EstimatingDstindices and exospheric temperatures from equatorial magnetic fields measured by DMSP satellites

[1] We explore the feasibility of using variations in the horizontal component (ΔBH) of the Earth's magnetic field as measured by DMSP satellites while crossing the dip equator to estimate the provisional Dst index and the state of the thermosphere in near real time. Equatorial crossings are identified as locations where the vertical component of the main field measured by DMSP satellites vanishes. Local differences between measured and IGRF (epoch 2005) horizontal components (δBH) were calculated for the years 2005 to 2009. Each year quiet time (0 ≥ Dst ≥ – 7 nT) subsets of δBH were identified to establish offset baselines (δBH B) as functions of longitude along the magnetic equator (ϕeq) for each spacecraft. Year-to-year changes in δBH B reflect variations of the Earth's main field, indicating that baseline calculations must be updated at regular intervals for each spacecraft. Running-averaged values of ΔBH(t) = δBH (ϕeq, t) − δBH B (ϕeq, t) inferred from combined DMSP F16 and F17 data streams are shown to follow variations in Dst during the test interval. The method is also shown to apply during the magnetic superstorms of late 2003. Except during the late main phase, increases in globally averaged exospheric temperatures inferred from ΔBH and provisional Dst time series are in reasonable agreement with those inferred from measurements by accelerometers on the GRACE satellites.