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Abnormal Phase-shift Quiet Days (APQDs) in Earth’s horizontal magnetic field were compared during low (2009) and high (2015) solar activities using 1-min data from 30 INTERMAGNET observatories. Quiet days were selected using Symmetric-H (SYM-H) index, \( |\mathrm {SYM-H}| \le 10\,\textrm{nT} \) . Solar quiet (Sq) variations of the H-component were calculated after converting to solar local time and correcting non-cyclic variations. Sq foci positions were analysed across three longitude sectors between (± 60 \(^{\circ }\) ) magnetic latitudes (North/South America, Europe/Africa, Asia-Japan-Australia). Most Sq focus position variations in 2009 occurred in the D season (Jan, Feb, Nov, Dec) and J Season (May-Aug). Most Sq focus position variations in 2009 occurred in the D season and during the J season in the Southern Hemisphere (SH) in all sectors. In the D season, low-latitude (|LL| \(\le \) 30 \(^{\circ }\) ) APQDs were \(30\%\) and \(31\%\) in the Northern Hemisphere (NH), \(9\%\) and \(13\%\) in SH. At mid-latitudes (30 \(^{\circ }\) \(\le \) \(|\text {ML}|\) \(\le \) 60 \(^{\circ }\) ), APQDs in 2009 peaked in the D season ( \(23\%\) NH, \(28\%\) SH) and in 2015, in the E season (April, May, September and October; \(14\%\) NH, \(24\%\) SH). CZT showed APQDs of \(57\%\) and \(71\%\) in 2009 and 2015. At Sq focus positions, 9 NH and 5 SH APQDs occurred in 2009, with 4 NH APQDs in 2015.

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Statistical Analysis of Abnormal Phase-Shift Quiet Days (APQDs) in Low/Mid-Latitudes During Low and High Solar Activities in Solar Cycle 24

  • 会议论文

  • 发表日期：

    2026年

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  • Muneeza Ali,
  • Emmanuel Nahayo,
  • Zama Katamzi-Joseph,
  • Mpho Tshisaphungo

摘要

Abnormal Phase-shift Quiet Days (APQDs) in Earth’s horizontal magnetic field were compared during low (2009) and high (2015) solar activities using 1-min data from 30 INTERMAGNET observatories. Quiet days were selected using Symmetric-H (SYM-H) index, \( |\mathrm {SYM-H}| \le 10\,\textrm{nT} \) . Solar quiet (Sq) variations of the H-component were calculated after converting to solar local time and correcting non-cyclic variations. Sq foci positions were analysed across three longitude sectors between (± 60 \(^{\circ }\) ) magnetic latitudes (North/South America, Europe/Africa, Asia-Japan-Australia). Most Sq focus position variations in 2009 occurred in the D season (Jan, Feb, Nov, Dec) and J Season (May-Aug). Most Sq focus position variations in 2009 occurred in the D season and during the J season in the Southern Hemisphere (SH) in all sectors. In the D season, low-latitude (|LL| \(\le \) 30 \(^{\circ }\) ) APQDs were \(30\%\) and \(31\%\) in the Northern Hemisphere (NH), \(9\%\) and \(13\%\) in SH. At mid-latitudes (30 \(^{\circ }\) \(\le \) \(|\text {ML}|\) \(\le \) 60 \(^{\circ }\) ), APQDs in 2009 peaked in the D season ( \(23\%\) NH, \(28\%\) SH) and in 2015, in the E season (April, May, September and October; \(14\%\) NH, \(24\%\) SH). CZT showed APQDs of \(57\%\) and \(71\%\) in 2009 and 2015. At Sq focus positions, 9 NH and 5 SH APQDs occurred in 2009, with 4 NH APQDs in 2015.