scholarly journals Reversal of Sun’s polar magnetic field in solar cycle

2018 ◽  
pp. 17-21
Author(s):  
M. Pishkalo
Keyword(s):  
Magnetic Field ◽  
Northern Hemisphere ◽  
Maximum Activity ◽  
Solar Observatory ◽  
Polar Field ◽  
Field Reversal ◽  
Activity Maximum ◽  
Polar Zone ◽  
Polar Magnetic Field ◽  
24Th Cycle

The connection of solar activity expressed by international sunspot (Wolf) numbers in the northern and southern hemispheres of the Sun in the current 24th cycle with the time of polar magnetic field reversal in the corresponding hemisphere is investigated. It was obtained that: – The change of the sign of the polar magnetic field at the southern pole occurs almost a year later than in the north. – The polar magnetic field reversals do not coincide with the maximum activity in each of the hemispheres. In the northern hemisphere, the activity maximum was observed almost one and a half years earlier than the first polar field reversal and two and a half years earlier than the third or final one. In the southern hemisphere, the activity maximum was observed almost a year earlier from the change of the field sign at the pole. – The maximum of the 24th cycle almost coincides with the time of the change of the sign of the magnetic field at the northern pole. – In each of the hemispheres, the change in the sign of a magnetic field in the polar zone above 55 degrees occurred almost two years earlier than the final polar field reversal. The second and third changes of the sign of the total field in the polar zone above 55 degrees occurred shortly after the corresponding polar field reversal. – In the northern hemisphere, the polar field reversals occur at the time of maximum values of the inclination of the heliospheric current sheet, and in the south – almost two years after the maximum inclination of the HCS. – Three-fold polar field reversal at the northern pole occurs at small values of polar magnetic field measured at the Wilcox Solar Observatory while single reversal at the southern pole occurs at sufficiently high value of the corresponding measured polar field.

Polar Magnetic Field Reversals of the Sun in Maunder Minimum

2000 ◽  
Vol 179 ◽  
pp. 193-196
Author(s):  
V. I. Makarov ◽  
A. G. Tlatov
Keyword(s):  
Magnetic Field ◽  
Maunder Minimum ◽  
The Sun ◽  
Annual Rings ◽  
Field Reversal ◽  
Polar Magnetic Field ◽  
Pine Trees ◽  
Using Data ◽  
Magnetic Field Reversal

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.

scholarly journals Solar cycle 24: An unusual polar field reversal

2018 ◽  
Vol 618 ◽  
pp. A148 ◽  
Author(s):  
P. Janardhan ◽  
K. Fujiki ◽  
M. Ingale ◽  
S. K. Bisoi ◽  
D. Rout
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Field Strength ◽  
Polar Field ◽  
Line Of Sight ◽  
Zero Field ◽  
Field Reversal ◽  
Reversal Process ◽  
Solar Cycle 24 ◽  
Cycle 24

Context. It is well known that the polarity of the Sun’s magnetic field reverses or flips around the maximum of each 11 year solar cycle. This is commonly known as polar field reversal and plays a key role in deciding the polar field strength at the end of a cycle, which is crucial for the prediction of the upcoming cycle. Aims. We aim to investigate solar polar fields during cycle 24, using measurements of solar magnetic fields in the latitude range 55°–90° and 78°–90°, to report a prolonged and unusual hemispheric asymmetry in the polar field reversal pattern in solar cycle 24. Methods. This study was carried out using medium resolution line-of-sight synoptic magnetograms from the magnetic database of the National Solar Observatory at Kitt Peak (NSO/KP), USA for the period between February 1975 and October 2017, covering solar cycles 21–24 and high-resolution line-of-sight synoptic magnetograms from the Michaelson Doppler Imager instrument onboard the Solar Heliospheric Observatory. Synoptic magnetograms using radial measurements from the Heliospheric Magnetic Imager instrument onboard the Solar Dynamics Observatory, covering solar cycle 23 and 24, were also used. Results. We show that the southern solar hemisphere unambiguously reversed polarity in mid-2013 while the reversal in the field in the northern solar hemisphere started as early as June 2012, was followed by a sustained period of near-zero field strength lasting until the end of 2014, after which the field began to show a clear rise from its near-zero value. While this study compliments a similar study carried out using microwave brightness measurements which claimed that the field reversal process in cycle 24 was completed by the end of 2015, our results show that the field reversal in cycle 24 was completed earlier that is, in late 2014. Signatures of this unusual field reversal pattern were also clearly identifiable in the solar wind, using our observations of interplanetary scintillation at 327 MHz which supported our magnetic field observations and confirmed that the field reversal process was completed at the end of 2014.

scholarly journals Polar magnetic field reversals on the Sun

2006 ◽  
Vol 2 (14) ◽  
pp. 273-274 ◽  
Author(s):  
Elena E. Benevolenskaya
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Polar Region ◽  
Small Scale ◽  
The Sun ◽  
Field Reversal ◽  
Polar Magnetic Field ◽  
The North ◽  
Magnetic Elements ◽  
Polar Magnetic Fields

