On the climate of the solar-terrestrial space

Crisan Demetrescu, Venera Dobrica, Georgeta Maris Muntean, Institute of Geodynamics, Romanian Academy, Bucharest, Romania, crisan@geodin.ro

Katya Georgieva, Boian Kirov Space Research and Technologies Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria

Acknowledgements: Research funded by the Project UEFISCDI – IDEI 93/2011

Outline

Some definitions

Geomagnetic variability – geomagnetic indices

Review of instrumental data

Reconstructions

Space climate features

Conclusions

Space weather refers to conditions on the Sun and in the solar wind,magnetosphere, ionosphere, and thermosphere that can influence the performanceand reliability of space-borne and ground-based technological systems and canendanger human life or health.

We are interested in Space climate...

…the long-term change in the Sun, and its effects in the heliosphere and uponthe Earth, including the atmosphere and climate.

Effects

Disruption of - satellite operations- comunication- navigation- electric power grids on ground (GICs)- hydrocarbon distribution grids

Exposure of astronauts

Heart/mental conditions

Study data – annual means

- Heliosphere (1AU): B, V, N, PwTSI, CR

- Magnetosphere: aa, IDV, IHV, AE,PC, Dst

- Sun: R

- linear correlations- physical model + linearcorrelation

Space era - 1964

1868

1700

Reconstructions explicitly assume that one couldextrapolate before 1964:- the correlation between SW and HMF parameters and geomagnetic indices;- the validity of the Parker spiral theory;- the heliolatitudinal independence of the heliospheric magnetic flux from the Sun;- the coupling function between the solar wind and the magnetosphere.

The magnetosphere The ionosphere

Geomagnetic activity- geomagnetic indices

- effects of electric current systems in the magnetosphere and ionosphere as a result of theinteraction with the solar wind and the heliospheric magnetic field.

Geomagnetic indices: Dst, AE

- Dst index (magnetospheric ringcurrent) derived from geomagneticvariations in the horizontal componentfrom 4 selected observatories relativelyclose to the equator (hourly valuesstarting in 1957)

- AE index (auroral electrojet), derivedfrom geomagnetic variations in thehorizontal component from 12 selectedobservatories along the auroral zone inthe northern hemisphere (hourly valuesstarting in 1957)

PC~Em=Vsw*BT*sin(q/2)*sin(q/2)q=acos(Bz/BT)

PC (n

T)

Em

(mV

/m)

- PC index (Polar Cap magnetic activitygenerated by the geoeffectiveinterplanetary electric field Em(fifteen-minute index starting in 1975)

Dst, AE, PC affect the geomagnetic activity at local scale

Geomagnetic indices: PC

- Ap index (intensity of planetary magneticactivity) derived from 13 observatories atsubauroral latitudes (3-h values, starting in1932)

Geomagnetic indices: aa, Ap

- aa index (level of global geomagneticactivity) derived from 2 antipodalobservatories at mid-latitude (3-h values,starting in 1868)

0

100

200

300

400

1932 1942 1952 1962 1972 1982 1992 2002 2012Year

0

100

200

300

400

1932 1942 1952 1962 1972 1982 1992 2002 2012Year

1940 1950 1960 1970 1980 1990 2000 2010

B

V

N

aa

PC

Dst

AE

CR

R

IDV

18 19 20 21 22 23

TSI

10 15 20 25 30 35 40aa (nT)

-40

-30

-20

-10

0

10

Dst = -0.986 * aa + 6.95R2 = 0.60

10 15 20 25 30 35 40aa (nT)

100

150

200

250

300

350

AE = 8.698 * aa + 11.81R2 = 0.94

c.c. 0.88

c.c. 0.90

c.c. -0.81

c.c. 0.88

c.c. -0.77

Though designed to describe various current systems in magnetosphere & ionosphere,- separation of effects is not total- the long-term variability of various parts of the magnetosphere/ionosphere

system is similar

Long-term geomagnetic variabilityInterannual scale

11-year smoothed

Long-term geomagnetic variabilityInterdecadal scale

18 20 22 24 26 28aa (nT)

160

180

200

220

240

260

AE11 = 10.70 * aa11 - 39.62R2 = 0.75

c.c. 0.96

c.c. 0.82

c.c. -0.55

c.c. 0.87

c.c. -0.93

- the geomagnetic indices correlate well with eachother at interannual time scales and the correlationgenerally improves if the solar cycle effect isremoved

