Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle
<p>Predicting the maximum intensity of geomagnetic activity for an upcoming solar cycle is important in space weather service and for planning future space missions. This study analyzed the highest and lowest 3-hourly <span class="inline-formula"><i>a</i><i>a&...
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Copernicus Publications
2020-12-01
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| Series: | Annales Geophysicae |
| Online Access: | https://angeo.copernicus.org/articles/38/1237/2020/angeo-38-1237-2020.pdf |
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doaj-57c6d854ec81421a8c45957a78906664 |
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Article |
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DOAJ |
| language |
English |
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Article |
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DOAJ |
| author |
Z. Du Z. Du |
| spellingShingle |
Z. Du Z. Du Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle Annales Geophysicae |
| author_facet |
Z. Du Z. Du |
| author_sort |
Z. Du |
| title |
Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle |
| title_short |
Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle |
| title_full |
Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle |
| title_fullStr |
Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle |
| title_full_unstemmed |
Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle |
| title_sort |
estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle |
| publisher |
Copernicus Publications |
| series |
Annales Geophysicae |
| issn |
0992-7689 1432-0576 |
| publishDate |
2020-12-01 |
| description |
<p>Predicting the maximum intensity of geomagnetic activity for an
upcoming solar cycle is important in space weather service and for
planning future space missions. This study analyzed the
highest and lowest 3-hourly <span class="inline-formula"><i>a</i><i>a</i></span> index (<span class="inline-formula"><i>a</i><i>a</i><sub>H</sub>∕<i>a</i><i>a</i><sub>L</sub></span>)
in a 3 d interval, smoothed by 363 d to analyze their variation
with the 11-year solar cycle. It is found that the maximum of
<span class="inline-formula"><i>a</i><i>a</i><sub>H</sub></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="e4bab275520ea3f63927603c5ed18c4a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00001.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00001.png"/></svg:svg></span></span>) is well correlated with the
preceding minimum of either <span class="inline-formula"><i>a</i><i>a</i><sub>H</sub></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">min</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="ccd24d12f306e83ebeafabab51d03aaf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00002.svg" width="30pt" height="12pt" src="angeo-38-1237-2020-ie00002.png"/></svg:svg></span></span>,
<span class="inline-formula"><i>r</i>=0.85</span>) or <span class="inline-formula"><i>a</i><i>a</i><sub>L</sub></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">L</mi><mi mathvariant="normal">min</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="d6d4c4b79e0e68f778692d4e761ff5a1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00003.svg" width="29pt" height="12pt" src="angeo-38-1237-2020-ie00003.png"/></svg:svg></span></span>, <span class="inline-formula"><i>r</i>=0.89</span>) for
the solar cycle. Based on these relationships, the intensity of
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="dbaf00dd8342df378c868a18de160465"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00004.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00004.png"/></svg:svg></span></span> for solar cycle 25 is estimated to be
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub><mo>(</mo><mn mathvariant="normal">25</mn><mo>)</mo><mo>=</mo><mn mathvariant="normal">83.7</mn><mo>±</mo><mn mathvariant="normal">6.9</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="112pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="ba699b31eeee7950508c29fb22d84734"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00005.svg" width="112pt" height="15pt" src="angeo-38-1237-2020-ie00005.png"/></svg:svg></span></span> (nT), about 29 % stronger than
that of solar cycle 24. This value is equivalent to the <span class="inline-formula"><i>a</i><i>p</i></span> index
of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>p</mi><mi mathvariant="normal">max</mi></msub><mo>(</mo><mn mathvariant="normal">25</mn><mo>)</mo><mo>=</mo><mn mathvariant="normal">47.4</mn><mo>±</mo><mn mathvariant="normal">4.4</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="111pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="929be1c1601d65673acd51a4addbeab3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00006.svg" width="111pt" height="13pt" src="angeo-38-1237-2020-ie00006.png"/></svg:svg></span></span> (nT) if employing the high
correlation between <span class="inline-formula"><i>a</i><i>p</i></span> and <span class="inline-formula"><i>a</i><i>a</i></span> (<span class="inline-formula"><i>r</i>=0.93</span>). The maximum of
<span class="inline-formula"><i>a</i><i>a</i><sub>L</sub></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">L</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="6381010e8d5856597fd44d8244156ddc"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00007.svg" width="31pt" height="12pt" src="angeo-38-1237-2020-ie00007.png"/></svg:svg></span></span>) is also well correlated with
