Dominant spatial and temporal patterns of horizontal ionospheric plasma velocity variation covering the northern polar region, from 1997.0 to 2009.0 - VERSION 2.0

We present a concurrent series of 144 monthly reanalyses of Super Dual Auroral Radar Network (SuperDARN) plasma velocity measurements, using the method of data-interpolating Empirical Orthogonal Functions (EOFs). For each monthly reanalysis, the 5-minute median values of the northern polar region's radar-measured line-of-sight Doppler plasma velocities are binned in an equal-area grid defined in quasi-dipole latitude and quasi-dipole magnetic local time (MLT). The grid cells each have an area of approximately 110,000km2, and the grid extends to 30 degrees colatitude. Within this spatial grid, the sparse binned data are infilled to provide a measurement at every spatial and temporal location via two different EOF analysis models: one tailored to instances of low data coverage, the other tailored to higher data coverage. These two models each comprise 144 monthly sets of orthogonal modes of variability (spatial and temporal patterns), along with the timestamps of each epoch, and the spatial coordinate information of all bin locations. A companion dataset determines which of the two models should be chosen in each location for each month, in order to ensure the best accuracy of the infill solution. We also provide the temporal mean of the data in each spatial bin, which is removed prior to the EOF analysis. Collectively, the reanalysis delivers the SuperDARN data in terms of cardinal north and east vector components (in the quasi-dipole coordinate frame), without its usual extreme sparseness, for studies of ionospheric electrodynamics for the period 1997.0 to 2009.0. Funding was provided by NERC Standard grant NE/N01099X/1, titled 'Thermospheric Heating Modes and Effects on Satellites' (THeMES) and the NERC grant NE/V002732/1, titled 'Space Weather Instrumentation, Measurement, Modelling, and Risk: Thermosphere' (SWIMMR-T).

我们提出了144组月度并发再分析结果，针对超级双极光雷达网（Super Dual Auroral Radar Network, SuperDARN）的等离子体速度测量数据，采用数据插值经验正交函数（Empirical Orthogonal Functions, EOFs）方法。每个月度再分析中，北极地区雷达测量的视线路径多普勒等离子体速度的5分钟中值，被分箱到基于准偶极纬度（quasi-dipole latitude）和准偶极磁地方时（magnetic local time, MLT）定义的等面积网格中。每个网格单元面积约为110,000平方公里，网格延伸至余纬30度。在此空间网格内，稀疏的分箱数据通过两种不同的EOF分析模型进行填充，以在每个时空位置提供测量值：一种针对低数据覆盖情况，另一种针对高数据覆盖情况。这两种模型各包含144组月度正交变率模态（时空模式），以及每个时间点的时间戳和所有分箱位置的空间坐标信息。配套数据集用于确定每月每个位置应选择哪种模型，以确保填充解的最佳精度。我们还提供了每个空间分箱数据的时间均值，该均值在EOF分析前被移除。总体而言，该再分析结果以准偶极坐标系下的正北和正东矢量分量形式呈现SuperDARN数据，消除了其通常的极端稀疏性，适用于1997.0至2009.0期间的电离层电动力学（ionospheric electrodynamics）研究。本研究由英国自然环境研究理事会（Natural Environment Research Council, NERC）标准基金NE/N01099X/1（项目名称：《热层加热模式及其对卫星的影响》，THeMES）和NERC基金NE/V002732/1（项目名称：《空间天气仪器、测量、建模与风险：热层》，SWIMMR-T）资助。