Long‐term variation of Ampère force by geomagnetic Sq currents and thermospheric pressure difference. Issue 11 (12th November 2016)

• Record Type: Journal Article
• Authors: Takeda, Masahiko
• Is Part Of: Journal of geophysical research. Volume 121:Issue 11(2016:Nov.)
• Page Start: 11, 407
• Page End: 11, 412
• Publication Date: 2016-11-12
• Subjects: Sq variation -- geomagnetism -- Ampère force -- thermospheric pressure -- long term; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022845
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The long‐term variation of the Ampère force exerted by geomagnetic Sq currents was studied in relation to the thermospheric pressure. First, the long‐term trend of the pressure difference was estimated using a linear regression coefficient based on a high correlation between the Ampère force and the pressure difference in recent years. The pressure difference may be inferred from solar parameters such as solar sunspot number; inspection of the difference from Sq has a merit that it gives the "response" of the thermosphere in contrast with the "input" parameters of the solar activity index. Next, the effect of the version up of sunspot number was examined. The correlation of the Ampère force with sunspot number updated in 2015 (version 2) is slightly higher than that with old sunspot number (version 1), which suggests that the later version is an improved index for the solar activity and its effect on the state of the thermosphere. Last, the correlation between total Sq currents and sunspot number was found to be less than that between the Ampère force and sunspot number, although the difference is small and could not be statistically significant. This suggests that the geomagnetic main field affects the relation between the Ampère force and the pressure difference. Key Points: Long‐term variation of a neutral pressure difference can be estimated from the geomagnetic field only Correlation of Ampère force with solar sunspot number version 2 is slightly higher than that with version 1 Correlation between Ampère force and solar sunspot number is generally better than total Sq currents