A minimum in the latitude variation of spread-F at March equinox

作者：Balan, N.^*; Maruyama, T.; Patra, A. K.; Narayanan, V. L.

来源：Progress in Earth and Planetary Science, 2018, 5(1): 27.

DOI：10.1186/s40645-018-0180-y

• Low-mid latitude spread-F
• Minimum and maximum in spread-F

This short paper presents the statistics of spread-F occurrence at four low-mid latitude locations (17.0 degrees N, 21.2 degrees N, 26.5 degrees N and 36.5 degrees N mag. lat.) in Japan longitude sector (similar to 135 degrees E) in March to April 2002, 2003 and 2006 ( high, medium and low solar activity). The location of a spread-F minimum predicted by theoretical models is identified for the first time. The spread-F minimum occurs at the poleward side of the equatorial ionisation anomaly crest and shifts equatorward from similar to 25 degrees N mag. lat. at high solar activity to below 17 degrees N at low solar activity. The corresponding spread-F maximum occurring on the poleward side of the minimum also shifts equatorward from similar to 35 degrees N (or beyond) at medium solar activity to 20 degrees-25 degrees N at low solar activity. The spread-F occurrence increases with decreasing solar activity at all locations especially at higher latitudes (> similar to 25 degrees N) where there is almost no occurrence at high solar activity.

• 出版日期2018-5-2
• 单位中国科学院地质与地球物理研究所; 中国科学院地质与地球物理研究所兰州油气资源研究中心