EARTH SCIENCE > Sun-earth Interactions > Ionosphere/Magnetosphere Dynamics
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We have produced 20-year archives of electron density measurements, at 1 hour and 10-minute integration times, by reanalysing measurements from the EISCAT UHF and VHF radars between 2001-2021. We are specifically looking at altitudes 50-200 km to capture the variability in the Mesosphere Lower Thermosphere Ionosphere (MLT-I) region. We have also separately included power profile data, providing measurements of the raw electron density which can be added (with careful assumptions) to improve data resolution at the lower altitudes. Funding was provided by NERC project NE/V018426/1 (MesoS2D)
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The data files in this directory were used to create Figures 2-7 in the paper: Horne et al. (in press - 2018/7/18). Figure 1 of the paper was constructed using publically available data from other sources.
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We conduct a global survey of magnetosonic waves and compute the associated bounce and drift averaged diffusion coefficients, taking into account co-located measurements of fpe/fce, to assess the role of magnetosonic waves in radiation belt dynamics, where fpe is the plasma frequency and fce is the electron gyrofrequency.. The average magnetosonic wave intensities increase with increasing geomagnetic activity and decreasing relative frequency with the majority of the wave power in the range fcp < f < 0.3fLHR during active conditions, where fcp is the proton gyrofrequency and fLHR is the lower hybrid resonance frequency. In the region 4.0 <= L* <= 5.0, the bounce and drift averaged energy diffusion rates due to magnetosonic waves never exceed those due to whistler mode chorus, suggesting that whistler mode chorus is the dominant mode for electron energisation to relativistic energies in this region. Further in, in the region 2.0 <= L* <= 3.5, the bounce and drift averaged pitch angle diffusion rates due to magnetosonic waves can exceed those due to plasmaspheric hiss and very low frequency (VLF) transmitters over energy-dependent ranges of intermediate pitch angles. We compute electron lifetimes by solving the 1D pitch angle diffusion equation including the effects of plasmaspheric hiss, VLF transmitters and magnetosonic waves. We find that magnetosonic waves can have a significant effect on electron loss timescales in the slot region reducing the loss timescales during active times from 5.6 to 1.5 days for 500 keV electrons at L* = 2.5 and from 140.4 days to 35.7 days for 1 MeV electrons at L* = 2.0. The research leading to these results has received funding from the Natural Environment Research Council (NERC) Highlight Topic grant NE/P01738X/1 (Rad-Sat) and the NERC grants NE/V00249X/1 (Sat-Risk) and NE/R016038/1.
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Whistler mode chorus is an important magnetospheric wave emission playing a major role in radiation belt dynamics, where it contributes to both the acceleration and loss of relativistic electrons. In this study we compute bounce and drift averaged chorus diffusion coefficients for 3.0 < L* < 6.0, using the TS04 external magnetic field model, taking into account co-located near-equatorial measurements of the wave intensity and fpe/fce, by combining the Van Allen probes measurements with data from a multi-satellite VLF wave database. The variation of chorus wave normal angle with spatial location and fpe/fce is also taken into account. We find that chorus propagating at small wave normal angles has the dominant contribution to the diffusion rates in most MLT sectors. However, in the region 4 <= MLT < 11 high wave normal angles dominate at intermediate pitch angles. In the region 3 < L* < 4, the bounce and drift averaged pitch angle and energy diffusion rates during active conditions are primarily larger than those in our earlier models by up to a factor of 10 depending on energy and pitch angle. Further out, the results are similar. We find that the bounce and drift averaged energy and pitch angle diffusion rates can be significantly larger than the new model in regions of low fpe/fce,eq, where the differences can be up to a factor of 10 depending on energy and pitch angle. Funding was provided by the Natural Environment Research Council (NERC) Highlight Topic grant NE/P01738X/1 (Rad-Sat) and the NERC grants NE/V00249X/1 (Sat-Risk), NE/R016038/1 and NE/X000389/1.
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Radiation belts are hazardous regions found around several of the planets in our Solar System. They consist of very hot, electrically charged particles that are trapped in the magnetic field of the planet. At Saturn the most important way to heat these particles has for many years been thought to involve the particles drifting closer towards the planet. This paper builds on previous work on the emerging idea at Saturn that a different way to heat the particles is also possible where the heating is done by waves, in a similar way to what we find at the Earth. This work is reported in the paper "Acceleration of electrons by whistler-mode hiss waves at Saturn" by E.E. Woodfield et al., 2021. The data provided here enable reconstruction of all the figures in the paper. E.E.W., R.B.H., and S.A.G. were funded by STFC grant ST/S000496/1. R.B.H., S.A.G. and A.J.K. were funded by NERC grant NE/R016038/1 and R.B.H. and S.A.G. by NERC grant NE/R016445/1. J.D.M. and Y.Y.S. were supported by NASA grants NNX11AM36G and NNX16AI47G. University of Iowa (J.D.M.) was supported by NASA contract 1415150 with JPL. Y.Y.S. was supported by EC grant H2020 637302.
