GE SPACE Geomagnetic Earth Observation from SPAce

Fit to NERC’s Science Priorities Understanding the complex interactions and feedbacks within the Earth system over a range of space and time scales

Fit to NERC’s Science Priorities Understanding the complex interactions and feedbacks within the Earth system over a range of space and time scales climate change –magnetic field sensitive to some atmospheric parameters, a measure of ocean circulation, and measures effect of solar cycle

Interaction of Magnetic Field with Atmosphere Air drag at 450 km altitude as measured by CHAMP during geomagnetically disturbed and quiet periods Crossings of the northern (southern) polar region are indicated by blue (red) line segments, accordingly disturbed quiet

Measuring Oceanic Circulation Elevation and transport due to M2 tide and magnetic field at 400 km altitude B r [nT] h [m] Measurement of oceanic transport (depth integrated velocity) ? Electric field: E = v x B 0 Sheet current density: J = h  E B 0 = nT v = 0.1 m/s  = 3.2 S  m h = 4 km E = 5  V/m J = 70 mA/m  B = 14 nT (at surface) results in

Fit to NERC’s Science Priorities Understanding the complex interactions and feedbacks within the Earth system over a range of space and time scales climate change –magnetic field sensitive to some atmospheric parameters, a measure of ocean circulation, and measures effect of solar cycle sustainable economies –energy (ensuring security of electricity supply) –hazard mitigation (magnetic storms, radiation effects)

UK magnetic observatories Measured GIC Arrows denote measured ionospheric field variations during the July 2000 magnetic storm at various observatories and survey points Circles denote size and polarity of measured GIC (red = positive current flow to ground) Application of External Field Studies: Using Models of Surface Electric Fields in the UK for Study of GIC Model GIC Arrow head denotes direction of a simple model plane wave ionospheric field variation (E-field scale = 1.6 V/km; max GIC = 40 A)

South Atlantic Anomaly radiation hazard Sites of Topex anomalies , at approximately 1000km. Red star is site of MODIS failure.

NERC’s other strategic priorities Skilled people - attracting mathematicians and physicists

NERC’s other strategic priorities Skilled people - attracting mathematicians and physicists Leadership - world class researchers have ensured access to satellite data without a UK financial contribution to the missions

NERC’s other strategic priorities Skilled people - attracting mathematicians and physicists Leadership - world class researchers have ensured access to satellite data without a UK financial contribution to the missions Using knowledge – directional drilling for hydrocarbons – exploring for and exploiting natural resources – predicting geomagnetically induced currents in power systems

Major Questions To Address: How to unscramble the combined source effects? How does the dynamo work? Can we predict changes in the Earth’s magnetic field? What is the core’s contribution to the Earth’s angular momentum budget? What is the 3D conductivity structure of the mantle? What is the nature of lithospheric magnetization? What is the signal associated with flow in the oceans?

Core Magnetic Field Core Fluid Flow Space Environment Crust & Lithosphere No other measurable physical parameter can be used to sense so many diverse regions of the Earth

Geomagnetic Data Eskdalemuir observatory Ørsted

How does the geodynamo work? The combination of progress in numerical modeling of the geodynamo and new satellite observations promises to greatly advance our understanding of the origin of the Earth’s magnetic field. What is the dominant mechanism of angular momentum exchange in the solid Earth-core-inner core system (at each timescale)? How do core-mantle interactions influence the geodynamo? What accounts for the time- averaged field morphology? What causes abrupt changes in the field (jerks)? Can we forecast the magnetic field using techniques of data assimilation?

by nearly 10%. This is ten times faster than if the dynamo were switched off. The current decay rate is characteristic of magnetic reversals. Geographically, the dipole decay is largely due to changes in the field beneath the south Atlantic Ocean, connected to the growth of the South Atlantic Anomaly. Is the Earth’s magnetic field entering a reversal? Over the last 150 years, the Earth’s axial dipole component has decayed Can we explain the decay of the Earth’s dipole? The map shows the contribution to changes in the dipole component. The map is dominated by changes beneath the south Atlantic Ocean.

How Will Changes inEarth’s Magnetic Field Affect Satellite Operations and Communications? In 2000, the field is about 35% weaker in this region than would be expected. This weakness in the field has serious implications for low-Earth orbit satellite operations since it impacts the radiation dosage at these altitudes. How much longer will the South Atlantic Magnetic Anomaly continue to grow? How deep will it become? Long-term satellite observations allow us to model future evolution of this anomaly nT nT

Field in 1990 at core surface South Atlantic reverse flux patch is responsible for radiation doses experienced by satellites

“Jerks”: Rapid changes in secular variation: Proxies for core fluid velocity Niemegk observatory, Germany.