the preceding <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">min</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="d2856882850b11d389fc60a9dc0e29f3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00008.svg" width="30pt" height="12pt" src="angeo-38-1237-2020-ie00008.png"/></svg:svg></span></span> (<span class="inline-formula"><i>r</i>=0.80</span>). The maximum amplitude
of the sunspot cycle (<span class="inline-formula"><i>R</i><sub>m</sub></span>) is much better correlated
with high geomagnetic activity (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M25" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="7ecba83ef361bf620144ecd0bf06ca1e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00009.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00009.png"/></svg:svg></span></span>, <span class="inline-formula"><i>r</i>=0.79</span>)
than with low geomagnetic activity (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M27" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">L</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="e44bcfa019069d57ee9b4f8d66452b8d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00010.svg" width="31pt" height="12pt" src="angeo-38-1237-2020-ie00010.png"/></svg:svg></span></span>, <span class="inline-formula"><i>r</i>=0.37</span>). The rise
time from <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M29" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">min</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="032c0c106f467d5f03ea5b9da754e765"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00011.svg" width="30pt" height="12pt" src="angeo-38-1237-2020-ie00011.png"/></svg:svg></span></span> to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M30" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="afb9d013c02a9e0f3f85ef08fc9e7f67"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00012.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00012.png"/></svg:svg></span></span> is weakly
anti-correlated to the following <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M31" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="9c4127e092458fddcaabe7a54dbdd9e3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00013.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00013.png"/></svg:svg></span></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M32" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>r</mi><mo>=</mo><mo>-</mo><mn mathvariant="normal">0.42</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="3cc7caedea4d6450e8263247af803c11"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00014.svg" width="49pt" height="10pt" src="angeo-38-1237-2020-ie00014.png"/></svg:svg></span></span>).
Similar correlations are also found for the 13-month smoothed
monthly mean <span class="inline-formula"><i>a</i><i>a</i></span> index. These results are expected to be useful
in understanding the geomagnetic activity intensity of solar cycle 25.</p> |
| url |
https://angeo.copernicus.org/articles/38/1237/2020/angeo-38-1237-2020.pdf |
| work_keys_str_mv |
AT zdu estimatingthemaximumofthesmoothedhighest3hourlyiaiiaiindexin3thinspdbytheprecedingminimumforthesolarcycle AT zdu estimatingthemaximumofthesmoothedhighest3hourlyiaiiaiindexin3thinspdbytheprecedingminimumforthesolarcycle |
| _version_ |
1724382450064293888 |
| spelling |
doaj-57c6d854ec81421a8c45957a789066642020-12-15T12:32:14ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762020-12-01381237124510.5194/angeo-38-1237-2020Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycleZ. Du0Z. Du1Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, People's Republic of ChinaUniversity of Chinese Academy of Science, Beijing, People's Republic of China<p>Predicting the maximum intensity of geomagnetic activity for an upcoming solar cycle is important in space weather service and for planning future space missions. This study analyzed the highest and lowest 3-hourly <span class="inline-formula"><i>a</i><i>a</i></span> index (<span class="inline-formula"><i>a</i><i>a</i><sub>H</sub>∕<i>a</i><i>a</i><sub>L</sub></span>) in a 3 d interval, smoothed by 363 d to analyze their variation with the 11-year solar cycle. It is found that the maximum of <span class="inline-formula"><i>a</i><i>a</i><sub>H</sub></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="e4bab275520ea3f63927603c5ed18c4a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00001.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00001.png"/></svg:svg></span></span>) is well correlated with the preceding minimum of either <span class="inline-formula"><i>a</i><i>a</i><sub>H</sub></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">min</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="ccd24d12f306e83ebeafabab51d03aaf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00002.svg" width="30pt" height="12pt" src="angeo-38-1237-2020-ie00002.png"/></svg:svg></span></span>, <span class="inline-formula"><i>r</i>=0.85</span>) or <span class="inline-formula"><i>a</i><i>a</i><sub>L</sub></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">L</mi><mi mathvariant="normal">min</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="d6d4c4b79e0e68f778692d4e761ff5a1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00003.svg" width="29pt" height="12pt" src="angeo-38-1237-2020-ie00003.png"/></svg:svg></span></span>, <span class="inline-formula"><i>r</i>=0.89</span>) for the solar cycle. Based on these relationships, the intensity of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="dbaf00dd8342df378c868a18de160465"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00004.