Differences in monthly medians of foF2 within seasons in the mid-latitude ionosphere during the period of low solar activity in 2007–2008 years

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Abstract

The paper presents a comparative analysis of diurnal variations in the monthly median critical frequency of the regular ionospheric F2 layer (foF2) for all “standard” seasons during the period of low solar activity in 2007–2008. The hourly data from manual processing of measurements taken at mid-latitude ground-based vertical ionospheric sounding stations Wakkanai (Japan) and Hobart (Australia) located almost symmetrically relative to the geographic equator were analyzed. It is found that the relative differences in the median of the third month of any of the “standard” seasons compared to the median of the second month of the season are significantly higher than the differences in the median of the first month of the season relative to the median of the second month of the season. It is also shown using a specific example of these two mid-latitude stations that, according to their characteristics, the median of November (the last month of the autumn season) corresponds to the beginning of the winter season, and the median of May (the last month of the spring season) – to the beginning of the summer season. It has been established that the relative contribution of solar radiation to changes in the value of the electron concentration at the maximum of the F region (NmF2) under conditions of low solar activity in equinoctial seasons, associated with variations in the value and rate of change of the solar zenith angle, is no less than half of the relative contribution to changes in NmF2 made by variations in the composition of the neutral atmosphere.

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About the authors

V. V. Hegai

Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN)

Author for correspondence.
Email: hegai@izmiran.ru
Russian Federation, Moscow, Troitsk

A. D. Legenka

Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN)

Email: leg@izmiran.ru
Russian Federation, Moscow, Troitsk

L. P. Korsunova

Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN)

Email: lpkors@rambler.ru
Russian Federation, Moscow, Troitsk

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Supplementary files

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2. Fig. 1. Daily distributions of monthly foF2med medians for the “standard” winter (left panels) and autumn (right panels) months for the Wakkanai NSWZ in the Northern Hemisphere (lower panels) and Hobart in the Southern Hemisphere (upper panels). The dashed-dotted lines show the medians of the first month of the corresponding season, the dashed lines show the medians of the second month, and the solid lines show the medians of the third month. The shaded rectangles below the abscissa axis mark the local time (LT) intervals from 18:00 to 06:00, and are centered at the top by a stylized image of a clock face that marks local midnight.

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3. Fig. 2. The same as Fig. 1, but for the “standard” summer (left panels) and spring (right panels) months.

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4. Fig. 3. Same as Fig. 1, but for the “standard” winter (left panels) and summer (right panels) months. The added solid lines with dots correspond to November (left panels) and May (right panels), respectively.

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5. Fig. 4. March (solid line) and September (dash-dotted line) medians of foF2med for the Hobart (upper panel) and Wakkanai (lower panel) NSWZIs. The dashed vertical line marks the time moment 04 UT, which corresponds to 13 LT for Wakkanai station and 15 LT for Hobart station. Additional designations are the same as in Fig. 1.

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6. Fig. 5. ε values in the “standard” winter (left) and spring (right) seasons for the Hobart (upper panels) and Wakkanai (lower panel) NSWZIs. Additional notations are the same as in Fig. 1.

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7. Fig. 6. The same as Fig. 5, but for the “standard” summer (left) and autumn (right) seasons.

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8. Fig. 7. Changes over an annual interval (from 01.12.2007 to 30.11.2008, abscissa axis) of the solar zenith angle (χ) for 12 LT, left ordinate axes (open circles) and median values of foF2med (for the same local time), right ordinate axes (solid lines with darkened circles) for the Hobart (upper panel) and Wakkanai (lower panel) NSWZIs, respectively. The day of the corresponding month is indicated in fractions above the open circles for ease of perception.

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