Post on 20-Jan-2016
Neutral Density During the Recent Solar Minimum
Contributions from Solar, Geomagnetic Activity, and Anthropogenic
Rodney ViereckNOAA Space Weather Prediction Center
Drag Data provided by John Emmert
NRL
MURI Workshop, Boulder
October 2010
400 km Neutral Density Derived from Satellite Drag(thanks to John Emmert, NRL)
1970 1975 1980 1985 1990 1995 2000 2005 2010
0.0
5.0x10-14
1.0x10-13
1.5x10-13
D
en
sity
(g
m/c
m3)
Year
Density (4 day running avg.) Density (365 day running avg.)
Drag Density at Solar Minima(log plot)
1970 1975 1980 1985 1990 1995 2000 2005 201010-15
10-14
10-13
7.44x10-15
8.49x10-15
4.578x10-15
D
en
sity
(g
m/c
m3)
Year
Density (4 day running avg.) Density (365 day running avg.)
9.397x10-15
Thermospheric DriversSolar EUV (F10), Geomagnetic Storms (Ap), Climate Change(CO2)
October 2010 Viereck: MURI 2010 4
1970 1975 1980 1985 1990 1995 2000 2005 2010-100
-80
-60
-40
-20
0
20
40
60
80
100
120
140
160
180
200
220
F
10
Year
F10
-20
-10
0
10
20
30
40
50
60
Ap
Ap
300320340360380400420440460480500520540560580600620640660680700
CO2
CO
2 (pp
mv)
Drag Density vs MSIS Density(again thanks to John Emmert)
1970 1975 1980 1985 1990 1995 2000 2005 201010-15
10-14
10-13
-0.96x10-15-0.44x10-15 -1.27x10-15
D
ensi
ty (
gm
/cm
3 )
Year
Drag Density (365 day running avg.) MSIS Density (365 day running avg.)
9.397x10-15
Delta: Difference between MSIS and Observed Neutral Density
MSIS only has Solar (F10) and Geomagnetic (Ap) inputs (no climate change)
Estimating the Anthropogenic Contribution
1975 1980 1985 1990 1995 2000 2005 2010
4.00E-016
6.00E-016
8.00E-016
1.00E-015
1.20E-015
1.40E-015
1.60E-015
1.80E-015
2.00E-015 Correction Polynomial Fit
De
nsi
ty C
orr
ect
ion
for
CO
2
Date
330 335 340 345 350 355 360 365 370 375 380 385 390 395 400
4.00E-016
6.00E-016
8.00E-016
1.00E-015
1.20E-015
1.40E-015
1.60E-015
1.80E-015
2.00E-015
2.20E-015
2.40E-015
2.60E-015
2.80E-015
3.00E-015
De
lta
Mauna Loa CO2 Density
Density offset (delta) vs CO2 data. (fitting a line to only the first three minima)
Extrapolating the correction to the full extent if the time seriesNote: This is about twice the rate of Roble’s estimate
Subtracting the Anthropogenic Correction
1970 1975 1980 1985 1990 1995 2000 2005 2010
1E-14
1E-13
D
en
sit (
gm
/cm
3 )
Year
Drag MSIS MSIS-CO2
Detailed Plot of the Observations vs MSIS(With and without the CO2 correction)
1970 1975 1980 1985 1990 1995 2000 2005 2010
4E-15
6E-15
8E-15
1E-14
1.2E-14
1.4E-14
1.6E-14
1.8E-14
2E-14
4.57E-15
5.20E-15
D
en
sit (
gm
/cm
3)
Year
Drag MSIS MSIS-CO2
7.11E-15
Note the excellent fit during the first three minima
Note the improved fit during the last minimum
Minimum Values
Solar IrradianceObservations vs Proxies
1996 1998 2000 2002 2004 2006 2008 2010
0.265
0.270
0.275
0.280
0.285
0.290
Daily MgII Index Mg II (365 Day Running Avg)
0.2632
Mg
II In
dex
(Rat
io)
Year
0.2644
F10 solar min to min variation is too small (2.3% of max-min)
1996 1998 2000 2002 2004 2006 2008 201050
100
150
200
250
300 Daily F10 F10 (365 Day Running Avg)
68
F10
Year
71
SEM 304 solar min to min variation is too large (14% of max-min)
1996 1998 2000 2002 2004 2006 2008 20105.00E+009
1.00E+010
1.50E+010
2.00E+010
2.50E+010
3.00E+010
3.50E+010
1.17E10
SEM 304 SEM 304 (365 Day Running Avg.)
SE
M 3
04 (
Pho
tons
/cm
2/se
c)
Year
9.42E9
Mg II index solar min to min variation is about right (7% of max-min)
Solar Data and Proxies Scaled to F10
1970 1975 1980 1985 1990 1995 2000 2005 201040
60
80
100
120
140
160
180
200
220
F
10
Year
F10 Mgfit SEMfit
Fitting SEM 304 and Mg II to F10 at the last minimum
MSIS Results Using the Three Solar Inputs(Corrected for CO2)
1970 1975 1980 1985 1990 1995 2000 2005 2010
1E-14
1E-13
N
eu
tra
l De
nsi
ty
Year
Drag MSIS With Mg II - CO2 MSIS With SEM - CO2 MSIS With F10 - CO2
MSIS Results Using the Three Solar Inputs(Details)
Mg II Index provides the best fit to the observed density
1970 1975 1980 1985 1990 1995 2000 2005 2010
4E-15
6E-15
8E-15
1E-14
1.2E-14
1.4E-14
1.6E-14
1.8E-14
2E-14
N
eu
tra
l De
nsi
ty
Year
Drag MSIS With Mg II - CO2 MSIS With SEM - CO2 MSIS With F10 - CO2
Relative Magnitude of the Density ChangesModeled density changes for each input while holding the other two constant
March 2008 Viereck: SDO and Space Weather 13
1970 1975 1980 1985 1990 1995 2000 2005 2010
1E-14
De
nsi
ty (
gm
/cm
3)
Year
CO2 Solar Geomag
Relative Contributions of the change from(1996 to 2009)Solar 1.49E-15 = 48%Geomag 1.03E-15 = 33%Anthro 0.61E-15 = 19%
Conclusions
• Neutral density at 400 km shows a decrease during the last solar minimum– Significantly lower than previous three minima
• Both F10 and Ap are also significantly lower during this most recent solar minimum.– Still can’t account for the observed decrease (using MSIS).
• Adjusting for Anthropogenic (CO2) forcing and climate change accounts for some of the remaining difference– Still some density drop that cannot be accounted for
• Using the SOHO SEM 304 data instead of F10 provides too much of a decrease in the neutral density
• Using the Mg II Index instead of F10 provides a more accurate estimate of the density during this last solar minimum.
– Solar 1.49E-15 = 48%– Geomag 1.03E-15 = 33%– Anthro 0.61E-15 = 19%
March 2008 Viereck: SDO and Space Weather 14