Solar cycle 24: An unusual polar field reversal

doi:10.1051/0004-6361/201832981

CORC > 国家天文台 > 中国科学院国家天文台

	Solar cycle 24: An unusual polar field reversal
	Janardhan, P.1; Fujiki, K.2; Ingale, M.1; Bisoi, S. K.3; Rout, D.4
刊名	ASTRONOMY & ASTROPHYSICS
	2018-10-24
卷号	618 页码:10
关键词	Sun: activity Sun: magnetic fields Sun: photosphere Sun: heliosphere sunspots
ISSN号	1432-0746
DOI	10.1051/0004-6361/201832981
英文摘要	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 degrees-90 degrees and 78 degrees-90 degrees, 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.
资助项目	ISEE International Collaborative Research Program ; PIFI program of the Chinese Academy of Sciences[2015PM066] ; NSFC[117550110422]
WOS关键词	INTERPLANETARY SCINTILLATION OBSERVATIONS ; PHOTOSPHERIC MAGNETIC-FIELDS ; CORONAL HOLES ; WIND ; SUN ; EVOLUTION ; VELOCITY ; MODEL ; FLUX ; MHZ
WOS研究方向	Astronomy & Astrophysics
语种	英语
出版者	EDP SCIENCES S A
WOS记录号	WOS:000448101800001
资助机构	ISEE International Collaborative Research Program ; ISEE International Collaborative Research Program ; PIFI program of the Chinese Academy of Sciences ; PIFI program of the Chinese Academy of Sciences ; NSFC ; NSFC ; ISEE International Collaborative Research Program ; ISEE International Collaborative Research Program ; PIFI program of the Chinese Academy of Sciences ; PIFI program of the Chinese Academy of Sciences ; NSFC ; NSFC ; ISEE International Collaborative Research Program ; ISEE International Collaborative Research Program ; PIFI program of the Chinese Academy of Sciences ; PIFI program of the Chinese Academy of Sciences ; NSFC ; NSFC ; ISEE International Collaborative Research Program ; ISEE International Collaborative Research Program ; PIFI program of the Chinese Academy of Sciences ; PIFI program of the Chinese Academy of Sciences ; NSFC ; NSFC
内容类型	期刊论文
源URL	[http://ir.bao.ac.cn/handle/114a11/23016]
专题	中国科学院国家天文台
通讯作者	Janardhan, P.
作者单位	1.Phys Res Lab, Astron & Astrophys Div, Ahmadabad 380009, Gujarat, India 2.Inst Space Earth Environm Res, Furocho, Nagoya, Aichi 4648601, Japan 3.Chinese Acad Sci, Natl Astron Observ, Key Lab Solar Act, Beijing 100012, Peoples R China 4.Phys Res Lab, Space & Atmospher Sci Div, Ahmadabad 380009, Gujarat, India
推荐引用方式 GB/T 7714	Janardhan, P.,Fujiki, K.,Ingale, M.,et al. Solar cycle 24: An unusual polar field reversal[J]. ASTRONOMY & ASTROPHYSICS,2018,618:10.
APA	Janardhan, P.,Fujiki, K.,Ingale, M.,Bisoi, S. K.,&Rout, D..(2018).Solar cycle 24: An unusual polar field reversal.ASTRONOMY & ASTROPHYSICS,618,10.
MLA	Janardhan, P.,et al."Solar cycle 24: An unusual polar field reversal".ASTRONOMY & ASTROPHYSICS 618(2018):10.