# On a Novel Approach to Correcting Temperature Dependencies in Magnetic Observatory Data
## 1 Introduction  
The study of the nature of the Earth's magnetic field (EMF) and the development of mathematical models to describe it are inseparable from improvements in methods for measuring and processing geomagnetic data. Despite a constant increase in the quantity and quality of measurements performed by research satellites in near-Earth space, ground-based continuous magnetic field measurements are still the most accurate and long-term series of observations of secular changes in the EMF [1; 2]. The organization of the first magnetic observatories goes back to [PERSON], who, as the founder of the EMF modelling method, realized the need for continuous observations of the EMF in specially equipped magnetic observatories. A major step towards building a global observation network was the International Geophysical Year (IGY), during which more than 1000 magnetic observatories were launched around the world [3]. The system of World Data Centers established during the IGY became the prototype of modern data repositories and anticipated the idea of distributed storage and exchange of scientific information [4]. The growing scientific and applied importance of high precision geomagnetic observations led to the foundation of the INTERMAGNET international network of magnetic observatories in 1991, which now includes about 130 observatories worldwide [1]. One of the main aims of the network was to ensure the high reliability of the accumulated geomagnetic data achieved by introducing new methods of measurement quality control, multistep reconciliation, and supplementing measurements with metadata. Since the formation of INTERMAGNET, the quality criteria for the network's observation data [5] have become the de facto standard foruse in modelling the Earth's main magnetic field [6]. Highly accurate models are essential for both fundamental research in geophysics and space physics, as well as applications such as global satellite navigation [7], support for directional drilling [8; 9; 10], and many others. In order to achieve the required accuracy of observations, magnetic observatories are placed in locations free of local magnetic anomalies and away from sources of electromagnetic noise, such as roads, railways, and power lines. The main measuring instrument of the magnetic observatory is a vector three-component magnetometer (varioneter), which allows to measure variations of the total magnetic induction vector **B**. Obtaining the vector **B** total components from the variometer data is done by adding baseline values to the variations [11; 12; 13]. Observatories calculate baseline values based on absolute measurements, which are performed manually 1-2 times per week. One known disadvantage of the variometer is the temperature drift of the readings [14; 15]. The temperature dependencies of a fluxgate sensor are often caused by temperature-dependent variations in the magnetic susceptibility of the material from which the coil cores are made. In addition, the temperature-dependent components of the sensor electronics also contribute to temperature drifts [16; 17]. In order to reduce the drift effect, variometers are installed in thermostatically controlled pavilions that maintain the daily variation in sensor temperature at 1-2 \({}^{\circ}\)C. Such stability is difficult to achieve over the entire calendar year due to the dramatic summer and winter temperature variations. Magnetic observatories located in sharply continental climates are affected by annual variations of outdoor temperatures from \(-40\)\({}^{\circ}\)C to \(+30\)\({}^{\circ}\)C. Maintaining a stable sensor temperature in such conditions becomes problematic, especially due to the limited power supply in areas of distant observatories. Absolute measurements allow correcting temperature distortions on seasonal or monthly scales, while correcting daily or weekly scale distortions is a non-trivial task when preparing the definitive data [18; 19].