The dependence of polarized emission from local sources on the sun on the stage of development in the active region

1973 ◽  
Vol 16 (12) ◽  
pp. 1418-1421
Author(s):  
Sh. B. Akhmedov ◽  
N. G. Peterova
Keyword(s):  
Active Region ◽  
The Sun ◽  
Stage Of Development ◽  
Local Sources ◽  
Polarized Emission

scholarly journals Energetics of magnetic transients in a solar active region plage

2019 ◽  
Vol 623 ◽  
pp. A176 ◽  
Author(s):  
L. P. Chitta ◽  
A. R. C. Sukarmadji ◽  
L. Rouppe van der Voort ◽  
H. Peter
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Flux ◽  
Numerical Simulations ◽  
Extreme Ultraviolet ◽  
Spatial Scales ◽  
Coronal Loops ◽  
The Sun ◽  
Flux Emergence ◽  
Transient Events

Context. Densely packed coronal loops are rooted in photospheric plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plage areas are patches of mostly unidirectional magnetic field extending several arcsec on the solar surface. Aims. We aim to explore the transient nature of the magnetic field, its mixed-polarity characteristics, and the associated energetics in the active region plage using high spatial resolution observations and numerical simulations. Methods. We used photospheric Fe I 6173 Å spectropolarimetric observations of a decaying active region obtained from the Swedish 1-m Solar Telescope (SST). These data were inverted to retrieve the photospheric magnetic field underlying the plage as identified in the extreme-ultraviolet emission maps obtained from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). To obtain better insight into the evolution of extended unidirectional magnetic field patches on the Sun, we performed 3D radiation magnetohydrodynamic simulations of magnetoconvection using the MURaM code. Results. The observations show transient magnetic flux emergence and cancellation events within the extended predominantly unipolar patch on timescales of a few 100 s and on spatial scales comparable to granules. These transient events occur at the footpoints of active region plage loops. In one case the coronal response at the footpoints of these loops is clearly associated with the underlying transient. The numerical simulations also reveal similar magnetic flux emergence and cancellation events that extend to even smaller spatial and temporal scales. Individual simulated transient events transfer an energy flux in excess of 1 MW m−2 through the photosphere. Conclusions. We suggest that the magnetic transients could play an important role in the energetics of active region plage. Both in observations and simulations, the opposite-polarity magnetic field brought up by transient flux emergence cancels with the surrounding plage field. Magnetic reconnection associated with such transient events likely conduits magnetic energy to power the overlying chromosphere and coronal loops.

Isolated Sunspot with a Dark Patch in the Coronal Emission

2012 ◽  
Vol 21 (4) ◽  
Author(s):  
D. A. Bezrukov ◽  
B. I. Ryabov ◽  
K. Shibasaki
Keyword(s):  
Active Region ◽  
Normal Mode ◽  
Plasma Density ◽  
Specific Region ◽  
The Sun ◽  
Coronal Emission ◽  
Plasma Parameters ◽  
X Ray ◽  
Dark Patch ◽  
Chromospheric Line

AbstractOn the base of the 17 GHz radio maps of the Sun taken with the Nobeyama Radio Heliograph we estimate plasma parameters in the specific region of the sunspot atmosphere in the active region AR 11312. This region of the sunspot atmosphere is characterized by the depletion in coronal emission (soft X-ray and EUV lines) and the reduced absorption in the a chromospheric line (He I 1.083 μm). In the ordinary normal mode of 17 GHz emission the corresponding dark patch has the largest visibility near the central solar meridian. We infer that the reduced coronal plasma density of about ~ 5 × 10

scholarly journals Magnetic Helicity and Filaments

1998 ◽  
Vol 167 ◽  
pp. 102-110 ◽  
Author(s):  
M.A. Berger
Keyword(s):  
Active Region ◽  
Solar Physics ◽  
Helical Structure ◽  
Structural Features ◽  
Magnetic Helicity ◽  
The Sun

AbstractSome of the most dramatic images of prominences show helical structure. Helical structure, as well as other structural features such as twist, shear, and linking, can be quantified using helicity integrals. This paper reviews how the calculation of helicity may be applied to prominence models. Recent observations indicate that the sign of helicity in an active region depends on which hemisphere the region is in. The source of this asymmetry is an important problem in solar physics. The total helicity of each hemisphere obeys a Poynting-like theorem which describes how helicity is transferred across the photosphere and the equator. Estimating this helicity transfer may help us in understanding the helicity balance of the sun.

