Collaborative Research: Long Term Structure and Variability in the Geomagnetic Field: The View from Lavas, Sediments and Magnetic Anomalies

熔岩流、海洋沉积物和磁异常数据将用于模拟地磁场的长期结构和变化。熔岩流和沉积物的数据表明，在过去5Ma的正极性和反极性时期，平均场结构不同，尽管基于每种数据的单个模型的约束都很差。PI的建议是研究需要多长时间间隔来采样整个长期变化范围，以获得一个良好的地磁场平均值。PI还将使用古强度数据来推导新的古长期变化模型。现有的古强度数据与Constable & Parker目前的模型不相容，即同位素在任何地心坐标系下都具有可变性。新的模型将寻求，使用进化规划，允许沿地理轴的各向异性。通过寻找时间平均场的异常和与历史场中类似结构相对应的古长期变化，研究可能反映核-幔边界条件控制的极长期（数百万年）地磁场非纬向结构。

9526682 Johnson Lava flows, marine sediments and magnetic anomaly data will be used to model the long term structure and variability in the geomagnetic field. Data from both lava flows and sediments indicated different average field configurations during normal and reverse polarity periods for the past 5Ma, although the individual models based on each type of data are poorly constrained. The PI's propose to investigate how long a time interval is required to sample the full range of secular variation to get a good average of the geomagnetic field. The PI's will also use paleointensity data to derive new paleosecular variation models. Existing paleointensity data are incompatible with the current model of Constable & Parker, that is isotopic in variability with respect to any geocentric coordinate system. New models will sought, using evolutionary programming, that allow for anisotropy along the geographic axis. Very long-term (millions of years) non-zonal structure in the geomagnetic field, that may reflect control by core-mantle boundary conditions will be investigated by looking for anomalies in the time-averaged field and the paleosecular variation that correspond to similar structures seen in the historical field.