1860 1880 1900 1920 1940 1960 1980 2000Year

100

200

300

400

500

600

V (k

m/s

)

10 15 20 25 30 35 40aa (nT)

40

80

120

160

200

240

280

BV

02

BV02 = 6.3924 * aa - 13.7732

R2 = 0.91

1860 1880 1900 1920 1940 1960 1980 2000Year

0

2

4

6

8

10

B (n

T)

6 8 10 12 14 16 18IDV (nT)

5

6

7

8

9

10

B (n

T)

B = 0.400 * IDV + 2.64R2 = 0.8120

2122

23

Svalgaard&Cliver (JGR2005)Rouillard et al., (JGR2007)Svalgaard&Cliver (JGR2007)Demetrescu&Dobrica (ASR2010)

- based on correlations: B-IDVBV2-aa

Reconstructions to 1870

- the long geomagnetic time series recorded atgeomagnetic observatories have provided means tocharacterize the Sun-Earth interaction at times priorto space era, via geomagnetic indices

1

1.5

2

2.5

3

3.5

Pw11

(nPa

)

1860 1880 1900 1920 1940 1960 1980 2000Year

10

15

20

25

30

aa11(nT

)

measured Pw11reconstructed Pw11aa11

In terms of 11-year averages

aa

PwPw

11 (n

Pa)

Reconstructions to 1870- based on correlations: Pw - aa

Dobrica et al., Sun&Geosphere 2012

Standoff distance of the dayside magnetopause (L)

612 /wo /PMμkL

M - the magnetic moment of the Earth's dipolePw - the dynamic pressure of the solar wind atmagnetopauseµo - the permeability of the vacuumk - constant 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

Year

7.6

8

8.4

8.8

9.2

9.6

M (1

022 A

m2 )

GUFMIGRFCM4

Reconstructions to 1870- based on correlations: Pw - aa

L11

(RE)

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010Year

8.8

9.2

9.6

10

10.4

10.8

L (R

E)

Dobrica et al., Sun&Geosphere 2012

c.c. 0.90

c.c. 0.88

Reconstructions to 1870- based on correlations: PC – AE

PC – aa

TSI – model linking the solar radiative output withthe contributing features of the photosphere(sunspots&faculae) (Lean et al., 1995; Lean etal.,2000), orwith the solar surface magnetic flux (Solanki et al.,2002; Krivova et al.,2007)

Fs – model using solar magnetograph data in thePotential Field Source Surface (PFSS) method(Wang&Sheely, 1995; 2002)

- model for the emergence and long-termevolution of the solar flux (Solanki et al., 2000,2002; Lean et al.,2002; Wang et al., 2005)

GCR flux, Ф – reconstruction of the open flux fromsunspot numbers (Solanki et al., 2002) inconjunction with a spherically symmetric model ofthe heliosphere (Usoskin et al., 2002a) toreconstruct the intensity of GCR at Earth (Usoskinet al., 2002b)

Reconstructions to 1700- based on physical models + correlations (R)

Trends in data (interdecadal and centennial)Standardized 11, 22 and ~88-year running averages

Curves are reduced to their means over the common time interval andscaled with their standard deviations about the mean as a unit

Signature of the Hale and Gleissberg cycles

The solar-heliospheric-magnetospheric environment

Demetrescu&Dobrica, JGR 2008Demetrescu et al., ASR 2010

Stan

dard

dev

iatio

n

Standard deviation

Stan

dard

dev

iatio

n

Stan

dard

dev

iatio

n

Standard deviation

Stan

dard

dev

iatio

n

Conclusions

- V, B, PC (indirectly Em), Pw, L were reconstructed prior to space era;

- signatures of the magnetic (Hale) cycle and of the Gleissberg cycle of the solaractivity have been evidenced in the HMF, in the SW speed, in the dynamicalpressure of the SW at magnetopause, in the TSI, in the open solar magnetic flux, inthe GCR flux and in the geomagnetic activity;

- the long-discussed centennial increase of geomagnetic activity and the doubling ofsolar open flux in the twentieth century, defined in terms of 11-year averages ofgeomagnetic indices and, respectively, FS, have been shown to be the result of thesuperposition of the MC and GC signatures in the data;

- when scaled by the standard deviation from the average value for the commoninterval covered by the data, the MC and GC signals are quite similar in theheliosphere – magnetosphere environment, pointing to a common pacing source,the solar dynamo;

- the results contribute to better defining the space climate concept.