1. Variable Sun-Earth energy coupling: dependence on solar cycle strength
M. Yamauchi
Swedish Institute of Space Physics, Kiruna
Acknowledgements:
Kp is an official IAGA endorsed index that is provided by GFZ, Adolf-Schmidt-Observatory Niemegk, Germany, through
ftp://ftp.gfz-potsdam.de/pub/home/obs/kp-ap/
The sunspot numbers are provided by the Royal Observatory of Belgium, Brussels, through
(EGU ) Wednesday 1

2. Extremely low solar activity since last solar minimun
 Effect on the Earth?
(SCOSTEP VarSITI program)
Kiruna (65° GMLat) K index during the current maximum #24 (2011~) is nearly the same as values at solar minimums.
note: UT means LT, and magnetic midnight sector when aurora activity causes large K 2

3. Monthly Sunspot number (SSN) – Kp relation3

4. SSN – Kp (subdivided by different phases)
Min
Incl.
Max
Decl.
1. Each solar cycle must be subdivided by different phases (the solar wind condition is different for the same SSN)
2. Kp since 2004 are the lowest for the same SSN 4

5. Reconstruct Kp from SSN
(note: subdivide by different phases)
⇒ reconstruct within standard deviation except the last 10 years.
⇒ change from 2004 is clear 5

6. Further sorting out by different SSN level
Distribution of different Kp level (monthly averaged∑Kp/day) for given SSN range. Different colors (left) or panels (top) correspond to different solar cycles. 6

7. cf. probability of Kp≥5 (instead of average Kp)
The graph for "probabilities of Kp≥5" (numbers of 3-h periods/month) instead of "daily sum ∑Kp". 7

8. Summary & conclusions
Monthly-averaged Geomagnetic activities GMLat and for the same monthly sunspot numbers (SSN) are different between (a) different phases of a solar cycle & (b) different solar cycles.
If these differences are considered, it is possible to reconstruct 3-month averaged Kp from 3-month averaged SSN.
This "monthly averaged SSN-to-Kp response" depends on the amplitude of the solar cycle (peak SSN at maximum). In this sense, this relation during 1930's and 1960's are in between the most recent 10 years and the other period.
The extremely low "monthly averaged SSN-to-Kp response" of the current solar cycle started around January (but this & variation of general Sun-Earth coupling should be reexamined using actual solar wind data in future). 8

9. “Chance of minor storm@high-latitude” by NOAA vs. observed Kp
(Anna Larsson, high-school student project)
% of observed Kp (largest of the day)
For the same prediction level (model is different between 2000 ⇔ 2011), observed Kp values are : < & < 9