamics and energy balance of the solar atmosphere, related to the general problem of chromospheric and coronal heating. To penetrate this problem we have to focus our attention more on the physical conditions in the ‘quiet’ regions than on the conspicuous phenomena in active regions.

Numerical Short-Term Solar Activity Forecasting

2017 ◽  
Vol 13 (S335) ◽  
pp. 243-249 ◽  
Author(s):  
Huaning Wang ◽  
Yihua Yan ◽  
Han He ◽  
Xin Huang ◽  
Xinghua Dai ◽  
...  
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Active Regions ◽  
Short Term ◽  
Solar Active Regions ◽  
Solar Eruptions ◽  
Dimensional Reconstruction

AbstractIt is well known that the energy for solar eruptions comes from magnetic fields in solar active regions. Magnetic energy storage and dissipation are regarded as important physical processes in the solar corona. With incomplete theoretical modeling for eruptions in the solar atmosphere, activity forecasting is mainly supported with statistical models. Solar observations with high temporal and spatial resolution continuously from space well describe the evolution of activities in the solar atmosphere, and combined with three dimensional reconstruction of solar magnetic fields, makes numerical short-term (within hours to days) solar activity forecasting possible. In the current report, we propose the erupting frequency and main attack direction of solar eruptions as new forecasts and present the prospects for numerical short-term solar activity forecasting based on the magnetic topological framework in solar active regions.

Prediction of upcoming grand episodes of solar activity

2018 ◽  
Vol 13 (S340) ◽  
pp. 325-326
Author(s):  
G. L. Jayalekshmi ◽  
P. R. Prince
Keyword(s):  
Solar Activity ◽  
Active Regions ◽  
Phase Changes ◽  
Activity Level ◽  
Time Interval ◽  
The Sun ◽  
Strong Magnetic Fields ◽  
Periodicity Analysis ◽  
Long Time ◽  
Grand Minima

AbstractSunspots are active regions on the surface of the Sun having strong magnetic fields. Activity level of the Sun shows long-time scale phenomena known as grand episodes-Grand maxima and Grand minima. Present study examines grand episodes shown by sunspot numbers (1090-2017), using methods of wavelet transform and sinusoidal regression. Time interval analysed includes two grand maxima and four grand minima. Interval in between grand episodes are regular oscillations. Phase changes found from periodicity analysis clearly show the presence of upcoming grand episodes. The forthcoming grand episodes are suggested to be two grand minima which are likely to occur between the years 2100-2160 and 2220-2300.

scholarly journals RX J1015.5+0904: A New Polar at the Lower Period Limit

1996 ◽  
Vol 158 ◽  
pp. 229-230
Author(s):  
V. Burwitz ◽  
K. Reinsch ◽  
A. D. Schwope ◽  
K. Beuermann ◽  
S. Mengel ◽  
...  
Keyword(s):  
Orbital Period ◽  
Optical Observations ◽  
Optical Data ◽  
X Ray ◽  
First Results ◽  
Period Limit ◽  
Lower Period

AbstractWe present X-ray and optical observations of the ROSAT discovered polar (AM Her binary) RX J1015.5+0904 and first results of our analysis of the X-ray and optical data. These results indicate a one-pole accretion geometry and an orbital period of P = 79.88 m for this V ~ 17 mag system.

scholarly journals 50 MHz continuous wave interferometer observations of the unstable mid-latitude E-region ionosphere

2003 ◽  
Vol 21 (7) ◽  
pp. 1589-1600 ◽  
Author(s):  
C. Haldoupis ◽  
A. Bourdillon ◽  
A. Kamburelis ◽  
G. C. Hussey ◽  
J. A. Koehler
Keyword(s):  
Electric Fields ◽  
Continuous Wave ◽  
Isotropic Turbulence ◽  
Doppler Radar ◽  
Active Regions ◽  
Field Of View ◽  
Ionosphere Plasma ◽  
First Results ◽  
Sporadic E

Abstract. In this paper we describe the conversion of SESCAT (Sporadic-E SCATter experiment), a bistatic 50 MHz continuous wave (CW) Doppler radar located on the island of Crete, Greece, to a single (east-west) baseline interferometer. The first results show that SESCAT, which provides high quality Doppler spectra and excellent temporal resolution, has its measurement capabilities enhanced significantly when operated as an interferometer, as it can also study short-term dynamics of localized scattering regions within mid-latitude sporadic E-layers. The interferometric observations reveal that the aspect sensitive area viewed by the radar often contains a few zonally located backscatter regions, presumably blobs or patches of unstable metallic ion plasma, which drift across the radar field-of-view with the neutral wind. On average, these active regions of backscatter have mean zonal scales ranging from a few kilometers to several tens of kilometers and drift with westward speeds from ~ 20 m/s to 100 m/s, and occasionally up to 150 m/s. The cross-spectral analysis shows that mid-latitude type 1 echoes occur much more frequently than has been previously assumed and they originate in single and rather localized areas of elevated electric fields. On the other hand, typical bursts of type 2 echoes are often found to result from two adjacent regions in azimuth undergoing the same bulk motion westwards but producing scatter of opposite Doppler polarity, a fact that contradicts the notion of isotropic turbulence to which type 2 echoes are attributed. Finally, quasi-periodic (QP) echoes are observed simply to be due to sequential unstable plasma patches or blobs which traverse across the radar field-of-view, sometimes in a wave-like fashion.Key words. Ionosphere (ionospheric irregularities; mid-latitude ionosphere; plasma waves and instabilities)

scholarly journals The solar activity 1833-1900

1901 ◽  
Vol 68 (442-450) ◽  
pp. 285-300 ◽  
Keyword(s):  
Solar Activity ◽  
Royal Society ◽  
Magnetic Elements ◽  
First Results

A close examination of the curves representing the varying amount of spotted area on the Sun’s surface, shows that no two successive cycles are alike either in form or area. The individuality of the cycles seems, on further inspection, to be repeated after a certain period of time, and this peculiarity, coupled with a like variation in the curves representing the variations of the magnetic elements, and with suspected cycles of change in various terrestrial phenomena, suggested a new investigation of the whole subject. The object of this communication is to place before the Royal Society the first results which an examination of the various records has furnished.

Optical observations of large-scale undulations in the 23rd cycle of solar activity

2012 ◽  
Vol 52 (2) ◽  
pp. 197-203 ◽  
Author(s):  
D. G. Baishev ◽  
E. S. Barkova ◽  
K. Yumoto
Keyword(s):  
Solar Activity ◽  
Large Scale ◽  
Optical Observations ◽  
23Rd Cycle

scholarly journals Structural and Evolutionary Features of Flare-Producing Active Regions During 1988-1990

1993 ◽  
Vol 141 ◽  
pp. 388-390
Author(s):  
A. A. Golovko
Keyword(s):  
Solar Activity ◽  
Radio Emission ◽  
Solar Radio ◽  
Active Regions ◽  
Magnetic Activity ◽  
High Solar Activity ◽  
Solar Radio Emission ◽  
Evolutionary Features ◽  
Siberian Solar Radio Telescope ◽  
Flare Productivity

During the period of high solar activity (1988-1990) the Sayan and Baikal Observatories of the ISTP carried out observations of the chromosphere in the H-alpha line, the photosphere and of sunspot magnetic fields; at the Siberian Solar Radio Telescope, solar radio emission observations at 5.2 cm wavelength were made. Using those observations a study is made of the evolution of “centers of magnetic activity” (Bumba, 1986) in nine active regions with different flare productivity, for which the most complete observations were available. In three cases (NOAA Nos. 5229, 5643 and 5669) they were the targets of the cooperative international Max’91 program.

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