AbstractThe polar magnetic fields on the Sun have been an attractive subject for solar researches since Babcock measured them in solar cycle 19. One of the remarkable features of the polar magnetic fields is their reversal during the maxima of 11-year sunspot cycles. I have present results of the investigations of the polar magnetic field using SOHO-mdi data. It is found, that the polar magnetic field reversal is detected with mdi data for polar region within 78°–88°. The North Pole has changed polarity in CR1975 (April 2001). The South reversed later in CR1980 (September 2001). The total unsigned magnetic flux does not show the dramatic decreasing during the polar reversals due to omnipresent bi-polar small-scale magnetic elements. The observational and theoretical aspects of the polar magnetic field reversals are discussed.

scholarly journals Magnetic field evolution in magnetars and its implication to accreting system

2012 ◽  
Vol 8 (S290) ◽  
pp. 235-236
Author(s):  
Yasufumi Kojima
Keyword(s):  
Magnetic Field ◽  
Theoretical Study ◽  
Time Dependent ◽  
Polar Field ◽  
Nonlinear Coupling ◽  
Polar Magnetic Field ◽  
Field Evolution ◽  
Dipole Magnetic Field ◽  
The Magnetic Field

AbstractThe evolution of magnetic field is numerically studied for an isolated magnetar, assuming vacuum exterior. Nonlinear coupling between poloidal and toroidal components of the magnetic field can be seen in the initial Hall-drift timescale. Consequently, the polar field at the surface is highly distorted during the phase. This result is suggestive. Fixed dipole magnetic field has been used so far in the theoretical study of the interaction between magnetosphere and accreting matter. In the accretion to magnetar, time-dependent polar magnetic field should be taken into account.

Magnetic flux transport in the photosphere of the Sun

2020 ◽  
Author(s):  
Dmitrii Baranov ◽  
Elena Vernova ◽  
Marta Tyasto ◽  
Olga Danilova
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Polar Field ◽  
The Sun ◽  
Time Diagram ◽  
Weak Magnetic Fields ◽  
The Magnetic Field

<p>On the basis of the synoptic maps of the photospheric magnetic field obtained by the National Solar Observatory Kitt Peak for 1978-2016, a latitude-time diagram of the magnetic field was built. When averaging intensity values over the heliolongitude, the magnetic field sign was taken into account. In order to consider the characteristics of the distribution of weak magnetic fields an upper limit of 5 G was set.</p><p>The latitude-time diagram clearly shows inclined bands corresponding to positive and negative polarity magnetic flows drifting towards the poles of the Sun. Two groups of flows are observed: 1. Relatively narrow bands, with alternating polarity, beginning near the equator and reaching almost the poles of the Sun. Along the time axis, the flow length of one polarity is on the order of 1-2 years; 2. short powerful flows, 3-4.5 years wide, propagating from the spot zone to the poles. These flows reach the poles simultaneously with the begin of the polar field reversal, apparently representing  the so-called “Rush to the Poles” phenomenon.</p><p>The pattern of magnetic field transport is significantly different for the northern and southern hemispheres. Alternating flows of positive and negative polarities most clearly appear in the southern hemisphere during periods of positive polarity of the southern polar field. For the northern hemisphere the picture is much less clear but for individual time intervals alternating flows of opposite polarities can be traced. The slopes of magnetic flux bands allow us to estimate the rate of meridional drift of magnetic fields, which was slightly different for the two hemispheres: V = (16±2) m/s for the southern hemisphere and V = (21±4) m/s for the northern hemisphere. The results obtained indicate that the distribution of weak magnetic fields over the surface of the Sun has a complex structure that is different for the two hemispheres and varies from cycle to cycle.</p>

Synchronized periodic maser flares of multiple OH and CH3OH lines in G323.459–0.079

2021 ◽  
Vol 502 (4) ◽  
pp. 5658-5667
Author(s):  
G C MacLeod ◽  
Derck P Smits ◽  
J A Green ◽  
S P van den Heever
Keyword(s):  
Magnetic Field ◽  
Excited State ◽  
Central Region ◽  
Time Lags ◽  
Field Reversal ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Upper Limit ◽  
Methanol Masers ◽  
Magnetic Field Reversal

ABSTRACT The first confirmed periodically varying 6.031 and 6.035 GHz hydroxyl masers are reported here. They vary contemporaneously with the 6.7 GHz methanol masers in G323.459–0.079. The 1.665 GHz hydroxyl and 12.2  GHz methanol masers associated with G323.459–0.079 are also periodic. Evidence for periodicity is seen in all features in all transitions save a single 1.665 GHz hydroxyl maser feature. Historical excited-state hydroxyl maser observations set a stricter upper limit on the epoch in which a significant accretion event occurred. The associated burst in 6.7 GHz methanol maser activity has subsided significantly while the hydroxyl transitions are brightening possibly the result of changing physical conditions in the masing cloudlets. Time lags in methanol are confirmed and may be the result of the periodic flaring propagating outward from the central region of maser activity. A possible magnetic field reversal occurred during the accretion event.

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