The 158 MHz Solar Interferometer at Culgoora

1967 ◽  
Vol 1 (2) ◽  
pp. 59-61 ◽  
Author(s):  
R. T. Stewart
Keyword(s):  
Active Region ◽  
Radio Burst ◽  
Solar Radio ◽  
Second Harmonic ◽  
Solar Observatory ◽  
Solar Radio Burst ◽  
The Sun ◽  
Harmonic Frequency ◽  
The North ◽  
East West

The function of the 158 MHz interferometer operating at the CSIRO Solar Observatory, Culgoora, N.S.W., is the measurement of solar radio burst positions at a frequency close to the second harmonic frequency of the radioheliograph. The interferometer is designed to measure the north-south and east-west position co-ordinates of an isolated active region on the Sun with an accuracy of ~1′ arc, at rates up to 16 s−1.

scholarly journals A solar tornado caused by flares

2013 ◽  
Vol 8 (S300) ◽  
pp. 235-238
Author(s):  
N. K. Panesar ◽  
D. E. Innes ◽  
S. K. Tiwari ◽  
B. C. Low
Keyword(s):  
Active Region ◽  
Magnetic Energy ◽  
Magnetic Pressure ◽  
The Sun ◽  
Active Region Noaa ◽  
Quiescent Prominence ◽  
Triggering Mechanism ◽  
Free Magnetic Energy ◽  
Cavity System ◽  
Region Noaa

AbstractAn enormous solar tornado was observed by SDO/AIA on 25 September 2011. It was mainly associated with a quiescent prominence with an overlying coronal cavity. We investigate the triggering mechanism of the solar tornado by using the data from two instruments: SDO/AIA and STEREO-A/EUVI, covering the Sun from two directions. The tornado appeared near to the active region NOAA 11303 that produced three flares. The flares directly influenced the prominence-cavity system. The release of free magnetic energy from the active region by flares resulted in the contraction of the active region field. The cavity, owing to its superior magnetic pressure, expanded to fill this vacated space in the corona. We propose that the tornado developed on the top of the prominence due to the expansion of the prominence-cavity system.

SOME OBSERVATIONS ON THE BIOLOGY AND BEHAVIOUR OF CAMNULA PELLUCIDA (ORTHOPTERA: ACRIDIDAE)

1967 ◽  
Vol 99 (9) ◽  
pp. 952-971 ◽  
Author(s):  
P. W. Riegert
Keyword(s):  
Meteorological Factors ◽  
Historical Review ◽  
Pest Species ◽  
The Sun ◽  
Life Stages ◽  
Embryological Development ◽  
Recent Information ◽  
Stage Of Development ◽  
Sandhill Cranes ◽  
Incubation Temperatures

AbstractA brief historical review of the occurrence of the clear-winged grasshopper, Camnula pellucida (Scudd.), is presented as well as recent information pertaining to the biology of its various life stages. In the egg stage, diapause is more successfully terminated by chilling at 5 °C for 70 days than at either 0 or −7 °C. Embryological development proceeded very favourably at incubation temperatures of 30 °C while 35 °C produced excessive mortality especially to pre-blastokinesis embryos. Most embryos in eggs of this species reach the same pre-blastokinesis stage of development more consistently every year than do those of other pest species of grasshopper in Saskatchewan. Thirty days of chilling at −12, −18, and −23 °C reduced the viability of the eggs by about 10, 20, and 50% respectively. Exposure to −29 °C killed all eggs in 3.5 to 5 hours.The phototactic and thermokinetic reactions of nymphs and adults, leading to aggregation, basking, and dispersal, are discussed and compared with those of other species. Details of nymphal migrations are described and related to such meteorological factors as wind, temperature, and position of the sun. Some further details of mating and oviposition are described, especially aggregation on egg beds and oviposition in stubble fields. Observations of predation by sandhill cranes and skunks are also recorded.

