Evolution of geomagnetic <i>aa</i> index near sunspot minimum
The smoothed values of the minima of sunspot number <i>Rz</i> and the geomagnetic index <i>aa</i> were compared for sunspot cycles 12–23. In one cycle, <i>aa</i>(min) occurred earlier than <i>Rz</i>(min), but remained at that low from a few month...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2002-10-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/20/1519/2002/angeo-20-1519-2002.pdf |
| _version_ | 1818961362951340032 |
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| author | R. P. Kane R. P. Kane |
| author_facet | R. P. Kane R. P. Kane |
| author_sort | R. P. Kane |
| collection | DOAJ |
| description | The smoothed values of the minima of sunspot
number <i>Rz</i> and the geomagnetic index <i>aa</i> were compared for sunspot
cycles 12–23. In one cycle, <i>aa</i>(min) occurred earlier than <i>Rz</i>(min),
but remained at that low from a few months before <i>Rz</i>(min) to a few
months after <i>Rz</i>(min). In two cycles, <i>Rz</i>(min) and <i>aa</i>(min)
coincided within a month or two. In nine cycles, <i>aa</i>(min) occurred more
than three months later than <i>Rz</i>(min). The <i>aa</i>(min) coincided with
the minima of some solar radio emission indices originating in the solar
corona. For sunspot cycles 21, 22, 23, the minimum of solar wind velocity <i>V</i>
occurred 0–9 months later than the <i>aa</i>(min). The minimum of solar wind
total magnetic field <i>B</i> occurred near <i>Rz</i>(min). The solar wind ion
density <i>N</i> had maxima (instead of minima) near <i>Rz</i>(min), and again
near <i>Rz</i>(max), indicating a ~5-year periodicity, instead of an
11-year periodicity. The maxima of <i>aa</i>, <i>V</i> and <i>B</i> occurred
near <i>Rz</i>(max) and/or later in the declining phase of <i>Rz</i>. The <i>aa</i>
index was very well correlated with the functions BV and BV<sup> 2</sup>.<br><br><b>Key words.</b> Geomagnetism and paleomagnetism (time
variations, diurnal to secular – time variations, secular and long term)
Interplanetary physics (interplanetary magnetic field) |
| first_indexed | 2024-12-20T12:12:14Z |
| format | Article |
| id | doaj.art-19a26b7c96f24d0481b5637c8c288f09 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-20T12:12:14Z |
| publishDate | 2002-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-19a26b7c96f24d0481b5637c8c288f092022-12-21T19:41:14ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762002-10-01201519152710.5194/angeo-20-1519-2002Evolution of geomagnetic <i>aa</i> index near sunspot minimumR. P. Kane0R. P. Kane1Correspondence to: R. P. Kane (kane@laser.inpe.br)Instituto Nacional de Pesquisas Espacias, C. P. 515, São Jose dos Campos, 12201-970, SP, BrazilThe smoothed values of the minima of sunspot number <i>Rz</i> and the geomagnetic index <i>aa</i> were compared for sunspot cycles 12–23. In one cycle, <i>aa</i>(min) occurred earlier than <i>Rz</i>(min), but remained at that low from a few months before <i>Rz</i>(min) to a few months after <i>Rz</i>(min). In two cycles, <i>Rz</i>(min) and <i>aa</i>(min) coincided within a month or two. In nine cycles, <i>aa</i>(min) occurred more than three months later than <i>Rz</i>(min). The <i>aa</i>(min) coincided with the minima of some solar radio emission indices originating in the solar corona. For sunspot cycles 21, 22, 23, the minimum of solar wind velocity <i>V</i> occurred 0–9 months later than the <i>aa</i>(min). The minimum of solar wind total magnetic field <i>B</i> occurred near <i>Rz</i>(min). The solar wind ion density <i>N</i> had maxima (instead of minima) near <i>Rz</i>(min), and again near <i>Rz</i>(max), indicating a ~5-year periodicity, instead of an 11-year periodicity. The maxima of <i>aa</i>, <i>V</i> and <i>B</i> occurred near <i>Rz</i>(max) and/or later in the declining phase of <i>Rz</i>. The <i>aa</i> index was very well correlated with the functions BV and BV<sup> 2</sup>.<br><br><b>Key words.</b> Geomagnetism and paleomagnetism (time variations, diurnal to secular – time variations, secular and long term) Interplanetary physics (interplanetary magnetic field)https://www.ann-geophys.net/20/1519/2002/angeo-20-1519-2002.pdf |
| spellingShingle | R. P. Kane R. P. Kane Evolution of geomagnetic <i>aa</i> index near sunspot minimum Annales Geophysicae |
| title | Evolution of geomagnetic <i>aa</i> index near sunspot minimum |
| title_full | Evolution of geomagnetic <i>aa</i> index near sunspot minimum |
| title_fullStr | Evolution of geomagnetic <i>aa</i> index near sunspot minimum |
| title_full_unstemmed | Evolution of geomagnetic <i>aa</i> index near sunspot minimum |
| title_short | Evolution of geomagnetic <i>aa</i> index near sunspot minimum |
| title_sort | evolution of geomagnetic i aa i index near sunspot minimum |
| url | https://www.ann-geophys.net/20/1519/2002/angeo-20-1519-2002.pdf |
| work_keys_str_mv | AT rpkane evolutionofgeomagneticiaaiindexnearsunspotminimum AT rpkane evolutionofgeomagneticiaaiindexnearsunspotminimum |