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Introduction to Global Navigation Satellite Systems - CCAR

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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 NADIR Meeting 25–26 October 2011
A Compressed Thermosphere Leads to a Greater % Change in Density
Response Given the Same Energy Input – Preconditioning by EUV Flux

    Absolute Density at 400 km          h
                                                                                      P2




                                                                             B




                                      Altitude
                                                                                      P1

                                                  A                          C
                                                                                    Satellite altitude




   Relative Perturbations



                                                 Quiet                     Active

                                 Relative changes in thermosphere
                                 density response to geomagnetic forcing
                                 is stronger under low EUV conditions
In 2008, the Solar EUV Flux was at an Extreme Minimum with
Little Change over the Year While 38 CIRS were Catalogued!!
                                           Solar wind density

                                                 IMF |B|


                                            Solar wind speed

                                                 IMF Bz

                                                 IMF Bx

                                         Geomagnetic Activity Index


                                          Density - 400km altitude
      Superposed Epoch Analysis of 29
      CIR/HSS in 2008
                Classical CIR
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.




        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.
Superposed-Epoch Analysis of CHAMP Thermosphere
                        Density in 2008




                                 Calm




                      Thermospheric response to CIRs globally
                   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.
   Altitude Response of Mass Density using CHAMP and
   GRACE Measurements



                                                GRACE Satellite – NASA / DLR
                                                Inclination              88.9
                                                Lifetime                 March 2002-present
                                                Nominal Orbit Altitude   ~500 km
CHAMP Satellite – GFZ Potsdam
Inclination              87.3
Lifetime                 July, 2000-September
                         2010
Nominal Orbit Altitude   ~400 km
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.



                                                                                                        7
Altitude Response in Thermosphere
Mass Density to Geomagnetic Activity

  h



           B0        B1
                                GRACE altitude
Altitude




           A0        A1
                               CHAMP altitude




           Quiet      Active
   Geomagnetic Activity
   Dec 2008
   During a CHAMP
   and GRACE
   Common Local
   Time Orbits


Quiet Time: December 9-11, 2008
         <F10.7> = 67
         <Ap> = 15

Active Time: December 5 – 7, 2008
          <F10.7> = 68
          <Ap>= 2




                                    9
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




                                                                     10
MSIS VS. CHAMP and GRACE Observations
December 2008
 Active time density      Quiet time density
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 2007–2009 solar minimum, J. Geophys.
                           Res., 116, A00H07, doi:10.1029/2011JA016508.




                                                                             12
  CHAMP and GRACE Densities with Adjusted F10.7 based on
  Mg II During the Active Period of the Geomagnetic Storm
Before                                           After




  During the active time, a good MSIS representation is achieved by lowering f10.7 by 11.
GRACE Densities with MSIS adjusted for F10.7, Ap, and
Helium Density


              Original Values
                                       Adjust F10.7 - 14




        Adjust F10.7 – 14, Ap+2        Adjust F10.7 – 14, Ap+2,
                                       30% increase in Helium
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
Quiet Time Mass Density at GRACE Altitudes is
Significantly Impacted by the Presence of Helium
Mass Density Response as a Function of Altitude in Winter
High latitudes is significantly lessened at GRACE Altitudes
                                                by Helium




                                                              17
Latitude Dependence in Altitude Response to December
2008 Geomagnetic Activity




                                                       18
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:
   q 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
Cont’d
    Response at GRACE Altitudes:
    q 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
    q 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.
    q 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

								
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