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This data set contains the ULF wave model output data required to produce the figures in the article: A. W. Degeling, I. J. Rae, C. E. J. Watt, Q. Q. Shi, R. Rankin and Q. G. Zong, "Control of ULF Wave Accessibility to the Inner Magnetosphere by the Convection of Plasma Density", J. Geophys. Res. (accepted Dec. 2017) doi:10.1002/2017JA024874 The dataset has a Matlab binary file format. It consists of a structure array "d" (with 325 elements). These elements correspond to the 2D parameter scan in driver frequency and elapsed time during plume development performed for this study. The elapsed time parameter has 25 elements, ranging 0 to 24 hours (i.e. 1 hour spacing), and the driver frequency parameter has 13 elements ranging from 1 to 7 mHz (with 0.5 mHz spacing). e.g. use "d = reshape(d,25,13);" to reshape the structure array into 2D with columns for the frequency scan and rows for the elapsed time scan. The Matlab function "make_PDP_figs.m" is used to read the data, perform the necessary post-processing operations and output the article figures. To produce all six figures, simply run the file without any input arguments.
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Signals from manmade VLF transmitters, used for communications with submarines, can leak into space and contribute to the dynamics of energetic electrons in the inner radiation belt and slot region. We use ~5 years of plasma wave data from the Van Allen Probe A satellite to construct new models of the observed wave power from VLF transmitters both as a function of L* and MLT and geographic location. This work is reported in Meredith et al. (2019) and the data provided here enable reconstruction of all of the figures in the paper.
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Whistler mode chorus is an important magnetospheric emission, playing fundamental roles in the dynamics of the Earth''s outer radiation belt and the production of the Earth''s diffuse and pulsating aurora. In this study we extend our existing database of whistler mode chorus by including ~3 years of data from RBSP-A and RBSP-B and an additional ~6 years of data from THEMIS A, D, and E, greatly improving the statistics and coverage in the near-equatorial region (|MLAT|<18^o). We produce new global maps of whistler mode chorus as a function of spatial location and frequency. This work is reported in Meredith et al. [2020] and the data provided here enable reconstruction of all of the figures in the paper. The research leading to these results has received funding from the Natural Environment Research Council (NERC) Highlight Topic grant NE/P01738X/1 (Rad-Sat) and the NERC grant NE/R016038/1. Wen Li and Xiao-Chen Shen received funding from NASA grants NNX17AG07G and 80NSSC19K0845, NSF grant AGS-1847818, and the Alfred P. Sloan Research Fellowship FG-2018-10936. Jacob Bortnik received funding from NASA grants NNX14AI18G, and RBSP-ECT and EMFISIS funding provided by JHU/APL contracts 967399 and 921647 under NASA''s prime contract NAS5-01072.
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Auroral oval boundary locations derived from IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite FUV (Far Ultra Violet imager) data covering the period from May 2000 until October 2002. Three sets of boundary data were derived separately from the WIC (Wideband Imaging Camera) and SI12/SI13 (Spectrographic Imager 121.8/135.6 nm) detectors. For each image, the position of each pixel in AACGM (Altitude Adjusted Corrected Geomagnetic) coordinates was established. Each image was then divided into 24 segments covering 1 hour of magnetic local time (MLT). For each MLT segment, an intensity profile was constructed by finding the average intensity across bins of 1 degree magnetic latitude in the range of 50 to 90 degrees (AACGM). Two functions were fit to each intensity profile: a function with one Gaussian component and a quadratic background, and a function with two Gaussian components and a quadratic background. The function with a single Gaussian component should provide a reasonable model when the auroral emission forms in a continuous oval. When the oval shows bifurcation, the function with two Gaussian components may provide a better model of the auroral emission. Of the two functions fit to each intensity profile, we determine the one with the lower reduced chi-square goodness-of-fit statistic to be the better model for that profile. For the version 1.1 boundary location data, the fitting process was performed over 200 iterations to achieve each fit. The auroral boundaries were then determined to be the position of the peak of the poleward Gaussian curve, plus its FWHM (full-width half-maximum) value of the Gaussian, to the peak of the equatorward Gaussian, minus its FWHM. In the case of the single Gaussian fit, the same curve is used for both boundaries. A number of criteria were applied to discard poorly located auroral boundaries arising from either poor fitting or incomplete data. A further correction can be applied to the data, to estimate the location of the Earth''s magnetic field''s OCB (open-close boundary). These corrections have been tabulated in a separate file; if this correction is required the adjustments should be made to the poleward boundary value.
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This dataset comprises the output from a series of eight simulations with the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model as used in the study by Cnossen and Foerster (2016).The first six simulations were run with observed solar radiative forcing, specified by F10.7 values, and observed solar wind conditions. In the last two simulations (dsol-lh and jsol-lh), the solar radiative forcing was artificially reduced by setting the F10.7 values to a constant low value of 80 solar flux units. The dsol-lh and jsol-lh are otherwise identical to the dsol-hh and jsol-mh simulations, respectively. Further details about the simulations and a brief description of the CMIT model are provided by Cnossen and Foerster (2015, in review). Wiltberger et al. (2004) and Wang et al. (2004, 2008) provide further details of the CMIT model. The CMIT simulations were performed on the Yellowstone high-performance computing facility (ark:/85065/d7wd3xhc) provided by the Computational and Information Systems Laboratory of the National Centre for Atmospheric Research, sponsored by the National Science Foundation.
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