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00004.png"/></svg:svg></span></span> for solar cycle 25 is estimated to be <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub><mo>(</mo><mn mathvariant="normal">25</mn><mo>)</mo><mo>=</mo><mn mathvariant="normal">83.7</mn><mo>±</mo><mn mathvariant="normal">6.9</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="112pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="ba699b31eeee7950508c29fb22d84734"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00005.svg" width="112pt" height="15pt" src="angeo-38-1237-2020-ie00005.png"/></svg:svg></span></span> (nT), about 29 % stronger than that of solar cycle 24. This value is equivalent to the <span class="inline-formula"><i>a</i><i>p</i></span> index of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>p</mi><mi mathvariant="normal">max</mi></msub><mo>(</mo><mn mathvariant="normal">25</mn><mo>)</mo><mo>=</mo><mn mathvariant="normal">47.4</mn><mo>±</mo><mn mathvariant="normal">4.4</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="111pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="929be1c1601d65673acd51a4addbeab3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00006.svg" width="111pt" height="13pt" src="angeo-38-1237-2020-ie00006.png"/></svg:svg></span></span> (nT) if employing the high correlation between <span class="inline-formula"><i>a</i><i>p</i></span> and <span class="inline-formula"><i>a</i><i>a</i></span> (<span class="inline-formula"><i>r</i>=0.93</span>). The maximum of <span class="inline-formula"><i>a</i><i>a</i><sub>L</sub></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">L</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="6381010e8d5856597fd44d8244156ddc"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00007.svg" width="31pt" height="12pt" src="angeo-38-1237-2020-ie00007.png"/></svg:svg></span></span>) is also well correlated with the preceding <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">min</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="d2856882850b11d389fc60a9dc0e29f3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00008.svg" width="30pt" height="12pt" src="angeo-38-1237-2020-ie00008.png"/></svg:svg></span></span> (<span class="inline-formula"><i>r</i>=0.80</span>). The maximum amplitude of the sunspot cycle (<span class="inline-formula"><i>R</i><sub>m</sub></span>) is much better correlated with high geomagnetic activity (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M25" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="7ecba83ef361bf620144ecd0bf06ca1e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00009.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00009.png"/></svg:svg></span></span>, <span class="inline-formula"><i>r</i>=0.79</span>) than with low geomagnetic activity (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M27" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">L</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="e44bcfa019069d57ee9b4f8d66452b8d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00010.svg" width="31pt" height="12pt" src="angeo-38-1237-2020-ie00010.png"/></svg:svg></span></span>, <span class="inline-formula"><i>r</i>=0.37</span>). The rise time from <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M29" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">min</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="032c0c106f467d5f03ea5b9da754e765"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00011.svg" width="30pt" height="12pt" src="angeo-38-1237-2020-ie00011.png"/></svg:svg></span></span> to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M30" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="afb9d013c02a9e0f3f85ef08fc9e7f67"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00012.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00012.png"/></svg:svg></span></span> is weakly anti-correlated to the following <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M31" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>a</mi><msub><mi>a</mi><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mi mathvariant="normal">max</mi></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="9c4127e092458fddcaabe7a54dbdd9e3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00013.svg" width="32pt" height="12pt" src="angeo-38-1237-2020-ie00013.png"/></svg:svg></span></span> (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M32" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>r</mi><mo>=</mo><mo>-</mo><mn mathvariant="normal">0.42</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="3cc7caedea4d6450e8263247af803c11"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-38-1237-2020-ie00014.svg" width="49pt" height="10pt" src="angeo-38-1237-2020-ie00014.png"/></svg:svg></span></span>). Similar correlations are also found for the 13-month smoothed monthly mean <span class="inline-formula"><i>a</i><i>a</i></span> index. These results are expected to be useful in understanding the geomagnetic activity intensity of solar cycle 25.</p>https://angeo.copernicus.org/articles/38/1237/2020/angeo-38-1237-2020.pdf |