The morphology of flare phenomena, magnetic fields, and electric currents in active regions. II - NOAA active region 5747 (1989 October)

1993 ◽  
Vol 411 ◽  
pp. 370 ◽  
Author(s):  
K. D. Leka ◽  
Richard C. Canfield ◽  
A. N. McClymont ◽  
J.-F. de La Beaujardiere ◽  
Yuhong Fan ◽  
...  
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Active Regions ◽  
Electric Currents ◽  
Noaa Active Region

scholarly journals Sensitivity of low-degree solar p modes to active and ephemeral regions: frequency shifts back to the Maunder minimum

2019 ◽  
Vol 489 (1) ◽  
pp. L86-L90 ◽  
Author(s):  
William J Chaplin ◽  
Rachel Howe ◽  
Sarbani Basu ◽  
Yvonne Elsworth ◽  
Timothy W Milbourne ◽  
...  
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Spatial Scales ◽  
Active Regions ◽  
Activity Cycle ◽  
Maunder Minimum ◽  
Field Frequency ◽  
Frequency Shifts ◽  
Near Surface ◽  
Low Degree

ABSTRACT We explore the sensitivity of the frequencies of low-degree solar p modes to near-surface magnetic flux on different spatial scales and strengths, specifically to active regions with strong magnetic fields and ephemeral regions with weak magnetic fields. We also use model reconstructions from the literature to calculate average frequency offsets back to the end of the Maunder minimum. We find that the p-mode frequencies are at least 3 times less sensitive (at 95  per cent confidence) to the ephemeral-region field than they are to the active-region field. Frequency shifts between activity cycle minima and maxima are controlled predominantly by the change of active region flux. Frequency shifts at cycle minima (with respect to a magnetically quiet Sun) are determined largely by the ephemeral flux, and are estimated to have been $0.1\, \rm \mu Hz$ or less over the last few minima. We conclude that at epochs of cycle minimum, frequency shifts due to near-surface magnetic activity are negligible compared to the offsets between observed and model frequencies that arise from inaccurate modelling of the near-surface layers (the so-called surface term). The implication is that this will be the case for other Sun-like stars with similar activity, which has implications for asteroseismic modelling of stars.

Electric currents and coronal heating in NOAA active region 6952

1994 ◽  
Vol 428 ◽  
pp. 860 ◽  
Author(s):  
T. R. Metcalf ◽  
R. C. Canfield ◽  
H. S. Hudson ◽  
D. L. Mickey ◽  
J.-P. Wulser ◽  
...  
Keyword(s):  
Active Region ◽  
Coronal Heating ◽  
Electric Currents ◽  
Noaa Active Region

scholarly journals The Evolution of Unstable 'Beta-Gamma' Magnetic Fields of Active Region AR 2222

2015 ◽  
Vol 48 ◽  
pp. 95-102
Author(s):  
Zety Sharizat Hamidi ◽  
S.N.U. Sabri ◽  
N.N.M. Shariff ◽  
C. Monstein
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Solar Flares ◽  
Active Regions ◽  
Group Type ◽  
Solar Burst ◽  
Type Iv ◽  
Fine Structures ◽  
Using Data

This event allows us to investigate how plasma–magnetic field interactions in the solar corona can produce suprathermal electron populations over periods from tens of minutes to several hours, and the interactions of wave-particle and wave-wave lead to characteristic fine structures of the emission. An intense and broad solar radio burst type IV was recorded by CALLISTO spectrometer from 240-360 MHz. Using data from a the KRIM observatory, we aim to provide a comprehensive description of the synopsis formation and dynamics of a a single solar burst type IV event due to active region AR2222. For five minutes, the event exhibited strong pulsations on various time scales and “broad patterns” with a formation of a group type III solar burst. AR 2222 remained the most active region, producing a number of minor C-Class solar flares. The speed of the solar wind also exceeds 370.8 km/second with 10.2 g/cm3 density of proton in the solar corona. The radio flux also shows 171 SFU. Besides, there are 3 active regions, AR2217, AR2219 and AR2222 potentially pose a threat for M-class solar flares. Active region AR2222 have unstable 'beta-gamma' magnetic fields that harbor energy for M-class flares. As a conclusion, we believed that Sun’s activities more active in order to achieve solar maximum cycle at the end of 2014.

scholarly journals Flows, Evolution of Magnetic Fields, and Flares

1993 ◽  
Vol 141 ◽  
pp. 323-332 ◽  
Author(s):  
Haimin Wang
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Solar Flares ◽  
Active Regions ◽  
Magnetic Polarity ◽  
Flux Emergence ◽  
Electric Currents ◽  
Magnetic Shear ◽  
Before And After

AbstractThis paper reviews observations on the evolution of magnetic fields and flows in active regions which produce major flares. It includes the following topics: (1) Relationship between magnetic shear and flares; (2) Relationship between electric currents and flares; (3) Flows in active regions, particularly the emergence of new flux inside sheared penumbrae, and the mixed magnetic polarity nature of this kind of flux emergence; and (4) Changes of magnetic structure immediately before and after major solar flares; in particular, I will describe some recent findings that shear may increase after major flares.

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. I - Introduction and methods

1993 ◽  
Vol 411 ◽  
pp. 362 ◽  
Author(s):  
Richard C. Canfield ◽  
J.-F. de La Beaujardiere ◽  
Yuhong Fan ◽  
K. D. Leka ◽  
A. N. McClymont ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Active Regions ◽  
Electric Currents

scholarly journals Irradiance Models Based on Solar Magnetic Fields

1994 ◽  
Vol 143 ◽  
pp. 217-225 ◽  
Author(s):  
Karen L. Harvey
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Coronal Holes ◽  
Active Regions ◽  
Spectral Irradiance ◽  
Solar Magnetic Fields ◽  
Quiet Sun ◽  
Possible Cause

A method to separate the active region and quiet network components of the magnetic fields in the photosphere is described and compared with the corresponding measurements of the He I λ 10830 absorption. The relation between the total He I absorption and total magnetic flux in active regions is roughly linear and differs between cycles 21 and 22. There appears to no relation between these two quantities in areas outside of active regions. The total He I absorption in the quiet Sun (comprised of network, filaments, and coronal holes) exceeds that in active regions at all times during the cycle. As a whole, active regions of cycle 22 appear to be less complex than the active regions of cycle 21, hinting at one possible cause for a differing relation between spectral-irradiance variations and the underlying magnetic flux for these two cycles.

Filling of Magnetic Loops by an Electric Current

1994 ◽  
Vol 144 ◽  
pp. 211-213
Author(s):  
S. I. Gopasyuk
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Electric Current ◽  
Observational Data ◽  
Magnetic Loop ◽  
The Self ◽  
Electric Currents

AbstractResults of investigations of the magnetic fields and electric currents in the active region are presented. The calculations based on the observational data showed that the electric currents are more concentrated in lower magnetic loops. The cause of this is the magnetic loop stretching. For a stretching magnetic loop the self-inductance increases and the current decreases.

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