International geomagnetic reference field — 2000

Mandéa, Mioara; Macmillan, Susan; Bondar, T. N.; Golovkov, V. P.; Langlais, B.; Lowes, F. J.; Olsen, Nils; Quinn, John M.; Sabaka, T.

doi:10.1016/s0031-9201(00)00153-9

Cited by 27 publications

(11 citation statements)

References 1 publication

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“…Magnetic data were corrected for the International Geomagnetic Reference Field [ International Association of Geomagnetism and Aeronomy et al , 2000] to obtain magnetic anomalies. We then compared magnetic anomalies measured along flow line‐parallel profiles, with synthetic magnetic anomaly profiles, and identified a sequence of magnetic anomalies starting with the central anomaly and including anomalies 2, 2A, 3, 3A and 5 (Figure 2).…”

Section: Data Acquisition and Processingmentioning

confidence: 99%

Melt supply variations to a magma‐poor ultra‐slow spreading ridge (Southwest Indian Ridge 61° to 69°E)

Cannat

Rommevaux-Jestin

Fujimoto

2003

Geochem Geophys Geosyst

106

156

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[1] The Southwest Indian Ridge (SWIR) to the east of the Melville Fracture zone receives anomalously low volumes of melt on average. However, a small number of ridge segments appear to receive more melt than this regional average. We use off-axis bathymetry, gravity, and magnetic data to show that this melt distribution pattern, quite distinct from what is observed at the Mid-Atlantic Ridge (MAR), has been a characteristic of the easternmost SWIR for at least the past 10 myr. We also show that segments of the easternmost SWIR are substantially shorter lived than most segments of the MAR. Melt distribution in our SWIR study area is therefore both more focused and more variable in time than at the MAR. We tentatively propose a mechanism by which strong and transient melt-focusing events could be initiated by a localized increase in the volume of melt supplied by the melting mantle to the base of the axial lithosphere, causing thermal thinning of this lithosphere and along-axis melt migration. These two processes may combine to effectively focus larger volumes of melt toward the center of future thick crust segments. Rapid melt extraction by dikes that feed large volcanic constructions on the seafloor, followed by tectonic disruption of these volcanic constructions by deep-reaching faults, may then cool the axial lithosphere back to its original thickness and end the melt-focusing events. The easternmost SWIR is also characterized by a common departure from isostatic compensation of seafloor topography and by a pronounced asymmetry of crustal thickness and seafloor relief between the two ridge flanks. At the faster spreading MAR, similar characteristics are found near the ends of ridge segments. We propose that spreading at the ultra-slow SWIR during periods when the melt supply is low (i.e., most of the time for the easternmost SWIR) is dominated by large offset asymmetric normal faulting, with significant flexural uplift of the footwalls. Faults face either north or south, and changes in fault polarity are frequent, both along axis and along flow lines (i.e., with time). Producing large faults and maintaining high uncompensated reliefs require the axial lithosphere to be thick, a predictable characteristic for this ultra-slow ridge, which has an anomalously low regionally averaged melt supply.

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Section: Data Acquisition and Processingmentioning

confidence: 99%

Melt supply variations to a magma‐poor ultra‐slow spreading ridge (Southwest Indian Ridge 61° to 69°E)

Cannat

Rommevaux-Jestin

Fujimoto

2003

Geochem Geophys Geosyst

106

156

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“…Prior to calculating a pole position, the 1999 data had to be updated to 2001. Since there is no magnetic observatory or repeat station close to the region, we determined secular variation from three magnetic reference field models: the International Geomagnetic Refer ence Field (IGRF) [Mandea et al, 2000], the World Magnetic Model (WMM) [MacMillan and Quinn, 2000], and the Canadian Geomag netic Reference Field (CGRF) [Haines and Newitt, 1997] .The three models gave comparable values, so the uncertainty in the resultant updating should not exceed a few nanoteslas.…”

Section: Eos Vol 83 No 35 27 August 2002mentioning

confidence: 99%

Recent acceleration of the north magnetic pole linked to magnetic jerks

Newitt

Mandéa²,

McKee³

et al. 2002

EoS Transactions

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Surveys to determine the location of the North Magnetic Pole (NMP) have been conducted regularly since 1947 to serve two basic functions: to educate, and to provide valuable research. The public has always been fascinated and often misinformed about the nature and significance of the NMP. Thus, an NMP survey offers an ideal opportunity for public outreach and education. Scientifically, NMP surveys test the veracity of global magnetic field models such as the International Geomagnetic Reference Field. The act of determining the NMP's position also reveals facts about its motion that might otherwise be overlooked when using global models. The most recent survey of the NMR completed in May 2001, showed an unprecedented increase in the pole's rate of motion.

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“…Figure 4 shows the simulations of the BTs as a function of B , with cos(θ B ) fixed at 0.9, for the standard temperature profile shown in Figure 2. The B range plotted in the figure covers the values estimated on a global scale using the 10th International Goemagnetic Reference Field (IGRF) model [ Mandea et al , 2000]. Notice that the BT increases with B in channels 19 and 20, but decreases in channel 21.…”

Section: Radiometric Characteristics Of Channels 19–22mentioning

confidence: 99%

A fast radiative transfer model for SSMIS upper atmosphere sounding channels

et al. 2007

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[1] Special Sensor Microwave Imager/Sounder (SSMIS) on board the Defense Meteorology Satellite Program (DMSP) F-16 satellite probes the atmospheric temperature from surface to 100 km. SSMIS channels 19-22 are significantly affected by Zeeman splitting, which is dependent on the Earth's magnetic field. Thus, in satellite data assimilation or retrieval systems, SSMIS brightness temperatures and their Jacobians (or gradient with respect to temperature) must be computed with a fast radiative transfer (RT) scheme that takes into account the Zeeman-splitting effect. In this study, an averaged transmittance within the channel frequency passbands is parameterized and predicted with atmospheric temperature, geomagnetic field strength, and the angle between the geomagnetic field vector and the electromagnetic wave propagation direction. The coefficients of predictors are trained with a line-by-line (LBL) radiative transfer model that accurately computes the monochromatic transmittances at fine frequency steps within each passband. The new radiative transfer scheme is compared to the results from the line-by-line model for the dependent and independent data sets. It is shown that the differences between the two models are well below the instrument noise levels but the new scheme is much faster. It is also shown that the SSMIS measurements agree well with the simulations that are based on the atmospheric profiles from the sounding of the atmosphere using broadband emission radiometry (SABER) on the Thermosphere-lonosphere-Mesosphere Energetics and Dynamics satellite and the COSPAR international reference atmosphere (CIRA) model.

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International geomagnetic reference field — 2000

Cited by 27 publications

References 1 publication

Melt supply variations to a magma‐poor ultra‐slow spreading ridge (Southwest Indian Ridge 61° to 69°E)

Melt supply variations to a magma‐poor ultra‐slow spreading ridge (Southwest Indian Ridge 61° to 69°E)

Recent acceleration of the north magnetic pole linked to magnetic jerks

A fast radiative transfer model for SSMIS upper atmosphere sounding channels

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