What is the contribution of the core to the Earth’s angular momentum balance? On inter-annual and decadal timescales the core, solid Earth, oceans and atmosphere are coupled. Length-of-day observations give the rotation rate of the solid Earth - dataset extends back ~150 years Geomagnetic observations give the rotation rate of the core - dataset extends back ~300 years Meteorological observations give the mean rotation rate of the atmosphere -dataset extends back a few decades Can we estimate the mean rotation of atmosphere before direct observations from core and mantle rotation? Can we detect short-term variations in core circulation on inter-annual timescales?

Decadal angular momentum exchanges between core and mantle

Electrical conductivity varies by orders of magnitude within the Earth and provides a source of information complementary to that obtained from seismology. Conductivity studies have relied largely on ground based magnetic observatories with poor spatial distribution. Satellite-based magnetic induction promises to open a new era in mapping the electrical structure of the crust and mantle. The Electrical Structure of the Crust and Mantle Induced magnetic field, expressed as a fraction of the inducing field as found by analysing Magsat data There is a strong correlation between smaller induced fields (blue) and equatorial landmasses, implying lower conductivity under the continents than in the oceans.

The Lithospheric Magnetic Field Magnetic fields of lithospheric origin at satellite altitude (400km) Lithospheric magnetization addresses: Origin of magnetization of the upper continental crust Lithospheric tectonics and hazards Influence of large impacts on Earth’s early tectonic development Regional and global distribution of energy and mineral resources

CHAMP CHAMP & South Atlantic CHAMP TMI CHAMP Vert. Der.

Trans Brasilian Lineament Aeromagnetic Data CHAMP CHAMP & Brazil CHAMP TMI Cret. Alkaline Volcanics RED Cret. Kimberlites BLUE Trans Brasilian Lineament Analytic Signal (Suscep.) Craton Trans Brasilian Lineament Kimberlite Trend

Core Field and Secular Variation Unmodelled large-scale external (magnetospheric) sources are at present the major limitation in field modelling This improvement was partly possible because data from Ørsted-2 were used to determine (and to correct for) magnetospheric contributions Power spectrum shows improvement from Magsat to CHAMP/Ørsted/Ørsted-2 field models Secular variation is now resolvable up to n=12; higher terms still masked by contributions from external sources mean SV

External field signal remains after selection on basis of LT and indices

Important Magnetospheric Current Systems Symmetric ring current, usually parameterised by Dst index or even the ‘pressure corrected’ Dst (i.e. removing CF contribution) Partial ring current, which strengthens on dusk side with increasing magnetospheric activity and is connected to Region 2 system Cross-tail current, which moves Earthward with increasing magnetospheric activity Region 1 and 2 Birkeland (field aligned) currents, Region 1 system closing on magnetopause Chapman-Ferraro (magnetopause) currents, shielding the internal (dipole) field Not modelled or less well understood: polar latitude currents - the ‘Region 0’ and ‘North Bz’ (NBZ) systems Courtesy of Igor Alexeev (MSU) Sun

An Example of an Existing External Field Model: The Tsyganenko Model (2001 Version) Mean External Field at Ørsted Satellite Orbit ( ) Under Quiet External Field Conditions (e.g. Kp<1+) Current Main Field Modelling Methodologies Typically Only Represent the Symmetric Ring Current (in Yellow) from Night-side Measurements Averaged External Field in 1 Degree Bins; Averaged Over Dipole Longitude; BGS Main Field Model (D&O 13) Subtracted

Comparison of Tsyganenko Model with Ørsted Data > Shown is mean external field in 1 degree colatitude bins > Model appears best at low to mid latitudes. > Poorer model, compared with real data, at high latitudes > Low latitude field is similar to the P 1 0 potential often assumed in main field modelling > Fine scale detail, especially at high latitudes, needs further study/modelling

Fit to q 2 0 with cos(local time) cos(time of year)

Summary Geomagnetism can play a significant role in answering fundamental questions about the core, mantle, oceans, lithosphere and the near-Earth environment Requires interdisciplinary collaboration (space physics, geodesy, oceanography, numerical simulation) GEOSPACE can play a leading role; members are sizable and high-profile part of international community Technology and missions for collecting new datasets are in place