scholarly journals Enormous Eruption of 2.2 X-Class Solar Flares on 10th June 2014

2014 ◽  
Vol 36 ◽  
pp. 249-257 ◽  
Author(s):  
Zety Sharizat Hamidi ◽  
N.N.M. Shariff
Keyword(s):  
Active Region ◽  
Solar Flare ◽  
The Sun ◽  
X Rays ◽  
Solar Dynamics Observatory ◽  
Time Data ◽  
High Frequencies ◽  
The North ◽  
Solar Dynamics ◽  
Radio Blackout

The observational of active region emission of the Sun contain an critical answer of the time-dependence of the underlying heating mechanism. In this case, we investigate an X2.2 solar flare from a new Active Region AR2087 on the southeast limb of the Sun. The solar flare peaked in the X-rays is around 11:42 UT. It was found that the snapshot of this event from the Solar Dynamics Observatory (SDO) channel with the GOES X-ray plot overlayed. The flare is very bright causes by a diffraction pattern. We explore a parameter space of heating and coronal loop properties. Based on the wavelength, it shows plasma around 6 million Kelvin. At the same time, data from the NOAA issued an R3 level radio blackout, which is centered on Earth where the Sun is currently overhead at the North Africa region. This temporary blackout is caused by the heating of the upper atmosphere from the flare. The blackout level is now at an R1 and this will soon pass. Other than the temporary radio blackout for high frequencies centered over Africa this event will not have a direct impact on us. Until now, we await more data concerning a possible Coronal Mass Ejections (CMEs) but anything would more than likely not head directly towards Earth. An active region AR2087 just let out an X1.5 flare peaking at 12:52 UT. This shows plasmas with temperatures up to about 10 Million Kelvin. This event is considered one of the massive eruption of the Sun this year.

scholarly journals Locating the solar source of 13 April 2006 magnetic cloud

2008 ◽  
Vol 26 (10) ◽  
pp. 3159-3168 ◽  
Author(s):  
K. Steed ◽  
C. J. Owen ◽  
L. K. Harra ◽  
L. M. Green ◽  
S. Dasso ◽  
...  
Keyword(s):  
Active Region ◽  
High Speed ◽  
Magnetic Cloud ◽  
Active Regions ◽  
Propagation Time ◽  
Central Meridian ◽  
The Sun ◽  
Solar Source ◽  
In Situ Data ◽  
Spacecraft Trajectory

Abstract. Using Advanced Composition Explorer (ACE) in situ data we identify and describe an interplanetary magnetic cloud (MC) observed near Earth on 13 April 2006. We also use multi-instrument and multi-wavelength observations from the Solar and Heliospheric Observatory (SOHO), the Transition Region and Coronal Explorer (TRACE) and ground-based solar observatories to determine the solar source of this magnetic cloud. A launch window for the MC between 9 and 11 April 2006 was estimated from the propagation time of the ejecta observed near Earth. A number of large active regions (ARs) were present on the Sun during this period, which were initially considered to be the most likely candidate source regions of the MC. However, it was determined that the solar source of the MC was a small, spotless active region observed in the Northern Hemisphere. Following an eruption from this region on 11 April 2006, the ACE spacecraft detected, 59 h later, the passage of the MC, preceded by the arrival of a weak, forward fast shock. The link between the eruption in this active region and the interplanetary MC is supported by several pieces of evidence, including the location of the solar source near to the disk centre and to the east of the central meridian (in agreement with the spacecraft trajectory through the western leg of the magnetic cloud), the propagation time of the ejecta, the agreement between the amount of flux in the magnetic cloud and in the active region, and the agreement between the signs of helicity of the magnetic cloud and the active region (which differs from the sign of helicity of each of the other active regions on the Sun at this time). In addition, the active region is located on the boundary of a coronal hole, and a high speed solar wind stream originating from this region is observed near Earth shortly after the passage of the magnetic cloud.

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