Altitude Response of Thermosphere Mass Density to Geomagnetic Activity in the Recent Solar Minimum...
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Altitude Response of Thermosphere Mass Density to Geomagnetic Activity in the Recent Solar Minimum Jeffrey P. Thayer, Xianjing Lui, and Jiuhou Lei MURI
Altitude Response of Thermosphere Mass Density to Geomagnetic
Activity in the Recent Solar Minimum Jeffrey P. Thayer, Xianjing
Lui, and Jiuhou Lei MURI NADIR Meeting 2526 October 2011
Slide 2
A Compressed Thermosphere Leads to a Greater % Change in
Density Response Given the Same Energy Input Preconditioning by EUV
Flux Relative changes in thermosphere density response to
geomagnetic forcing is stronger under low EUV conditions Absolute
Density at 400 km Relative Perturbations Quiet A Active B C P 2 P 1
Satellite altitude Altitude h
Slide 3
In 2008, the Solar EUV Flux was at an Extreme Minimum with
Little Change over the Year While 38 CIRS were Catalogued!! Density
- 400km altitude Solar wind density IMF Bx Geomagnetic Activity
Index Solar wind speed IMF Bz IMF |B|
Slide 4
Classical CIR The interplanetary conditions for different types
of geomagnetic activity are indicated by numbers: (1) geomagnetic
quiet, (2) a storm initial phase, (3) a magnetic storm main phase,
and (4) the storm extended recovery phase. Tsurutani, B. T., et al.
(2006), Corotating solar wind streams and recurrent geomagnetic
activity: A review, J. Geophys. Res., 111, A07S01,
doi:10.1029/2005JA011273. Superposed Epoch Analysis of 29 CIR/HSS
in 2008
Slide 5
Thermospheric response to CIRs globally Calm Lei, J., J. P.
Thayer, W. Wang, and R. L. McPherron (2011), Impact of CIR storms
on thermosphere density variability during the solar minimum of
2008, Sol. Phys., doi:10.1007/s11207-010-9563-y. Superposed-Epoch
Analysis of CHAMP Thermosphere Density in 2008
Slide 6
Altitude Response of Mass Density using CHAMP and GRACE
Measurements CHAMP Satellite GFZ Potsdam Inclination 87.3
LifetimeJuly, 2000-September 2010 Nominal Orbit Altitude~400 km
GRACE Satellite NASA / DLR Inclination 88.9 LifetimeMarch
2002-present Nominal Orbit Altitude~500 km
Slide 7
NADIR 7 Occasions of Common Local Time Passes of CHAMP and
GRACE Satellites Bruinsma, S. L., and J. M. Forbes (2010),
Anomalous behavior of the thermosphere during solar minimum
observed by CHAMP and GRACE, J. Geophys. Res., 115, A11323,
doi:10.1029/2010JA015605.
Slide 8
A0A0 QuietActive CHAMP altitude Altitude h A1A1 Altitude
Response in Thermosphere Mass Density to Geomagnetic Activity GRACE
altitude B0B0 B1B1
Slide 9
NADIR 9 Geomagnetic Activity Dec 2008 During a CHAMP and GRACE
Common Local Time Orbits Quiet Time: December 9-11, 2008 = 67 = 15
Active Time: December 5 7, 2008 = 68 = 2
Slide 10
NADIR 10 Thermosphere Mass Density Ratio (Active/Quiet) for Dec
2008 HSS Event: Thermosphere Composition Effect GRACE Normalized to
476 km CHAMP Normalized to 332 km MSIS Density Ratio
Slide 11
MSIS VS. CHAMP and GRACE Observations December 2008 Active time
densityQuiet time density
Slide 12
NADIR 12 Mg II Correction to F10.7 Index at Solar Minimum
Solomon, S. C., L. Qian, L. V. Didkovsky, R. A. Viereck, and T. N.
Woods (2011), Causes of low thermospheric density during the
20072009 solar minimum, J. Geophys. Res., 116, A00H07,
doi:10.1029/2011JA016508.
Slide 13
CHAMP and GRACE Densities with Adjusted F10.7 based on Mg II
During the Active Period of the Geomagnetic Storm During the active
time, a good MSIS representation is achieved by lowering f10.7 by
11. Before After
Slide 14
Original Values GRACE Densities with MSIS adjusted for F10.7,
Ap, and Helium Density Adjust F10.7 - 14 Adjust F10.7 14, Ap+2
Adjust F10.7 14, Ap+2, 30% increase in Helium
Slide 15
CHAMP Densities with MSIS adjusted input values of F10.7, Ap,
and Helium same as for GRACE Original Values Adjust F10.7 - 14
Adjust F10.7 14, Ap+2 Adjust F10.7 14, Ap+2, 30% increase in
Helium
Slide 16
Quiet Time Mass Density at GRACE Altitudes is Significantly
Impacted by the Presence of Helium
Slide 17
NADIR 17 Mass Density Response as a Function of Altitude in
Winter High latitudes is significantly lessened at GRACE Altitudes
by Helium
Slide 18
NADIR 18 Latitude Dependence in Altitude Response to December
2008 Geomagnetic Activity
Slide 19
Thermosphere Mass Density During CIR/HSS Events Recurrent
geomagnetic activity enabled isolation of CIR/HSS processes on the
preconditioned solar minimum state of the thermosphere. Response at
CHAMP Altitudes: The recurrent geomagnetic activity and constant
EUV flux in 2008 enabled a superposed epoch analysis that
demonstrated the typical global thermosphere response at 400 km to
CIR/HSS events was on average a 75% increase with recovery taking a
week or more. Integrated effect rivals CMEs but also demonstrated
significant variability
Slide 20
Contd Response at GRACE Altitudes: Significant concentrations
of helium exist at GRACE altitudes (472 km) during quiet
geomagnetic activity in the winter hemisphere at solstice in 2008,
i.e., the wintertime helium bulge The mass density response to
geomagnetic activity in the contracted winter hemisphere is
lessened by the presence of helium leading to strongly varying mass
density response with altitude. F10.7 input to MSIS during December
2008 required a downward adjustment (concomitant with Mg II index)
to adequately represent mass density observations and subsequently
the modeled drag coefficient requires reevaluation to account for
the significant presence of helium. Need information of composition
to adequately describe the thermosphere density response to
geomagnetic activity