Where are the solar magnetic poles?

Yabar, A. Pastor; González, M. J. Martínez; Collados, M.

doi:10.1093/mnrasl/slv108

Cited by 13 publications

(7 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our study shows that the reversal occurred much earlier, in late 2014. Confirmation of our results also came from an entirely different study aimed at examining the alignment of the sun's magnetic and rotational axis (Pastor Yabar et al 2015) using line-of-sight HMI magnetograms for a 5 year period starting from April 2010. Apart from finding a monthly oscillation at all solar latitudes which they attributed to a non-alignment in the solar magnetic and rotational axis, their data also indicated the time of occurrence of the solar polar field reversals to be in ∼ April 2014 for the Northern hemisphere and ∼ Feb. 2013 for the Southern Hemisphere [see Fig.…”

Section: Discussionsupporting

confidence: 80%

“…From Table 1 it is clear that there is a difference of about a year between our estimate for the end of the reversal in the North and that of Gopalswamy (2016). There is also a difference of about a year between the estimates of Pastor Yabar et al, (2015) and Sun et al, (2015) for the reversal time in the south.…”

Section: Introductionmentioning

confidence: 91%

“…In another study, Sun et al (2015) reported, using high cadence HMI 720s magnetograms, that the reversal of polar fields in the Northern hemisphere occurred in November 2012, while the reversal in the Southern hemisphere occurred in March 2014. Using line-of-sight HMI magnetograms for a 5 year period starting from April 2010, Pastor Yabar et al (2015 reported the reversal times in the north and south to be April 2014 and Feb 2013, respectively. More recently, using 17 GHz microwave images and high latitudes prominence activity, Gopalswamy et al (2016) reported, that the polar reversal in the Southern hemisphere occurred around June 2014, while in the Northern hemisphere the reversal was completed only by October 2015.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Solar cycle 24: An unusual polar field reversal

Janardhan

Fujiki²,

Ingale

et al. 2018

A&A

View full text Add to dashboard Cite

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. 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 (Gopalswamy et al. 2016) 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 i.e. 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.

show abstract

Section: Discussionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Solar cycle 24: An unusual polar field reversal

Janardhan

Fujiki²,

Ingale

et al. 2018

A&A

View full text Add to dashboard Cite

show abstract

“…Another feature we notice in Figure 3 are the wiggles of the observed (left panels) and reconstructed (right panels) field, more clearly seen in the regions of high latitude. This modulation is due to the viewing angle of the solar poles due to the inclination of the solar rotation axis with respect to the ecliptic (Pastor Yabar et al 2015). The left panels in Figure 3 for example show that the wiggles near the poles are in anti-phase between northern and southern hemispheres.…”

Section: Polarity Reversals In the Large-scale Fieldmentioning

confidence: 98%

The magnetic field vector of the Sun-as-a-star – II. Evolution of the large-scale vector field through activity cycle 24

Vidotto

Lehmann

Jardine

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

In the present work, we investigate how the large-scale magnetic field of the Sun, in its three vector components, has evolved during most of cycle 24, from 2010 Jan to 2018 Apr. To filter out the small-scale field of the Sun, present in high-resolution synoptic maps, we use a spherical harmonic decomposition method, which decomposes the solar field in multipoles with different degrees. By summing together the low-multipoles, we reconstruct the large-scale field at a resolution similar to observed stellar magnetic fields, which allows the direct comparison between solar and stellar magnetic maps. During cycle 24, the 'Sun-as-a-star' magnetic field shows a polarity reversal in the radial and meridional components, but not in the azimuthal component. The large-scale solar field remains mainly poloidal with 70% of its energy contained in the poloidal component. During its evolution, the large-scale field is more axisymmetric and more poloidal when near minima in sunspot numbers, and with a larger intensity near maximum. There is a correlation between toroidal energy and sunspot number, which indicates that spot fields are major contributors to the toroidal large-scale energy of the Sun. The solar large-scale magnetic properties fit smoothly with observational trends of stellar magnetism reported in See et al. The toroidal ( B 2 tor ) and poloidal ( B 2 pol ) energies are related as B 2 tor ∝ B 2 pol 1.38±0.04 . Similar to the stellar sample, the large-scale field of the Sun shows a lack of toroidal non-axisymmetric field.

show abstract

“…We construct a training set with 10 months and an evaluation set with two months, and both are selected for each year without any duplication between the two sets. In order to train and evaluate various inclination conditions, which cause different distributions of southern/northern magnetic field strength for each month (Pastor Yabar et al 2015), the months are selected randomly. We take 3412 pairs for the training data set and 819 pairs for the evaluation data set.…”

Section: Datamentioning

confidence: 99%

Solar Coronal Magnetic Field Extrapolation from Synchronic Data with AI-generated Farside

Jeong,

Moon,

Park

et al. 2020

Preprint

View full text Add to dashboard Cite

Solar magnetic fields play a key role in understanding the nature of the coronal phenomena. Global coronal magnetic fields are usually extrapolated from photospheric fields, for which farside data is taken frontside, about two weeks earlier. For the first time we have constructed the extrapolations of global magnetic fields using frontside and artificial intelligence (AI)-generated farside magnetic fields at a near-real time basis. We generate the farside magnetograms from three channel farside observations of Solar Terrestrial Relations Observatory (STEREO) Ahead (A) and Behind (B) by our deep learning model trained with frontside Solar Dynamics Observatory extreme ultraviolet images and magnetograms. For frontside testing data sets, we demonstrate that the generated magnetic field distributions are consistent with the real ones; not only active regions (ARs), but also quiet regions of the Sun. We make global magnetic field synchronic maps in which conventional farside data are replaced by farside ones generated by our model. The synchronic maps show much better not only the appearance of ARs but also the disappearance of others on the solar surface than before. We use these synchronized magnetic data to extrapolate the global coronal fields using Potential Field Source Surface (PFSS) model. We show that our results are much more consistent with coronal observations than those of the conventional method in view of solar active regions and coronal holes. We present several positive prospects of our new methodology for the study of solar corona, heliosphere, and space weather.

show abstract

Where are the solar magnetic poles?

Cited by 13 publications

References 29 publications

Solar cycle 24: An unusual polar field reversal

Solar cycle 24: An unusual polar field reversal

The magnetic field vector of the Sun-as-a-star – II. Evolution of the large-scale vector field through activity cycle 24

Solar Coronal Magnetic Field Extrapolation from Synchronic Data with AI-generated Farside

Contact Info

Product

Resources

About