Variations of the Magnetic Fields of the Sun and the Earth In 7–50 Day Periods

Bobova, V. P.; Stepanian, N. N.

doi:10.1007/978-94-011-0950-5_43

Cited by 3 publications

(2 citation statements)

References 2 publications

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“…This result expands on the finding by Mursula and Zieger [1996] that the 13.5 day period at Earth was found predominantly during the solar minimum, owing to the occurrence of two high‐speed solar wind streams per solar rotation. Alternatively, Bobova and Stepanina [1994] suggested that a 13.5 day period is due to similar periodic variations in the solar chromospheres occurring mainly around solar cycle maxima. The same 13.5 day periodicities are also observed in the X‐ray, extreme ultraviolet, and ultraviolet [ Donnelly and Puga , 1990; Hocke , 2008; Liang et al , 2008].…”

Section: Resultsmentioning

confidence: 99%

Response of the topside ionosphere to recurrent geomagnetic activity

Liu

Wan

et al. 2010

J. Geophys. Res.

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[1] In the present study we investigate the solar activity, local time, and latitudinal dependence of the topside ionosphere response to recurrent geomagnetic activity, using 8 years (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) of data on total ion density (Ni) retrieved from Defense Meteorological Satellites Program observations at about 840 km altitude. It is the first attempt to explore the presence of oscillations in the topside ionosphere in response to recurrent geomagnetic activity. Results indicate that striking periodic oscillations around 9 days in Ni are present during the latter part of the declining phase of solar cycle 23. The percentage of the magnitude of 9 day oscillations relative to background values in Ni at 2130 LT tends to be 5%-10% larger than at three other local times (0930, 0510, and 1710 LT). Moreover, latitudinal profiles of bandpass-filtered 9 day perturbations in Ni show multiple peaks as a function of local time and day of the year, which is distinctly different from previous results at or around the F2 layer peak. There are in-phase correlations between Kp and the Ni responses in the winter hemisphere and at middle and low latitudes, and approximately anti-phase at high latitude in the summer hemisphere. Additionally, the 9 day oscillations in ion temperature are is mainly restricted to high latitudes. The combined effects of neutral winds, E × B drift, auroral ionization precipitation, and migration of subauroral trough region are possible candidates to explain the latitudinal profiles of the 9 day variations in Ni.

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Section: Resultsmentioning

confidence: 99%

Response of the topside ionosphere to recurrent geomagnetic activity

Liu

Wan

et al. 2010

J. Geophys. Res.

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“… Bobova and Stepanian [1994] suggested that the 13.5 day periodicity in geomagnetic activity is due to similar periodicity in solar chromospheric variables and can be associated with solar fluxes. However, Mursula and Zieger [1996] found that the prominent 13.5 day periodicity in the solar wind is more related to geomagnetic activity indices than the solar irradiances during the declining phase of solar cycles.…”

Section: Ionospheric Responses To the Recurrent Geomagnetic Activitymentioning

confidence: 99%

Ionosphere response to recurrent geomagnetic activity in 1974

Fang

Forbes

2012

J. Geophys. Res.

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[1] The 9 day variation of Earth's thermosphere neutral density in 2005 and 2006 is known to have been influenced by rotating solar coronal holes and the quasiperiodic solar wind high-speed streams (HSSs) and by the concomitant recurrent geomagnetic activity that they induce. The corresponding responses in ion temperature, ionospheric electron density, and total electron content have also been reported during the same period. In 1974, a significant 13.5 day periodicity in geomagnetic activity was created by the quasiperiodic HSS associated with two major solar coronal hole regions separated by about 180°. In the present paper, ionospheric F-region peak plasma density (N m F 2 ) and height (h m F 2 ) in the daytime and nighttime from 12 ionosonde stations are analyzed to delineate the responses to this epoch of HSS forcing of the geospace system. Results show that the ionospheric responses to this 13.5 day periodic forcing are similar in some ways to responses to the 9 day periodicity. For instance, in middle and high latitudes, daytime and nighttime N m F 2 is mostly out of phase with the fluctuations in the daily mean K p index (K p ), while the daytime h m F 2 are in phase with the K p fluctuations. Empirical model results confirm the important role of thermal expansion in connecting thermospheric and ionospheric changes driven by high-speed streams and recurrent geomagnetic activity. At low latitudes, the 13.5 day signatures are not as straightforward as those at middle and high latitudes, and significant spectral energy thought to be connected with planetary waves and perhaps other lower-atmosphere influences exists at periods of less than 13.5 days.

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