SORCE 2010, Keystone, CO, May 19, 2010
http://arxiv.org/ftp/arxiv/papers/1002/1002.2934.pdf
Svalgaard & Cliver JGR 2009JA015069 (in press)
Stanford University, CA
leif@leif.org
http://www.leif.org/research
Leif Svalgaard
Heliospheric Magnetic Field
1835-2010
1
A quantitative measure of the effect can be formed as a series of the unsigned
differences between consecutive days: The InterDiurnal Variability, IDV-index
24-hour running means of the Horizontal Component of the low- & midlatitude geomagnetic field remove most of local time effects and leaves a
Global imprint of the Ring Current [Van Allen Belts]:
2
0
2
4
6
8
10
0
B nT
2
4
6
0.6444
y = 1.4771x
2
R = 0.8898
8
10
12
14
y = 0.4077x + 2.3957
2
R = 0.8637
HMF B as a Function of IDV09
1963-2010
Coverage
B std.dev
16
IDV
1995 2000 2005 2010
100% =>
1975 1980 1985 1990
B obs median
B calc from IDV
B obs
1960 1965 1970
10
9
8
7
6
5
4
3
2
1
0
nT
10
9
8
7
6
5
4
3
2
1
0
B
1970
1980
1990
2000
?
IDV Independent of Solar Wind Speed
2010
V
IDV
400
2
450
R = 0.0918
500
0
100
200
300
400
500
600
3
550
V km/s
IDV vs. Solar Wind Speed V (1963-2010)
IDV
0
350
2
4
6
8
10
12
14
16
18
0
1960
5
10
15
20
nT
IDV is strongly correlated with HMF B,
but is blind to solar wind speed V
0
1830
2
4
6
8
10
B nT
1840 1850
1840 1850
1870 1880
1890
1900 1910
1920 1930
1940
1950 1960
IDV Index and Number of Contributing Stations
1970
1860
1870 1880
1890
1900 1910
13
B (IDV)
1920 1930
1940
1950 1960
1970
1980 1990
B (obs)
1980 1990
Heliospheric Magnetic Field Strength B (at Earth) Inferred from IDV and Observed
1860
Individual stations
IDV nT
0
1830
5
10
15
20
25
2010
N
0
10
20
30
40
50
60
70
2000 2010
Year
23
2000
IDV and Heliospheric Magnetic Field Strength B for years 1835-2009
4
1890
1900
1910
B = 1.333 IDV
0.7
1920
1930
1940
Floor
1950
1960
13-rotation running means
1970
1980
B obs.
1990
2000
Heliospheric Magnetic Field Magnitude B from Geomagnetic Activity IDV (27-Day Bartels Rotations)
2010
5
The Figure shows how well the HMF magnitude B can be constructed from IDV.
Some disagreements in the 1980s are due to the HMF being only sparsely sampled
by spacecraft: in some rotations more than two thirds of the data is missing
0
1880
2
4
6
8
10
12
14
16
The previous Figures showed yearly average values. But we can also
do this on the shorter time scale of one solar rotation:
1910
1920
-0.45 <-Ds t>
<IDV>
IDV nT
0
1900
2
4
6
8
10
12
14
16
18
1930
1940
1950
1960
1970
1980
1990
Negative D st and IDV measure the same effect
2000
2010
J. Love has reconstructed Dst back to 1905 using data from several
geomagnetic observatories. For yearly averages: IDV = -0.45 [-Dst]
The negative part of the Dst-index is a measure of the strength of
the Ring Current. IDV has an excellent correlation with Dst
computed only from times when Dst was negative.
6
1890
1900
1910
IDV05
1920
1930
IDV09
1940
1950
L1999
1960
R2007
1970
1980
L2009
1990
2000
HMF obs
Convergence of HMF B of Lockwood & Rouillard et al. to Svalgaard & Cliver
B nT
0
1880
2
4
6
8
10
12
2010
The HMF [and the ‘open flux’
calculated from B] has been
controversial in the past, with
claims of a centennial doubling
of the Sun’s coronal magnetic
field. This is no longer the case.
Several groups have converged
to a firm consensus:
7
B nT
1850
B McC
1870
1890
Krakatoa?
1910
B LR&F
B S&C
1930
1950
1970
Be data spliced to Ionization Chamber data spliced to Neutron Monitor data
10
B OBS
1990
8
2010
The splicing of the ionization chamber data to the neutron monitor data around
1950 seems to indicate an upward jump in B of 1.7 nT which is not seen in the
geomagnetic data. The very low values in ~1892 are caused by excessive
10Be deposition [of unknown origin]
0
1830
2
4
6
8
10
Heliospheric Magnetic Field Comparisons
Reconstruction of HMF B from cosmic ray modulation [measured (ionization
chambers and neutron monitors) and inferred from 10Be in polar ice cores]
first gave results [McCracken 2007] discordant from our geomagnetic method:
Webber & Higbie [2010] point out “those are most likely not solely related to
changes in solar heliospheric modulation, but other effects such as local and
regional climate near the measuring sites may play a significant role.
~1890 is still a problem for cosmogenically-based reconstructions [25-yr means]:
A reconstruction by Steinhilber et al [2010] on basis of 10Be agrees
much better with ours based on IDV. The excessive deposition of 10Be
9
1840
1850
1860
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
Year
There seems to be both a Floor and a Ceiling and most importantly no longterm trend since the 1830s.
0
1830
1
2
Floor
R2 = 0.0019
4
3
Ceiling
Br nT
Radial Component of Heliospheric Magnetic Field at Earth
5
6
Since we can also estimate solar wind speed from geomagnetic indices
[Svalgaard & Cliver, JGR 2007] we can calculate the radial magnetic flux
from the total B using the Parker Spiral formula:
10
And that brings us within the subject of this meeting
The absence of long-term trend probably means that there was no long-term
trend in TSI as well:
11