Lecturer: M. Yamauchi and B. Olsthoorn Date: 2015-03-26 10:00 Place: Aniara
Long-term variation of Sun-Earth coupling efficiency: Is coming declining phase the most risky among past 100 years?
M. Yamauchi and B. Olsthoorn*
Swedish Institute of Space Physics, Kiruna
* leave Hague University, Applied Sciences, Delft, for undergraduate thesis
Abstract
The geoeffect of extremely low solar (sunspot) activity starting from the last solar minimum is one of the major space science issues. Instead of long-term variations of the solar wind or irradiation, the present study examines long-term variations of efficiency of how much energy actually reach the ground or ionosphere for the same solar wind conditions (density, velocity, energy flux and magnetic flux). The analyses indicate that the geomagnetic activities (e.g., Dst, Kp, and AL indices) for a given solar wind condition, namely the Sun-Earth coupling efficiency, decreased quantitatively from around 2006 until now compared to the previous four decades. This explains why we had so little aurora until last season despite of solar maximum.
However, the efficiency seems to be higher during recent year than previous sunspot cycles if the solar wind input exceeds 10^3 W/m^2 (this which corresponds to CME). In other word, we might have "deadly" magnetic storms with major power failure during the coming declining phase of the current solar cycle when we expect large CMEs. Problem of this urgent prognosis is that statistics is too little for any conclusion, and we need more data of high solar winds input. Since we cannot wait data from coming declining phase, we should use data from the past, i.e., before the solar wind data is available. This requires construction of database from old observations at least back to solar cycle 15 (100 years ago).
In the seminar, we should both the analyses result with the solar wind data and method of constructing database.
Created 2015-03-11 10:56:29 by Mats Holmström Last changed 2015-03-24 00:14:01 by Mats Holmström
